Low temperature is a major constraint for crop productivity. To cope with this challenge, plants have developed several mechanisms to adapt to low temperature. Developing breeding strategies to enhance cold stress tolerance in crops requires an understanding of the mechanisms by which plants perceive and transmit cold stress-related signals to their cellular machinery, thereby activating adaptive responses. Only one quantitative trait locus for tolerance to low-temperature germination, qLTG3-1, has been narrowed down to the gene level in rice. A 71 bp indel that can be used to distinguish between tolerant and susceptible parents has been identified. We tested the 71 bp indel on 65 diverse rice genotypes including those adapted to colder climates of North and Northeastern India to find evidence of the tolerant allele (insertion) and to see whether it is associated with low-temperature germinability in these genotypes. Our results show that 48% of the rice genotypes tested carried the tolerant allele. The insertion was found to be significantly associated with cold tolerance during germination. Moreover, several landraces/improved varieties known for their superior performance in other abiotic stress conditions such as drought and high salinity conditions, and which were previously never exposed to low temperature, carry the beneficial allele for qLTG3-1, suggesting an additional role of this allele in adverse climatic conditions. This study enhances current understanding of the distribution of the tolerant allele qLTG3-1 in rice germplasm, which could help in the identification of suitable donors for potential marker-assisted breeding programmes.
Low temperature (LT) severely affects rice growth and grain yield. Recently, we reported contrasting genotypes including ARR 09 and Takyer for seedling stage long duration low temperature response. Here we show that susceptible rice genotypes show an increase in lipid peroxide levels and decrease in relative water content (RWC) to a higher extent in comparison to tolerant genotypes in response to 3 h LT. Stress induced NAC family members (OsNAC1, OsNAC2, OsNAC3, and OsNAC5) showed a higher transcript accumulation in tolerant genotypes than in sensitive genotypes after LT treatment suggesting stress tolerance might be due to higher expression of stress-responsive transcription factors. Furthermore, ARR 09 can be used as an important genetic resource to better understand LT tolerance mechanism.
Low temperature stress is one of the major limiting factors affecting rice productivity in higher altitudes. DREB1A and DREB1B, are two transcription factors that have been reported to play key regulatory role in low temperature tolerance. In order to understand whether natural genetic variation in these two loci leads to cold tolerance or susceptibility, OsDREB1A and OsDREB1B were targeted across several rice genotypes showing differential response to low temperature. Expression data suggests induction of gene expression in shoots in response to low temperature in both tolerant and susceptible genotypes. Upon sequence analysis of 20 rice genotypes, eight nucleotide changes were identified including two in the coding region and six in the 5'UTR. None of the discovered novel variations lie in the conserved region of the genes under study, thereby causing little or no changes in putative function of the corresponding proteins. In silico analysis using a diverse set of 400 O. sativa revealed much lower nucleotide diversity estimates across two DREB loci and one other gene (MYB2) involved in DREB pathway than those observed for other rice genes. None of the changes showed association with seedling stage cold tolerance, suggesting that nucleotide changes in DREB loci are unlikely to contribute to low temperature tolerance. So far, data concerning the physiological role and regulation of DREB1 in different genetic background are very limited; it is to be expected that they will be studied extensively in the near future.
Potato is one of the most important food crops in the world. Late blight, viruses, soil and tuber-borne diseases, insect-pests mainly aphids, whiteflies, and potato tuber moths are the major biotic stresses affecting potato production. Potato is an irrigated and highly fertilizer-responsive crop, and therefore, heat, drought, and nutrient stresses are the key abiotic stresses. The genus Solanum is a reservoir of genetic diversity, however, a little fraction of total diversity has been utilized in potato breeding. The conventional breeding has contributed significantly to the development of potato varieties. In recent years, a tremendous progress has been achieved in the sequencing technologies from short-reads to long-reads sequence data, genomes of Solanum species (i.e., pan-genomics), bioinformatics and multi-omics platforms such as genomics, transcriptomics, proteomics, metabolomics, ionomics, and phenomics. As such, genome editing has been extensively explored as a next-generation breeding tool. With the available high-throughput genotyping facilities and tetraploid allele calling softwares, genomic selection would be a reality in potato in the near future. This mini-review covers an update on germplasm, breeding, and genomics in potato improvement for biotic and abiotic stress tolerance.
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