J.P. Jaiswal

A comprehensive study on dehydration-induced antioxidative responses during germination of Indian bread wheat (Triticum aestivum L. em Thell) cultivars collected from different agroclimatic zones.

To explore the adaptability of bread wheat to dehydration stress, we screened 28 cultivars collected from different agroclimatic zones, on the basis of malonaldehyde content as biochemical marker in roots of wheat seedlings during germination and classified them as highly tolerant, tolerant, sensitive and highly sensitive. From this primary screening, ten cultivars that showed differential responses to dehydration stress were selected to understand the biochemical and physiological basis of stress tolerance mechanisms. The highly tolerant cultivars showed lower levels of lipid peroxidation, less membrane damage, increased levels of antioxidants, enzymes like catalase, ascorbate peroxidase, glutathione reductase activities, and maintained higher relative water content in comparison to sensitive cultivars, indicating better protection mechanism operating in tolerant cultivars. Correspondingly, highly tolerant cultivars exhibited more accumulation of proline and less H2O2 content across different time points of polyethylene glycol treatments in comparison to sensitive ones. The above biochemical and physiological parameters were further validated through northern analysis of catalase (CAT1) gene, that showed differential expression patterns in tolerant and sensitive cultivars largely in confirmation with the biochemical and physiological analyses. Our study positively correlates the differences in the redox status and antioxidant defense system between tolerant and sensitive cultivars for the establishment of wheat seedlings in typical dehydration conditions.

Genotyping-by-Sequencing Analysis for Determining Population Structure of Finger Millet Germplasm of Diverse Origins

GBS analysis generated 33 GB of data with 160 million raw reads. Population structure analysis revealed three subpopulations among the finger millet accessions. A total of 1128 GO terms were assigned to SNP carrying genes. GBS analysis would be useful for future marker‐assisted breeding applications.

Genome Wide Single Locus Single Trait, Multi-Locus and Multi-Trait Association Mapping for Some Important Agronomic Traits in Common Wheat (T. aestivum L.)

Genome wide association study (GWAS) was conducted for 14 agronomic traits in wheat following widely used single locus single trait (SLST) approach, and two recent approaches viz. multi locus mixed model (MLMM), and multi-trait mixed model (MTMM). Association panel consisted of 230 diverse Indian bread wheat cultivars (released during 1910–2006 for commercial cultivation in different agro-climatic regions in India). Three years phenotypic data for 14 traits and genotyping data for 250 SSR markers (distributed across all the 21 wheat chromosomes) was utilized for GWAS. Using SLST, as many as 213 MTAs (p ≤ 0.05, 129 SSRs) were identified for 14 traits, however, only 10 MTAs (~9%; 10 out of 123 MTAs) qualified FDR criteria; these MTAs did not show any linkage drag. Interestingly, these genomic regions were coincident with the genomic regions that were already known to harbor QTLs for same or related agronomic traits. Using MLMM and MTMM, many more QTLs and markers were identified; 22 MTAs (19 QTLs, 21 markers) using MLMM, and 58 MTAs (29 QTLs, 40 markers) using MTMM were identified. In addition, 63 epistatic QTLs were also identified for 13 of the 14 traits, flag leaf length (FLL) being the only exception. Clearly, the power of association mapping improved due to MLMM and MTMM analyses. The epistatic interactions detected during the present study also provided better insight into genetic architecture of the 14 traits that were examined during the present study. Following eight wheat genotypes carried desirable alleles of QTLs for one or more traits, WH542, NI345, NI170, Sharbati Sonora, A90, HW1085, HYB11, and DWR39 (Pragati). These genotypes and the markers associated with important QTLs for major traits can be used in wheat improvement programs either using marker-assisted recurrent selection (MARS) or pseudo-backcrossing method.

CORRELATION AND HEAT SUSCEPTIBILITY INDEX ANALYSIS FOR TERMINAL HEAT TOLERANCE IN BREAD WHEAT

Six generations namely, P1, P2, F2, F3, BC1s and BC2s (2006-07) and P1, P2, F3, F4, BC1ss and BC2ss (2007-08) developed from four parental genotypes viz. DBW 14 (heat tolerant), NP 846 (heat and drought tolerant), WH 147 and Raj 4014 (heat susceptible for late sown). All the six generations from four crosses were evaluated during Rabi 2006-07 and Rabi 2007-08 in a compact family block design with three replications on two sowing dates. Heat susceptibility index values revealed reduction in grain yield in both the years for all the generations of the four crosses. Significant estimates of correlation of grain yield with days to heading, days to anthesis and days to maturity were recorded in late sown condition during first year. While under timely sown condition spike length has high estimate correlation with grain yield in first year itself. Significant estimated were recorded for tillers per plant in both the environments in second year. Lowest yield loss was reported in backcross populations of Cross I in both years and among segregating populations of Cross IV observed to be least affected and therefore suggested to be forwarded to further generations and further selection of heat tolerant genotypes.

Molecular mapping of the grain iron and zinc concentration, protein content and thousand kernel weight in wheat (Triticum aestivum L.)

Genomic regions responsible for accumulation of grain iron concentration (Fe), grain zinc concentration (Zn), grain protein content (PC) and thousand kernel weight (TKW) were investigated in 286 recombinant inbred lines (RILs) derived from a cross between an old Indian wheat variety WH542 and a synthetic derivative (Triticum dicoccon PI94624/Aegilops squarrosa [409]//BCN). RILs were grown in six environments and evaluated for Fe, Zn, PC, and TKW. The population showed the continuous distribution for all the four traits, that for pooled Fe and PC was near normal, whereas, for pooled Zn, RILs exhibited positively skewed distribution. A genetic map spanning 2155.3cM was constructed using microsatellite markers covering the 21 chromosomes and used for QTL analysis. 16 quantitative trait loci (QTL) were identified in this study. Four QTLs (QGFe.iari-2A, QGFe.iari-5A, QGFe.iari-7A and QGFe.iari-7B) for Fe, five QTLs (QGZn.iari-2A, QGZn.iari-4A, QGZn.iari-5A, QGZn.iari-7A and QGZn.iari-7B) for Zn, two QTLs (QGpc.iari-2A and QGpc.iari-3A) for PC, and five QTLs (QTkw.iari-1A, QTkw.iari-2A, QTkw.iari-2B, QTkw.iari-5B and QTkw.iari-7A) for TKW were identified. The QTLs together explained 20.0%, 32.0%, 24.1% and 32.3% phenotypic variation, respectively, for Fe, Zn, PC and TKW. QGpc.iari-2A was consistently expressed in all the six environments, whereas, QGFe.iari-7B and QGZn.iari-2A were identified in two environments each apart from pooled mean. QTkw.iari-2A and QTkw.iari-7A, respectively, were identified in four and three environments apart from pooled mean. A common region in the interval of Xgwm359-Xwmc407 on chromosome 2A was associated with Fe, Zn, and PC. One more QTL for TKW was identified on chromosome 2A but in a different chromosomal region (Xgwm382-Xgwm359). Two more regions on 5A (Xgwm126-Xgwm595) and 7A (Xbarc49-Xwmc525) were found to be associated with both Fe and Zn. A QTL for TKW was identified (Xwmc525-Xbarc222) in a different chromosomal region on the same chromosome (7A). This reflects at least a partly common genetic basis for the four traits. It is concluded that fine mapping of the regions of the three chromosomes of A genome involved in determining the accumulation of Fe, Zn, PC, and TKW in this mapping population may be rewarding.

Investigating the role of cystatin in conferring stage dependent resistance against Karnal bunt of wheat

Abstract Two wheat varieties, one highly resistant (HD29) and another susceptible (WH542) and their recombinant lines were taken for expression profiling of cystatins at three stages (WS1, WS2 and WS3) of the developing spikes. Different biochemical and immunological techniques like protease inhibitor assay, ELISA, DOT-BLOT immunoassay and SDS-PAGE analysis were employed to reveal the relationship of cystatin expression with stage dependent resistance (P<0.01). Interestingly, in all the genotypes cystatin expression was the highest at WS2 stage which is most susceptible to Karnal bunt (KB) pathogen. Expression was higher in the resistant recombinant inbred lines than in the susceptible ones (P<0.0001). Percent disease severity results were also in accordance with cystatin expression studies and thus suggesting a direct role of cystatins in providing resistance against KB. Based on the presence of potential component markers like cystatins which are involved in defence, identification of resistant wheat germplasms can prove to be an important strategy for successful KB management.

Characterization of wheat genotypes using morpho-physiological traits for heat tolerance

Constant or transitory high temperatures affect plant growth and development inducing diverse morphological and physiological changes in plants which ultimately causes yield decrease. The traits like relative injury (RI%), chlorophyll content, canopy temperature depression (CTD), heat susceptibility index (HSI), 1000-kernel weight (TKW), grain filling duration (GFD) were used in present study to assess the capability of plants to tolerate heat stress. The study revealed that the evaluated wheat genotypes showed variable degree of tolerance against heat for different traits. On the basis of morpho-physiological traits such as RI, chlorophyll content at 15 days after anthesis (DAA), CTD at 15 DAA, HSI, TKW, GFD, genotypes HD2329 x HD2967 (19.2%), WH1021 (−21.7%), JOB666 X WH1105 (−37.5%), WH1124 X HD2967 (0.55), HD2891 (2.1%) and WAXWING X HD2967 (−2.15%) were identified as the most heat tolerant genotypes for respective characters. For grain yield out of 54 wheat genotypes, DBW90, HD2329, UP2843 × HD2967, WH1124 × HD3059, WH1124 × HD2967, MACS6272 × WH1105, MACS6272 × HD2967, HD2891 × WH1105 and UP2338 were classified as heat tolerant.

Genotype-environment interaction for grain iron and zinc concentration in recombinant inbred lines of a bread wheat (Triticum aestivum L.) cross

A set of 306 recombinant inbred lines (RILs) along with the two parents and hitherto popular wheat variety in India, PBW 343, were evaluated in three environments over two years for grain iron (Fe) and zinc (Zn) concentration. Considerable genetic variation for both grain iron and zinc concentration exists. The environment effect was the most important source of variation for grain Fe and Zn concentration, explaining 37.42% and 57.78% of the total sum of squares respectively. Genotype-environment interaction (G x E) for Fe and Zn accounted for 29.46% and 23.24% of the total sum of squares, respectively. The magnitude of G x E interaction was relatively high. High heritabilities were observed for iron (0.81) and zinc (0.71) concentrations reflecting non-crossover type of interaction. The positive and moderately high correlation (0.677**) between Fe and Zn concentration suggest good prospect of simultaneous improvement of both the micronutrients. Additive main effects and multiplicative interaction biplot and environmental indices indicated the most favorable environment for Fe to be at Delhi, which was the second most favorable environment after Samastipur in Bihar for Zn. A poor environment for grain Fe and Zn accumulation was at Pantnagar. Four stable RILs each for grain Fe and grain Zn concentration were identified.

Harnessing genetic potential of wheat germplasm banks through impact-oriented-prebreeding for future food and nutritional security

The value of exotic wheat genetic resources for accelerating grain yield gains is largely unproven and unrealized. We used next-generation sequencing, together with multi-environment phenotyping, to study the contribution of exotic genomes to 984 three-way-cross-derived (exotic/elite1//elite2) pre-breeding lines (PBLs). Genomic characterization of these lines with haplotype map-based and SNP marker approaches revealed exotic specific imprints of 16.1 to 25.1%, which compares to theoretical expectation of 25%. A rare and favorable haplotype (GT) with 0.4% frequency in gene bank identified on chromosome 6D minimized grain yield (GY) loss under heat stress without GY penalty under irrigated conditions. More specifically, the ‘T’ allele of the haplotype GT originated in Aegilops tauschii and was absent in all elite lines used in study. In silico analysis of the SNP showed hits with a candidate gene coding for isoflavone reductase IRL-like protein in Ae. tauschii. Rare haplotypes were also identified on chromosomes 1A, 6A and 2B effective against abiotic/biotic stresses. Results demonstrate positive contributions of exotic germplasm to PBLs derived from crosses of exotics with CIMMYT’s best elite lines. This is a major impact-oriented pre-breeding effort at CIMMYT, resulting in large-scale development of PBLs for deployment in breeding programs addressing food security under climate change scenarios.

Identification and characterization of finger millet OPAQUE2 transcription factor gene under different nitrogen inputs for understanding their role during accumulation of prolamin seed storage protein

In this study, we report the isolation and characterization of the mRNA encoding OPAQUE2 (O2) like TF of finger millet (FM) (Eleusine coracana) (EcO2). Full-length EcO2 mRNA was isolated using conserved primers designed by aligning O2 mRNAs of different cereals followed by 3′ and 5′ RACE (Rapid Amplification of cDNA Ends). The assembled full-length EcO2 mRNA was found to contain an ORF of 1248-nt coding the 416 amino acids O2 protein. Domain analysis revealed the presence of the BLZ and bZIP-C domains which is a characteristic feature of O2 proteins. Phylogenetic analysis of EcO2 protein with other bZIP proteins identified using finger millet transcriptome data and O2 proteins of other cereals showed that EcO2 shared high sequence similarity with barley BLZ1 protein. Transcripts of EcO2 were detected in root, stem, leaves, and seed development stages. Furthermore, to investigate nitrogen responsiveness and the role of EcO2 in regulating seed storage protein gene expression, the expression profiles of EcO2 along with an α-prolamin gene were studied during the seed development stages of two FM genotypes (GE-3885 and GE-1437) differing in grain protein content (13.8 and 6.2%, respectively) grown under increasing nitrogen inputs. Compared to GE-1437, the EcO2 was relatively highly expressed during the S2 stage of seed development which further increased as nitrogen input was increased. The Ecα-prolamin gene was strongly induced in the high protein genotype (GE-3885) at all nitrogen inputs. These results indicate the presence of nitrogen responsiveness regulatory elements which might play an important role in accumulating protein in FM genotypes through modulating EcO2 expression by sensing plant nitrogen status.