RESUMO
Potato is a temperate crop consumed globally as a staple food. High temperature negatively impacts the tuberization process, eventually affecting crop yield. DNA methylation plays an important role in various developmental and physiological processes in plants. It is a conserved epigenetic mark determined by the dynamic concurrent action of cytosine-5 DNA methyltransferases (C5-MTases) and demethylases (DeMets). However, C5-MTases and DeMets remain unidentified in potato, and their expression patterns are unknown under high temperatures. Here, we performed genome-wide analysis and identified 10 C5-MTases and 8 DeMets in potatoes. Analysis of their conserved motifs, gene structures, and phylogenetic analysis grouped C5-MTases into four subfamilies (StMET, StCMT3, StDRM, and StDNMT2) and DeMets into three subfamilies (StROS, StDML, and StDME). Promoter analysis showed the presence of multiple cis-regulatory elements involved in plant development, hormone, and stress response. Furthermore, expression dynamics of C5-MTases and DeMets were determined in the different tissues (leaf, flower, and stolon) of heat-sensitive (HS) and heat-tolerant (HT) genotypes under high temperature. qPCR results revealed that high temperature resulted in pronounced upregulation of CMT and DRM genes in the HT genotype. Likewise, demethylases showed strong upregulation in HT genotype as compared to HS genotype. Several positive (StSP6A and StBEL5) and negative (StSP5G, StSUT4, and StRAP1) regulators are involved in the potato tuberization. Expression analysis of these genes revealed that high temperature induces the expression of positive regulators in the leaf and stolon samples of HT genotype, possibly through active DNA demethylation and RNA-directed DNA methylation (RdDM) pathway components. Our findings lay a framework for understanding how epigenetic pathways synergistically or antagonistically regulate the tuberization process under high-temperature stress in potatoes. Uncovering such mechanisms will contribute to potato breeding for developing thermotolerant potato varieties.
RESUMO
Salinity stress is a major constraint to sustainable crop production due to its adverse impact on crop growth, physiology, and productivity. As potato is the fourth most important staple food crop, enhancing its productivity is necessary to ensure food security for the ever-increasing population. Identification and cultivation of salt-tolerant potato genotypes are imperative mitigating strategies to cope with stress conditions. For this purpose, fifty-three varieties of potato were screened under control and salt stress conditions for growth and yield-related traits during 2020. Salt stress caused a mean reduction of 14.49%, 8.88%, and 38.75% in plant height, stem numbers, and tuber yield, respectively in comparison to control. Based on percent yield reduction, the genotypes were classified as salt-tolerant (seven genotypes), moderately tolerant (thirty-seven genotypes), and salt-sensitive genotypes (nine genotypes). Seven salt-tolerant and nine salt-sensitive genotypes were further evaluated to study their responses to salinity on targeted physiological, biochemical, and ionic traits during 2021. Salt stress significantly reduced the relative water content (RWC), membrane stability index (MSI), photosynthesis rate (Pn), transpiration rate (E), stomatal conductance, and K+/Na+ ratio in all the sixteen genotypes; however, this reduction was more pronounced in salt-sensitive genotypes compared to salt-tolerant ones. The better performance of salt-tolerant genotypes under salt stress was due to the strong antioxidant defense system as evidenced by greater activity of super oxide dismutase (SOD), peroxidase (POX), catalase (CAT), and ascorbate peroxidase (APX) and better osmotic adjustment (accumulation of proline). The stepwise regression approach identified plant height, stem numbers, relative water content, proline content, H2O2, POX, tuber K+/Na+, and membrane stability index as predominant traits for tuber yield, suggesting their significant role in alleviating salt stress. The identified salt-tolerant genotypes could be used in hybridization programs for the development of new high-yielding and salt-tolerant breeding lines. Further, these genotypes can be used to understand the genetic and molecular mechanism of salt tolerance in potato.
RESUMO
Tubers of forty four indigenous potato varieties were assessed for storage behaviour at room temperature, tuber dry matter content and cooking quality during 2010, 2011 and 2012. The maximum, minimum temperatures and relative humidity during storage period ranged between 26 to 40 °C, 17-28 °C and 18 to 82 %, respectively. The lowest total weight loss was recorded in variety Kufri Pushkar (7.7 %) followed by Kufri Lalima (7.9 %), Kufri Surya (8.3 %), Kufri Red (9.2 %), Kufri Dewa, Kufri Sheetman (9.3 %), Kufri Chandramukhi, Kufri Jyoti (9.5 %), Kufri Sindhuri (9.6 %), Kufri Kuber (9.7 %), Kufri Chipsona-1 (9.8 %), Kufri Kundan (9.9 %) and Kufri Chamatkar (10.0 %). Highest tuber dry matter content (%) was observed in Variety Kufri Kundan (24.2) followed by Kufri Himsona (23.7), Kufri Frysona (23.6), Kufri Kuber (22.7), Kufri Chipsona-2 (22.3). Kufri Khasigaro (22.0), Kufri Sheetman (21.9), Kufri Chipsona-3 (21.7) and lowest in Variety Kufri Khyati and Kufri Pukhraj (16.1 %). Of the total varieties, 14 were adjudged as floury, 15 mealy, 14 waxy and one (Kufri Ashoka) as soggy. The total weight loss had highly significant and positive correlation with sprout weight/Kg tubers (r = 0.76**), physiological weight loss (r = 0.97**). Based on the results potato varieties namely, Kufri Chamatkar, Kufri Chipsona-1, Kufri Chandramukhi, Kufri Dewa, Kufri Jyoti, Kufri Kuber, Kufri Kundan, Kufri Lalima, Kufri Lauvkar, Kufri Pushkar, Kufri Red, Kufri Safed, Kufri Sheetman, Kufri Sindhuri possessed excellent keeping quality with medium to long tuber dormancy, low storage losses, medium to high tuber dry matter and good flavour. The information generated in this study can be utilized in the breeding programme. This can also help the farmer to choose and cultivate the potato varieties as per demand of the consumers.