A regulator of early flowering in barley (Hordeum vulgare L.)

Abstract

Heading date (HD) of cereals is an important trait for adaptation to diverse environments and is critical for determining yield and quality and the number of genes and gene combinations that confer earliness in barley under short days is limited. In our study, a QTL for early flowering was identified from the cross between an Australian malting barley cultivar and a Chinese landrace. Four sets of near isogenic lines (NILs) were developed with a QTL located on chromosome 5H at the interval of 122.0-129.0 cM. Further experiments were conducted to investigate how this gene was regulated by photoperiod using the NILs with three sowing dates from autumn to summer. The NILs carrying the earliness allele were significantly earlier than the late genotype at all sowing dates. This gene was different from previously reported vernalisation genes that are located at a similar position as no vernalisation was required for all the NILs. The difference between this gene and Eam5 (HvPHYC) locus which also located between two co-segregated markers (3398516S5, 122.5 cM, and 4014046D5, 126.1 cM), is that with the existence of Ppd-H1 (Eam1), Eam5 has no effect on ear emergence under long days while the gene from TX9425 still reduced the time to ear emergency. The locus showed no pleiotropic effects on grain pasting properties and agronomic traits except for spike length and number of spikelets per spike, and thus can be effectively used in breeding programs. The array of early heading dates caused by interactions of Eam5 gene with other maturity genes provides an opportunity to better fine tune heading dates with production environments, which can be critical factor in barley breeding.

Fig 1. Comparison between genotypes of near isogenic lines (Eps5HL-317-1-E, left, vs Eps5HL-317-1-L, right) from the cross of TX9425/Franklin.

Red: Franklin genotype; blue: TX9425 genotype. The major difference is on 5H at the position of 122 to 129 cM (circled).

Fig 2. Comparison of genotypes of 5H for different pairs of near isogenic lines from the cross of TX9425/Franklin.

A) Eps5HL-316-E/L; B) Eps5HL-317-1-E/L; C) Eps5HL-317-2-E/L; and D) Eps5HL-322-E/L. Red: Franklin genotype; blue: TX9425 genotype; white: heterozygous.

Fig 3. Relative heading date of different pairs of NILs, TX9425 and Franklin from different sowing dates.

Fig 4. Effect of the Eps5HL locus on the starch pasting properties.