Acquired Thermo‐Tolerance and Trans‐Generational Heat Stress Response at Flowering in Rice

Abstract

In rice, pre-exposure to sublethal treatment followed by harsh lethal treatment is known to improve tolerance of different abiotic stresses at the vegetative stage within and across generations. Our major aim was to test the phenomenon of thermo-tolerance at flowering across (trans)-generations and within generation using rice cultivars contrasting for heat stress tolerance at flowering. To test trans-generational response, plants were exposed to higher temperature at flowering stage and seeds obtained from previous generations were exposed to heat stress during flowering, which recorded significantly lower fertility when exposed to the same degree of stress in their subsequent generations. A pre-acclimation to moderately high acclimating temperatures imposed over three different durations during the vegetative and initial reproductive stage showed positive response in the tolerant N22, particularly under severe heat stress (40°C). This finding indicates the possibility of acquiring ameliorative thermo-tolerant mechanisms at anthesis, restricted to tolerant genetic backgrounds to combat subsequent harsh conditions within the same generation. However, trans-generational memory was ineffective in mitigating spikelet sterility losses in both tolerant and susceptible backgrounds. Rice is extremely sensitive to heat stress during flowering; hence, similar exercise across other crops of interest needs to be carried out before generalizing conclusions.

Individual and Combined Effects of Booting and Flowering High-Temperature Stress on Rice Biomass Accumulation

“…Additionally, the heat tolerance of Wuyunjing-24 has also been reported in earlier studies [12,15]. So, these results are in line with [34], which suggested that the strategy of mitigating heat stress could be more prevalent in the tolerant genetic background such as Wuyunjing-24 in this study than in sensitive backgrounds.…”

“…The impacts of high-temperature stress on biomass accumulation and yield formation in rice are not only reliant on the high-temperature level, duration, and growth stage but also the frequency of its incidence. Subjecting plants to high-temperature stress twice (pre-exposure to a sub-lethal high temperature at vegetative and early reproductive stages, accompanied by severe lethal treatment at the flowering stage) can improve the heat resistance of rice and may partially compensate for the adverse effects of high temperature [34]. Consequently, yield, biomass accumulation, and photosynthetic property parameters under heat stress at booting, flowering, and combined (booting + flowering) stages were analyzed to compare the effects of single-stage heat stress with combined stages of heat stress.…”

“…Therefore, it is important for the production of heat-tolerant varieties to consider how rice plants adapt to heat stress. Attempts have been made to establish thermo-tolerance in the plant by pre-treatment using a high sub-lethal temperature prior to a lethal temperature [33][34][35]. However, few attempts have been made using pre-treatment with accompanying lethal followed by lethal temperatures in rice.…”

Dynamic Transcriptome Analysis of Anther Response to Heat Stress during Anthesis in Thermotolerant Rice (Oryza sativa L.)

“…Rice (Oryza sativa L.) is one of the most important and widely cultivated crops for global food security. However, rice farming is constantly subjected to various abiotic and biotic stresses; heat stress is a major abiotic stress that significantly affects rice growth and development [1,2]. It is estimated that rice grain yields decline by 10% for each 1 • C increase in minimum temperature during the growing season [3].…”

“…Rice production is particularly susceptible to high temperature, especially during the flowering and grain-filling stages, which directly affects grain yields and quality [2,5]. Even a short period of high temperature during these stages, such as >35 • C for 5 d at anthesis, could cause sterility [6,7].…”