Marker Assisted Pyramiding of Southern Leaf Blight Resistance QTLs (qSLB3.1 and qSLB8.1) in Maize Inbred CM140
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Date
2022
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Punjab Agricultural University, Ludhiana
Abstract
Southern corn leaf blight (SLB) caused by Cochliobolus heterostrophus is the most destructive disease of maize. It is predominant in warm and humid climate and can result in yield lossesof about 40 percent. The present study was undertaken to pyramid SLB resistance QTLs (qSLB3.1 and qSLB8.1) in the background of CM140 using backcross populations developed from crosses LM5 (resistant parent) × CM140 (susceptible parent) and CM139 (resistant) × CM140 (susceptible). CM139 is the donor of qSLB3.1 while LM5 is the donor of qSLB8.1. The BC2F1 populations along with three parental lines were evaluated for SLB
disease reaction by inoculating plants at 7-9 leaf stage and the disease data were recorded twice at an interval of 15 days. The disease data showed considerable variation for SLB resistance within the backcross populations. The BC2F1 progenies were subjected to foreground selection with flanking SSR markers for the identification of target QTL. The individuals which were heterozygous for both the markers were selected and possessed a disease score of less than or equal to 3 were selected. Three plants from each cross (CM139 × CM140 and LM5 × CM140) were inter-crossed for the generation of F1s. The F1 plants were
assessed using the four SSR markers (two for each QTL) to check for the hybridity. The plants having both QTLs were self-pollinated for raising the F2 population and for the selection of pyramided QTLs both genotypic and phenotypic selection was conducted. The genotypic selection of the F2 population was carried out using SSRs and the individuals were
categorized on the basis of presence of both the marker alleles (homozygous for each QTL), presence of a single QTL (qSLB3.1 or qSLB8.1), and no QTL present. A total of twelve plants were obtained which were having both the QTLs with homozygous donor alleles. The F2 population was also evaluated phenotypically for SLB resistance as well as flowering characteristics. The plants that were homozygous to both the QTLs (qSLB3.1 and qSLB8.1) showed enhanced level of SLB resistance. The present results indicated that additive effects of the QTLs for SLB resistance played an important role among these plants. Our findings
also revealed non-significant association between flowering timings and SLB disease ratings. The pyramided lines so generated can accelerate the process of marker assisted breeding in maize for SLB resistance.
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Prabhmeet Kaur (2022). Marker Assisted Pyramiding of Southern Leaf Blight Resistance QTLs (qSLB3.1 and qSLB8.1) in Maize Inbred CM140 (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.