Achla Sharma

Unlocking the genetic diversity of Creole wheats.

Climate change and slow yield gains pose a major threat to global wheat production. Underutilized genetic resources including landraces and wild relatives are key elements for developing high-yielding and climate-resilient wheat varieties. Landraces introduced into Mexico from Europe, also known as Creole wheats, are adapted to a wide range of climatic regimes and represent a unique genetic resource. Eight thousand four hundred and sixteen wheat landraces representing all dimensions of Mexico were characterized through genotyping-by-sequencing technology. Results revealed sub-groups adapted to specific environments of Mexico. Broadly, accessions from north and south of Mexico showed considerable genetic differentiation. However, a large percentage of landrace accessions were genetically very close, although belonged to different regions most likely due to the recent (nearly five centuries before) introduction of wheat in Mexico. Some of the groups adapted to extreme environments and accumulated high number of rare alleles. Core reference sets were assembled simultaneously using multiple variables, capturing 89% of the rare alleles present in the complete set. Genetic information about Mexican wheat landraces and core reference set can be effectively utilized in next generation wheat varietal improvement.

Evaluation of Different Mn Efficiency Indices and their Relation to Morphophysiological Traits in Diverse Wheat Genotypes

Wheat genotypes display differential tolerance to manganese (Mn) deficiency. Growing Mn-efficient cultivars in Mn deficient soil could be effective in improving yields. A pot experiment was conducted with eight genotypes grown in Mn deficient soil treated with 0 (no Mn fertilizer) and 50 ppm (50 mg Mn kg−1soil applied as mangansese sulfate monohydrate (MnSO4.H2O) Mn. The genotypes were classified on the basis of grain yield and grain physiological efficiency as efficient and responsive (SAMNYT 410, GLUPRO 200, PBW 621, and BW 9178), efficient and nonresponsive, inefficient and responsive (HD 2967), and inefficient and nonresponsive (PDW 314, PDW 291, and PBW 636). The genotypes in different groups differed in morphophysiological characteristics; efficient and responsive genotypes recorded more leaf area, higher SPAD index, higher Fv/Fm ratio, and longer roots than inefficient and nonresponsive. Efficient and responsive genotypes are desirable by farmers, whereas inefficient and responsive genotypes in a breeding program for their Mn-responsive characteristics.

Corrigendum: Unlocking the genetic diversity of Creole wheats.

Scientific Reports 6: Article number: 23092; 10.1038/srep23092 published online: March152016; updated: May202016. Mark Ellis was omitted from the author list in the original version of this Article. In addition, there was a typographical error in the spelling of the author Kai Sonder which was incorrectly given as Kai Sonders. These errors have been corrected in the PDF and HTML versions of the Article. The Acknowledgements section now reads: The authors duly acknowledge the financial support received from Mexico’s Secretariat of Agriculture, Livestock, Rural Development, Fisheries and Food (SAGARPA) through the Seeds of Discovery-Sustainable Modernization of Traditional Agriculture project (Mas-Agro). We acknowledge Diversity Array Technology (DArT), Canberra, Australia, for the genotyping service provided. Authors extend sincere thanks to Drs Kanwarpal Singh Dhugga, Julio Huerta-Espino, Ky Mathews, Dave Marshall. The direct and indirect support of research technicians is duly acknowledged. We extend our special thanks to Seeds of Discovery project leader and Director of the Genetic Resources Program, Dr. Kevin Pixley, for his valuable support and encouragement to the team. The Author Contributions section now reads: S.S. and P.V. conceived and designed the experiments; J.F., J.B., H.L., P.V., D.S. and C.S. performed the diversity, statistical and association analyses; C.S.P., M.R. and M.T. carried out large scale evaluation for heat-drought; C.G. evaluated landraces for grain quality; S.S., C.O., C.P.S. M.E and P.W. contributed to Genotyping; K.S. performed climate data analysis and prepared maps; G.F.D., P.S., A.S., N.S.B., G.P.S., P.V. and S.S. screened core set for diseases; T.P. provided seed material from gene bank; J.C. and S.S. were in-charge to oversee the data collection and analyses; P.V. and S.S. wrote the manuscript and other authors contributed later on; and all authors reviewed the manuscript.

Inheritance of spot blotch resistance in barley (Hordeum vulgare L.)

Singh, S., Singh, H., Sharma, A., Meeta, M., Singh, B., Joshi, N., Grover, P., Al-Yassin, A. and Kumar, S. 2014. Inheritance of spot blotch resistance in barley (Hordeum vulgare L.). Can. J. Plant Sci. 94: 1203-1209. Spot blotch, caused by Bipolaris sorokiniana, is a major disease of barley hampering its commercial production in many parts of the world. Growing resistant cultivars is the most effective, economical and eco-friendly approach to control the disease. To understand the inheritance of resistance, F1, F2 and F3 generations of two crosses, involving susceptible (PL426 and RD2503) and resistant (BL9 and BL10) parents were studied. The susceptibility of F1 plants and a ratio of 13 susceptible:3 resistant in F2 populations in both crosses indicated that the reaction to spot blotch is hypostatic and is governed by two genes with an epistatic/inhibitory effect of first on the second one. The resistant reaction appeared due to the presence of dominant allele of the second gene. The first gene in dominant homozygous or heterozygous condition had an inhibitory effect over the second gene. The inheritance pattern was confirmed from the segregation pattern of F3 progenies of both the crosses. One hundred-fifty F2:6 recombinant inbred lines (RIL) derived from PL426/BL10 cross gave a good fit to the ratio of 1 resistant:3 susceptible lines under artificial and natural epiphytotic conditions. Recovery of transgressive segregants in the RIL population indicated the presence of some modifiers or minor genes. Test of allelism involving susceptible (PL426)×susceptible (RD2503) and resistant (BL9)×resistant (BL10) parents revealed that both the susceptible parents as well as resistant parents were allelic to each other.

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.

Rht8 gene as an alternate dwarfing gene in elite Indian spring wheat cultivars

Optimizing wheat height to maximize yield has been an important aspect which is evident from a successful example of green revolution. Dwarfing genes (Rht) are known for yield gains due to lodging resistance and partitioning of assimilates into ear. The available and commercially exploited sources of dwarfism in Indian spring wheat are Rht1 and Rht2 genes inspite of availability of over 20 dwarfing genes. Rht8 a Gibberellic acid sensitive dwarfing gene is another reduced height gene commercially exploited in some Mediterranean countries. Two F2 populations segregating for Rht1 and Rht8 genes with each comprising 398 and 379 plants were developed by crossing European winter wheat cultivars Beauchamp and Capitole with Indian spring wheat cultivar PBW 621. Different genotypic combinations for Rht1 and Rht8 genes were selected from these populations through linked molecular markers and selected F3:4 lines were evaluated for various agronomic traits in a replicated trial. Reduction in plant height with Rht8 and Rht1 averaged 2.86% and 13.3% respectively as compared to the group of lines lacking dwarfing gene. Reduction was spread along all the internodes of wheat culm and reduction was lower as progress towards the lower internode. Grain number per spike and highest yield was observed in lines carrying only Rht1 gene. Reduction in plant biomass was observed with either of the dwarfing gene. Longest coleoptile length and seedling shoot length averaged 4.4 ± 0.09 cm and 19.5 ± 0.48, respectively was observed in lines lacking any of the dwarfing gene. Negligible reduction of 6.75% and 2.84% in coleoptile length and seedling shoot length, respectively was observed in lines carrying only Rht8 gene whereas F3:4 lines with Rht1 gene showed 21.64% and 23.35% reduction in coleoptile length and seedling shoot length, respectively. Additive effect of genes was observed as double dwarfs showed 43.31% and 43.34% reduction in coleoptile length and seedling shoot length.

Canopy Temperature an Effective Measure of Drought Stress Tolerance in RIL Population of Wheat

Field experiments were conducted for evaluating recombinant inbred lines (RILs) of wheat cross of C518 and PBW343 under rainfed conditions by using plant water related traits viz; canopy temperature and stomatal density during rabi seasons 2012-13 and 2013-14. Both parents belonging to distinct adaptation group, offer several morpho-physiological contrasting traits. Canopy temperature (CT) and stomatal density (SD) were recorded under irrigated and rainfed conditions. Analysis of variance showed that CT and SD differed significantly under both conditions, indicating the existence of sufficient genetic variability among the populations. Frequency distribution for canopy temperature at anthesis among RIL population showed transgressive segregation under irrigated and rainfed conditions. Skewness (0.22) and kurtosis (0.27) was higher under rainfed conditions. Stomatal density does not vary greatly under water-deficit conditions. However, reduction in stomatal density was found under water stress conditions and recorded minimum stomatal density suggesting less transpiration rate under drought conditions resulting in minimize of loss of water. Under irrigated environment, canopy temperature at anthesis (CTA) showed non-signification correlation with stomatal density. While, under rainfed condition, canopy temperature among RILs showed significant negative correlation with stomatal density and yield attribute characters. This indicated that the selection for traits viz, canopy temperature and stomatal density may be effective measure of drought tolerance of wheat cultivars and yield improvement under drought stress conditions.

Bread wheat cultivar PBW 343 carries residual additive resistance against virulent stripe rust pathotype

ABSTRACT With continuous outbreaks of stripe rust (Puccinia striiformis f. sp. tritici) epidemics and rapid breakdown of deployed resistance in bread wheat (Triticum aestivum L.) cultivars in North West Plains Zone (NWPZ) in India warrant knowledge and deployment of new and durable sources of resistance to stripe rust. Bread wheat cultivar PBW 343, until recently the most widely cultivated wheat variety in India, is now highly susceptible to stripe rust (score 9 on a 1–9 scale), whereas PBW 621 (score 5.05–5.65) and HD 2967 (score 5.40–6.20) show low levels of resistance. We conducted an experiment, spanning three crop seasons (2013–2014 to 2015–2016), in which parental lines, F1 and F2 populations, F3 and F4 families from two bread wheat crosses, PBW 621/PBW 343 and HD 2967/PBW 343 were generated and evaluated for stripe rust resistance against a virulent pathotype. While the F1 revealed partial dominance, the segregation pattern for stripe rust resistance in F2 and F3 showed transgressive segregation for resistance in both crosses. Chi-square analysis indicated that resistant segregants possessed two genes, one contributed by PBW 621 or HD 2967 (depending on the cross) and the other, unexpectedly but obviously, came from the most susceptible cultivar, PBW 343. Possible genetic mechanisms for this residual resistance and implications for breeding programs are discussed.

Genetic basis of stripe rust resistance in transgressive derivatives of a cross between susceptible bread wheat parents

Parental lines, F1s, F2 populations as well as F3 and F4 families and F6, F7 RILs from bread wheat cross PBW 621 x HD 2967 were evaluated for stripe rust resistance against a highly virulent pathotype in experiments spanning six crop seasons. HD2967, the widely cultivated wheat variety in North Western Plains of India and PBW 621 have shown successively lowered levels of stripe rust resistance over the years. F1 of these parents showed lack of dominance. The segregation pattern for stripe rust resistance in F2, F3 and F4 showed transgressiveness for resistance. Chi-square analysis indicated that resistant segregants possess two genes, one contributed by PBW 621 and the other by HD 2967. These results were confirmed over two years using F6 and F7 RILs. Possible genetic mechanisms for this residual resistance and implications for breeding programme are discussed.

Evaluation of RIL Population Derived from Traditional and Modern Cultivar of Wheat (C 518/2* PBW 343) for Yield Potential under Drought Stress Conditions

Evaluation of RIL Population Derived from Traditional and Modern Cultivar of Wheat (C 518/2* PBW 343) for Yield Potential under Drought Stress Conditions Present study was carried out to assess the yield potential of C518 and their potential utility in context of drought tolerance when introgressed in to a modern day wheat variety (PBW 343). These two cultivars (PBW 343 and C 518) belongs to distinct adaptation groups, offer several morpho-physiological and biochemical contrasts. C518 is tall and adapted to low input rainfed conditions whereas PBW 343 is semi-dwarf and input responsive. 175 recombinant inbred lines (C 518/2* PBW 343) along with parents and checks were evaluated for drought tolerance in account of yield potential under irrigated and rainfed environments during 2013 to 2014. Water stress was created by withholding irrigation. Different drought tolerance indices viz., stress susceptibility index, relative drought index, mean productivity, stress tolerance index, geometric mean productivity, yield stability index, drought resistance index were evaluated based on grain yield under irrigated and rainfed conditions. Out of 175 inbred lines, seven lines recorded higher grain yield under irrigated as well as rainfed environments. STI, DRI and MP showed highly significant positive correlation with yield in both stress and nonstress environments and with other drought tolerance indices. Thus application of these indices could be appropriate while screening the varieties for drought tolerance and on the basis of theses indices, the inbred lines 108, 84, 80 and 32 were found tolerance lines with high yield under both environments better than the parents...