Heat Tolerance In Rice Research Articles

Effects of High Air Temperature in the Summer of 2010 on the Kernel Quality of the Heat-tolerant Rice Cultivar ‘Genkitsukushi’

Effects of High Air Temperature in the Summer of 2010 on the Kernel Quality of the Heat-tolerant Rice Cultivar ‘Genkitsukushi’

Identifying Heat Tolerant Rice Genotypes under Field Conditions

Identifying Heat Tolerant Rice Genotypes under Field Conditions

Mapping QTL for heat tolerance at flowering stage in rice using SNP markers

With 3 figures and 5 tablesAbstractTo identify quantitative trait loci (QTL) controlling heat tolerance in rice, the progeny of BC1F1 and F2 populations derived from an IR64 × N22 cross were exposed to 38/24°C for 14 days at the flowering stage, and spikelet fertility was assessed. A custom 384‐plex Illumina GoldenGate genotyping assay was used to genotype the F2 and selected BC1F1 plants. Four single nucleotide polymorphisms were associated with heat tolerance in the BC1F1 population using selective genotyping and single marker analysis, and four putative QTL were found to be associated with heat tolerance in the F2 population. Two major QTL were located on chromosome 1 (qHTSF1.1) and chromosome 4 (qHTSF4.1). These two major QTL could explain 12.6% (qHTSF1.1) and 17.6% (qHTSF4.1) of the variation in spikelet fertility under high temperature. Tolerant allele of qHTSF1.1 was from the susceptible parent IR64, and that of qHTSF4.1 was from tolerant parent N22. The effect of qHTSF4.1 on chromosome 4 was confirmed in selected BC2F2 progeny from the same IR64 × N22 cross, and the plants with qHTSF4.1 showed significantly higher spikelet fertility than other genotypes.

Identification for Heat Tolerance in Backcross Recombinant Lines and Screening of Backcross Introgression Lines with Heat Tolerance at Milky Stage in Rice

The present study aimed at breeding new rice germplasms with similar genome but significantly differed in heat tolerance during the grain filling stage. A total of 791 BC 1F 8 backcross recombinant lines, derived from the cross of Xieqingzao B / N 22 // Xieqingzao B, were used as materials. Each rice line was separated evenly into two groups, and the heat tolerance of all rice lines were evaluated at natural high temperature in fields. The rice lines with heat tolerant index higher than 90% or lower than 40% were selected to compare the phenotypic characters and further identify heat tolerance at the early milky stage in a phytotron. Rice lines with similar phenotypic characters but significantly differed in heat tolerance at the milky stage were analyzed by 887 simple sequence repeat markers that were evenly distributed on the 12 rice chromosomes. In the result, 12 (6 pairs) rice lines with similar phenotypic characters but significantly differed in heat tolerance at the milky stage were obtained. Molecular marker analysis indicated that the genomic polymorphism between 703T and 704S was the smallest in the 6 pairs of rice lines, with only 16 polymorphic sites, including 22 different alleles. The application of these two backcross introgression rice lines for future study on the mechanisms of heat tolerance in rice at the milky stage will be theoretically beneficial in reducing the interference caused by genetic differences from experimental materials.

Heat tolerance in rice mutants is associated with reduced accumulation of reactive oxygen species

Four mutants induced by ethylmethane sulphonate (N22-H-dgl56, N22-H-dgl101, N22-H-dgl162 and N22-H-dgl219) with conspicuous dark green leaves were identified in the drought and heat-tolerant rice cultivar Nagina22 (N22), when screened under prolonged drought and heat conditions in field. During dark-induced senescence, these mutants maintained higher chlorophyll and carotenoid contents, and photochemical efficiency of photosystem 2 in comparison with N22. Following heat treatment, these mutants accumulated less reactive oxygen species (assayed by histochemical staining for H2O2 and superoxide radicals) and maintained higher chlorophyll content than N22.

Quantitative Trait Loci Associated with Pollen Fertility under High Temperature Stress at Flowering Stage in Rice ( Oryza sativa)

High temperature stress (HTS), an increasingly important problem in rice production, significantly reduces rice yield by reducing pollen fertility and seed setting rate. Breeding rice varieties with tolerance to HTS at the flowering stage is therefore essential for maintaining rice production as the climate continues to become warm. In this study, two quantitative trait loci (QTLs) underlying tolerance to HTS were identified using recombinant inbred lines derived from a cross between an HTS-tolerant rice cultivar 996 and a sensitive cultivar 4628. Pollen fertility was used as a heat-tolerance indicator for the lines subjected to HTS at the flowering stage in field experiments. Two QTLs that affected pollen fertility, qPF4 and qPF6, were detected between RM5687 and RM471 on chromosome 4, and between RM190 and RM225 on chromosome 6, by using the composite interval mapping (CIM) analysis. The two QTLs explained 15.1% and 9.31% of the total phenotypic variation in pollen fertility, and increased the pollen fertility of the plants subjected to HTS by 7.15% and 5.25%, respectively. The positive additive effects of the two QTLs were derived from the 996 alleles. The two major QTLs identified would be useful for further fine mapping and cloning of these genes and for molecular marker-assistant breeding of heat-tolerant rice varieties.

登熟期における高温耐性水稲品種「元気つくし」の乾物動態および炭水化物供給能からみた生育特性

登熟期における高温耐性水稲品種「元気つくし」の乾物動態および炭水化物供給能からみた生育特性

Proteomics of rice in response to heat stress and advances in genetic engineering for heat tolerance in rice

Rice is the most important food crop worldwide. Global warming inevitably affects the grain yields of rice. Recent proteomics studies in rice have provided evidence for better understanding the mechanisms of thermal adaptation. Heat stress response in rice is complicated, involving up- or down-regulation of numerous proteins related to different metabolic pathways. The heat-responsive proteins mainly include protection proteins, proteins involved in protein biosynthesis, protein degradation, energy and carbohydrate metabolism, and redox homeostasis. In addition, increased thermotolerance in transgenic rice was obtained by overexpression of rice genes and genes from other plants. On the other hand, heterologous expression of some rice proteins led to enhanced thermotolerance in bacteria and other easily transformed plants. In this paper, we review the proteomic characterization of rice in response to high temperature and achievements of genetic engineering for heat tolerance in rice.

Quantitative trait loci associated with seed set under high temperature stress at the flowering stage in rice (Oryza sativa L.)

High temperature stress (HTS), an increasingly important problem in rice production, significantly reduces rice yield by reducing seed set percentage (SSP). Breeding rice varieties with tolerance to HTS at the flowering stage is therefore essential for maintaining rice production as the climate continues to warm. In this study, two quantitative trait loci (QTL) underlying tolerance to HTS were identified using the recombinant inbred lines (RILs) derived from a cross between the HTS-tolerant rice cultivar 996 and the sensitive cultivar 4628. SSP was used as the heat-tolerance indicator for the lines, which were subjected to HTS at the flowering stage in both field and growth chamber experiments. Two major QTL that affected SSP in both conditions were detected in the interval between RM5687 and RM471 on chromosome 4, and between RM6132 and RM6100 on chromosome 10. The QTL located on chromosome 4 explained 21.3% in field and 25.8% in growth chamber of the total phenotypic variation in SSP, and increased the SSP of plants subjected to HTS by 9.1% in field and by 9.3% in growth chamber. The second QTL located on chromosome 10 explained 11.5% in field and 11.6% in growth chamber of the total phenotypic variation in SSP, and increased the SSP of plants subjected to HTS by 7.2% in field and 7.0% in growth chamber. The positive additive effects of the two QTL were derived from the 996 alleles. The two major QTL identified in this study could be useful for further fine mapping and cloning of these genes and for molecular marker-aided breeding of heat-tolerant rice cultivars.

Bulked Segregant Analysis to Detect QTL Related to Heat Tolerance in Rice ( Oryza sativa L.) Using SSR Markers

The study was undertaken to assess the genetic effect of quantitative trait loci (QTLs) conferring heat tolerance at flowering stage in rice. A population consisting of 279 F 2 individuals from the cross between 996, a heat tolerant cultivar and 4628, a heat-sensitive cultivar, was analyzed for their segregation pattern of the difference of seed set rate under optimal temperature condition and high temperature condition. The difference of seed set rate under optimal temperature condition and high temperature condition showed normal distribution, indicating the polygenic control over the trait. To identify main effect of QTL for heat tolerance, the parents were surveyed with 200 primer pairs of simple sequence repeats (SSR). The parental survey revealed 30% polymorphism between parents. In order to detect the main QTL association with heat tolerance, a strategy of combining the DNA pooling from selected segregants and genotyping was adopted. The association of putative markers identified based on DNA pooling from selected segregants was established by single marker analysis (SMA). The results of SMA revealed that SSR markers, RM3735 on chromosome 4 and RM3586 on chromosome 3 showed significant association with heat tolerance respectively, accounted for 17 and 3% of the total variation respectively. The heat tolerance during flowering stage in rice was controlled by multiple gene. The SSR markers, RM3735 on chromosome 4 and RM3586 on chromosome 3 showed significant association with heat tolerance respectively, accounted for 17 and 3% of the total variation respectively. The two genetic loci, especially for RM3735 on chromosome 4, can be used in marker-assistant-selected method in heat tolerance breeding in rice.

Effect of High Temperature During Heading and Early Filling on Grain Yield and Physiological Characteristics in Indica Rice

To disclose the physiological mechanism of heat tolerance in rice ( Oryza sativa L.), this article investigated the pollen development, yield components, and some physiological parameters of indica rice genotypes under high temperature (HT) treatment during heading and early filling stages. Two heat-sensitive genotypes, Shuanggui 1 and T219, and 2 heat-tolerant genotypes, Huanghuazhan and T226, were used in pot experiments with HT treatment (mean temperature during the day above 33ºC) and natural temperature (control) treatments from 0 to 10 d and 10 to 20 d after heading. Compared with the control, the HT treatment significantly reduced the rates of pollen and spikelet fertility in the heat-sensitive genotypes, but had no significant effects on the heat-tolerant genotypes. Seed-setting rate decreased significantly in the heat-sensitive genotypes under HT, leading to a significant reduction in grain yield. Moreover, the reductions of yield of heat-sensitive genotypes were greater in the HT treatment at heading stage (0–10 d after heading) than in the HT treatment at early grain-filling stage (11–20 d after heading). However, the heat-tolerant genotypes were in minor influence under the HT treatment. The activities of enzymes from rice leaves, which were involved in antioxidant system, significantly increased in the heat-tolerant genotypes when treated with HT, whereas they were maintained at relative high levels in the control. The ATPase activity in grains was significantly reduced in the heat-sensitive genotypes, but slightly influenced in the heat-tolerant genotypes. The high temperature increased leaf temperature and malondialdehyde content in leaves, and reduced root activity and photosynthetic rate of flag leaf in all genotypes. However, variation range was much less in heat-tolerant genotypes than in heat-sensitive genotypes. The results suggest that the relative high yield in heat-tolerant genotypes under high-temperature stress is associated with low leaf temperature, high root activity, and the high levels of ATPase activity in grains, photosynthetic rate, and activities of antioxidant enzymes in leaves.

Changes in NMR Relaxation of Rice Grains, Kernel Quality and Physicochemical Properties in Response to a High Temperature after Flowering in Heat-Tolerant and Heat-Sensitive Rice Cultivars

Rice productivity is related to the ability of plants to adapt to heat stress. The heat-tolerant cultivars ‘Nikomaru’ and ‘Chikushi 64’ and heat-sensitive cultivar ‘Hinohikari’ were grown at 30ºC and 25ºC for 49 days after flowering. At 30ºC, only a few white immature kernels were produced in ‘Nikomaru’ and ‘Chikushi 64’, but about 22% of grains had immature kernels in ‘Hinohikari’. The high temperature(30ºC) caused no significant changes in grain dry weight, water content, and the NMR T1 value during the early ripening stage in ‘Nikomaru’ and ‘Chikushi 64’. It also did not affect grain development, especially with respect to the nucellar epidermis, in ‘Nikomaru’ and ‘Chikushi 64’, but caused clear cessation of development of the nucellar epidermis at 14 days after flowering in ‘Hinohikari’. In addition, high temperature decreased the amylose content and increased hardnessvs. adhesion ratio of cooked rice in both ‘Nikomaru’ and ‘Chikushi 64’ resulting a softer, less sticky texture, but not in ‘Hinohikari’. The maximum viscosity and breakdown values were increased, and final viscosity decreased at 30ºC in all three cultivars. These results suggested that starch in the endosperm of grains changed from a fluid state to a doughy state more slowly in ‘Nikomaru’ and ‘Chikushi 64’ than in ‘Hinohikari’, in which the water content and NMR relaxation time decreased, and transported assimilates accumulated slowly during grain development.

高温耐性水稲品種「にこまる」の良好な登熟には穂揃期の茎のＮＳＣが多いことが貢献している

高温耐性水稲品種「にこまる」の良好な登熟には穂揃期の茎のＮＳＣが多いことが貢献している