Fine-mapping Of A QTL For Deep-seeding Tolerance And Gene Mapping Of A Drought-sensitive Mutant Swl3 In Maize

Drought stress is one of the most important environmental factors affecting maize yield.Deep-seeding tolerant maize can absorb moisture from deep soil and thus have strong drought tolerance.Therefore,it is of great significance to study the genetic mechanism of deep-seeding tolerance.In the laboratory’s previous work,a major QTL qMES20-10 related to deep-seeding tolerance was identified on the long arm of maize chromosome 10 in the F_2:3 families of maize inbred lines X178 and 3681-4,and a BC₃F_3:4 family was constructed by back crossed with X178.In this study,qMES20-10 was validated by analyzing the phenotype and genotype of 100 BC₃F_3:4 lines.On this basis,combined with molecular marker-assisted selection,advanced backcross population and self-crossing population were constructed,and qMES20-10 was mapped within the interval of 133.3-136.0 Mb on chromosome 10.Moreover,two near-isogenic lines were screened from the BC₃F_3:4 families,and differentially expressed genes were identified.By GO analysis,it was found that the differentially expressed genes were mainly involved in chemical stimulus response,oxidation reduction,and oxidative stress response.The QTL related to the deep-seeding tolerance was fine-mapped and might be useful for molecular breeding projects,the advanced lines produced in the process provided invaluable starting materials for isolating the underlying gene.The leaf is the photosynthetic organ of the plant,and the leaf morphology is one of the important components of the ideotype.In this experiment,a drought-sensitive mutant swl3（sensitive to water loss）was identified during the seed reproduction.The mutant showed severely curlled leaves toward the proximal in the field,leaf color was whitished,and the leaf surface became smooth and soft.By measuring the photosynthetic physiological indices of the swl3 mutant and B73,it was found that the energy conversion efficiency and relative chlorophyll content of the swl3 were significantly lower than that of B73,and the leaf temperature was higher than that of B73,indicating that the SWL3 gene may affect photosynthesis and transpiration.Two F₂ populations were constructed by crossing swl3 with B73and Mo17 respectively,and the SWL3 gene was initially mapped to the 107-130 Mb on chromosome 6using BSR-Seq（Bulked Segregant RNA-Seq）method.Taking map-based cloning strategy,the SWL3was fine mapped between two InDel markers,swl3InD13 and swl3InD19 by combining the mapping results of the two F₂ population.The distance between the two markers was 183 Kb according to the B73 RefGen_v3.There are 6 candidate genes in the interval.This study provided information and materials for the cloning of the gene for the swl3 mutant.