Variation in seed and seedling vigor in wet-seeded rice
1999
Kyu, H. | Amarante, S.T. | Gomez, A.A. | Samonte, H.P. | Robles, R.P. | Wade, L.J. (International Rice Research Inst., Los Banos, Laguna (Philippines))
In rainfed lowland, use of wet seeding in rice is increasing because of inadequate labor for transplanting and the need to increase cropping intensity. The establishment of a vigorous plant stand with adequate weed suppression is a major constraint to wet-seeded rice. A better understanding of variation in seed and seedling vigor and the implications for yield stability is needed. This paper examines variation in seed vigor in the germination cabinet of four varieties under four temperature regimes using two seed sources and two seed ages. Variation in seedling vigor is then examined using the same varieties and seed ages, but with four nutrient treatments in two water regimes in the greenhouse. In the germination cabinet, variation in seed vigor was dominated by the interaction between variety and temperature, with only 3 percent of the variation contributed by seed age. Germination of IR20 was less affected than those of other varieties at 15 deg C; germination was less in NSG19, slower in IR72, and slower and less in PSBRc 14. Model-based analysis was then used to examine base temperature and temperature responsiveness of the varieties in relation to seed lot. In the greenhouse, variation in seedling vigor was dominated by two interactions: between water and variety, and among water, nutrient and seed age. Seedling vigor was more severely reduced by water stress when N was applied as urea and when aged seeds were used. Water stress reduced the seedling vigor of NS19 and IR72 more severely. The results demonstrate a substantial capacity to manipulate seed and seedling vigor in wet-seeded rice. Subsequent experiments will examine the implications for yield performance and stability
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