Development of near-isogenic lines for photoperiod-insensitive genes, Ppd-B1 and Ppd-D1, carried by the Japanese wheat cultivars and their effect on apical development

In order to clarify the characteristics of the photoperiod-insensitive genes Ppd-B1 and Ppd-D1 carried by the Japanese wheat cultivars, we produced near-isogenic lines (NILs) and investigated their effects on apical development. The NIL 'H(A)' was produced by backcrossing the Japanese photoperiod-sensitive cultivar 'Haruhikari' as a recurrent parent and the insensitive cultivar 'Saitama 27' (Ppd-D1) as a nonrecurrent parent. The other three NILs 'H(B)', 'H(C)' and 'H(D)' were produced using the insensitive cultivar 'Fukuwasekomugi' (Ppd-B1 Ppd-D1) as another nonrecurrent parent. Genetic analysis of the photoperiod response showed that 'H(A)', 'H(B)', 'H(C)' and 'H(D)' carried Ppd-D1, Ppd-D1, Ppd-B1 and Ppd-B1 Ppd-D1, respectively. Ppd-B1 and Ppd-D1 were incompletely dominant and exhibited an interaction, the former displaying a stronger effect on insensitivity to photoperiod. The analysis of apical development indicated that both Ppd-B1 and Ppd-D1 had significant effects on accelerating double-ridge initiation and on the following spike development under a short photoperiod.