Showing papers by "Central Tuber Crops Research Institute published in 2012"

Elicitor recognition, signal transduction and inducedresistance in plants

Abstract: The most viable and practical option for the management of plant diseases is disease resistance. However, in most of the crop plants, natural resistance against pathogens is rare. Breeding resistant varieties is a long-term process and the possibility of resistance being broken always exists. Induced resistance exploiting natural defense machinery of plants is indeed an alternative, nonconventional and ecologically friendly approach for plant protection. Its introduction into agricultural practice could minimize the scope of chemical control, thus contributing to the development of sustainable agriculture. Induced resistance can be defined as an increased expression of natural defense mechanisms of plants against various types of pathogens, provoked by a range of factors: pathogens causing hypersensitive necrotic reaction, avirulent or attenuated pathogenic strains, and elicitors of pathogenic origin (glucans, proteins, lipids, etc.). Induced resistance, being based on the expression of latent ge...

Synthesis, characterization and swelling behaviour of superabsorbent polymers from cassava starch‐graft‐poly(acrylamide)

Abstract: Superabsorbent polymers (SAPs) were prepared from cassava starch by graft copolymerization of acrylamide on to starch using ceric ammonium nitrate (CAN) as free radical initiator, followed by alkali saponification. The reaction parameters such as concentration of acrylamide, concentration of CAN, temperature, and duration of polymerization reaction were optimized for maximum water absorbency using a 4-factor 3-level Box-Behnken design. The highest values of percentage grafting and absorbency obtained were 174.8% and 425.2 g/g, respectively. The polymers were characterized by determination of grafting efficiency, N-content, acrylamide content, FTIR analysis, SEM and XRD analyses. Thermogravimetric analysis (TG) showed that the SAP has higher thermal stability. The rate of water absorbency and the swelling behaviour of the SAP under different conditions of pH, and different salts were determined. The de-swelling pattern of the hydrogels over different time durations was also determined.

Identification of antimicrobial compound, diketopiperazines, from a Bacillus sp. N strain associated with a rhabditid entomopathogenic nematode against major plant pathogenic fungi

Abstract: Aims To purify and characterize antimicrobial compounds from Bacillus sp. strain N associated with rhabditid entomopathogenic nematode (EPN). Methods and Results The cell-free culture filtrate of a bacterium associated with an EPN, Rhabditis (Oscheius) sp., exhibited strong antimicrobial activity. The ethyl acetate extract of the bacterial culture filtrate was purified by silica gel column chromatography to obtain three diketopiperazines (DKPs). The structure and absolute stereochemistry of this compound were determined based on extensive spectroscopic analyses (FABMS, 1H NMR, 13C NMR, 1H-1H COSY, 1H-13C HMBC) and Marfey's method. The compounds were identified as cyclo(l-Pro-l-Leu), cyclo(d-Pro-l-Leu) and cyclo(d-Pro-l-Tyr), respectively. Three DKPs were active against all the five fungi tested (Aspergillus flavus, Candida albicans, Fusarium oxysporum, Rhizoctonia solani and Penicillium expansum) and are more effective than the standard fungicide bavistin. The highest activity of 4 μg ml−1 by cyclo(l-Pro-l-Leu) and cyclo(d-Pro-l-Tyr) was recorded against P. expansum, a plant pathogen responsible for causing postharvest decay of stored apples and oranges. Cyclo(d-Pro-l-Leu) recorded good antibacterial activity against all the four bacteria tested (Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa), and cyclo(l-Pro-l-Leu) and cyclo(d-Pro-l-Tyr) recorded good activity only against Gram-positive bacteria. To our knowledge, this is the first report of antifungal activity of the DKPs against the plant pathogenic fungi F. oxysporum, R. solani and P. expansum. The production of cyclo(l-Pro-l-Leu), cyclo(d-Pro-l-Leu) and cyclo-(d-Pro-l-Tyr) by a bacterium associated with EPN is also reported here for the first time. Conclusions Isolated DKPs demonstrated high antimicrobial activity against bacteria and fungi, especially against plant pathogenic fungi. We conclude that the bacterium associated with EPN is a promising source of natural bioactive secondary metabolites which may receive great benefit in the field of agriculture. Significance and Impact of the Study This study is a significant contribution to the knowledge of compounds unique from EPN bacteria as potential sources of new drugs in the agricultural and pharmacological industry.

Higher yield, profit and soil quality from organic farming of elephant foot yam

Abstract: Alternative agricultural systems, like organic farming, that are less chemical intensive, less exploitative and environment friendly are gaining popularity. Elephant foot yam (Amorphophallus paeoniifolius (Dennst.) Nicolson) is an important starchy tuberous vegetable with high nutritive and medicinal values. Since information on the organic farming of tuberous vegetables is scanty, field experiments were conducted in this crop at the Central Tuber Crops Research Institute, India, over a 5-year period. The impact of organic, conventional, traditional and biofertilizer production systems on growth, yield, quality, soil physico-chemical properties and economics were evaluated in elephant foot yam. Our results show that organic farming favoured canopy growth, corm biomass and lowered collar rot disease. Dry matter and starch contents of organic corms were significantly higher than those of conventional corms by 7% and 13%, respectively. Organic corms had 12% higher crude protein and 21% significantly lower oxalate contents. The content of K, Ca and Mg in corms were slightly higher, by 3–7% under organic farming. After 5 years of farming, the organic plots showed significantly higher pH, by 0.77 unit, and higher organic C by 19%. The exchangeable Mg, available Cu, Mn and Fe contents were also significantly higher. Organic management lowered the bulk density by 2.3%, improved the water-holding capacity by 28.4% and the porosity of soil by 16.5%. In short, organic farming proved superior and produced 20% higher yield (57.097 t ha−1) over conventional practice (47.609 t ha−1). The net profit was 28% higher and an additional income of Indian Rs. 47,716 ha−1 was obtained. Thus organic farming was found to be an eco-friendly management strategy in elephant foot yam for sustainable yield of quality tubers and higher profit besides maintaining soil health. Technologies for organic production involving farmyard manure incubated with bioinoculants, green manuring, neem cake, biofertilizers and ash were also standardized.

Evaluation of nutritional and physico-mechanical characteristics of dietary fiber-enriched sweet potato pasta

Abstract: The objective of the present study was to enhance the utilization of sweet potato (Ipomoea batatas Lam.) as a slowly digestible food by developing dietary fiber-fortified pasta from it. Swelling index as well as cooking loss (%) was more for the pasta made from the pale cream-fleshed variety, Sree Arun (V1) than that from the orange-fleshed variety, Sree Kanaka (V2), and least values were obtained in the pasta fortified with rice bran. Fortification with oat bran, wheat bran, and rice bran elevated the crude protein content to 5–10% in the pasta. Total and insoluble dietary fiber fractions were more in the pasta from Sree Arun (6–17 and 5–14%, respectively) than those from Sree Kanaka (5.25–15 and 3.7–11%, respectively) with the highest values in the wheat bran-fortified pastas. All the fiber-fortified pastas (10 and 20% level of fortification) had slow and progressive starch digestibility over 2 h compared to the control pastas. While approximately 70% of the total starch was rapidly digestible for the control pastas from both the varieties, this was drastically reduced to 45–54% in the test pasta from V1 and 37–50% in V2. Accordingly, the retention of resistant starch (RS; undigested starch after 2 h) in the control pastas was only 14–17%, while it was 38–49% in the test pastas from V1 and 39–55% from V2, with higher RS in the 20% fortified pastas. Texture profile analysis showed that the firmness (N) and toughness (Ns) increased with increase in the fortification level of fiber sources. The progressive starch digestibility coupled with high-resistant starch after 2 h indicated the potential of fiber-fortified sweet potato pasta as an ideal food for the diabetic and obese people.

Activity and synergistic interactions of stilbenes and antibiotic combinations against bacteria in vitro.

Abstract: The synergistic antibacterial activity of two stilbenes [3,4′,5-trihydroxystilbene (1) and 3,5-dihydroxy-4-isopropylstilbene(2)] purified from a Bacillus sp. N strain associated with entomopathogenic nematode Rhabditis (Oscheius) in combination with ciprofloxacin and cefotaxime was investigated. The activity of the stilbenes and standard antibiotics on bacteria were determined using the macrodilution method. The minimum inhibitory concentration and minimum bactericidal concentration of the stilbenes was compared with that of the standard antibiotics. The antibacterial activities of stilbenes against pathogenic bacteria were assessed using the checkerboard and time-kill methods to evaluate the synergistic effects of stilbenes in treatment with ciprofloxacin or cefotaxime. The results of the present study showed that the combination effects of both stilbenes with ciprofloxacin were synergistic (FIC index <0.5). Whereas stilbene 2 with cefotaxime recorded additive. Furthermore, time-kill study showed that the growth of the tested bacteria was completely attenuated with 12–24 h of treatment with 50:50 ratios of stilbenes and antibiotics. These results suggest that stilbenes combined with antibiotics may be microbiologically beneficial and not antagonistic. These findings have potential implications in delaying the development of resistance as the antibacterial effect is achieved with lower concentrations of both drugs (antibiotics and stilbenes). The in vitro synergistic activity of stilbenes and antibiotics against bacteria is reported here for the first time.

Proximate composition and sensory evaluation of anthocyanin-rich purple sweet potato (Ipomoea batatas L.) wine

Abstract: Purple sweet potato (PSP) is a special type of sweet potato having high anthocyanin pigment in the root. The starch contents of PSP (root/water homogenised in 1:1 ratio) were enzymatically saccharified [using commercial thermostable enzymes Termamyl® (0.2%) and Dextrozyme®GA (1%)] to fermentable sugars, and the filtrate was ameliorated with cane sugar to achieve 20° Brix, for subsequent fermentation into a red wine using 2% yeast (Saccharomyces cerevisiae) as starter culture. The wine had the following proximate compositions: total soluble sugar (TSS), 2.25° Brix; starch, 0.15 g per 100 mL; total sugar, 1.35 g per 100 mL; TA, 1.34 g tartaric acid per 100 mL; phenol, 0.36 g (caffeic acid equivalent) per 100 mL; anthocyanin, 55.09 mg per 100 mL; tannin, 0.64 mg per 100 mL; lactic acid, 1.14 mg per 100 mL; ethanol, 9.33%(v/v); and pH, 3.61. 2, 2‐Diphenyl‐1‐picrylhydrazyl (DPPH) scavenging activity of the wine was 58.95% at a dose of 250 I¼g mL−1. Principal component analysis reduced the eleven original analytical and proximate variables (TSS, starch, total sugar, TA, phenol, anthocyanin, tannin, lactic acid, ethanol, pH, DPPH) to four independent components, which accounted for 76.65% variations. Sensory evaluation was carried out by sixteen trained panellists on various attributes such as clarity, colour, viscosity, odour, flavour, spritz and finish. Independent ‘t’ test confirmed that all the sensory attributes of the PSP wine scored closely (within 10% variation) to that of a commercial grape wine. The red wine produced contains essential antioxidants and acceptable sensory qualities.

Phosphorus Solubilization by Thermotolerant Bacillus subtilis Isolated from Cow Dung Microflora

Abstract: Soil inoculation with phosphate-solubilizing bacteria is known to improve solubilization of fixed soil phos- phorus (P). Cow dung (CD) is normally used as an organic manure for enhancing soil fertility in tropical agriculture. Thermotolerant (\50 C) Bacillus subtilis strains isolated from CD solubilized tricalcium phosphate (CP) to available (soluble) phosphate in culture and in autoclaved soil amended with 1 % CP. The solubilization of CP was associated with the phosphatase activity of the bacterium, particularly acid phosphatase (AcP). Autoclaved soil amended with CD (10 %) showed 25.3 and 12.6 % higher solubilization of P and AcP activity, respectively, than autoclaved soil inoculated with B. subtilis. Also, B. subtilis inoculation and CD amendment resulted in higher P solubilization and phosphatase activity in both rhizosphere and nonrhizosphere of soil planted with cowpea (Vigna unguiculata L.) than without these two treatments. Similarly, root length, plant height, and plant biomass of cowpea seedlings were higher in bacterium- or CD-treated soil than in untreated soil. These results suggest that these thermotolerant B. subtilis strains as bio-inoculant or CD amendment can be successfully employed in tropical agriculture for solubilization of P and maintaining soil health, being useful in the context of global warming.

Modeling the Response of Cassava to Fertilizers: A Site-Specific Nutrient Management Approach for Greater Tuberous Root Yield

Abstract: Conventional fertilizer-management strategy results in decreased fertilizer-use efficiency and unbalanced nitrogen (N)–phosphorus (P)–potassium (K) applications. The quantitative evaluation of fertility of tropical soils (QUEFTS) model was used for determining region-specific balanced NPK uptake requirements and recommendations for a target yield of cassava. Minimum and maximum internal efficiencies of N, P, and K were estimated as 35 and 80 for N, 250 and 750 for P, and 32 and 102 for K (kg tuberous root per kg nutrient removed). Linear increases in tuberous root yield with N, P, and K uptakes of 17.6, 2.2, and 15.6 kg N, P, and K per 1000 kg tuberous root yield were observed. Relationships between soil supply and soil chemical properties and between fertilizer nutrient recovery efficiencies with their rates of application were developed for major cassava-production regions. Good agreement between measured and predicted yields was observed while calibrating the model, which shows that the model can be us...

Effect of Tillage, Irrigation, and Nutrient Levels on Growth and Yield of Sweet Potato in Rice Fallow

Abstract: A field experiment was conducted during the year 2007-2008 and 2008-2009 in Bhubaneswar, India to study the effect of tillage, irrigation and nutrient levels on growth and yield of sweet potato (Ipomoea batatas L.) in rice fallow. The results revealed that the conventional tillage system of sweet potato planting recorded maximum fresh root yield. During the year 2007-2008 and 2008-2009, the fresh root yield in this system was 4.6% and 30.3% higher than the minimum tillage treatment, respectively. Similarly 5.6% and 21.7% higher green fodder yields were obtained in conventional tillage compared to minimum tillage treatment during the year 2007-2008 and 2008-2009, respectively. But lower consumptive use and water use efficiency (WUE) were observed in conventional tillage than minimum tillage. Increasing irrigation and nutrient levels increased root and fodder yield significantly in both the years as well as reduced the soil compactness. The consumptive use and WUE were decreased with increasing irrigation levels, and increased with increasing levels of nutrients. Minimum tillage has advanced planting of sweet potato 15 to 17 days and produced 80–90% root and fodder yield of conventional tillage.

Bioactive stilbenes from a Bacillus sp. N strain associated with a novel rhabditid entomopathogenic nematode.

Abstract: Aims: The aim of the present study was to purify and characterize a natural antimicrobial compound from Bacillus sp. strain N associated with a novel rhabditid entomopathogenic nematode. Methods and Results: The cell-free culture filtrate of a bacterium associated with a novel entomopathogenic nematode (EPN), Rhabditis (Oscheius) sp. exhibited strong antimicrobial activity. The ethyl acetate extract of the bacterial culture filtrate was purified by column chromatography, and two bioactive compounds were isolated and their chemical structures were established based on spectral analysis. The compounds were identified as 3,4′,5-trihydroxystilbene (1) and 3,5-dihydroxy-4-isopropylstilbene (2). The presence of 3,4′,5-trihydroxystilbene (resveratrol) is reported for the first time in bacteria. Compound 1 showed antibacterial activity against all the four test bacteria, whereas compound 2 was effective against the Gram-positive bacteria only. Compounds 1 and 2 were active against all the five fungi tested and are more effective than bavistin, the standard fungicide. The antifungal activity of the compounds against the plant pathogenic fungi, Rhizoctonia solani is reported for the first time. Conclusions: Cell-free extract of the bacterium and isolated stilbenes demonstrated high antibacterial activity against bacteria and fungi especially against plant pathogenic fungi. We conclude that the bacterium-associated EPN are promising sources of natural bioactive secondary metabolites. Significance and Impact of the Study: Stilbene compounds can be used for the control of fungi and bacteria.

Water sorption kinetics of superabsorbent hydrogels of saponified cassava starch-graft-poly(acrylamide)

Abstract: Superabsorbent polymers (SAPs) are hydrophilic polymeric networks that can absorb, swell and retain large quantity of water and other physiological fluids. In this paper, the water sorption pattern and kinetics of cassava starch based SAP hydrogels were studied under different conditions of swelling such as soaking duration, pH, presence of salts, and particle size of the hydrogel. The kinetics was studied using Voigt-based viscoelastic model to determine the rate parameter and the swelling rate (SR). It was noted that under all conditions, the water sorption followed a second order kinetics. The absorbency was directly proportional to the rate of swelling. But when the sample was allowed to swell in aqueous solutions of CaCl2 and AlCl3, the absorbency as well as the SR was irregular. The particle size also had significant effect on water absorption by the SAP and the polymer with smaller particles showed more absorption than those with larger particle size. The solvent induced phase transition of the superabsorbent hydrogel was also studied.

Effect of Fortification with Different Starches on Starch Digestibility, Textural and Ultrastructural Characteristics of Sweet Potato paghetti

Abstract: The effect of fortification with various sources of starch such as banana, lentil, black gram and sweet potato in reducing the in vitro starch digestibility and glycaemic index of sweet potato spaghetti was investigated at Central Tuber Crops Research Institute, Thiruvananthapuram, India. Swelling index and cooking loss were more for the starch-fortified spaghetti than the control spaghetti. Among the starches, highest cooking loss was obtained for 10% lentil starch fortified sample. Crude protein content was higher for black gram and sweet potato starch fortified spaghetti. In vitro starch digestibility increased very slowly from 20-120 min, for the fortified samples compared to the unfortified controls. Accordingly, the rapidly digestible starch (RDS) was less and resistant starch (RS) was more for the starch-fortified samples. The estimated glycaemic index (EGI) was low for the spaghetti fortified with banana, lentil and sweet potato starches at 5 and 10% levels, indicating that these could be considered as low glycaemic foods. Firmness of cooked spaghetti was maximum for black gram starch fortification, while toughness was the maximum for lentil starch based cooked samples. Ultrastructural studies showed starch gelatinization and leaching with diffused granular shape for most spaghetti samples. Whey protein concentrate promoted starch-protein network formation leading to slow starch digestibility.

Activity and Synergistic Antimicrobial Activity Between Diketopiperazines Against Bacteria In Vitro

Abstract: The aim of the present study was to determine the synergistic effects of diketopiperazines [cyclo-(L-Pro-L-Leu) (1), cyclo-(D-Pro-L-Leu) (2), and cyclo-(D-Pro-L-Tyr) (3)] purified from a Bacillus sp. N strain associated with entomopathogenic nematode Rhabditis (Oscheius) sp. on the growth of bacteria. The minimum inhibitory concentration and minimum bactericidal concentration of the diketopiperazines was compared with that of the standard antibiotics. The synergistic antibacterial activities of the combination of diketopiperazines against pathogenic bacteria were assessed using the checkerboard assay and time-kill methods. The results of the present study showed that the combination effects of diketopiperazines were predominately synergistic (FIC index <0.5). Furthermore, time-kill study showed that the growth of the tested bacteria was completely attenuated with 4-12 h of treatment with 50:50 ratios of diketopiperazines. These results suggest that the combination of diketopiperazines may be microbiologically beneficial. The three diketopiperazines are nontoxic to normal human cell line (L231 lung epithelial) up to 200 m μg/ml. The in vitro synergistic activity of cyclo-(L-Pro-L-Leu), cyclo-(D-Pro-L-Leu), and cyclo-(D-Pro-L-Tyr) against bacteria is reported here for the first time. These findings have potential implications in delaying the development of resistance as the antibacterial effect is achieved with lower concentrations of both drugs (diketopiperazines).

Polymerase Chain Reaction Assay for Rapid, Sensitive Detection, and Identification of Colletotrichum gloeosporioides causing Greater Yam Anthracnose

Abstract: Anthracnose caused by Colletotrichum gloeosporioides is an economically important disease which affects greater yam (Dioscorea alata L.) worldwide. Apart from airborne conidia, the pathogen propagules surviving in soil and planting material are the major sources of inoculum. A nested PCR assay has been developed for specific detection of C. gloeosporioides in soil and planting material. In conventional (single-round) PCR, the limit of detection was 20 pg, whereas in nested PCR the detection limit increased to 0.2 pg of DNA. The primers designed were found to be highly specific and could be used for accurate identification of the pathogen up to species level. The protocol was standardized for detection of the pathogen in artificially and naturally infected field samples.

Organic Production of Tuberous Vegetables: Agronomic, Nutritional and Economic Benefits

Abstract: Global awareness of health and environmental issues has stimulated interest in alternative agricultural systems like organic farming. Elephant foot yam ( Amorphophallus paeoniifolius ) and yams ( Dioscorea spp.) are ethnic starchy vegetables with high energy, nutritive and medicinal values. Field experiments were conducted at the Central Tuber Crops Research Institute, Thiruvananthapuram, India, during 2004-2011 to assess the agronomic, nutritional and economic advantages of organic farming over conventional system in these crops. Organic farming resulted in 10-20% higher yield over conventional practice in these crops. A net profit of Rs 2,15,776 ha -1 , which was 28% higher over chemical based farming was obtained under organic management in elephant foot yam. Elite and local varieties responded equally well to organic and conventional farming in elephant foot yam. White yam, greater yam and lesser yam responded similarly to both the systems, with slightly higher yield under organic practice. Soil physico-chemical properties and microbial count were also improved under organic management. Organic farming scored significantly higher soil quality index (1.93) than conventional practice (1.46). The soil quality index was driven by water holding capacity, pH and available Zn followed by soil organic matter. Tuber quality was improved with higher dry matter, starch, crude protein and lower oxalate contents. Cost effective technologies were field validated.

Inheritance pattern of tetraploid Dioscorea alata and evidence of double reduction using microsatellite marker segregation analysis

Abstract: Recent studies have shown that the basic chromosome number of the three major edible yams, Dioscorea alata, Dioscorea rotundata and Dioscorea trifida, is x = 20, and that the clones with 2n = 40 chromosomes are diploids. D. alata breeding programmes were limited to the production of diploid hybrids until 2006, when the tetraploids (2n = 80) were found to be fertile and polyploid hybrids were produced by conventional hybridisation. However, the nature of the polyploidy (autotetraploidy or allotetraploidy) was not known in D. alata tetraploid clones. In the present study, the inheritance pattern of simple sequence repeat markers was determined in a tetraploid progeny using a Bayesian approach and by examining double reduction events. Results obtained confirm the autotetraploid nature of the 2n = 80 clones of D. alata.

Purification, characterization and application of thermostable amylopullulanase from Streptomyces erumpens MTCC 7317 under submerged fermentation

Abstract: An amylopullulanase (AP) enzyme has a wide range of applications in the food processing and distillery industries, including the conversion of starch to sugars and the production of conversion syrups (maltose and fructose syrups). The aim of our study was to determine the culture parameters for optimum production of AP by Streptomyces erumpens MTCC 7317. We found that a temperature of 50°C, a pH of 7.0 and an incubation period of 48 h achieved optimal enzyme activity (222.5 units of α-amylase and 69.5 units of pullulanase). The use of soluble starch and beef extract as sources of carbon and nitrogen, respectively, resulted in a higher enzyme production than when other carbon (carboxy methyl cellulose, pectin and pullulan) and nitrogen (yeast extract, peptone, casein, ammonium chloride, etc.) sources were used. The purified enzyme (by ammonium sulphate precipitation) had a molecular mass 45.0 kDa, as determined by sodium dodecyl sulphate–polyacrylamide gel electrophoresis. This band was found to have both amylase and pullulanase activities, as confirmed by thin layer chromatography. As the major end products of the starch digest were maltose and, albeit at a lower amount, glucose, we suggest that this enzyme can be considered to be an AP. The AP of S. erumpens was tested for its ability to liquify cassava bagasse and showed 74% conversion efficiency, which is approximately equal to that of Termamyl

Variation in Morphological Characters and Storage Root Yield among Exotic Orange-Fleshed Sweet Potato Clones and their Seedling Population

Abstract: Clonal evaluation was carried out with 1630 orange-fleshed sweet potato seedlings from controlled crosses of ‘Jewel’ population introduced from International Potato Centre (CIP), Lima, Peru. Morphological observations like leaf shape, emerging leaf colour, skin colour and flesh colour of storage root, weight of vine and storage root yield per plant were recorded. Wide variation was observed for all the qualitative and quantitative characters. Three types of leaf shapes were exhibited by the clones (cordate-81.65%, slightly lobed-16.69% and narrowly lobed-1.66%), while emerging leaf colour ranged between green (92.5%) to purple (7.5%). Four shades were observed in skin colour of storage roots varying from pink (35.21%), green (22.39%), purple (19.69%) to light pink colour (13.74%). The flesh colour of storage roots were observed to range from orange (37.48%), light orange (28.71%), dark orange (6.38%), cream (15.46%) to yellow (0.55%). The vine weight and root weight, being a quantitative character, varied according to the clone and environmental conditions (0.17 to 1.3 kg per plant). The vine weights of all the clones were higher in the lowland conditions than the upland conditions. Based on the evaluation of 1630 clones for tuber yield, tuber shape, β -carotene content and other agronomic characters, 224 clones were selected as superior progenies for recombination and sib-mating from which promising orange-fleshed varieties of considerable value can be generated.

Biochemistry of post-harvest spoilage of mahula (Madhuca latifolia L.) flowers: changes in total sugar, ascorbic acid, phenol and phenylalanine ammonia-lyase activity

Abstract: Mahula (Madhuca latifolia L.) is a deciduous tree found in abundance in the tropical rain forests of Asian and Australian Continents. The flowers are rich in fermentable sugars (40–47%, on fresh weight basis [fwb]), which are utilised as carbohydrate source for bio-ethanol production. Biochemical alterations in mahula flowers infected by Aspergillus niger and Rhizopus oryzae were studied, and the changes in total sugar, ascorbic acid, phenol and phenylalanine ammonia-lyase (PAL) activity in infected and healthy flowers were evaluated. The results showed a decrease in all biochemical parameters except phenol and PAL activity following fungal infection. However, there was no significant difference in different biochemical parameters between the two fungal (A. niger and R. oryzae) infected samples.

Molecular diversity of Fusarium oxysporum causing rot diseases of vanilla in south India

Abstract: Incidence of root, stem and beans rot of vanilla (Vanilla planifolia Andrews) caused by Fusarium oxysporum Schlecht was surveyed in vanilla growing areas of south India during December 2008. The incidence of the disease varied from 1 to 100% in different locations. A total of 60 isolates of F. oxysporum were obtained from diseased samples, and nine morphologically different isolates were taken for molecular characterization using Randomly Amplified Polymorphic DNA (RAPD) markers to study the genetic variability if any, among them. PCR amplification of total genomic DNA with random oligonucleotide primers generated unique banding patterns depending upon primers and isolates. Nine oligonucleotide primers were selected for the RAPD assays, which resulted in 384 bands for nine isolates of F. oxysporum. The number of bands obtained was entered into a NTSYS and the results showed that the variability among the pathogen isolates was moderate. The nine isolates studied were grouped into single major cluster at 0....

In Vitro Propagation Strategies for Elephant Foot Yam (Amorphophallus paeoniifolius (Dennst.) Nicolson

Abstract: In vitro propagation method using petiole and corm explants for the cultivated species of Amorphophallus paeoniifolius var. campanulatus (Decne) Sivad. cv. Gajendra is reported. The petiole slices cultured on Murashige and Skoog (MS) medium containing 6-Benzyladenine (BA) and 1-Naphthaleneacetic acid (NAA) produced callus within four weeks of culture. Continuous maintenance of original explant along with developed callus in respective medium showed initiation of adventitious shoot buds, roots and protocorm like bodies (PLB) or corm like structures (CLS). The CLS subsequently developed into complete plants. MS medium supplemented with NAA (2.5 μM) in combination with BA (5.0 μM) was identified as the best medium for CLS induction. Histological studies of the callus revealed three developmental stages. Complete plantlets were obtained from CLS within 16-24 weeks, by maintaining the culture continuously on the same combination of initiation medium. The culturing of apical bud explants of corms on BA or Thidiazuron (TDZ) in combination with NAA resulted in the proliferation of adventitious buds. But further development was arrested. The response of corm explants to callus induction and CLS formation was very slow as compared to petiole explants. The corm explant based propagation recorded less number of CLS compared to petiole based method. Thus, plant development through CLS from petiole explants can be adopted for the large scale production of plantlets.

Photosynthesis, Dry Matter Production and Partitioning in Cassava (Manihot esculenta Crantz) Under Partial Shade of a Coconut Plantation

Abstract: Photosynthetic rate of cassava (Manihot esculenta Crantz) varieties showed variation under partial shade of a coconut plantation at Coconut Research Station, Bhubaneswar, Odisha, India. The varieties, Sree Jaya, Sree Prakash, Sree Vijaya and H-165 had greater photosynthetic rate during the early crop growth period of 2 and 4 months after planting (MAP), which decreased later. Decrease in intercellular CO2 concentrations was observed during the later crop growth period in the above varieties. The intercellular CO2 concentrations had influenced the photosynthetic rate. Transpiration rate was observed to be maximum at 4 and 6 MAP when the crop was in the active growth period. Photosynthetic rate, intercellular CO2 concentrations and transpiration rate decreased with decrease in stomatal conductance. Among the varieties, Sree Jaya and H-165 showed higher dry matter production and partitioning to the tubers. Higher dry matter accumulation in shoot than in the tuber was observed in the varieties, Sree Prakash, M-4, Meg-36, H-226, H-97 and Sree Visakham. The photosynthetic rate exhibited strong and positive correlation with tuber bulking rate. Higher tuber yield was observed in Sree Jaya and H-165 due to more number of tubers per plant and tuber girth apart from greater biomass accumulation under partial shade.

Sol–gel behavior of a novel nanodroplet biomaterial for drug delivery

Abstract: Nanodroplets can be considered as those nano/microemulsions in which the oil itself forms the active agent and the droplet size ambits in the nanometer range. Eugenol is an anti-inflammatory agent and its nanodroplet gel (NDG) has immense potential for topical use. Topical gels oblige some rheological characteristics to nail down the demands of proper application, stability and storage. Thus, the purpose of our study was to comprehend the effect of eugenol on the sol–gel tranisition properties of its NDGs. Towards this goal nanodroplets of eugenol were prepared and evaluated and the three selected nanodroplet formulations with 5, 10 and 5% v/v eugenol were converted into topical gel formulation using 1% w/w Carbopol 940. The NDGs were characterized using frequency sweep, creep recovery and thixotropy. All these tests pointed out that eugenol concentration has significant effect on the sol–gel behavior of NDGs. The NDGs exhibited more viscous (sol) properties than elastic (gel) properties as observed from the frequency sweep studies. The thixotropy of the NDGs was found to decrease with increase in eugenol concentration. Efforts have been made to explain the study results using mechanistic approach. The outcomes of our research studies could be of great use in future endeavors towards development of a topical NDG of eugenol with tailored sol–gel behavior.

Relative importance of Farmers’ Characteristics in Predicting their Knowledge about Indigenous Agricultural Practices

Abstract: This study was conducted to identify the farmers’ characteristics that act as factors in influencing their knowledge on indigenous agricultural practices. The study was conducted in the state of Kerala among 40 farmers each of ten selected horticultural crops. Step wise regression analysis and multiple linear regression analysis were employed to identify the influencing factors. The study revealed that age, farm power status, innovativeness, rational orientation, communication status, and social participation status positively influence knowledge of farmers on indigenous agricultural practices whereas material status, educational status, and family status were the important characteristics of farmers negatively influencing the knowledge of indigenous practices.

Arbuscular mycorrhizal associations and its influence on phenotypic and growth characters of sweet potato genotypes under varied soil phosphorus availability 216

Abstract: Arbuscular mycorrhizal (AM) associations and thier influence on phenotypic and growth characters of sweet potato (Ipomoea batatas (Lam.) L.) genotypes under varied soil phosphorus (P) availability were examined through a field trial. The study was conducted at the Central Tuber Crops Research Institute, Thiruvananthapuram, India in an acidic laterite (Oxisol) soil. Two fields with and without P fertilization were chosen to yield a wide range of plant characters and AM colonization levels. Sweet potato germplasm comprising 257 indigenous and exotic accessions was evaluated for AM colonization and plant phenotypic/growth characters under two levels of P availability. To study the AM composition and structure in relation to soil P level, the frequency of occurrence (%), relative abundance (%), species richness and diversity index were calculated. Frequency of root colonization by AM, intensity of colonization and AM spore density in soil around roots (rhizosphere) differed between genotypes and within genotypes grown in soils with different levels of available P. Intensity of root colonization by AM increased in parallel with increasing frequency of root colonization irrespective of soil P level. AM spore density in the rhizosphere increased with increasing frequency of root colonization at a level between 26-50% in low P soil, while spore density in high P soils was positively correlated with frequency of colonization between 0-25%. AM communities associated with the sweet potato genotypes consisted of eight species in genera Acaulospora (1), Gigaspora (3)and Glomus (4). Among the various AM fungal isolates, Glomus microcarpum was most abundant in both types of soil. Frequency of occurrence, relative abundance, species richness and diversity index of AM fungi were higher in low P soils than in high P soils. In general a higher frequency of colonization and intensity of colonization showed a positive influence on most plant characters in lower P levels only. In low P soil, there was no relationship between root characters and spore density in the rhizosphere, whereas in high P soil, root growth was positively correlated with higher spore density. Frequency of colonization by AM, intensity of colonization, spore density and community diversity in the rhizosphere of sweet potato genotypes are substantially altered by soil P availability. We conclude that the variation in the magnitude of growth response of the genotypes could be related to the changes in population of specific AM fungi in root and soil.

Rhizome Yield and Starch Properties of Canna edulis

Abstract: The major tropical tuber crops are cassava, sweet potato, yams and aroids. In addition to these major crops there are many types of lesser known starchy tuber crops available in different parts of the country and Queensland arrowroot (Canna edulis Ker Gawler) is one among them. It is a perennial herb, growing to a height of 1.0-2.5 m. The leaves are arranged spirally with a prominent midrib and numerous lateral veins. It is widely distributed throughout the tropics and sub-tropics. It is grown for the branched, fleshy rhizomes (Joseph and Peter, 1985). The plant is hardy and in view of the low incidence of pests and diseases as well as wind resistance of the crop, it is considered to be grown best in the typhoon prone regions (Kurtia, 1967). It is commercially cultivated in Australia for its starch. The crop is lesser known to people or remain restricted only to certain areas. Reports are available on morphological and anatomical features of Canna (Jayakumari and Princymol Stephen, 2009). Duration of the crop varies from 8-12 months. The fleshy rhizomes are formed in a compact mass and are eaten boiled or baked. Previous studies have revealed the presence of arbuscular mycorrhizal fungal (Glomus microcarpum) association with edible Canna growing naturally under field condition (Jayakumari and Potty, 2007). This mycorrhiza is inferred to possess the potential to boost rhizome yield even in unfertilized fields (Jayakumari and Potty, 2008; 2009). Young rhizomes can also be used as a vegetable. The crop is very important due to its high productivity and starch value. The starch is easily digestible and used as food for children and invalids. The starch granules are oval or polyhedral in shape (Kay, 1987). There are two types of Canna, ornamental and edible. The flowers of ornamental Canna are larger, more beautiful and variable in colours than the edible types. Although both types of Canna store starch in the root-stocks, the edible types have more fleshy rhizomes with better flavour, taste, low fibre and less tannin content than the ornamental types (Arbizu, 1994). The Central Tuber Crops Research Institute, Thiruvananthapuram, Kerala, India, maintains five accessions of Canna in the minor tuber crops germplasm (Vimala and Bala Nambisan, 2005). Based on leaves, emerging leaf colour and other morphological characters, they are grouped as dark purple, purple and green accessions. Out of the five accessions, only two accessions (dark purple and green accession) produced edible rhizomes. The physico-chemical properties of one edible and two non-edible accessions of Canna were studied by Moorthy et al. (2002). The present paper deals with the evaluation of the dark purple and green accessions for rhizome yield and starch properties.