Marker-assisted mapping and backcross breeding for late wilt disease resistance in NAI-137, the seed parent of public bred single cross maize (Zea mays L.) hybrid Hema

Development and deployment of late wilt disease (LWD) resistant cultivar(s) is a cost-effective and eco-friendly strategy to reduce losses due to LWD. DNA markers could be potential surrogates for selection of complexly inherited resistance to LWD. Two linkage maps were constructed using the genotypic data of 64 and 40 polymorphic SSR markers on BC ₁ F ₁ populations derived from NAI-137×97B and NAI-137×MAI-345, respectively. Three main effect-QTL were detected on chromosomes 1, 4 and 10 in NAI-137×97B, while one QTL on chromosome 9 in NAI-137×MAI-345. Therefore, only the BC ₁ F ₁ population of NAI-137×97B was back-crossed to NAI-137. Linkage map was constructed in BC ₂ F ₁ population using the genotypic data of 64 SSR, 3456 unbinned-SNP and 104 binned-SNP + 64 SSR markers in combination. A total of 5, 2 and 11 main effect-QTL were detected on SSR, unbinned-SNP and binned-SNP + SSR based QTL maps, respectively. In NAI-137×97B derived BC ₁ F ₁ and BC ₂ F ₁ , 2 QTL on chromosomes 4 and 10 flanked by common SSR markers i.e. , mmc0371 and umc2350, respectively were detected. Sixteen NAI-137×97B derived BC ₁ F ₁ plants carried QTL controlling LWD resistance with > 80% recovery of recipient parent genome and LWD score ≤ 4. Ten NAI-137×97B derived BC ₂ F ₁ plants carried QTL controlling LWD resistance with > 90% recovery of recipient parent genome and LWD score ≤ 3. They were selfed and evaluated for response to LWD. Three BC ₂ F ₂ families (BC ₂ F ₂ -84, BC ₂ F ₂ -88 and BC ₂ F ₂ -179) with LWD score 2, lower than the donor parent (NAI-137, LWD score 8) were identified. LWD resistant version of NAI-137 developed from the present study shall be used to cross with MAI-105 (the male parent of maize hybrid Hema) to generate improvised “Hema” after evaluating the grain yield potential in comparison to original “Hema” hybrid.