Showing papers by "Central Tuber Crops Research Institute published in 2019"

Plant Growth Promoting Traits of Indigenous Phosphate Solubilizing Pseudomonas aeruginosa Isolates from Chilli (Capsicumannuum L.) Rhizosphere

Abstract: Phosphorus (P) is the second key nutrient for plants and it affects several attributes of plant growth. Identification of a potent phosphate solubilizing microorganism capable of transforming the i...

Nanopore-based detection and characterization of yam viruses

Abstract: We here assessed the capability of the MinION sequencing approach to detect and characterize viruses infecting a water yam plant. This sequencing platform consistently revealed the presence of several plant virus species, including Dioscorea bacilliform virus, Yam mild mosaic virus and Yam chlorotic necrosis virus. A potentially novel ampelovirus was also detected by a complimentary Illumina sequencing approach. The full-length genome sequence of Yam chlorotic necrosis virus was determined using Sanger sequencing, which enabled determination of the coverage and sequencing accuracy of the MinION technology. Whereas the total mean sequencing error rate of Yam chlorotic necrosis virus-related MinION reads was 11.25%, we show that the consensus sequence obtained either by de novo assembly or after mapping the MinION reads on the virus genomic sequence was >99.8% identical with the Sanger-derived reference sequence. From the perspective of potential plant disease diagnostic applications of MinION sequencing, these degrees of sequencing accuracy demonstrate that the MinION approach can be used to both reliably detect and accurately sequence nearly full-length positive-sense single-strand polyadenylated RNA plant virus genomes.

Bioethanol From Biorenewable Feedstocks: Technology, Economics, and Challenges

Abstract: Among the various alcohols, biobased ethanol is known as the most suited renewable and ecofriendly fuel for spark-ignition engines. With technological improvements, inputs, such as the first-generation feedstock (i.e., corn and sugarcane) have been the primary sources for bioethanol production. Nevertheless, their seasonal availability, competition with food/feed, and the fluctuating prices play significant roles in commercial bioethanol industries. In consequence, waste-based biofuels, such as lignocelluloses and algal biomass, which have the potential to fight aforesaid bottlenecks are targeted for cost-effective bioethanol production. Although these biomasses offer encouraging economic potential through varied value chains and low feedstock costs, relatively immature technologies, demanding logistics for sourcing, and wavering investors pose barricades in their utilization potential. Fostering the use of feedstock requires setting ambitious targets for the use of biofuels in transport for cost-competitive waste-based ethanol production and stringent policy supports. In recent year, the life cycle analysis methodology has been implied to assess the potential economic benefits as well as ecological and possible environmental impacts owing to biobased ethanol industries.

Genome-Wide Identification and Analysis of Biotic and Abiotic Stress Regulation of C 4 Photosynthetic Pathway Genes in Rice

Abstract: Photosynthetic fixation of CO2 is more efficient in C4 than in C3 plants. Rice is a C3 plant and a potential target for genetic engineering of the C4 pathway. It is known that genes encoding C4 enzymes are present in C3 plants. However, no systematic analysis has been conducted to determine if these C4 gene family members are expressed in diverse rice genotypes. In this study, we identified 15 genes belonging to the five C4 gene families in rice genome through BLAST search using known maize C4 photosynthetic pathway genes. Phylogenetic relationship of rice C4 photosynthetic pathway genes and their isoforms with other grass genomes (Brachypodium, maize, Sorghum and Setaria), showed that these genes were highly conserved across grass genomes. Spatiotemporal, hormone, and abiotic stress specific expression pattern of the identified genes revealed constitutive as well as inductive responses of the C4 photosynthetic pathway in different tissues and developmental stages of rice. Expression levels of C4 specific gene family members in flag leaf during tillering stage were quantitatively analyzed in five rice genotypes covering three species, viz. Oryza sativa, ssp. japonica (cv. Nipponbare), Oryza sativa, ssp. indica (cv IR64, Swarna), and two wild species Oryza barthii and Oryza australiensis. The results showed that all the identified genes expressed in rice and exhibited differential expression pattern during different growth stages, and in response to biotic and abiotic stress conditions and hormone treatments. Our study concludes that C4 photosynthetic pathway genes present in rice play a crucial role in stress regulation and might act as targets for C4 pathway engineering via CRISPR-mediated breeding.

First report of genome size and ploidy of the underutilized leguminous tuber crop Yam Bean (Pachyrhizus erosus and P. tuberosus) by flow cytometry

Abstract: Cytological understanding is an important parameter to understand the genetic architecture of yam bean. The ploidy level and genome size of two cultivated species of yam bean (Pachyrhizus erosus and P. tuberosus) were estimated using flow cytometric analysis of young leaf tissue, with propidium iodide as a fluorescent dye. Six genotypes of P. erosus and three genotypes of P. tuberosus were analysed. Rice (Oryza sativa cv. Nipponbare) and Mung bean (Vigna radiata cv Berken) were used as internal reference standards. Variation of 2C nuclear DNA content among the six P. erousus lines was 4.18%, ranging from 1.17 to 1.22 pg, whereas only 1.8% variation was observed among the three P. tuberosus lines, which ranged from 1.07 to 1.09 pg. Moreover, it was found that the nuclear DNA content of P. tuberosus was lower than that of P. erosus. The result of the flow cytometric analysis showed that all the species were diploid (2n = 2x) and coefficient of variation (CV%) of all the accessions of the two species was less than 3.5%. This is the first report of ploidy analysis and genome size estimation of the leguminous underutilized tuber crop yam bean using flow cytometry. This result will be helpful for yam bean genome sequencing and crop improvement programmes.

Forest Bioresources for Bioethanol and Biodiesel Production With Emphasis on Mohua (Madhuca latifolia L.) Flowers and Seeds

Abstract: Forest biomass is comprised of lignocellulosic stocks, which principally include woody materials, such as hardwoods and softwoods, and forest wastes (i.e., sawdust and pruning, and bark thinning residues, wood chips, and branches from dead trees). At present, the market of woody biomass for the production of bioethanol is very limited because of limited capital, state-of-the-art technology, and strict forest laws and rules prevalent in many countries. However, forest biomass, such as Mohua (Madhuca latifolia L.), sal (Shorea robusta L.) and bamboo (Bambusa vulgaris) trees commonly found in the tropical deciduous forests of Asian and Australian continent, have been investigated for biofuel production. The flowers and seeds of Mohua are a rich source of fermentable sugars (glucose and fructose) and have been used for bioethanol and biodiesel production, respectively. Sal seeds are also used for biodiesel production.

Quantitative determination of NPK uptake requirements of taro (Colocasia esculenta (L.) Schott)

Abstract: Taro yield in many parts of the world is stagnant mainly due to conventional blanket recommendation of fertilizers, lower nutrient use efficiency and imbalance in the use of nutrients. The Quantita...

Heterologous expression of rice RNA-binding glycine-rich (RBG) gene OsRBGD3 in transgenic Arabidopsis thaliana confers cold stress tolerance.

Abstract: Imparting cold stress tolerance to crops is a major challenge in subtropical agriculture. New genes conferring cold tolerance needs to be identified and characterised for sustainable crop production in low-temperature stress affected areas. Here we report functional characterisation of OsRBGD3, classified previously as a class D glycine-rich RNA recognition motif (RRM) containing proteins from a drought-tolerant Indica rice cultivar N22. The gene was isolated by screening yeast one-hybrid library using the minimal promoter region of the OsMYB38 that is necessary for cold stress-responsive expression. OsRBGD3 exhibited cold, drought and salt stress inductive expression in a drought tolerant N22 rice cultivar as compared with susceptible variety IR64. OsRBGD3 was found to be localised to both nuclear and cytoplasmic subcellular destinations. Constitutive overexpression of the OsRBGD3 in transgenic Arabidopsis conferred tolerance to cold stress. ABA sensitivity was also observed in transgenic lines suggesting the regulatory role of this gene in the ABA signalling pathway. OsRBGD3 overexpression also attributed to significant root development and early flowering in transgenics. Hence, OsRBGD3 could be an important target for developing cold tolerant early flowering rice and other crops' genotypes for increasing production in low temperature affected areas.

In vitro and in vivo studies of 5,7-dihydroxy flavones isolated from Alpinia galanga (L.) against human lung cancer and ascetic lymphoma

Abstract: Alpinia galanga (A. galanga) of Zingiberaceae family has been widely studied for their potential biological and medicinal properties. In this study, chrysin, isolated from A. galanga, was screened for the presence of the flavonoid compound 5,7-dihydroxyflavone. Chrysin was found to induce cytotoxicity and apoptosis in human lung cancer cells and murine lymphoma cells at 25, 50, and 75 µg/ml concentrations sparing the normal fibroblast cells and lymphocytes. Cell cycle analysis using flow cytometry showed that there was a dose-dependent increase of accumulation of the S-phase cells, causing a G1/S-phase arrest induced by chrysin at these concentrations. Annexin V- and active caspase-3-positive cells were found to increase dose dependently in these cells as evidenced by flow cytometry. The ascetic tumor reduction studies in Dalton’s lymphoma ascites mice models revealed that a dose of 1.3 mg/kg body weight of chrysin decreased the tumor volume significantly and increased the lifespan of mice to 52.6%. Moreover, the compound showed chemoprotective effects when administered along with cyclophosphamide, thereby reducing the toxic effects. These observations were confirmed using the evaluations of hematological parameters and liver and kidney function tests from animal studies. The synergistic interaction of chrysin with cyclophosphamide in terms of reducing the tumor size and increasing the lifespan of mice compared with the individual treatments suggests the possibility of reducing cyclophosphamide concentrations in the combination treatment.

Sweet Sorghum for Bioethanol Production: Scope, Technology, and Economics

Abstract: The major fuels used for transportation are obtained from nonrenewable resources, such as crude oil. One alternative to these nonrenewable fuels is bioethanol. The sweet sorghum is a crop rich in sugars that can be exploited for ethanol production. From its stalks, a juice can be obtained, which contains high content of fermentable sugars that can be directly converted into ethanol, whereas the cellulose and hemicellulose rich bagasse needs to be pretreated before being fermented to ethanol. Sweet sorghum also contains starch in its grains (panicle), which is generally enzymatically hydrolyzed to glucose before its conversion into ethanol. Ethanol production processes from various parts of sweet sorghum, its technoeconomic feasibility and real-time applications are discussed in detail in the upcoming sections. Different biotechnology approaches for improving sorghum fermentation, such as biotechnology tools to improve ethanol yield from sorghum grains, solid state fermentation, simultaneous saccharification, and fermentation technology, use of mixed culture, and immobilized techniques, in bioethanol production from sweet sorghum are discussed in this chapter.

Jerusalem Artichoke: An Emerging Feedstock for Bioethanol Production

Abstract: In recent year, sugar- and starch-based feedstocks have not been sustainable for biorefinery due to the fact that their cultivation for food use covers the biggest percentage of production. Although lignocellulosic biomass, mainly in the form of agricultural residues, is extensively available, its conversion and utilization as biorefinery (biofuels) is still not financially competitive. One solution to this problem is the development of an alternative energy crop/tuber crop, such as the Jerusalem artichoke (JA) (Helianthus tuberosus L.). JA is native to North America and recently has been recognized as a promising biomass for the production of biofuel. The use of its tubers offers numerous benefits over conventional crops, including low input cultivation, high crop yield, ability to grow in a wide range of climates and soil conditions and high tolerance to environmental stresses, such as drought, salinity, pest, and plant diseases. Furthermore, the tubers are highly rich in inulin, which can be converted to fermentable sugars through hydrolysis. This chapter provides an overview of the potential uses of JA for the production of biofuels as well as an overview of the relevant production technologies.

Nutrient release pattern of organic and inorganic resources used in cassava production (Manihot esculenta crantz).

Abstract: The major constraint in the promotion of organic farming, a safe and sustainable alternative, is lack of availability of quality organic resources in sufficient quantities. The quality of resources...

Induction of systemic resistance in chilli (Capsicum annuum L.) by Pseudomonas aeruginosa against anthracnose pathogen Colletotrichum capsici

Abstract: Colletotrichum capsici Butler and Bisby, the causal agent of chilli anthracnose disease, sternly affects chilli yield and quality worldwide. Biocontrol agents and resistance inducers could be a valid alternative to chemical pesticides. The capability of two phosphate solubilizing Pseudomonas aeruginosa isolates viz ., Ps 2 and Ps 3 (KR270346 and KR270347) against chilli anthracnose both under in vitro and in vivo conditions was demonstrated. Pseudomonas aeruginosa Ps 2 showed maximum mycelial growth inhibition of 93.41% and the isolate Ps 3 showed 72.5% inhibition of Colletotrichum capsici in dual culture inhibition assay after 5 days of incubation. There was a greater reduction of anthracnose infection caused by C. capsici on matured fruits in Pseudomonas aeruginosa treated plants when compared to untreated control. The strain possessed chitinolytic and proteolytic activities, produced HCN, siderophores, and was able to produce salicylic acid at a moderate level. The isolate produced amylase. However both of them are unable to produce lipase. The isolates induced systemic resistance in chilli corroborated with increased levels of phenylalanine ammonia lyase, peroxidase and polyphenol oxidase under greenhouse experiments. The results indicate the potential of the indigenous Pseudomonas aeruginosa isolates as biocontrol agents against chilli anthracnose.

Process optimization by response surface methodology and quality attributes of orange fleshed sweet potato (Ipomoea batatas L.) vacuum fried chips

Abstract: Vacuum frying is a promising technology for the production of healthy and nutritional snacks. The optimization of vacuum frying technology was carried out using oranged fleshed sweet potato slices by using a three-level Box–Behnken design of response surface methodology. The orange fleshed sweet potato chips were prepared using vacuum fryer. The effects of different processing conditions on nutritional and sensorial qualities were studies. The variables considered for the study were frying temperature—FT (110–130 °C), vacuum pressure—VP (14.79–17.46 Kpa) and frying time—Ft (7–9 min) while the responses were moisture content, oil content, total carotenoid content, change in colour and texture. It was observed that increasing FT and VP at constant Ft decreases moisture content and decrease in oil content in chips with increase in FT and VP at constant frying time during the vacuum frying process. FT, VP, Ft significantly (p < 0.05) affected the retention of carotene content in fried chips. The results confirmed the significant (p < 0.05) effect of VP and Ft on the color of chips. It was also found that, increasing FT and Ft when VP was held constant and increasing FT and VP at a constant Ft gave lower breaking forces. By using the numerical optimizer the optimal conditions for vacuum frying was determined such as frying temperature 110 °C, vacuum pressure 16.12 Kpa and frying time 7 min. Having maximum retention of carotenoids in fried chips. When optimized, vacuum fried samples were compared with atmospheric fried samples; the former absorbed about 50.32% less oil, and retained higher carotenoid (6.32 mg/g), with lower breaking force (0.69 N). Sensory evaluation results showed accepted optimized vacuum fried samples in all the sensory attributes investigated.

Fed-Batch Saccharification as a Strategy towards Reducing Enzyme Dosage and Enhancing Fermentable Sugar Yield from Pretreated Lignocellulo-Starch Biomass

Abstract: Lignocellulo-starch biomass (LCSB) comprising root and vegetable processing residues contain starch also along with cellulose and hemicellulose and hence require whole slurry saccharification using an enzyme cocktail containing starch hydrolysing enzyme as well along with cellulase and xylanase. The cost-effective production of ethanol necessitates high fermentable sugar yield (> 80 g/l) in the hydrolysate which is possible through fed-batch saccharification as it overcomes issues such as low mass transfer and high viscosity of slurry encountered on high solids loading. To our knowledge no information is available on the fed-batch saccharification of LCSBs and hence the objective of the study was to investigate the possibility of enhancing the sugar yield at low enzyme dosage through fed-batch saccharification approach. Fed-batch saccharification of pretreated LCSBs [steam (ST), dilute sulphuric acid (DSA) and microwave-assisted DSA (MW-DSA)] in enhancing the sugar yield was investigated using a triple enzyme cocktail at two cumulative loading densities (15 g/100 ml and 20 g/100 ml) and compared with the respective batch system. The hydrolysis yield from ST fed-batch system was very high (84–95%) for the residues followed by 83–90% yield from MW-DSA system at 15 g/100 ml cumulative substrate loading. Glucose and xylose were uniformly present in all the hydrolysates with higher levels of glucose in the steam pretreated fed-batch system SFB1 (15 g/100 ml). High phenolic retention in the hydrolysates did not affect saccharification as detoxification chemicals were supplemented. Fed-batch saccharification enhanced the sugar yield from pretretated LCSBs and based on the hydrolysis yield, 15 g/100 ml cumulative substrate loading was better than 20 g/100 ml loading and steam pretreatment (45 min) emerged as the best. Pulsed addition of substrate with only one-time enzyme feeding at the start resulted in enzyme saving during the fed-batch saccharification.

Micromics: A Novel Approach to Understand the Molecular Mechanisms in Plant Stress Tolerance

Abstract: MicroRNAs (miRNAs) are small endogenous non-coding RNAs with 20–22 nucleotides acts as the regulatory RNA. Since their discovery in model plant Arabidopsis, curiosity in understanding the function of plant miRNAs increased and regulatory role of miRNA are now being understood by researchers. The ability of miRNA to repress or induce the expression of several genes based on homology of few nucleotides has intrigued the scientific community. The detailed study has elucidated the step-wise biogenesis of miRNA across the species. Plants has evolved to respond to various external stimuli just by tinkering the expression of master regulators like transcription factors, miRNAs, etc. These master regulators further regulate the expression of several hundreds of downstream genes. There are several miRNAs has been identified as regulators of expression of various abiotic stresses viz., drought, cold, salt and high temperature and biotic stresses viz., viruses, bacteria, fungi, nematodes and insect pests. Additionally, paradigm shift in terms of sequencing technology and computational approaches led to identification of differentially expressed miRNAs for various stresses in plants. This led to the identification of thousands of miRNAs across the species which in turn helps to understand the molecular mechanisms involved in providing the stress tolerance. The present review discusses the mechanism of miRNA biogenesis, and role of identified miRNAs in regulating stress response in plants. The understanding of molecular mechanism of tolerance mediated through miRNA may help in improving the crop yields during various stresses.

Association of Fruit and Shoot Borer Infestation in Eggplant with Morphological, Yield, Quality and External Weather Variables

Abstract: The association of the fruit and shoot borer (Leucinodes orbonalis Guen) Infestation in eggplant with morphological, yield, quality and weather variables was studied at Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India, during the spring–summer (February–June) of 2012–2013 and 2013–2014 and autumn–winter (September–March) of 2013–2014 and 2014–2015. Earlier infestation occurred on the plants during the spring–summer, while late infestation of the pest was observed during the autumn–winter. The Number of infested shoots per plant, per cent shoot infestation, number of infested fruits per plant, per cent fruit infestation and larvae per fruit were greater during the spring–summer months than during the autumn–winter months. The fruit infestation had a significant negative association with fruit yield per plant. The number of infested fruits per plant was positively and significantly associated with primary branches per plant, fruits per plant and fruit yield per plant. A significant negative correlation was observed between spines on stem and number of infested shoots per plant, and the correlation of number of infested fruits per plant with the spines on the stem, petiole and pigmentation on leaf lamina was positively significant. Genotypes with purple colour flowers and fruits had greater eggplant fruit and shoot borer (EFSB) infestation. The long slender fruit shape and clustered fruiting habit promoted the EFSB infestation. The TSS and anthocyanin in peel were found as the phagostimulants, while the high total phenols content and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging capacity were the feeding deterrents. The per cent of infested fruits per plant exhibited a positive correlation with maximum (Tmax), average (Tavg) and day temperatures. Larvae per fruit had a positive association with maximum temperature (Tmax), day temperature and helio-thermal units.

Engineering Properties of Different Commercial Grades of Sago (Sabudana)

Abstract: Sago is a traditional food product of India made exclusively from fresh wet cassava starch. The engineering properties of different commercial grades of sago, developed by roasting and steaming process were investigated. The physical properties (moisture content, size, shape (sphericity), bulk density, particle density, porosity), functional properties (solubility index, swelling power, cooking time, cooking loss, oil absorption index), pasting and dynamic rheological properties were studied. The size of the roasted commercial and steamed nylon sago varied from 3.57 to 4.11 mm and from 2.50 to 5.88 mm, respectively. The shape (sphericity) of different grades of sago ranged from 0.63 to 0.86. The bulk density and particle density of the different commercial and nylon sago varied from 420 kg m-3 to 800 kg m-3. The swelling power (39.59 g/g) of the steamed nylon sago was high as compared to that of roasted sago. The steamed nylon sago showed a reduction in peak viscosity, breakdown and final viscosity as compared with the roasted commercial sago. A decrease in cooking loss with an increase in cooking time was noticed in the roasted commercial sago, whereas increase in cooking loss with increase in cooking time was noticed in the steamed nylon sago. The elevated peak viscosity value showed reduction in pasting temperature for both steamed and roasted sago. The different grades of sago gel behaved like a dilute solution due to increase in loss modulus over storage modulus.

Comparison of SHF and SSF Processes under Fed Batch Mode on Ethanol Production from Pretreated Vegetable Processing Residues

Abstract: Vegetable wastes containing high starch in contrast to lignocellulosic biomass cause environmental threat due to non-judicious disposal and have not been exploited for bioethanol production. The ethanol production from steam or dilute sulphuric acid (DSA) pretreated residues was compared under fed-batch Separate Hydrolysis and Fermentation (F-SHF) or Simultaneous Saccharification and fermentation (F-SSF). The volumetric ethanol productivity, ethanol yields and ethanol contents (g/L) were higher from DSA than steam pretreatment in F-SHF, while latter two did not differ significantly between the pretreatments under F-SSF mode. High RS utilization was observed towards the last phase (72-120 h) in steam pretreatment under F-SSF. Fermented broth from F-SSF had higher levels of inhibitors such as phenolics, furfural and Hydroxymethyl furfural compared to F-SHF and also in the DSA pretreatment. A comparison of the ethanol production from the processes vis-a-vis enzyme and yeast feeding and pretreatment conditions, overall processing time etc. showed that F-SSF had higher requirement of enzymes and yeast than F-SHF. Possibility to curtail fermentation at 24 h under F-SHF mode due to very low ethanol production after 24 h equated the processing time under the two modes to 120 h and this made F-SHF the most advantageous process for the selected residues.

Next-generation sequencing reveals endosymbiont variability in cassava whitefly, Bemisia tabaci, across the agro-ecological zones of Kerala, India.

Abstract: Silverleaf whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is one of the most notorious invasive insect pests, infesting more than 900 species of plants and spreading more than 200 v...

Occurrence and Distribution of Sri Lankan Cassava Mosaic Virus in the Stems of Cassava

Abstract: The distribution of Sri Lankan cassava mosaic virus (SLCMV) in the buds regenerated from the nodes of stem cuttings varied with different varieties Using different diagnostic techniques (ELISA, PCR and NASH), the SLCMV distribution in 8 varieties of cassava viz, Sree Sahya, Sree Prakash, Sree Visakham, Sree Padmanabha, Sree Vijaya, M-4, H-165 and H-226 were diagnosed Top portions (one third of total stem used for planting) of the stems in all the varieties tested had maximum virus accumulation except Sree Padmanabha, which showed high virus accumulation in bottom portion Similar results were obtained from the diagnosis of bark samples of all the varieties with variation in the virus accumulation level

Evaluation of a crop growth model for sweet potato over a set of agro-climatic conditions in India

Abstract: A study was conducted to evaluate the wider applicability of sweet potato growth model, ‘SPOTCOMS’ for simulating the phenology and yield over a set of agroclimatic conditions in India. The model simulated the phenology of the crop as a function of growing degree days. The genetic coefficients required for the model were estimated from the field experiments conducted with sweet potato variety, Sree Bhadra and other local varieties at the study locations. The model simulated the yield of the sweet potato well and the statistical indices calculated between the simulated and observed yields stated the reliability of the model simulations. The agreement index (D-index) for Sree Bhadra ranged from 0.55 to 0.99, and the D-index for local varieties ranged from 0.51 to 1.00. The calculated values of normalized objective function ranged from 0.01 to 0.10 for Sree Bhadra and 0.00 to 0.22 for other local varieties, and indicated better agreement of simulated and observed yields. The normalized root mean square error ranged from 0.80% to 10.40% for Sree Bhadra and 0.00% to 22.44% for other varieties, and these results suggested the wider applicability of the model with excellent to good simulations. The model also simulated dry matter distribution in tubers pertaining to different stresses such as water, nitrogen and potassium. The study revealed that the simulation model ‘SPOTCOMS’ can be used for simulating the yield as well as to manage the stresses during the crop growth period and to optimize best management practices for the crop cultivation irrespective of the agroclimatic conditions.

Microbial Diversity in Rhizosphere Soils of Tropical Tuber Crops: Utilization for Pathogen Suppression and Growth Promotion

Abstract: Tuber crops are the third most important food crops, after cereals and legumes There are many pathogenic microbes, which affect the production of tuber crops Fungal and viral pathogens attack most of the tuber crops However, there is much variability among the crops in their susceptibility to pathogens Similarly, rhizosphere soil has a large diversity of the microbial community, which possesses plant growth-promoting activity as well as pathogen suppression In the present study, the culturable microorganisms (fungi, bacteria and actinomycetes), in the rhizosphere of sixteen varieties of tropical tuber crops viz , sweet potato, elephant foot yam, cassava and yam were enumerated and compared; their role on suppression of Sclerotium rolfsii, the pathogen that causes collar rot in elephant foot yam was studied, and the ability of the organisms for growth promotion, nitrogen fixation, P and K solubilization was assessed, and the efficient antagonistic organisms were characterized by amplifying 16S rRNA The microbial population varied significantly among the crops and varieties Among one hundered and fifty organisms isolated and screened for pathogen suppression, ten bacterial and twelve actinomycete isolates completely inhibited the mycelial growth in the preliminary round of screening Eight bacterial isolates chosen for further study based on consistency in pathogen suppression, exhibited IAA production while seven isolates showed nitrogen fixation None of the bacterial isolates showed the formation of P or K solubilization zones in the selective media Molecular studies based on 16S rRNA gene sequencing revealed that the most efficient antagonistic bacterial isolates with growth promotion potential were Bacillus spp The six Bacillus species identified were Bacillus siamensis , B amyloliquefaciens , B pumilus , B halotolerans , B subtilis and B altitudinis Six out of eight efficient bacterial isolates were obtained from rhizosphere soils of sweet potato The organisms, Bamyloliquefaciens and Bsubtilis can serve as excellent bio-agents for pathogen suppression and growth promotion in tuber crops ecosystem

Influence of Nutrients and Nutrient Use Efficient Genotypes on Tuber and Leaf Cyanogen and Tuber Starch in Cassava

Abstract: The present study reports the variation in tuber quality parameters like starch, cyanogenic glucosides (CN) and leaf CN content among four nutrient use efficient (NUE) cassava genotypes viz., Sree Pavithra, CI-905, CI-906 and 7 III E3-5. The impact of secondary nutrient Mg and micronutrients viz., Zn and B on the above parameters in cassava variety Sree Visakham (H-1687) towards the later period of maturity of cassava also was studied. Among the genotypes, Sree Pavithra had the least and 7 III E3- 5 had the highest tuber CN. A decreasing trend in tuber CN from 7-9 months after planting (MAP) was recorded in the genotypes. The leaf CN was very high compared to tuber CN. The highest leaf CN was in 7 III E3-5 as in the case of tuber CN. The genotype CI-906 had the lowest leaf CN followed by Sree Pavithra. But the leaf CN increased at 9 MAP compared to 7 and 8 MAP. There was a positive correlation between tuber and leaf CN. In the case of tuber starch, there was a significant difference among genotypes with Sree Pavithra on par with CI-906, having the highest, and 7 III E3-5 on par with CI-905 having lower starch contents. However, there was a significant increase during 8-8.5 MAP. As regards to the influence of secondary and micronutrients, compared to PoP, different combinations of these nutrients resulted in significantly low tuber CN which in turn were on par. The stage of plant growth did not impact on tuber CN. Leaf CN was considerably lowered due to the application of secondary and micronutrients. Compared to PoP, the leaf CN was highest under three nutrient combination of Mg, Zn and B as well as Zn along with Mg. A sharp decline in leaf CN was also noticed from7 to 9 MAP. Significant positive correlation was seen between tuber and leaf CN. In the case of tuber starch, application of Mg along with Zn resulted in significantly the highest tuber starch whereas application of Mg alone, resulted the lowest. Significant negative correlation was seen between tuber starch and tuber CN and between tuber starch and leaf CN.