オオムギ種子感水性のＱＴＬマッピング

Sensitivity to water condition during germination is an important character in malting barley because it affects malt poduction. Water sensitivity in malting barley is defined as the defference in germination percentage between the seeds in standard and excess-water conditions. Usually standard and excess-water condition means 4 and 8 ml water in a 90 mm perti dish, respectively. Takeda and Fukuyama (1983) examined more than 4,000 barley accessions and found 0～100% water sensitivity. This means complete to no suppression of germination by an excess-water condition. In this study, quantiative trait loci (QTL) analysis was applied to analize the inheritance of water sensitivity. Two sets of doubled haploid (DH) populations derived from Steptoe×Morex (S/M) and Harrington×TR306 (H/T) crosses,were grown in the experiment field of the Research Institute for Bioresources, Okayama University. Bulbosum method was adapted to develop DH lines (Chen and Hayes 1989). Water sensitivities of 150 (S/M) and (H/T) lines and their parents were evaluated using 50 seeds each and the germination test (25℃, 4 days) was repeated four times. Water sensitivity showed a large variation (Fig.1) and the heritability of the trait was 0.78 and 0.72 in S/M and H/T, respectively, indicating that about three-quarters of the phenotypic variance was genetic in origin. Three (S/M) and one (H/T) significant QTL were detected and 23% (S/M) and 25% (H/T) of the phenotypic variance was explained by the QTL. These QTL were located on chromosomes 2H,3H,6H and 7H (Table 1, Fig. 2). QTL relating to germination traits were lacated near the QTL controlling water sensitivity (Fig. 3).　Interaction among the QTL was small (Table 2). Marker-assisted selection was effective (Table 3).

Steptoe×Morex（S/M)およびHarrington×TR306（H/T)の倍加半数体（DH)系統を用いて種子の感水性のQTL解析を行った。DH系統は連続的な超越分離を示し、S/Mでは3個、H/Tでは1個の有意なQTLが見出され、それぞれ感水性の変異の約1/4が説明された。これらのQTLの近傍には発芽速度などの発芽に関する他のQTLが見出された。