Morphological and physiological properties of hybrid rice seeds with top-gray chalkiness

Yong Chen,Yihong Hu,Aiyu Liu,Jianliang Tang,Chenzhong Jin,Hui Yuan,Hao Zhang

doi:10.1590/1678-4499.20200228

Yong Chen, Yihong Hu + Show 5 more

Open Access

https://doi.org/10.1590/1678-4499.20200228

Copy DOI

Abstract

ABSTRACT Hybrid rice seeds from sterile lines have displayed a new type of heavy chalkiness in the subtropical zone of China in recent years, which was named top-gray chalkiness, resulting in a lower quality of hybrid rice seeds in large-scale production. In this study, the morphological characteristics of the chalky hybrid rice seeds were investigated, the microscopic structures of their chalky parts observed, the α-amylase activit and relative nutrient content analyzed, and the germination indexe and microorganism populations of the chalky hybrid seeds determined. The results revealed that top-gray chalkiness in hybrid rice seeds originated from the top site of the grain, and that the chalky part was probably infected by bacteri and fungi to form a gray colo and which further resulted in a lower germination rat and germination potential. This observed chalkiness in rice seeds differed from the previously reported rice chalkiness categories both in the occurrence positio and color. Besides, the amylopectin content declined in the chalky par and the protein content in the chalky part increased as compared to the normal seeds. This research could provide technical support for the hybrid rice breeding enterprises during the breeding of hybrid rice seeds in large-scale production.

Highlights

Rice (Oriza sativa L.) is the main staple food crop for more than 50% of the people all over the world
The results revealed that top-gray chalkiness in hybrid rice seeds originated from the top site of the grain, and that the chalky part was probably infected by bacteria and fungi to form a gray color and which further resulted in a lower germination rate and germination potential
The early research showed that the gibberellin acids (GA)-affinity receptors, which were polypeptides or proteins, were located in the plant plasma membranes (Walker et al 1994; Lovegrove et al 1998), whereas latter research indicated that GA signals were perceived in the plant nuclei mediated by a protein with a DELLA domain in plants (Yano et al 2015; Ueguchi-Tanaka et al 2007; Hartweck and Olszewski 2006)

Summary

Introduction

Rice (Oriza sativa L.) is the main staple food crop for more than 50% of the people all over the world. High temperature is a key factor responsible for the formation of chalky grains during the rice ripening period, resulting in a decrease of production and lower quality of products (Nakata et al 2017). High temperatures induce rice α-amylases expression which are strictly regulated by gibberellin acids (GA) to control the chalky grain process, loosen the package of starch granules in the endosperm, and form numerous pits on the surface of these starch granules (Ishimaru et al 2009). Guo et al (2011) reported a major quantitative trait locus for the percentage of chalky grains, and Ishimaru et al (2009) reported a different mechanism for chalkiness formation: The starch accumulated faster around the center of the endosperm than in the lateral part due to high-temperature stress, resulting in a loosened starch structure in the white-core chalky rice during the rice ripening period The ratio of nitrogen to potassium could regulate the rice chalkiness ratio (Bridgemohan and Bridgemohan 2014). Guo et al (2011) reported a major quantitative trait locus for the percentage of chalky grains, and Ishimaru et al (2009) reported a different mechanism for chalkiness formation: The starch accumulated faster around the center of the endosperm than in the lateral part due to high-temperature stress, resulting in a loosened starch structure in the white-core chalky rice during the rice ripening period

Objectives

Methods

Results

Discussion

Conclusion