Genetic Analysis Of Drought-related Traits At Seedling Stage In Maize

Maize (Zea mays L.) is the most important food crop of China. China’s corn production area mainly distributed in the rain fed agriculture region. Therefore, maize is frequently affected by drought. For example, drought often occurs in the spring in northern China, especially at seedling stage. Severe drought can lead to death of maize seedling and has critical influence on maize growth and development. Development of drought-tolerant varieties is an effective way to solve the problem. Consequently, genetic analysis of drought tolerance at seedling stage in maize and discovering genes that control maize seedling drought tolerance is of great importance to drought resistance breeding.In this study, drought tolerance at seedling stage of 27 maize material were identified. HUANGZAOSI and LV28 were selected as a pair of inbred lines display significant difference in drought tolerance. The drought tolerance-related traits of the RIL (recombinant Inbred Lines) population of HUANGZAOSI and LV28 at two water levels were phenotyped. Combined with a high density BinMap, quantitative trait locus (QTL) analysis to detect the major QTLs that control drought tolerance was conducted. In addition, an association population of 313 maize inbred lines was used to detect maize seedling drought tolerance related SPNs by genome-wide association study (GWAS). The main conclusions are as follows.1. HUANGZAOSI and LV28 were significantly different in terms of drought tolerance SCORE, RWC (relative water content), SW (shoot dry weight) and RW (root dry weight). In all the 27 maize material, HUANGZAISI belongs to the middle tolerance group, while LV28 is the most sensitive inbred to drought, appearing leaf rolling and wilting earliest.2. Combined with the BinMap of the HUANGZAOSI and LV28 RIL population (126 RILs), with 2091 bins, QTL analysis Showed that two QTLs for RWC wre detected on Chr.2 and Chr.4, with sources of favorable alleles from HUANGZAOSI and LV28, respectively. Three QTLs for LRT (leaf rolling time)were detected on Chr.1, Chr.2 and Chr.5, with all sources of favorable alleles from HUANGZAISI. One QTL for SW was detected on Chr.5, with source of positive alleles from LV28. Two QTLs for R/S (root/shoot ratio) were detected on Chr.1 and Chr.10, with sources of effect-increasing alleles from HUANGZAOSI and LV28, respectively. One QTL was detected on Chr.5 for DTI (drought tolerance index) of SW and one on Chr.l for DTI of RW.3. With standard of SCORE, correlation and regression of all traits were analyzed. The result showed that physiological traits of RWC and LRT had higher relationship with maize seedling drought tolerance than morphological traits., the former being reliable index for maize seedling drought tolerance identification. For RWC and LRT, five genes that reported previously were identified in their respective QTL intervals.4. The GWAS detected 61 SNPs that had significant correlation with drought tolerance related traits at seedling stage. The SNPs clustered on some regions of chromosomes, such as the 72,800,194-80,663,599 region on Chromosome 1, the 81,051,543 -82,335,038 region on Chromosome 10, the 136,006,812-136,016,953 region on Chromosome 6, and the 189,039,722-211,513,324 region on Chromosome 5.. The region on Chromosome 1 and the region on Chromosome 5 were suggested to be the key regions for maize seedling drought tolerance. Further, the gene GRMZM5G857944 and GRMZM2G085945 near maker PZA00500.5 on chromosome 5 might be candidate genes for maize seedling drought tolerance.