EFFECT OF BASIC VEGETATIVE PHASE, PHOTOPERIOD SENSITIVE PHASE AND YIELD PERFORMANCE ON RICE PARENT GENOTYPES AND F1 HYBRIDS IN NEUTRAL DAY LENGTH AND SHORT DAY LENGTH.

Short day conditions accelerated inflorescence initiation, headingor flowering in rice. In rice, the basic vegetative phase and photoperiod sensitive phase have contributed much to the understanding of the flowering behavior. The basic vegetative phase and photoperiod sensitive phase between parent genotypes and F1 hybrids was estimated and yield and yield component traits of parent genotypes and F1 hybrids were studied under short day length and neutral day length condition. Results showed that the basic vegetative phase of F1 hybrids (PSM x IR 24 and PSM x Thaichung 65) was longer than their parents. The photoperiod sensitive phase of PSM x IR 24 was 2 days longer than its male parent IR 24 and it was shorter than its female parent PSM. The photoperiod sensitive phase of PSM x Thaichung 65 was shorter than its female parent and male parents. The grain yield per plant of parent genotypes and F1 hybrids by giving short day treatment was lower than those by giving neutral day length. Our result indicated that short day treatment should be used to get early heading and synchronization for the varieties like Paw San Hmwe (PSM) which is late heading and photoperiod sensitive cultivar and F1 hybrids which are crossed with photoperiod sensitive and insensitive cultivars in breeding program.