Mapping QTLs for cold tolerance at germination and the early seedling stage in rice (Oryza sativaL.)

Abstract

Cold tolerance is an important breeding target in rice production. We studied quantitative trait loci (QTLs) controlling cold tolerance at germination (CTG) and early seedling (CTS) stages, using recombinant inbred lines derived from a japonica × indica cross. CTG was evaluated based on the percentage rate of germination at 15 °C for 12 days after pre-incubation of imbibed seeds at 20 °C for 2 days. For CTS, seven-day-old seedlings grown at 25 °C were subjected to two consecutive periods of three-day cold stress at 4 °C with an intervening eight-day recovery at 25 °C. CTS evaluation was according to an arbitrary five-point rating system at the fifth day of recovery after each stress period. No correlations were found between CTG and CTS, while a weak correlation was detected between CTS after the first and second stress. By the composite interval mapping, five QTLs for CTG explaining 5.7%–9.3% of the total phenotypic variance (PVE) and nine for CTS with PVE of 5.8%–35.6% were detected. Only one of these QTLs was common, indicating growth-stage specificity of cold tolerance. Four of the five QTLs after the second cold stress were different from the ones after the first cold stress. Analysis of variance test showed significant interactions between alleles at the QTL sites and the two stress conditions with respect to the mean CTS scores. A possible involvement of cold acclimation and usefulness of japonica germplasms in breeding for cold tolerance in indica rice was discussed.

Expression Profiles of Stress Responsive Genes in Rice (Oryza Sativa L.) Under Abiotic Stresses

“…two paralogs each of OsDREB1 and OsAldh2 showed a similar response to low temperature. in a previous study, we showed that both OsDREB1A and OsDREB1B responded more strongly to the low temperature stress than to the other three stresses and that a low temperature tolerant japonica cultivar accumulated more abundant OsDREB1 transcripts than a sensitive indica cultivar (21). These results agree with the findings that CBF/ DREB1 transcription factors are key regulators of the cold signal transduction in various plant species (6,7,13,15,27,30,31,33,35).…”

Identification of main-effect quantitative trait loci (QTLs) for low-temperature stress tolerance germination- and early seedling vigor-related traits in rice (Oryza sativa L.)

“…Compared with other cereal crops, rice is more sensitive to low-temperature stress (LTS)/cold stress (CS) as it has originated from tropical regions (Saito et al 2001;Hasanuzzaman et al 2009;Zeng et al 2017). In the temperate, tropical, and even subtropical rice-growing regions, cold stress adversely affects the rice crop throughout various growth stages, from germination to harvesting, and causes significant yield losses because of poor germination and seedling establishment, stunted growth pattern, non-vigorous plants, vast spikelet sterility, delay in flowering, and lower grain filling (Ranawake et al 2014;Martínez-Eixarch and Ellis 2015;Schläppi et al 2017;Shakiba et al 2017;Liang et al 2018;Xiao et al 2018;Najeeb et al 2019 (unpublished). Therefore, to minimize these yield losses, particularly in cold-affected regions, it is imperative to identify and develop high-yielding rice cultivars showing tolerance of LTS.…”

“…Uniform fast seed germination and early seedling vigor are important traits for seedling establishment. However, most rice varieties are severely affected during early seedling growth when the temperature falls below 17°C (Andaya and Mackill 2003a;Lou et al 2007;Ranawake et al 2014;Singh et al 2016). For better and more stable stand establishment, especially under direct-seeding conditions in temperate and sub-temperate regions, cold tolerance at germination is a pre-requisite (Teng et al 2001;Cruz and Milach 2004;Wang et al 2016a).…”

Deployment of cold tolerance loci from Oryza sativa ssp. Japonica cv. ‘Nipponbare’ in a high‐yielding Indica rice cultivar ‘93‐11’

“…Because high tolerance to abiotic stress has been shown to cause yield penalty under normal conditions due to a growth-tolerance trade-off (Deng et al, 2017;Joshi et al, 2017), we further investigated several yield-related traits for 93-11(qCTS11.1&2 NP ) in the field under normal cultivation conditions. Compared with '93- we identified a total of seven loci associated with cold tolerance in a Japonica rice cultivar, six of which were previously reported to be associated with seedling cold tolerance in other Japonica cultivars (Andaya & Tai, 2006;Han et al, 2007;Ranawakea et al, 2014;Ma et al, 2015;Mao et al, 2015; Table 1), suggesting a conserved mechanism of cold tolerance in Japonica rice subspecies. Moreover, two of these QTLs were found at positions coincident with the qCTS7 and qCTS11 regions identified in Dongxiang wild rice (Oryza rufipogon Griff.…”

“…QTLs have also been identified in other Japonica or wild rice accessions (Mao et al, 2015;Ranawakea et al, 2014). However, to date, no QTL has been fine mapped or cloned in the region of qCTS11.…”