Breeding targets for heat-tolerant rice varieties in Japan in a warming climate

Abstract

The breeding of heat-tolerant (HT) varieties is considered an effective adaptation measure to reduce the impacts of global warming on crops. However, little is known about how much heat tolerance needs to be attained in the breeding of HT varieties and by when the HT varieties should be introduced in a warming climate. Here, we assessed the effect of the introduction of HT rice varieties on the incidence of low-quality rice grains (chalky rice grain, CRG, as a result of high temperatures), and formulated a breeding target for rice in Japan, where high incidence of CRG is already a concern. Varieties with a 3 °C higher temperature tolerance should be bred and introduced until the 2040s under representative concentration pathways (RCPs) 2.6 and 8.5, in the pessimistic scenario, considering the uncertainties in climate models and an impact assessment model, which were large. In the median case, varieties with a 1 and 2 °C higher temperature tolerance are needed until the 2040s under RCPs 2.6 and 8.5, respectively. The findings revealed necessary efforts in breeding research and programs under conditions of global warming.

Effectiveness of heat tolerance rice cultivars in preserving grain appearance quality under high temperatures - A meta-analysis

“…The variable TaHD (cumulative temperature above the threshold value 26°C) was found to be a key factor, as reported elsewhere (Nishimori et al, 2020). Some researchers used a different base temperature for different genotypes, assuming that heat tolerance would raise the threshold temperature (Takimoto et al, 2019; Masutomi et al, 2022). We also examined this possibility by varying the base temperature for each HTR, but found that the best model fit was obtained with a base temperature of about 26 °C regardless of HTRs (Supplementary Figure 1).…”

“…A few studies have quantified the effects of air temperature and solar radiation on the occurrence of CG in specific conditions (Okada et al, 2011; Masutomi et al, 2015; Takimoto et al, 2019). Masutomi et al (2022) conducted a parameter sensitivity test to demonstrate the importance of CG dependence on temperature in the impacts of climate change on rice grain quality. It remains unclear, however, how much actual cultivars with high HTRs can alleviate the negative impacts of ongoing and projected climate change, which is necessary to develop concrete breeding targets in different regions and global warming levels.…”

“…A few studies have quantified the effects of air temperature and solar radiation on the occurrence of CG in specific conditions (Okada et al,2011;Masutomi et al,2015;Takimoto et al,2019). Masutomi et al (2022) Previous modelling studies often used parameters for individual cultivars, referred to as "genetic coefficients" (e.g., Mavromatis et al,2001), but lack of data availability frequently limits model applicability for a large number of cultivars. An option would be to use the same set of coefficients for all cultivars belonging to the same HTR groups, thus reducing the need for cultivarspecific coefficients.…”

Heat Tolerance and Genetic Diversity Analyses of Rice Accessions Using SSR Markers

“…Recently, agriculture production has incurred global warming impacts due to climate change (Dabi and Khanna, 2018;Ezin et al, 2022;Saud et al, 2022). The effects of global warming and arable land erosion are critical and need thorough attention worldwide for achieving food security (Masutomi et al, 2023). High temperatures adversely affect rice plants sensitive to extreme heat, especially at the flowering stage, which leads to sterility and low grain yield (Jagadish et al, 2010;Kinose et al, 2020).…”

“…Breeding of heat-tolerant cultivars validates an efficient approach to reducing the impact of global warming on rice and other major crops (Masutomi et al, 2023). Conventional rice breeding generally employs two main methods: the modified pedigree and recurrent selection (Villegas et al, 2018).…”