Development of improved photoperiod sensitive rices for rainfed lowland areas
1988
Pamplona, A.M. | Mackill, D.J. (International Rice Research Inst., Los Banos, Laguna (Philippines). Dept. of Plant Breeding)
In most rainfed areas farmers depend on photoperiod sensitive cultivars due to their insensitivity to delayed transplanting and fixed harvest period. Developing improved photoperiod sensitive varieties is now being important. The selection criteria for F2 populations and pedigree lines was modified under typical rainfed environments to identify photoperiod sensitive plants. The differences in flowering in consecutive plantings was one basis for determining photoperiod sensitivity. Sensitive lines flowered later than seeded in June but earlier in the December seeded nursery. Another method was by identifying lines that did not flower in a February seeded nursery. In a 1987 wet season study, days to flower was significantly reduced for photoperiod sensitive lines when seeded late. Flowering of insensitive lines, however, was not affected by late seeding. The tiller number of sensitive lines was not affected by late transplanting whereas in insensitive lines significant reduction in tiller number was observed. Plant height of sensitive lines decreased when seeded late but did not change for insensitive varieties. Late transplanting had no significant effect on plant height of sensitive lines as compared to insensitive lines. Improved photoperiod sensitive lines appear to have promise for rainfed lowland areas.
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