Effects of a photoperiod sensitivity gene on morphological characters in rice

Abstract

Photoperiod sensitivity is an important breeding objective for rainfed rice ( Oryza sativa L.) areas with variable rainfall patterns. An understanding of how plant morphological characters are influenced by photoperiod sensitivity will assist in the selection for photoperiod-sensitive lines with improved yield. The influence of seeding dates on different plant characters was studied for pairs of photoperiod-sensitive and -insensitive near-isogenic lines. The reduction in plant height, internode number, flag leaf length, panicle length and grains per panicle was similar to percent reduction in the days to flowering in the sensitive lines at later seeding dates (i.e. shorter daylength). Therefore, the influence of the photoperiod sensitivity gene on these plant characters was most likely due to the reduction of growth duration under shorter daylength. The number of panicles per plant and spikelet sterility of photoperiod-sensitive lines increased in the last seeding date. Length of the last internode, 100-grain weight and grain yield per plant were not affected by seeding dates or growth duration. These results indicate that the introduction of a photoperiod sensitivity gene into high-yielding cultivars should not reduce yields. The effect of seeding dates on plant characters in photoperiod-sensitive cultivars, however, has implications in plant selection in breeding nurseries and evaluation of advanced breeding lines.