Importance of anther dehiscence for low-temperature tolerance in rice at the young microspore and flowering stages

Low temperature, particularly during the reproductive stage in rice (Oryza sativa L.), leads to reduced fertility and yield and is a major constraint faced in temperate rice ecology. The floral trait anther dehiscence length has not been quantified in relation to low-temperature tolerance in rice. Two controlled-temperature glasshouse experiments evaluated 120 genotypes from BC1F6 recombinant inbred lines when exposed to low air temperature at the booting (young microspore) and flowering stages. Genotypic differences existed for spikelet sterility (SS) after low-temperature exposure at booting and flowering stages, and a significant positive correlation (R2=0.22**) was found between SS of individual genotypes at booting and flowering stages. Number of dehisced anthers had the highest correlation with SS, and accounted for 58% and 44% of variation in SS with exposure to low temperature at booting and flowering, respectively. Anther dehiscence length and number of dehisced anthers were highly correlated (r=0.90**). After low-temperature exposure at booting, pollen number in the anther as well as the pollen’s capacity to germinate effectively further differentiated low-temperature-tolerant and -susceptible genotypes. Positive relationships (r=0.56** and 0.46*) between SS in the glasshouse and in field experiments in 2015 and 2016 seasons, respectively, provided validation of the phenotypic glasshouse screening methods utilised for low-temperature tolerance in relation to target production environments. This repeatable phenotyping system in combination with improved understanding of underlying floral traits will lead to increased efficiency in breeding for low-temperature tolerance in rice.