QTLs and their interaction determining different heading dates of barley in Australia and China

Heading date is a major determinant of the regional and seasonal adaptation of barley varieties. The dogma is that introduced germplasm is more likely to be adapted if it is derived from a similar latitude. However, barley germplasm introduced from similar latitudes of South-East Asia is extremely early heading in the Australian environments and vice versa. A doubled-haploid population from a cross of an Australian barley Galleon and a Japanese barley Haruna Nijo was evaluated for heading date in Australia (Perth, 31°56′S) and China (Wuhan, 30°33′N) under normal autumn sowing, late sowing in the field, and extended-light glasshouse conditions. One major QTL was identified on chromosome 5H under the three conditions in China. The single QTL accounted for up to 50% of phenotypic variation for heading date. The Australian variety contributed to late heading date. Two QTLs on chromosomes 4H and 5H were detected for controlling heading date in Australia. The QTL/QTL interaction contributed up to 35.8% of phenotypic variation for heading date in Australia, which is the major reason for the extremely early heading date of the Japanese variety in the Australian environment. The chromosome 5H QTL was detected at the same chromosomal location when the population was grown in either China or Australia. In both environments the Australian variety contributed to the late heading date. Selection against the Japanese alleles of chromosomes 4H and 5H QTLs could eliminate the extremely early genotype in Australia and selection against the Australian allele of chromosome 5H QTL could eliminate the extremely late genotype in China when Australian and Japanese germplasms are used in the breeding programs.