M. Vanaja

Metabolic engineering using mtlD gene enhances tolerance to water deficit and salinity in sorghum

Sorghum bicolor L. Moench cv. SPV462 was transformed with the mtlD gene encoding for mannitol-1-phosphate dehydrogenase from E. coli with an aim to enhance tolerance to water deficit and NaCl stress. Transgene (pCAM mtlD) integration and expression were successfully confirmed by PCR, Southern, RT-PCR and Western analysis. Segregation analysis based on germination of T0 seed on hygromycin-supplemented medium revealed an expected Mendelian ratio 3:1 in lines 5, 72 and 75. Retention of leaf water content was remarkably higher in transgenic leaf segments when exposed to polyethylene glycol 8000 (−2.0 MPa), as compared to the untransformed controls. Another significant finding is that the transgenics maintained a 1.7 to 2.8 fold higher shoot and root growth, respectively, under NaCl stress (200 mM) when compared to untransformed controls. These results demonstrate that engineering mannitol biosynthetic pathway into sorghum can impart enhanced tolerance to water deficit and salinity.

Analysis of diversity and distribution of Jatropha curcas L. germplasm using Geographic Information System (DIVA-GIS)

Jatropha curcas L., an important biodiesel plant, has been studied for its distribution and diversity in south east coastal zone of India using DIVA-GIS. The Grid maps were generated on the distribution pattern, plant height, number of primary branches, collar length, number of fruits per cluster and oil content. Flowering in the collected accessions were grouped in to very early (35%), early (29%), medium duration (10%), late (20%), and very late (6%) types. Analysis for richness using rarefaction method of DIVA-GIS showed that Ranga Reddy district of Andhra Pradesh is the potential area for germplasm with high oil content. The present study revealed that diverse germplasm accessions of J. curcas are distributed all over the south east coastal zone and enabled us to find out gaps in collection and diversity richness from SEC zone of India for conservation.

Efficient plant regeneration from shoot apices of sorghum

An efficient and rapid regeneration protocol was developed using shoot apices from germinating seedlings of two cultivars of sorghum, SPV-462 and M35-1, as explants. A vertical slit given from the base of each dissected apex enhanced the efficiency of callusing response by two fold. MS medium containing 0.5 mg dm−3 each of 2,4-D and kinetin was most effective in producing friable and embryogenic calli. Scanning electron microscopy of these calli detected somatic embryogenesis. Calli thus induced gave rise to approximately 42 green shoots per callus in both the genotypes when transferred to regeneration medium containing 1.5 mg dm−3 kinetin.

Variability in Drought Stress Induced Responses of Groundnut (Arachis hypogaea L.) Genotypes

Drought stress is one of the important abiotic stresses which can limit the crop growth and yield by altering various physiological and biochemical processes. Groundnut (Arachis hypogaea L.) is an important oil seed cash crop and can be affected by dry spells during critical pheno-phases. A field trial was conducted with six genotypes- JL-24, ICGV 91114, Narayani, Abhaya, Dharani and Greeshma in order to identify genotypic variability in physiological and biochemical changes that are triggered during drought stress. Drought stress imposition at flowering stage reduced Anet, gs, Tr and WUE. Reduction of Anet ranged from 60% (Abhaya) to 77% (ICGV 91114) whereas the reduction in Tr was lower. The genotypes Dharani and Abhaya with higher Anet and better intrinsic WUE at leaf level during stress period along with highest membrane stability index (MSI), higher accumulation of proline, FAA and total soluble proteins with better yield potentials proved to be tolerant to drought stress. The results indicated that response of groundnut genotypes to drought stress differed significantly and genotypes Dharani and Abhaya are likely to be tolerant to drought stress.

Impact of Elevated CO2 on Growth and Physiological Parameters of Groundnut (Arachis hypogaea L.) Genotypes

Impact of Elevated CO2 on Growth and Physiological Parameters of Groundnut (Arachis hypogaea L.) Genotypes Five groundnut (Arachis hypogaea L.) genotypes- JL-24, ICGV 91114, Narayani, Abhaya, Dharani were evaluated at elevated (550 ppm) CO2 in OTCs during 2013 kharif to assess the variability in growth, biomass and physiological parameters. Elevated CO2 enhanced biomass and physiological parameters of all the selected groundnut genotypes, however the magnitude of response varied. Total biomass of genotypes was improved by 19% at 550 ppm and maximum response (34%) was recorded in ICGV 91114 and Narayani. The genotype ICGV 91114 recorded significant improvement of leaf and root biomass, total biomass and specific leaf weight with elevated CO2. Genotype Dharani recorded maximum root length, shoot length and leaf area at flowering stage and JL-24 at pegging stage. At elevated CO2, higher biomass was allocated to stem in JL-24, to roots in ICGV 91114, and no influence in Dharani as compared to other genotypes revealing its differential influence on biomass allocation. Increased Anet at enhanced CO2 was recorded in all the genotypes and it ranged from 18% (Abhaya) to 36% (Narayani), and the less efficient genotype at ambient condition recorded highest response and vice versa. The response of gs to elevated CO2 varied, whereas reduced Tr was recorded in all genotypes. At 550 ppm, groundnut genotypes showed 44% improvement in leaf level intrinsic WUE and maximum advantage (62%) was registered by Dharani. It is evident that the magnitude of groundnut crop response to elevated CO2 is cultivar, growth stage and component specific.

In vitro screening of Vigna mungo genotypes for PEG induced moisture deficit stress

Two black gram (Vigna mungo L. Hepper) genotypes LBG20 and PU19 were selected to study the impact of PEG induced drought stress on seed germination, metabolite concentration and activities of antioxidant enzymes. Stress caused considerable decrease in germination and fresh weight of seedlings of both the genotypes. It led to increase in protein concentration, contents of starch and total soluble sugars while decrease was observed in the activities of antioxidant enzymes, contents of free amino acids, reducing sugar and total phenols. SDS-PAGE analysis indicated accumulation of some proteins with the germination under stress conditions. LBG20 which showed increase in soluble sugars, starch, proteins and higher activities of antioxidant enzymes was observed to be relatively more tolerant to drought stress over PU19.

Physiological and Biochemical Basis of Extended and Sudden Heat Stress Tolerance in Maize

Effects of extended and sudden heat stress on various physiological and biochemical processes have been investigated in ten inbred lines of maize (Zea mays L.) at seedling stage. Among the various parameters studied, a significant decrease was observed in membrane stability, chlorophyll fluorescence and chlorophyll concentration under extended heat stress and sudden heat shock in sensitive genotypes which indicated their susceptibility to high temperature. However, heat tolerant genotypes exhibited less impact on these parameters which could be attributed to lesser oxidative stress injury. The free radical scavenging system in heat tolerant genotypes was observed to be better established as compared to heat sensitive genotypes. These findings suggested that the genotypes which performed better both under extended and sudden heat stress conditions could be partly due to their superior ability to cope up with oxidative damage caused by heat stress in maize.

Use of a root zone soil moisture model and crop spectral characteristics to estimate sorghum yields in a dryland Alfisol toposequence

This study investigated the relationship between sorghum grain yield over range of soil depth with seasonal crop water stress index based on relative evapotranspiration deficits and spectral vegetation indices. A root zone soil moisture model has been used to evaluate the seasonal soil moisture fluctuation and actual evapotranspiration within a toposequence having varying soil depth of 30 to 75 cm as well as different available water capacity ranging from 6.9% to 12.6% (V/V%). The higher r2 values between modeled and observed values of soil water (r2> 0.69 significant at <0.001) and runoff (r2 = 0.95, significant at P<0.001) indicated good agreement between model output and observed values. The spectral vegetation indices like simple ratio, normalized difference vegetation index (NDVI), green NDVI, perpendicular vegetation index, soil adjusted vegetation index (SAVI) and modified SAVI (MSAVI) was recorded through out the growth period of sorghum. The vegetation indices except perpendicular vegetation index measured during booting to anthesis stages were positively correlated (P<0.05) with leaf area index and yield. The MSAVI measured during booting to milk-grain stage have the highest positive correlation with yield. Variation was noticed when additive and multiplicative forms of water-production functions calculated from water budget model were used to predict crop yield. But the yield estimation was improved when spectral vegetation indices measured during booting to milk-grain is incorporated along with water production functions. The water budget model along with spectral vegetation indices gave satisfactory estimates of sorghum grain yields and appears to be a useful tool to estimate yield as a function of soil depth and available soil water.

Heterosis and combining ability studies in blackgram (Vigna mungo L. Hepper) under alfisols of SAT region, India

Forty two F1 hybrids of blackgram were produced in line x tester mode with fourteen lines and three testers. The F1 hybrids along with parental lines were raised during kharif, rabi and summer 2013-14 to assess the heterosis and combining ability for seed yield and yield attributes over different environments. The pooled ANOVA revealed significant variability for seed yield, number of branches, pods, clusters, 100 seed weight, fodder biomass and harvest index due to crosses, environment, environment × crosses, while significant variability for environment × line × tester effect for all characters except for number of branches. Among 42 hybrids, three hybrids tested IC 587753 × PU-19, IC 436720 × PU-19, IC 436652 × LBG-20 exhibited significant and positive heterosis over mid, better and standard parent for seed yield, as well as significant specific combining ability. Hence these hybrids of this important pulse crop can be used for seed yield improvement through recurrent selection. Two lines viz., IC 587753 and IC 519805 identified as good general combiners for seed yield and can serve as parental lines in crop improvement programs.

Cluster Analysis and Maxent Modelling of Black gram [Vigna mungo (L.)Hepper] Genotypes from Andhra Pradesh, India

Sixty four black gram genotypes, which included 61 germplasm accessions and three released check varieties, were analysed to study the genetic divergence pattern over rainy (kharif) and post rainy (rabi) seasons of 2008 and 2009. Multivariate analysis of the pooled data has grouped the 64 genotypes into nine distinct clusters with high genetic variance between the clusters (D2) and low variance within the clusters (D). Cluster II was the largest, consisting of 17 genotypes and cluster VI and VII were with only one genotype each. The intra cluster D values ranged from 0 (cluster VI and VII) to 7.68 (cluster IX). However the inter cluster D2 values varied from 2.82 to 22.32, the lowest value recorded between cluster I and II and the highest between clusters VI and IX. It was observed that the single genotype in cluster number VI with low perfor-mance for majority of the characters studied was the farthest to most of the diverse clusters. Crosses between genotypes of cluster VI with that of cluster III (for high 100 seed weight), cluster IV (for maximum number of pods per plant, pods per cluster, cluster per plant and seed yield per plant) and cluster IX (for better plant height, peduncle length, pod length and seeds per pod) may prove advantageous in real-izing new recombinants with desired traits. Maxent (Maximum Entropy) model predicted for the promising accessions of black gram geno-types indicated site suitability for cultivation of these accessions across geographical regions in the climate change regime.