A gene for photoperiod sensitivity in rice linked with apiculus colour

Abstract

Lack of appreciation of the importance of length of day in determining the onset of flowering has vitiated much of the earlier work on the inheritance of age in rice. No genetic analysis of photoperiod response in this plant has yet been published. In the past two years, I have investigated the inheritance of photoperiod sensitivity. The Ceylon pure line, Vellai Ilankalayan 28061, which blooms approximately one hundred days after sowing, and is relatively insensitive to the photoperiod, was crossed with the Burma lines, MLYC 401 and HMC 12, which have, in the short days of the North-East Monsoon season, about the same sowing-to-flowering interval as the former, but are, to a high degree, sensitive to the photoperiod. The annual variation in length of day in Ceylon (lat. 5° 55-9° 50 N.) is less than one hour, but this variation exerts a profound influence on the flowering of the sensitive varieties. The growing of segregating progenies in the long days of the South-West Monsoon season makes the separation of sensitive and day-neutral forms possible. The parents and the F₁ and F₂ generations were sown at the same time, namely, May 1, 1952, at the Rice Research Station, Batalagoda. The mean intervals from sowing to panicle emergence for the parents and the F₁ are shown in Table 1.