QTL mapping for salt tolerance based on snp markers at the seedling stage in maize (Zea mays L.)

Salinity is a major constraint to the sustainability and expansion of maize cultivation. Plant salt tolerance is a quantitative trait controlled by multiple genes. In the present study, we constructed a high density genetic map based on high quality SNP markers from 161 F-2:5 recombinant inbred line populations derived from the cross between two maize inbred lines contrasting in salinity tolerance. QTL analysis was conducted in saline field and the hydroponic culture. For saline field, field germination rate and field salt tolerance ranking were used as salinity tolerance indicators to conduct QTL detection. For hydroponic culture, salt tolerance ranking, shoot fresh weight, shoot dry weight, tissue water content, shoot Na+ concentration, shoot K+ concentration, and shoot K+/Na+ ratio were used. Through unconditional QTL analysis, we detected 20 additive and nine epistatic QTLs, of which 12 and two showed significant QTL by treatment (Q x T) interaction effects, respectively. Moreover, the use of conditional analysis model allowed us to detect nine conditional QTLs. The QTLs were mainly clustered on chromosomes 1, 3 and 5. The five unconditional and three conditional QTLs reported here could individually explain more than 20 % of the phenotypic variation. The QTLs identified here could be helpful to improve salt tolerance in maize by marker-assisted selection and shed new light on understanding the genetic basis of salt tolerance in maize.