Contribution of phytochrome a in the regulation of Sink capacity, starch biosynthesis, grain quality, grain yield and related traits in rice

Abstract

Low light (LL) intensity is a major abiotic constraint for grain yield in rice during wet season. Phytochromes principally perceive and respond to the red (R) and far-red (FR) region of light and regulate several aspects of photomorphogenesis. Most phytochromes are responsive under R-light and de-activated under FR-light, but phytochrome A (phyA) is biologically functional under both light conditions and plays an important role in the entire life cycle of the plant. Field experiment was conducted on the effect of LL intensity and subsequent exposure to natural light on japonica rice cultivar Akitokomachi (WT) and its phytochrome A mutant (phyA) to understand the role of phyA in the regulation of sink capacity, starch biosynthesis, grain quality, grain yield and related traits during wet season of 2018. Leaf soluble protein, photosynthetic CO2 assimilation rate, leaf non-structural carbohydrate content, sink capacity, grain quality traits such as hulling percentage, milling percentage, head rice recovery, water uptake, volume expansion, alkali spreading value, gel consistency, grain breadth, grain starch content, amylose content and yield attributes such as grain yield, panicle fertility, 1000-grain weight, panicle per plant, spikelets per panicle and grains per panicle along with the expression of starch biosynthesizing enzymes such as such as ADP-glucose pyrophosphorylase (AGPase), starch synthase III (SSIII) and granule bound starch synthase I (GBSSI) were reduced significantly in phyA than WT plants. However, % of grain chalkiness, length and amylopectin content increased in the phyA than WT plants. This study indicates the possible role of phyA in the regulation of source-sink communication, starch biosynthesis and grain quality in rice. Presumably, by participating in the control of several starch synthesizing pathways in the grains, phyA play a crucial role in the regulation of grain quality of rice which depends on the availability of the light intensity during grain-filling stage