Showing papers in "Australian Journal of Crop Science in 2011"

Annual intercrops: an alternative pathway for sustainable agriculture.

Abstract: Intercropping, the agricultural practice of cultivating two or more crops in the same space at the same time, is an old and commonly used cropping practice which aims to match efficiently crop demands to the available growth resources and labor. The most common advantage of intercropping is the production of greater yield on a given piece of land by making more efficient use of the available growth resources using a mixture of crops of different rooting ability, canopy structure, height, and nutrient requirements based on the complementary utilization of growth resources by the component crops. Moreover, intercropping improves soil fertility through biological nitrogen fixation with the use of legumes, increases soil conservation through greater ground cover than sole cropping, and provides better lodging resistance for crops susceptible to lodging than when grown in monoculture. Intercrops often reduce pest incidence and improve forage quality by increasing crude protein yield of forage. Intercropping provides insurance against crop failure or against unstable market prices for a given commodity, especially in areas subject to extreme weather conditions such as frost, drought, and flood. Thus, it offers greater financial stability than sole cropping, which makes the system particularly suitable for labor-intensive small farms. Besides, intercropping allows lower inputs through reduced fertilizer and pesticide requirements, thus minimizing environmental impacts of agriculture. However, intercropping has some disadvantages such as the selection of the appropriate crop species and the appropriate sowing densities, including extra work in preparing and planting the seed mixture and also extra work during crop management practices, including harvest. The selection of an appropriate intercropping system for each case is quite complex as the success of intercropping systems depend much on the interactions between the component species, the available management practices, and the environmental conditions. Plant breeding can contribute determinedly to increase of productivity of intercropping systems by investigating and exploiting the genetic variability to intercrop adaptation. This paper provides an overall view and evaluation of annual intercropping, summarizing its main advantages supported by a number of key examples from the literature which point out its great value in the context of sustainable agriculture.

Reactive Oxygen Species in Plants: Their Generation, Signal Transduction, and Scavenging Mechanisms

Abstract: Reactive oxygen species (ROS) are a by-product of normal cell metabolism in plants; however, under stress conditions, the balance between production and elimination is disturbed. ROS rapidly inactivate enzymes, damage vital cellular organelles in plants, and destroy membranes by inducing the degradation of pigments, proteins, lipids and nucleic acids which ultimately results in cell death. In addition to degrading macromolecules, ROS act as a diffusible signal in signal transduction pathways and also as a secondary messenger in various developmental pathways in plants. Plants possess a complex battery of enzymatic and non-enzymatic antioxidative defense systems that can protect cells from oxidative damage and scavenge harmful ROS that are produced in excess of those normally required for various metabolic reactions. The mechanism by which ROS is generated in aerobic organisms is poorly understood. This review paper describes the generation, origin, and role of ROS in signal transduction and cell death, and the removal of ROS by antioxidative defense systems in plants during various developmental pathways.

Role of Mineral Nutrition in Alleviation of Drought Stress in Plants

Abstract: Water, the most important component of life, is rapidly becoming a critically short commodity for humans and crop production. Limited water supply is one of the major abiotic factors that adversely affect agricultural crop production worldwide. Drought stress influences the normal physiology and growth of plants in many ways. It results in an increase of solute concentration outside the roots compared to the internal environment of the root and causes reverse osmosis. As a result, the cell membrane shrinks from the cell wall and may eventually lead to death of the cell. Water stress tends to shrink away from the interface with water-absorbing roots, creating a gap in the soil-plant-air continuum. As the plant continues to lose water via transpiration, water is drawn from root cells resulting in shrinkage of cell membranes and results in decreased integrity of the cell membrane and the living cell may be destroyed. Drought stress inhibits photosynthesis in plants by closing stomata and damaging the chlorophyll contents and photosynthetic apparatus. It disturbs the balance between the production of reactive oxygen species (ROS) and the antioxidant defence, causing accumulation of ROS which induces oxidative stress to proteins, membrane lipids and other cellular component. Mineral elements have numerous functions in plants including maintaining charge balance, electron carriers, structural components, enzyme activation, and providing osmoticum for turgor and growth .In this paper, an overview of some macronutrients (nitrogen, phosphorus, potassium, calcium and magnesium), micronutrients (Zinc, Boron, Copper) and silicon has been discussed in detail as how these nutrients play their role in decreasing the adverse effects of drought in crop plant.

The Role of Phytohormones in Alleviating Salt Stress in Crop Plants

Abstract: Phytohormones are chemical messengers produced in one part of plant and translocated to the other parts, where they play critical roles in regulating plant responses to stress at extremely low concentration. Phytohormones are natural products and they called plant growth regulators, when they are synthesized chemically. Plants are usually subjected to environmental factors such as drought or high soil and water salinity. The reduction in plant growth exposed to saline environments could be due to either the effects of specific ions on metabolism or adverse water relations. Different strategies are being employed to maximize plant growth under saline conditions. One of them is to produce salt tolerant genotypes of different crops. Attempts to improve tolerance to salinity through conventional plant breeding methods are time consuming, laborious and depended on existing genetic variability. In addition, many attempts have been made to overcome this disorder, including proper management and exogenous application of plant growth regulators. This article presents a review of the role of abscisic acid (ABA), indole acetic acid (IAA), cytokinins (CK), gibberellic acid (GA), brassinosteroids (BR), jasmonates (JA), salicylic acid (SA) and triazoles (TR) in alleviating salt stress in crops.

Genetic diversity of wheat (Triticum aestivum L.) genotypes based on cluster and principal component analyses for breeding strategies

Abstract: Determination of genetic diversity is useful for plant breeding and hence production of more efficient plant species under different conditions. Accordingly, the most common wheat (Triticum aestivum L.) genotypes including 36 winter wheat genotypes cultivated in different regions of Iran were selected, grown and analyzed for genetic diversity. The experiment was conducted at the Agricultural Research Farm of Shahed University, Tehran, Iran as a randomized complete block design with three replications. All traits, except emergence time and heading time were statistically significant among different genotypes. Cluster analysis based on squared Euclidean distance and ward's method, categorized the cultivars into seven groups. The highest genetic distance was observed between Sardari and Spn/Mcd/Cama/3/Nzr/4/Passarinho (SP) genotypes. Based on Principal Component Analysis (PCA), the first five components explained over 97% of genetic variation. Cluster analysis based on PCA using the first five principal components indicated six separate groups of genotypes, with the maximum genetic distance observed between Sardari and Vorona/Kauz (VO) genotypes. Such differences in genetic component of traits studied in this manuscript can be applied as a new source of variation in other breeding programs and crossing nurseries for wheat improvement.

Assessment of yield, yield-related traits and drought tolerance of durum wheat genotypes (Triticum turjidum var. durum Desf.).

Abstract: The main objective of this study was to evaluate 11 durum wheat breeding lines and three checks [two durum (Zardak and Saji) and one bread (Sardari) wheat] based on grain yield, agronomic traits and drought tolerance indices under rainfed and irrigated conditions in the west of Iran during the 2008-09 cropping season. A completely randomized block design with three replications was conducted for each environment. Based on grain yield under rainfed and irrigated conditions drought tolerance indices i.e., stress tolerance index, stress susceptibility index, tolerance, yield index, yield stability index, mean productivity and geometric mean productivity were calculated. The results of analysis of variance for relative water content, plant height, biomass, number of grains per spike and grain yield in rainfed and irrigated conditions indicated that genotypic differences were highly significant (P<0.01). A positive and significant correlation was observed between yield under irrigated (Yi) and rainfed (Yr) conditions and mean productivity (MP), geometric mean productivity (GMP), and stress tolerance index (STI). Based on principle component analysis a significantly positive correlation was observed between stress susceptibility index and tolerance. These indices were able to select the susceptible genotypes (i.e., G8, G2, G3, and G7). The check cultivars (Zardak and Sardari) and G5 were more stable and related to the rainfed environment while genotypes G11 and G4 were highly adapted to the irrigated conditions. Cluster analysis classified the genotypes into three groups i.e., resistant, susceptible and tolerant to drought conditions. In conclusion, this study showed that drought stress reduced the yield of some genotypes while others were tolerant to drought, suggesting genetic variability of drought tolerance in this material. Therefore, breeders can choose better (i.e., more stress-resistant) wheat genotypes based on some indices (e.g. MP, GMP and STI).

AMMI stability value and simultaneous estimation of yield and yield stability in bread wheat ('Triticum aestivum' l.)

Abstract: In order to determine stable bread wheat genotypes with high grain yield via a single parameter, field experiments were conducted with 14 genotypes for 3 consecutive years (2008-2011) under two different conditions (irrigated and rainfed) in a complete randomized block design with three replications in each environment. Combined analysis of variance showed highly significant differences for the GE (genotype-environment) interaction indicating the possibility of selection for stable entries. The results of AMMI (additive main effect and multiplicative interaction) analysis indicated that the first four AMMI (AMMI1-AMMI4) were highly significant (P<0.01). The partitioning of TSS (total sum of squares) exhibited that the environment effect was a predominant source of variation followed by GE interaction and genotype effect. The GE interaction was 5 times higher than that of the genotype effect, suggesting the possible existence of different environment groups. AMMI stability value discriminated genotypes 10 and 6 as the stable accessions, respectively. Based on the YSI (yield stability index) and new RS (rank-sum) the most stable genotypes with high grain yield were genotypes 13 and 10. The results of this investigation proved that SI (sustainability index) and I (stability index) are not suitable stability indices for discriminating stable genotypes with high grain yield.

Mechanisms of waterlogging tolerance in wheat: Morphological and metabolic adaptations under hypoxia or anoxia

Abstract: Waterlogging is a widespread limiting factor for wheat production throughout the world specially irrigated and high rainfall environments. The important biological consequence of waterlogging is the deficiency (hypoxia) or complete absence (anoxia) of oxygen in soil environment which restricts the growth, development and finally yield in wheat. The tolerant genotypes of wheat can adapt to transient waterlogging by developing mechanisms related to morphology and metabolism to cope with the stress. The morphological mechanisms include the development of adventurous roots with well formed aerenchyma and sometimes with a barrier for ROL. Aerenchyma is a continuous gas filled channel, which provides a low resistance internal pathway for the movement of O2 from the aerobic shoots to anaerobic roots to respire aerobically under hypoxia or anoxia. However, lack of oxygen induces the anaerobic roots to shift the energy metabolism from aerobic to anaerobic mode. Greater activities of glycolytic and fermentative enzymes, increased availability of soluble sugars, and involvement of antioxidant defense mechanism against post-stress oxidative damages are the main metabolic mechanisms for waterlogging tolerance in wheat.

Conservation of plant genetic resources by cryopreservation.

Abstract: Cryopreservation is a perfect method for long-term conservation of plant genetic resources, using very low temperature (liquid nitrogen, -196 C). This method has been recognized as a practical and efficient tool for the long-term storage of germplasm. Cryopreservation methods may provide the conditions for unlimited conservation of biological materials by reducing metabolic rates. During the cryopreservation all biochemical activities significantly reduced and biological deterioration are stopped. Conservation and subsequent sustainable use of genetic resources are essential to meet the demand for future food security. Several techniques have been developed yet to minimize the damaging effects of desiccation and freezing, ensuring high recovery of plant materials. Cellular division of germplasm is normally repressed after exposure to LN. In addition, metabolic and most physical processes are stopped at this temperature. Thus, plants can be stored for very long time and the problems such as genetic instability and the risk of loose accessions due to contamination or human error during subculture overcome. Techniques like cryopreservation collect and conserve plant genetic resources, especially plants with limited seed storage capability. There is only limited number of plants that cryopreservation techniques are used for their germplasm conservation, mainly because the techniques need to be adapted for each species. Therefore, continued efforts are needed in cryopreservation techniques to develop protocols for a wider range of plants. Formation of ice crystal during cryopreservation is detrimental to cellular structure integrity and causes physical damage to the cells. Air-drying, freeze dehydration, osmotic dehydration, addition of penetrating and non-penetrating cryoprotective substances, and hardening metabolism or combinations of these processes are cryogenic strategies. Nowadays, conservation of plant germplasm has altered from slow cooling to vitrification. However, the availability or developments of simple, reliable and cost-effective strategies and the subsequent regeneration of the plants are basic requirements for germplasm conservation.

High contents of proline and anthocyanin increase protective response to salinity in Oryza sativa L. spp. indica

Abstract: Pigmented rice cultivar is a good candidate for abiotic tolerance especially salt tolerant trait. Physiological and growth parameters of eight indica rice genotypes under control or salt stress conditions were subjected to Hierarchical cluster analysis. From cluster ranking, rice genotypes were classified into two groups, salt-tolerant (Sangyod, Khao Dang, Kulab Dang and TD49) and saltsensitive genotypes (Klum Sakol, Klum Khonkaen1, Klum Khonkaen2 and Black Sticky Rice). In salt stress (100 mM NaCl), the salt-tolerant genotypes showed the high percentages of proline and anthocyanin more than in the salt-sensitive genotypes. In addition, the photosynthetic pigment stabilizations of stressed-seedlings were positively correlated to the proline (R 2 = 0.98) and anthocyanin (R 2 = 0.70) accumulations. While, the malondialdehyde (MDA) contents of salt-stressed seedlings were negatively correlated to the proline (R 2 = 0.63) and anthocyanin (R 2 = 0.51) accumulations. Moreover, the total antioxidant activity of extraction from stressed-seedlings was assessed using the ABTS (2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid) method. The higher percentages of total antioxidant activity were determined in salt-tolerant (125-199%) than salt-sensitive genotypes (106-113%). From the results it can be concluded that accumulation of above mentioned metabolites is associated with cellular protection and salt detoxification in salinity rice seedlings.

Brassinosteroid (24-epibrassinolide) enhances growth and alleviates the deleterious effects induced by salt stress in pea (Pisum sativum L.)

Abstract: The response of pea (Pisum sativum L.) cv. Climax seeds imbibed with 24-epibrassinolide (EBL) and sodium chloride (NaCl) prior to sowing was evaluated. Soaking of seeds in two different concentrations of EBL (5 and 10 μM) for 4 hours, caused an increase in germination, embryo axis length and most of the aspects of shoot and root growth at seedling stage, maturity stage (90 DAS) along with seed yield at the time of harvest. Both the EBL treatments (5 and 10 μM) improved the above mentioned attributes but maximum improvement was observed in response to EBL concentration of 10 μM with respect to the control. At seedling stage, EBL (10 μM) significantly enhanced the fresh and dry biomass, seedling height (shoot + root), photosynthesis rate (Pn), stomatal conductance (gs), total chlorophyll contents (Chl), proline contents, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), nitrate reductase activity (NRA) and nitrite reductase activity (NiRA) as compared to control (water soaked alone). Similarly, at maturity stage the plants grown from seeds pre-imbibed in EBL (10 μM) also exhibited the augmentation in dry biomass, physiological aspects (Pn, gs and Chl), enzymatic activities (NRA, NiRA, SOD, POD, CAT), leaf proline contents, nodule number and nodule dry biomass in comparison to water imbibed control. Seed attributes like seed yield, seed number and seed protein contents also showed the improvement in response to EBL (10 μM) at the time of harvest. Although, plants subjected to saline stress exhibited a reduction in all the morpho-physiological and enzymatic attributes (NRA and NiRA) but proline contents and enzymatic activities of antioxidants were enhanced in response to NaCl stress. However, deleterious effects induced by salinity were reduced if seeds were treated with EBL before or after NaCl imbibitions.

Biochemical Responses of Gouan ('Aeluropus littoralis') to Heavy Metals Stress

Abstract: Heavy metals affect growth, morphology and metabolism of plants in several ways. To reveal relationship between metal toxicity, oxidative stress and detoxification responses, the effects of four different heavy metals (Cd, Co, Pb and Ag) on Aeluropus littoralis was determined. So, one-month-old plantlets were treated with different concentrations (50 μM and 100 μM) of heavy metals for one week and the contents of photosynthetic pigments, phenolic compounds, proline, soluble proteins and the activities of enzymatic antioxidants (superoxide dismutase, guiacol peroxidase and catalase) as marker for oxidative stress were investigated. Survey results indicated that the amount of non-enzymatic antioxidant compounds (phenol and proline) significantly were increased in all treatments but a significant decrease was observed in photosynthetic pigments in the most treatments. Also, the accumulation of soluble proteins and increase in superoxide dismutase activity of which are respectively recognized as primary and secondary response to metal toxicity that can be pointed to the great capability of A. littoralis for accumulation and tolerance to excess amount of heavy metals. These results collectively show that different response in control and treated plants is due to induction oxidative stress and heavy metal toxicity in plants because of the accumulation of reactive oxygen species in treated plants.

Wheat yield and grain protein response to nitrogen amount and timing.

Abstract: This research was carried out to study the effect of nitrogen rate application (0, 120, 240 and 360 kg Nitrogen ha-1) and nitrogen timing on grain yield, yield components, grain quality and protein banding pattern in different growth stages of wheat (Shiraz cultivar) which was grown at research station of the School of Agriculture, Shiraz University at Bajgah in the 2008-2009 Results indicate that the highest value for grain yield was obtained at 240 kg N ha−1 when it was applied through vegetative growth stages (8230 kg ha-1) Yield components were significantly increased with enhancing the level of nitrogen with no significant difference between 240 and 360 kg N ha-1 Results show that no N application at tillering stage decreased spikes number/m2 and seeds spike-1, and the minimum value of 1000 grain weight was observed when we remove N application in grain filling period Leaf protein did not influenced by N treatments However, the sharpness of a band with molecular weigh about 51 kDa, related to Rubisco enzyme, was increased in some treatments Furthermore, 240 kg N ha-1 application in all timing treatments resulted in maximum seed protein content (55 mg protein g -1 grain) At the same time, seed water soluble proteins, Albumin and Globulin, showed no polymorphism While different N rate treatments had no significant effect on seed gluten content, no N application in grain filling period declined it significantly All in all, obtaining high wheat grain yield beside a suitable bakery quality are possible in a proper farming management system without environmental impact of N over application These goals may be achieved with sufficient N application during vegetative growth for yield and late season N application for protein quality

Effect of drought stress and subsequent recovery on protein, carbohydrate contents, catalase and peroxidase activities in three chickpea ('Cicer arietinum') cultivars

Abstract: Drought stress is one of the major abiotic stresses in agriculture worldwide. This study was carried out to investigate the effects of drought stress and subsequent recovery on protein, carbohydrate content, catalase (CAT), and peroxidase (POX) activities in three varieties of chickpea (drought tolerant Bivaniej and ILC482 and drought sensitive Pirouz). A field experiment with four irrigation regimes was carried out in a randomized complete block design with three replications. Treatments included control (well-watering), drought stress imposed during the vegetative phase, drought stress imposed during anthesis and drought stress during the vegetative phase and anthesis. Drought stress imposed during vegetative growth or anthesis significantly decreased soluble protein content and increased water soluble carbohydrate concentration. The tolerant variety accumulated more soluble carbohydrate than the sensitive one. Drought stress at flowering stage had significantly higher POX activity compared to than that at vegetative stage. Compared with the stress, there was significantly more soluble protein after exposure to recovery conditions but POX decreased in all three varieties. These results suggest that CAT and POX activities play an essential protective role against drought stress in chickpea. Antioxidants act as a major defense against radical mediated toxicity by protecting the damages caused by free radicals. An increase was observed in POX and CAT activity of three cultivars under stress conditions throughout the experiment. Results showed that POX acts as the major antioxidant enzyme in chickpea leaves under oxidative stress condition. So activity of this enzyme in stress condition can be used as an index for chickpea cultivars tolerance assessment.

Bipolaris sorokiniana (Sacc.) Shoem.: The most destructive wheat fungal pathogen in the warmer areas

Abstract: In recent years, spot blotch disease, caused by Bipolaris sorokiniana (Sacc.) Shoem. syn. Drechslera sorokiniana (Sacc.) Subrm and Jain (syn. Helminthosporium sativum, teleomorph Cochliobolus sativus) have emerged as serious concern for cultivation of wheat in warmer and humid regions of the world. During past two decades, substantial economic loss in wheat production has occurred due to the severity of spot blotch, affecting the livelihood of millions of small-scale farmers. Besides spot blotch, this fungus is also the causal agent of other diseases like common root rot, foot rot, seedling blight and seed rot of wheat. In this review, we have focused on the details of the pathogen and its management approaches. The disease severity is directly related to the humidity, temperature and soil nutrient condition. The greatest yield losses occur when the flag leaf and the leaf below the flag leaf become infected before the emergence of head. Crop rotation and burying wheat stubble by tillage can reduce the level of disease early in the season. Seed treatments are effective in eliminating the fungus on the seed. Application of fungicides is another means of disease prevention. Several sources have also been identified for improving resistance among susceptible commercial cultivars. Although a number of attempts have been made to control the disease, still, field results show that spot blotch continues to cause substantial grain yield reductions and underscore the need for further research.

Weed management improves yield and quality of direct seeded rice

Abstract: Severe water shortage in Pakistan has led the researchers to develop different sowing methods of rice such as direct drilling of seed in the soil as an alternative or substitute to the flooded transplanted rice. But direct drilling of rice severs the weed proliferation which reduces crop yields. Weed control methods including hand hoeing, mechanical and chemical control were tested for weed management in direct seeded rice. All the weed control methods were effective in decreasing the total weed density and dry weight over control and improving the rice yield and quality. Higher weed suppression and increase in rice yield was resulted by hand pulling than by the mechanical hoeing. Both hand pulling and mechanical hoeing were better than herbicides in suppression of weed and increasing yield. All the herbicides resulted in more than 80 % reduction in weed density and 74-87 % decrease in weed dry weight. Maximum increase of 30 % in grain yield over control was observed in hand pulling and that of 25 % in mechanical hoeing. Both methods also resulted in improved quality and gave maximum percentage of normal kernels that is 60.47 in mechanical hoeing and 60.03 hand pulling. Increase in rice yield due to application of herbicides was 7-19 %. The order of herbicides in suppressing the weeds as well as increasing rice yield was pretilachlor>butachlor>pendimethalin.

Response of proline, soluble sugars, photosynthetic pigments and antioxidant enzymes in potato (Solanum tuberosum L.) to different irrigation regimes in greenhouse condition.

Abstract: To evaluate the response of proline and soluble sugars content, chlorophyll a (CHLa), chlorophyll b (CHLb), total chlorophyll (TC), catalase (CAT) and ascorbate peroxidase (APX) activity in potato (Solanum tuberosum L.) leaves to different irrigation regimes at two growth stages, a greenhouse factorial experiment was conducted in a completely randomized design (CRD) with three replications. The factors consisted of four different irrigation regimes as 100% (I0), 80% (I1), 60% (I2) and 40% (I3) of field capacity and growth stages: 50% emergence to 50% flowering (GS1) and 50% flowering to physiological maturity (GS2). Fresh leaf tissues were used to determine proline and soluble sugars content, CHLa, CHLb, TC and CAT and APX activity. According to the results, irrigation regimes had significant effect on proline content, soluble sugars and catalase (CAT) activity, but no significant differences were detected among irrigation regimes for CHLa, CHLb, TC and APX activity. Limited irrigation increased proline concentration and total soluble sugars in leaves. None of studied traits were affected by growth stages. Interaction between irrigation regimes and growth stages was not significant for all studied traits. Result also indicated that the highest proline content (4.9 micromol.g-1FW ), total soluble sugars (55.9 mg.g-1FW) and CAT activity (12.7 micromol H2O2 min-1 g-1FW) were related to irrigation at 40% of field capacity (I3). It was concluded that proline and soluble sugar levels were increased in potato leaves under deficit irrigation regimes.

Morpho-physiological Diversity and Its Implications for Improving Drought Tolerance in Grain Sorghum at Different Growth Stages

Abstract: Sorghum grown under rain-fed conditions is usually affected by drought stress at different stages resulting in negative effect on yield. The assessment and quantification of morpho-physiological diversity for the traits contributing towards drought tolerance at these stages is of vital importance. For this purpose, drought stress was imposed on 44 sorghum accessions at seedling stage and natural incidence of water stress at post anthesis stage. The data of 21 different morpho-physiological traits were subjected to different multivariate techniques, including correlation, principal component (PC) and cluster analysis to assess the diversity for drought tolerance in sorghum. The correlation analysis revealed that selection for long roots; higher root/shoot ratio, leaf area and leaf dry matter could be performed simultaneously. There was positive association between relative water contents and cell membrane stability but both of these traits were negatively correlated with residual transpiration and excised leaf weight loss. Principal component (PC) analysis showed first 7 PCs having Eigen value >1 explaining 77.653% of the total variation with head width, head weight, grain yield per plant, fresh and dry shoot weight being the most important characters in PC1. Cluster analysis classified 44 accessions into four divergent groups. The members of first two clusters exhibited adequate degree of drought tolerance on the basis of majority of morpho-physiological traits, whereas, cluster 3 and 4 included genotypes with lower level of drought tolerance. The D2 statistics revealed the highest distances between 2nd and 3rd clusters, while 3rd and 4th clusters displayed maximum similarity. Scatter plot and tree diagrams demonstrated sufficient diversity among the sorghum accession for various traits and some extent of association between different clusters. The results concluded that morpho-physiological diversity in the studied material is structured by genotypes and this diversity could be utilized for cultivar breeding and germplasm conservation programs aimed at improving drought tolerance in sorghum.

Recognition and localization of ripen tomato based on machine vision

Abstract: Fruits picking by human is a time consuming, tedious and expensive task. For this reason, the automation of fruit harvesting has achieved great popularity in the last decade. Tomato fruits do not ripe simultaneously and one of the main challenges in the design of a tomato harvester robot is its ability in recognition and localization of ripen tomato on the plant. In the current study, a new segmentation algorithm was developed for guidance of a robot arm to pick the ripen tomato using a machine vision system. To reach this aim, a vision system was used to acquire images from tomato plant. The recognition algorithm had to be adaptive to the lighting conditions of greenhouse. Totally 110 color images of tomato were acquired under greenhouse light conditions. The developed algorithm works in two steps: (1) by removing the background in RGB color space and then extract the ripen tomato using combination of RGB, HSI, and YIQ spaces and (2) localizing the ripen tomato using morphological features of image. According to the results, the total accuracy of proposed algorithm was 96.36%.

Genes induced by high concentration of salicylic acid in Mitragyna speciosa

Abstract: Mitragyna speciosa is rich in secondary metabolites which are similar in effects as opium. Treatment with plant growth regulator such as salicylic acid (SA) is able to increase plant defense mechanism which later induces the expression of genes that encode secondary metabolite production. To identify genes that respond to elicitation of high concentration of SA, suppression subtractive hybridization (SSH) library was constructed using mRNA from SA-treated leaves and mRNA from non-SA-treated leaves. A total of 292 EST clones were randomly sequenced and all cleaned clone sequences (111) were analyzed using BLASTX against nonredundant NCBI databases. Results showed that most genes responding to acute SA treatment are related to stress and signaling pathways which eventually led to cell death. This include genes encoding chaperone, heatshock proteins (HSPs), antioxidants and genes involved in secondary metabolite biosynthesis, such as sinapyl alcohol dehydrogenase (SAD), cinnamyl alcohol dehydrogenase (CAD) and Cytochrome P450 (CYP 450). Further analysis was carried out using 8 out of 60 differentially expressed unique sequences through semi-quantitative RT-PCR on samples before and after treatment with 5 mM SA in 4 consecutive days. The result revealed that their expression changed over time when the plant was treated with 5 mM SA.

Plant growth promoting rhizobacteria enhance growth and yield of chilli (Capsicum annuum L.) under field conditions.

Abstract: Plant growth promoting rhizobacteria (PGPR) can enhance the growth and productivity by exerting beneficial effects through direct and indirect mechanisms. The effect of PGPR on the growth and yield of chilli under field conditions has to date, not been substantiated. In this study, 15 bacteria were isolated from chilli rhizosphere and their morphological, biochemical, plant growthpromoting, and biocontrol characteristics were elucidated. Plant growth and yield attributes increased significantly when the 15 rhizospheric isolates were applied to a local chilli cultivar 'Suryamukhi' in pots. On the basis of their performance in the pot experiment, three rhizobacteria (C2, C25, and C32) were selected for further study in field. The 16S rDNA sequencing has identified C2 and C25 strains as Bacillus spp. and C32 strain as Streptomyces sp. Remarkable increase in growth characteristics such as total number of fruits, fruit-weight, and yield was recorded in plants with combined inoculation under field conditions. The results clearly demonstrate the rhizocompetence and plant growth enhancing efficacy of these strains. It can be surmised that the isolated strains have strong potential to be successful biofertilizers and bioenhacers.

Evaluation of drought tolerance in bread wheat genotypes under dryland and supplemental irrigation conditions.

Abstract: Drought is a wide spread problem seriously influencing wheat (Triticum aestivum L.) production, mostly in dryland regions. This study was conducted to determine drought tolerance genotypes with superiority in different stressed environments. Eighteen bread wheat genotypes were tested in a randomized complete block design with four replications in two years (2006- 2007 and 2007-2008). Stress intensity in the first and second year were low (SI=0.336) and high (SI=0.604), respectively. Five drought resistance indices include mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (TOL), susceptible stress index (SSI) and stress tolerance index (STI) were applied on the basis of grain yield in dryland and supplemental irrigation conditions. Based on different drought indices, genotypes G1, G3 and G4 had the best rank with low standard deviation. The results indicated they have stable yield performance. Bi-plot display and cluster analysis cleared superiority of these genotypes in both years. Synthetic-derived materials had 2.6 to 18% higher yield than the best local check cultivars. The synthetic derived cultivars could perform well across all environments with better agronomic performance, especially for thousand kernel weight. Results showed MP, GMP and STI indices were more effective in identifying high yielding cultivars in diverse water scarcity.

Alleviation of salt stress by seed treatment with abscisic acid (ABA), 6-benzylaminopurine (BA) and chlormequat chloride (CCC) optimizes ion and organic matter accumulation and increases yield of rice (Oryza sativa L.)

Abstract: Soil salinity is an increasing problem for agricultural production worldwide. Plant growth regulator (PGR)-treated seeds have the potential to produce plants with a greater salt tolerance as salt tolerance in established plants is greater than in germinating seeds. This study aimed at evaluating the effect of seed pre-soaking with abscisic acid (ABA), 6-benzylaminopurine (BA) and chlormequat chloride (CCC) on the amelioration of salt stress in rice cv. IR-6 in hydroponic culture and in saline field conditions. The study placed particular emphasis on osmoregulation and accumulation/partitioning of ions and organic osmotic matters. We found that the addition of PGRs as seed treatment agents or chemicals to rice cv. IR-6 has a significant role in reducing salinity stress. ABA was the most effective PGR in reducing Na + and Cl - concentrations and Na + /K + ratio, increasing K + and Ca 2+ concentrations, proline accumulation, soluble sugar content and grain yield. BA had the largest positive effect on soluble protein content. The three PGRs all had a significant positive effect on the grain yield of rice. Compared to control, ABA, BA and CCC treatments increased grain yield by 21%, 17% and 12%, respectively. Our results suggest that ABA was more effective than BA and CCC to ameliorate the toxic effects of salt stress in rice. It is economic to use these PGRs in the production system. Since they were used only for seed treatment and at very low concentration (10 -5 or 10 -6 M) their possible negative impact on human health can be avoided.

Impact of temperature on phenology and pollen sterility of wheat varieties

Abstract: Low temperature during reproductive stage of spring wheat causes sterility of pollen grains and reduced yield. Field experiment was conducted during the winter season in the farm of Indian Agricultural Research Institute with wheat crop to study the effect of temperature on phenology and pollen sterility of spring wheat crop. Lower mean temperature during the crop growth period led to enhanced the crop growth period in both aestivum and durum varieties of wheat crop. Results showed that in early sowing treatment pollen sterility percentage was very high (46.1%) in HD 2851 variety. This in turn led to decreased pollen germination and lesser yield in wheat crop. Pollen germination was maximum between mean temperatures of 18-20C, while at lower temperatures germination of pollen grains got reduced in all wheat varieties. A good positive correlation was obtained between pollen germination percentage and yield (R 2 =0.65) of wheat crop. Data from this experiment indicate that low temperature during reproductive phase could limit wheat yield by affecting its phenology and fertility of pollen grains. Adaptation measures need to be developed for reducing yield loss of wheat in areas experiencing very low temperature during anthesis stage.

SSR Analysis of Soybean ('Glycine max' (L.) Merr.) Genetic Relationship and Variety Identification in Thailand

Abstract: Simple sequence repeat (SSR) analysis was used to determine the genetic diversity and relatedness among 25 soybean (Glycine max (L.) Merr.) genotypes (15 certified varieties, 8 breeding lines and 2 plant introductions) in Thailand. Eleven SSR primer pairs could amplify polymorphic SSRs from all of these genotypes. A total of 53 alleles with an average of 4.82 alleles per locus were detected. The polymorphic information content (PIC) among genotypes varied from 0.13 (Soy satt 285) to 0.88 (Soy satt 173) with an average of 0.60. Pairwise coefficients of genetic similarity between all genotypes ranged from 0.73 to 1.00 with an average of 0.88. These eleven SSR markers successfully distinguished 23 of the 25 soybean genotypes, with the exception of a pair of closely related breeding lines from the same cross. Allelic variation was observed at the two SSR loci associated with agronomic traits. In addition, only the five most polymorphic SSR markers were able to clearly identify all 15 certified varieties and would be useful for DNA fingerprinting. Unweighted pair-group method arithmetic average (UPGMA) analysis allocated the genotypes in 4 major clusters containing 19, 2, 2 and 2 genotypes, respectively. The largest cluster (I) was divided into subclusters Ia and Ib consisting of 13 and 6 genotypes, respectively. The genetic relationships among genotypes generally agreed with known pedigrees. Principal coordinate analysis (PCoA) confirmed the separation of soybean genotypes into four groups comparable to those from UPGMA analysis. However, genotypes in subclusters Ia and Ib were more clearly separated. These results suggest that SSR markers are efficient for measuring genetic diversity and relatedness as well as identifying varieties of soybeans. Genetic diversity and relationship assessments among soybean genotypes in Thailand could provide useful information for efficient utilization of these materials, especially for genetic improvement.

Effect of Bio-phosphate and Chemical Phosphorus Fertilizer Accompanied with Micronutrient Foliar Application on Growth, Yield and Yield Components of Maize (Single Cross 704)

Abstract: The effects of bio-phosphate, chemical phosphorus fertilizer and micronutrient foliar application on growth, yield and yield components of maize (Zea mays L.) were studied in a field experiment at Kerman Agricultural and Natural Resources Research Centre (Iran). A split plot experiment based on randomized complete blocks design (RCBD) with four replications was followed in the study. The micronutrient foliar application in two levels (foliar application and non foliar application) were the main plots, and four levels of phosphate (T1: 0, T2: 100 kg/ha P2O5, T3: 100g bio-phosphate, T4: 100g bio-phosphate with 50 kg/ha P2O5) as the sub plots. Results showed that biological and chemical phosphorus fertilizers had a significant influence on growth, yield and yield components (except row number per ear). The maximum grain weight and grain number per ear was obtained by applying 50 kg/ha P2O5 plus bio-fertilizer. Significant effect of micronutrient foliar application was found on plant height, flag leaf length, grain and biological yield, however the effect of micronutrient foliar application on width of flag leaf, diameter of stem, number of rows per ear, number of grain per ear and weight of grain was not significant. Results indicate that applying the combined bio-phosphate and chemical phosphorus fertilizer can be practical and helpful method to increase maize yield and reduce the environmental pollution.

An overview of cotton leaf curl virus disease (CLCuD) a serious threat to cotton productivity.

Abstract: Cotton Leaf Curl Disease is among the most devastating natural calamity that inflicted huge losses to cotton crop productivity especially in Pakistan during the last 20 years The dilemma of CLCuD is still under discussion among the researchers since its appearance in 1967 In 1992-93, CLCuD appeared in epidemic form which caused a decline in yield down to 905 million bales and during 1993-94, to 804 million bales in Pakistan For screening against CLCuV to develop virus resistant cultivars disease was induced through grafting, delayed sowing and whitefly mediated transfer The disease epidemiology is changed by abiotic factors especially temperature and plant age Cotton leaf curl virus disease not only affect yield but also deteriorate fiber quality traits like Ginning out turn percentage, staple length, fiber uniformity index, fiber fineness, fiber bundle strength, maturity ratio because of change in composition of major fiber components including cellulose, protein, wax and pectin The uncertainty of inheritance of CLCuD also prevails whether it is under the control of dominant or recessive genes which may be monogenic or polygenic whereas, extrachrmosomal inheritance is also under discussion The resistance breakdown depends upon the evolutionary potential of the pathogen and the possibility of recombinations, by which new variants of viruses evolved The resistance gained for Multan-CLCuV became susceptible to Burewala-CLCuV due to virus mutation and lack of durable resistance Management of CLCuD is the only option that can command the disease in various ways inclusive of change in sowing dates, crop nutrition, cultural practices, vector control, buffer crops and systemic poisoning of cotton seed by seed treatment will make the cotton crop safe in initial 40-50days after sowing Biotechnology can also aid in controlling this disease through transcriptional gene silencing By using biotechnological tools broad spectrum resistance can be introduced against all viruses present in the field

Association of canopy temperature depression with yield of durum wheat genotypes under supplementary irrigated and rainfed conditions.

Abstract: The objectives of this study were to evaluate the ability of five selection indices to assess drought tolerance of durum wheat genotypes under a variety of environmental conditions and the relationships of canopy temperature depression (CTD) with drought indices. Eight durum wheat genotypes were planted in the rainfed and supplementary irrigation conditions for two years (2007-2009). Five drought tolerance indices including stress susceptibility index (SSI), stress tolerance index (STI), tolerance index (TOL), mean productivity (MP) and geometric mean productivity (GMP) were calculated. Canopy temperature depression (CTD) was used to estimate crop yield and to rank genotypes. CTD was measured at three stages, from the emergence of fifty percent of inflorescence (Zadoks Growth Scale54) to watery ripe stage (ZGS71). The results showed that the average values of CTD in durum wheat genotypes changed from 3.3 to 5.7°C at the ZGS69 stage. Genotypes in this stage (ZGS69) had highly significant differences and average of CTD showed that durum wheat canopy was the largest value in all ZGSs under both conditions. The significant and positive correlation of YP, MP, GMP, SSI, STI and CTD showed that these indices were more effective in identifying high yield genotypes under both conditions. Results also showed that CTD has played an important role to search physiological basis of grain yield of wheat, and can be successfully used as a selection criterion in breeding programs.

Effect of pyroligneous acid on growth, yield and quality improvement of rockmelon in soilless culture

Abstract: Three fertilizer formulations namely; (M), a local formulation commonly used by farmers, the recommended Cooper standard (CS), and Benoit (BEN) suggested for the lower cost of production were evaluated in combination with four levels of pyroligneous acid (0, 10, 20 and 30%) for enhancement of growth, fruit yield and quality of rockmelon in soilless culture. The addition of 30% pyroligneous acid was toxic as most plants died at this concentration. Twenty percent (20%) pyroligneous acid increased the growth and yield of rockmelon plants, but the local formulation in combination with 10% pyroligneous acid gave the best results. This combination significantly improved plant growth, fruit weight, fruit diameter and sweetness of fruits. Hence the local formulation in combination with 10% of pyroligneous acid is recommended for good fruit yields in rockmelons.

Antineoplastic Effect of Mushrooms: A Review

Abstract: Global awareness of cancer is one of the largest causes of death in people of various ages and racial backgrounds has led to research and many clinical studies in an effort to limit the progression of this disease. Chemoprevention by dietary constituents has emerged as a novel approach to control cancer incidence. A variety of mushrooms have been used traditionally for the maintenance of health, and for prevention and treatment of diseases. This review highlights some of the recent works that express promising anti-tumor effects. Mushroom extracts may modulate the response of host immune system; in particular, various mushroom polysaccharides are likely to effect promotion and progression stages towards cancer. Other substances contained in mushrooms may be able to interfere with tumor initiation through a variety of mechanisms.