Application of β-triketone herbicides improves the purity of two-line hybrid rice seed without compromising yield

Abstract

Abstract Two-line hybrid rice based on Photoperiod/thermo-sensitive genic male sterile (P/TGMS) lines has been developed and applied widely in agriculture due to the freedom in making hybrid combinations, less difficulty in breeding sterile lines, and simpler procedures for breeding and producing hybrid seed. However, there are certain risks associated with hybrid seed production; if the temperature during the P/TGMS fertility-sensitive period is lower than the critical temperature, seed production will fail due to self-pollination. In a previous study, we found that the issue of insufficient purity of two-line hybrid rice seed could be initially addressed by using the difference in tolerance to β-triketone herbicides (bTHs) between the female parent and the hybrid seeds. In this study, we further investigated the types of applicable herbicides, application methods, application time, and the effects on physiological and biochemical indexes and yield in rice. The results showed that this method could be used for hybrid purification by soaking seeds and spraying plants with the bTH benzobicylon (BBC) at safe concentrations in the range of 37.5-112.5 mg/L, and the seeds could be soaked in BBC at a treatment rate of 75.0 mg/L for 36–55 h without significant negative effects. The safe concentration for spraying in the field is 50.0-400.0 mg/L BBC at the three-leaf stage. The two methods of hybrid seed purification can reach 100% efficiency without compromising the nutritional growth and yield of hybrid rice. Unlike BBC, Mesotrione (MST) can only be sprayed to achieve hybrid purification at concentrations between 10.0 and 70.0 mg/L without affecting yield. bTH stress significantly increases the index of the reactive oxygen species (ROS) hydrogen peroxide (H2O2) in the hybrid LLY942 in the safe concentration range. The peroxidase (POD) enzyme activity showed a significant upward trend with increasing herbicide concentration, which kept the content of the lipid peroxide malondialdehyde (MDA) within a certain range that did not affect the normal growth of the rice hybrids. Our study establishes a foundation for the application of the bTH seed purification strategy and showed that it is the most economical, convenient, and effective way to improve the purity of two-line hybrid rice seeds.