Vigor Of Rice Research Articles

Basic Studies on Utiliization of Hybrid Vigor in Rice : IV. Heterosis under Different Cultural Conditions

F1 hybrids of eleven cross combinations were tested under 4 different cultural conditions, i.e., standard fertilizer-level with standard planting density (plot A), standard fertilizer-level with high planting density (plot B), high fertilizer-1evel with standard planting density (plot C), and high fertilizer-1evel with high planting density (plot D). The F1 hybrids of Norin 22×Araki, Suzu-nari×Zenith CI 7787 and Aikoku×Zenith CI 7787 showed marked heterosis in grain yield. Within the scope of the present experiment, the best cross combination was Suzunari × Zenith CI 7787 which significantly outyielded the highest yielding variety, Benisengoku. It was concluded that practical utilization of heterosis would be possible in rice, if hybrid seeds could be economically produced. In grain yield, spikelet number per panicle and culm length, the degrees of heterosis obtained under the four conditions were signifi-cantly correlated with one another.

The Basic Studies on Utilization of Hybrid Vigor in Rice. : I. The Degree of Heterosis and its Phenomenon

Thirty-three F1 hybrids of rice were examined to discuss the degree of heterosis and its phenomenon. The degree of heterosis was high in grain yield and number of spikelets per panicle. In grain yield 8 of 33 combinations exceeded their higher parent. Norin 22×Araki, which had the highest combining ability, exceeded higher parent by 50%.

Clonal Propagation as a Practical Means of Exploiting Hybrid Vigour in Rice

MARKED vigour has been observed in rice by a number of workers in the F1 generation of many crosses in respect of height, number of ear-bearing tillers, number of spikelets and yield. But it has not been possible to exploit this phenomenon, as hybrid seed production is a limiting factor in this crop. One method of taking advantage of the hybrid vigour might be to multiply the F1 plants vegetatively. The technique of vegetative propagation in rice varieties which possess perennating habit has been studied intensively at the Central Rice Research Institute from 1959 onwards. Its value has now been established as an aid to increased rice production. The great potentiality of this technique is shown by the fact that all the clones to be planted in an acre have been derived by repeated multiplication of the tillers produced from two to three stubbles (clones) of the preceding crop. The number of repeated multiplication (3–6 times) depends on the nature of rice variety utilized. The increased yield, obtained by this procedure, ranged from 17 to 61 per cent, as compared with crops raised from normal rice seedlings.