Marker assisted backcross to introgress late leaf spot and rust resistance in groundnut (Arachis hypogaea L.).

BACKGROUND: Groundnut is affected by a variety of abiotic and biotic stressors, including late leaf spot and rust, which cause significant economic loss. In this study, QTL for resistance to late leaf spot and rust from donor variety GPBD 4 were incorporated into a popular groundnut variety (ICGV 00350) through marker assisted backcross (MABC) breeding. METHODS: Eight foreground SSR markers [AhXII (GM1009, GM1573 and Seq8D09) and AhXV (GM1536, GM2009, GM2079, GM2301 and IPAHM103)] linked with disease resistant QTLs were utilized in this study. A set of 217 SSR markers spanning the whole groundnut genome were employed for background analysis. Three backcrosses with recurrent parent and selfing were followed in the cross ICGV 00350 × GPBD 4. Background analysis was carried out in BC3F2; while, phenotypic confirmation for resistance was carried out in BC3F3 generation. CONCLUSION: Five advanced backcross lines in BC3F2 were found, with more than 90% recurrent parent genome. The phenotyping of the eight ILs recorded disease scores ranging from 2.0 to 3.0 for LLS and from 1.0 to 3.0 for rust disease scores. All these lines had superior characteristics compared to the recurrent parent ICGV 00350 in terms of late leaf spot and rust resistance. The enhanced ILs will be evaluated further for commercial release.

Novel and stable QTL regions conferring resistance to MYMV disease and its inheritance in blackgram (Vigna mungo (L.) Hepper).

Mungbean yellow mosaic virus (MYMV) disease is a significant constraint for blackgram production. The present study employed a mapping population derived from a cross between susceptible (MDU 1) and resistant (TU 68) genotypes to identify quantitative trait loci (QTL) associated with MYMV disease resistance in addition to bruchine resistance loci identified from the previous study. Phenotyping was carried out in F2 generation under the disease spreader row method at field condition. Disease score observations were carried out 60 days after sowing (DAS). The chi-square goodness of fit test revealed inhibitory gene action with two genes controlling the expression of resistance to MYMV disease. However, QTL analysis revealed one major QTL region, i.e. qMYMVD_60 at LG 10 responsible for MYMV disease score at 60 DAS, accounted for 21 per cent of variation. The identified QTL has the flanking markers as CEDG180 and CEDG116. Hence, the QTL, qMYMVD_60 may be utilized in the breeding of MYMV disease resistance. Further, the marker-assisted introgression of both the MYMV and bruchine resistance QTLs can be performed in the near future.

Identification of QTLs for pod and kernel traits in cultivated peanut by bulked segregant analysis

Bulked segregant analysis was used to identify simple sequence repeat (SSR) markers associated with pod and kernel traits in cultivated peanut, to permit rapid selection of superior quality genotypes in the breeding program. SSR markers linked to pod and kernel traits were identified in two DNA pools (high and low), which were established using selected F2:6 recombinant individuals resulting from a cultivated cross between a runner (Tamrun OL01) and a Spanish (BSS 56) peanut. To identify quantitative trait loci (QTLs) for pod and kernel-related traits, parents were screened initially with 112 SSR primer pairs. The survey revealed 8.9 percent polymorphism between parents. Of ten SSR primer pairs distinguishing the parents, five (PM375, PM36, PM45, pPGPseq8D9, and Ah-041) were associated with differences between bulks for seed length, pod length, number of pods per plant, 100-seed weight, maturity, or oil content. Association was confirmed by analysis of segregation among 88 F2:6 individuals in the RIL population. Phenotypic means associated with markers for three traits differed by more than 40 percent, indicating the presence of QTLs with major effects for number of pods per plant, plant weight, and pod maturity. The SSR markers can be used for marker assisted selection for quality and yield improvement in peanut. To the best of our knowledge, this is the first report on the identification of SSR markers linked to pod - and kernel- related traits in cultivated peanut.