Effects of High Temperature during Flowering Period on Seed Setting Rate and Its Relationship with Sink to Source Ratios and Flowering Habit of Mid-season Hybrid Rice

Abstract

From 2011 to 2013, under the condition of high temperature injury during heading stage designed by applying different sowing dates in the field and controlling the temperature in intelligent artificial climate chamber, the relationship high temperature resistance index(HTRI) with sink to source ratio and flowering habit in mid-season hybrid rice was studied with 50 hybrid combinations as tested materials. By using variance, correlation and regression analyses, the results showed that there were significant differences in HTRI among hybrid combinations. Ten of the combinations were tested to show a higher levels of seed setting rate and HIRI during flowering stage, including Mianxiangyou 576, Rongdaoyou 415, Xiangluyou 727, Mianyou 5240, Chuanguyou 202, Chuanyou 6203, Gangyou 169, Neixiangyou 5828, Chuanguyou 7329, and Jiangyou 126. There existed a significant relation between HTRI and carbohydrate supply level during flowering stage. The smaller the number of effective panicles of hybrid combinations was, the higher the spikelets per panicle and grain-leaf ratio would be, namely, the less the occupancy of photosynthetic source per spikelets would be. As a consequence, significantly negative correlation were observed between HTRI and grain-leaf ratio during flowering stage. The flowering ratio from 9:30 to 11:00 and chlorophyll content of leaf had a significantly positive correlation with HTRI respectively. Choosing the hybrid combinations with a larger number of effective panicles and early intensive anthesis and raising the level of chlorophyll content of leaf are the vital ways to enhance HTRI during heading stage.