Articles written in Journal of Genetics

    • Introgression of a leaf rust resistance gene from Aegilops caudata to bread wheat

      Amandeep Kaur Riar Satinder Kaur H. S. Dhaliwal Kuldeep Singh Parveen Chhuneja

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      Rusts are the most important biotic constraints limiting wheat productivity worldwide. Deployment of cultivars with broad spectrum rust resistance is the only environmentally viable option to combat these diseases. Identification and introgression of novel sources of resistance is a continuous process to combat the ever evolving pathogens. The germplasm of nonprogenitor Aegilops species with substantial amount of variability has been exploited to a limited extent. In the present investigation introgression, inheritance and molecular mapping of a leaf rust resistance gene of Ae. caudata (CC) acc. pau3556 in cultivated wheat were undertaken. An F2 population derived from the cross of Triticum aestivum cv.WL711 – Ae. caudata introgression line T291-2 with wheat cultivar PBW343 segregated for a single dominant leaf rust resistance gene at the seedling and adult plant stages. Progeny testing in F3 confirmed the introgression of a single gene for leaf rust resistance. Bulked segregant analysis using polymorphic D-genome-specific SSR markers and the cosegregation of the 5DS anchored markers (Xcfd18, Xcfd78, Xfd81 and Xcfd189) with the rust resistance in the F2 population mapped the leaf rust resistance gene (LrAC) on the short arm of wheat chromosome 5D. Genetic complementation and the linked molecular markers revealed that LrAC is a novel homoeoallele of an orthologue Lr57 already introgressed from the 5M chromosome of Ae. geniculata on 5DS of wheat.

    • Mapping of stripe rust resistance gene in an Aegilops caudata introgression line in wheat and its genetic association with leaf rust resistance


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      A pair of stripe rust and leaf rust resistance genes was introgressed from Aegilops caudata, a nonprogenitor diploid species with the CC genome, to cultivated wheat. Inheritance and genetic mapping of stripe rust resistance gene in backcrossrecombinant inbred line (BC-RIL) population derived from the cross of a wheat–Ae. caudata introgression line (IL) T291-2(pau16060) with wheat cv. PBW343 is reported here. Segregation of BC-RILs for stripe rust resistance depicted a single major gene conditioning adult plant resistance (APR) with stripe rust reaction varying from TR-20MS in resistant RILs signifying the presence of some minor genes as well. Genetic association with leaf rust resistance revealed that two genes are located at a recombination distance of 13%. IL T291-2 had earlier been reported to carry introgressions on wheat chromosomes 2D, 3D, 4D, 5D, 6D and 7D. Genetic mapping indicated the introgression of stripe rust resistance gene on wheat chromosome 5DS in the region carrying leaf rust resistance gene LrAc, but as an independent introgression. Simple sequence repeat (SSR) and sequence-tagged site (STS) markers designed from the survey sequence data of 5DS enriched the target region harbouring stripe and leaf rust resistance genes. Stripe rust resistance locus, temporarily designated as YrAc, mapped at the distal most end of 5DS linked with a group of four colocated SSRs and two resistance gene analogue (RGA)-STS markers at a distanceof 5.3 cM. LrAc mapped at a distance of 9.0 cM from the YrAc and at 2.8 cM from RGA-STS marker Ta5DS_2737450, YrAc and LrAc appear to be the candidate genes for marker-assisted enrichment of the wheat gene pool for rust resistance.

    • Introgression and genetic mapping of leaf rust and stripe rust resistance in Aegilops triuncialis


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      The growing and cultivating resistant wheat crop varieties is important to meet the demands of the growing population andminimizing the yield losses due to foliar diseases. More important is the identification of novel resistance sources and transfer of resistancein ready to use form. In the current study, leaf rust (LR) and stripe rust (YR) resistant tetraploid nonprogenitors of wheat Aegilops triuncialis(UtUtCtCt) acc pau 3462 was crossed and backcrossed susceptible cultivar WL711(NN) by inducing homeologous pairing using CS ph1.Recurrent parent type plants were selected in subsequent generation with resistance to LR and YR and BC$_{2} $F$_{7} $ introgression line (2n=42)named ILtri have been developed. To understand the nature and inheritance of LR and YR resistance genes and to map their genomiclocation, F$_{2} $ and F$_{2:3 } $ mapping populations were developed by crossing ILtri with WL711(NN). In F$_{2} $ and F$_{2:3 } $, the seedlings and adult plantssegregated into 3R:1S and 1HR:2Seg:1HS ratios, respectively for both LR and YR, indicating inheritance of single dominant all stageresistance gene working against both the rusts. These genes were temporary designated as Lrtri and Yrtri and were inherited independently.Molecular mapping of 614 SSR markers mapped the Lrtri at a distance of 11.2 cM from SSR marker Xwmc606.

    • Molecular mapping of CLCuD resistance introgressed from synthetic cotton polyploid in upland cotton


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      Cotton leaf curl disease (CLCuD), caused by a geminivirus complex, is the most serious disease of upland cotton in northwest India and Pakistan. It results in substantial losses in cotton yield and fibre quality. Due to continuous appearance of new viral strains, all the established CLCuD resistant stocks, extant and obsolete cultivars of upland cotton have become susceptible. Therefore, it became crucial to explore the novel sources of CLCuD resistance, as development of CLCuD resistant varieties is the most practical approach to manage this menace. Here, for the first time, we report introgression and mapping of CLCuD resistance from a ‘synthetic cotton polyploid’ to uplandcotton. A backcross population (synthetic polyploid / Gossypium hirsutum Acc. PIL 43/G. hirsutum Acc. PIL 43) was developed for studying inheritance and mapping of CLCuD resistance. Dominance of CLCuD resistance was observed over its susceptibility. Two dominant genes were found to confer resistance to CLCuD. Molecular analysis through genotyping-by-sequencing revealed that chromosomes A01 and D07 harboured one CLCuD resistance gene each.

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