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Direct seeding is employed to circumvent the labor-intensive process of rice (Oryza sativa) transplantation, but this approach requires varieties with vigorous low-temperature germination (LTG) when sown in cold climates. To investigate the genetic basis of LTG, we identified the quantitative trait locus (QTL) qLTG11 from rice variety Arroz da Terra, which shows rapid seed germination at lower temperatures, using QTL-seq. We delineated the candidate region to a 52-kb interval containing GENERAL REGULATORY FACTOR14h (GF14h) gene, which is expressed during seed germination. The Arroz da Terra GF14h allele encodes functional GF14h, whereas Japanese rice variety Hitomebore harbors a 4-bp deletion in the coding region. Knocking out functional GF14h in a near-isogenic line (NIL) carrying the Arroz da Terra allele decreased LTG, whereas overexpressing functional GF14h in Hitomebore increased LTG, indicating that GF14h is the causal gene behind qLTG11. Analysis of numerous Japanese rice accessions revealed that the functional GF14h allele was lost from popular varieties during modern breeding. We generated a NIL in the Hitomebore background carrying a 172-kb genomic fragment from Arroz da Terra including GF14h. The NIL showed superior LTG compared to Hitomebore, with otherwise comparable agronomic traits. The functional GF14h allele from Arroz da Terra represents a valuable resource for direct seeding in cold regions. Author summary: Rice serves as a fundamental crop sustaining over half of the global population. With the rapid growth of the world's population, it will become increasingly important to improve rice productivity. On the other hand, the aging of rice farmers in Japan has resulted in a constant labor shortage. To address this, direct seeding, in which seeds are sown directly in rice fields without going through the most labor-intensive part of the rice cultivation process, i.e., seedling production and transplanting, has been recommended. However, prevalent elite rice varieties are known to be unsuitable for direct seeding due to their poor seed germination ability under low-temperature conditions. In this study, we show for the first time that GF14h gene from the Portuguese variety Arroz da Terra improves seed germination at low temperatures (LTG). In addition, a novel cross-bred line was generated by introducing the GF14h-containing genomic segment from Arroz da Terra into Hitomebore, a widely cultivated variety in northern Japan. This line is expected to be used as a pre-breeding material to enhance LTG. This study will provide a genetic basis for LTG and contribute to basic and applied research progress. [ABSTRACT FROM AUTHOR]

Isolation of an adequate quantity of high-quality RNA is a crucial step in gene expression analysis. Difficulties in sampling and RNA extraction of field-grown crops, especially from roots, are substantial obstacles to understanding actual gene expression in the field. We examined the effectiveness of the RNA extraction method (FRP) using pot- and field-grown soybean roots. High quantity and quality of total RNA could extract by the FRP method from both pot- and field-grown soybean roots at different growth stages. To determine the influence of root washing during the sampling process, roots were washed with water for 5 s, 1 min, and 5 min, then analyzed for aquaporin gene expression levels. Root washing for 5 min affected gene expression of some aquaporins. To obtain RNA that reflects the correct gene expression profile, it is necessary to minimize the effects of the sampling process. [ABSTRACT FROM AUTHOR]

Intraspecific variation of response to elevated CO2 (eCO2) is a powerful option to improve crop productivity under the future climate. We evaluated genotypic variation in the biomass response to eCO2, at 200 μmol/mol above ambient CO2 (aCO2) 33 to 38 days after transplanting in 7 African rice (Oryza glaberrima Steud.) genotypes and 10 Asian rice (Oryza sativa L.) genotypes during a 3‐year experiment. A comparison at vegetative growth at aCO2, African rice genotypes showed 60% to 76% greater biomass than Asian rice genotypes. eCO2 significantly increased biomass of both species, and the magnitude of the increase was similar between the African (by 12% to 19% of averaged over three years) and Asian accessions (7 to 24%). The genotypic variation in the biomass response to eCO2 could be explained by the leaf area response rather than by the efficiency of biomass production per unit leaf area or leaf photosynthesis across the species. Dry matter partitioning to leaves determines biomass responsiveness to elevated atmospheric CO2 in comparison between African and Asian rice genotypes. [ABSTRACT FROM AUTHOR]