Phenotypic Variation and Selection for Cold-Tolerant Rice (Oryza sativa L.) at Germination and Seedling Stages

Abstract

Owing to its origin in tropical and subtropical areas, rice is susceptible to cold stress. Low temperatures at the germination and seedling stages can result in seed loss, a delayed transplanting period, and lower final yield. In this study, 181 rice varieties from around the world were investigated for cold tolerance at the germination and seedling stages. At the germination stage, the responses of different rice varieties were examined based on the germination index, coleoptile length, and radicle length at low (13 °C) and control temperatures (25 °C). Significant variations in the germination index, coleoptile length, and radicle length were observed among varieties. Low temperature significantly decreased germination ability, and coleoptile and radicle growth in the studied varieties. At the seedling stage, cold tolerance of the rice varieties was evaluated based on the leaf color score under natural low temperature. Similar to the germination stage, at the seedling stage, significant variation in root and shoot growth was observed in the response of rice varieties to low temperature conditions. Based on the results from both the germination and seedling stages, two varieties (Hei-Chiao-Chui-Li-Hsiang and Ta-Mao-Tao) were selected as the best cold-tolerant varieties. Our results also indicate the benefits of warming treatments to protect rice seedlings from low temperature conditions.

Morpho-Physiological Characterization of Diverse Rice Genotypes for Seedling Stage High- and Low-Temperature Tolerance

“…It was observed that among the 19 moderately cold-tolerant genotypes, most of the genotypes were indica types, and among the 8 very highly cold-tolerant genotypes, most of them belonged to the japonica subspecies (Table 1). This indicated that japonica rice genotypes are more tolerant of low temperatures and perform better under such conditions, similar to other studies [12,36,60]. The lowest value of CLTRI was recorded in CT6510-24-1-2 (an indica line, 6.63), whereas RU1504114 (a japonica line) showed the highest value (11.09).…”

“…Attaining high yield under suboptimal growing conditions is one of the main challenges of this century. It is now clear that the emphasis on stress tolerance in plants has to be addressed from the vegetative to grain-filling stages because of their greater sensitivity to environmental variations [12,16,23]. Current constraints caused by extreme temperatures related to yield losses at the reproductive stage have gained much attention among researchers.…”

“…More than 15 million ha of rice areas suffer from a low-temperature injury at one or more growth stages [10,11]. For example, rice cultivation in the northern part of Vietnam is hampered by cold temperatures at the germination and seedling stages [12,13]. On the other hand, high precipitation, coupled with a colder climate, affects 7% of Africa's total rice area [14].…”

“…For instance, extreme temperatures can affect rice growth and development processes, including germination, emergence and seedling establishment, and reproductive and grain-filling stages. The low (cold) temperature in the vegetative stage can cause slow growth; reduced seedling vigor [12,17], number of seedlings, and tillering [18]; and increased plant mortality [11,19]. Cold tolerance at the early stages is essential to obtain the optimum plant population [20] required for successful crop production.…”

ATP Hydrolysis Determines Cold Tolerance by Regulating Available Energy for Glutathione Synthesis in Rice Seedling Plants

“…It has been reported that cold stress occurring at reproductive phase can result in a large reduction in grain yield (Thakur et al 2010;Ghadirnezhad and Fallah 2014). Additionally, slow seedling development, yellowing, withering, reduced tillering and stunted growth are always observed under cold stress at the seedling stage (Su et al 2010;Bonnecarrère et al 2011;Han et al 2017;Cong Dien and Yamakawa 2019). As a result, the cultivated area of early rice and double-season late rice is significantly reduced in China (Sun and Huang 2011;Yu et al 2012;Wang et al 2019).…”