TABLE 2.
Candidate genes identified under heat stress tolerance in plants for various agro-morphological, physiological and biochemical traits
| Traits | QTLs/Genes involved | Regulation in response to heat stress | References |
|---|---|---|---|
| Morphological/anatomical traits | |||
| Pollen viability | PolVia5.1, PolVia8.1 | 15%–16% and 20% of phenotypic variation respectively | Vargas et al. (2021) |
| Pollen development | Hsp100, Hsp90, Hsp70, Hsp60, smHsp | Reduce heat stress impact on pollen grain development by protecting cellular proteins from denaturation to retain their function | Kotak et al. (2007) |
| HSFA2a, HSFA2d, HSFA2f, HSFA9, HSFA3, HSFB2a, HSFB2b, HSFB2c | Helps in pollen development in plants under heat stress | Zhang et al. (2012), Giorno et al. (2013) | |
| Pollen germination | Ca_24217 | Reduced activity | Jha et al. (2021) |
| Pollen tube elongation | Ca_14063 | Reduced activity | |
| Root length | Ca_07091 | Increased activity | |
| Stigma receptivity | FER/AAK1/SIR/SRN | Decreased activity | Escobar-Restrepo et al. (2007) |
| Flower abscission | RAP2-11/ERF002 | Increased activity | Chen and Chen (2002) |
| Number of filled pods | qfpod02_5 | Cumulative phenotypic variation explained above 50% | Paul et al. (2018) |
| Grain yield per plot | qgy02_5 | ||
| Total number of seeds per plot | qts02_5 | ||
| % pod setting | q%podset06_5 | ||
| Grain filling | PdShr1.1 | Increased activity | Vargas et al. (2021) |
| SuSy (sucrose-synthase) | Poor pod filling and pollen development and germination | Basu et al. (2019) | |
| ERF3, GBSS1, GW2, ERL1 | Panicle compactness, and ethylene production negatively influences the grain filling | Sekhar et al. (2021) | |
| Discoloration of seed coat colour | Hbs-1, Hbs-2, Hbs-3 | Ethylene forming enzymes including ACC oxidase 2 and ACC synthase 1 | Pottorff et al. (2014) |
| Nodule thermotolerance | VuNSR10 | Negative regulation of Pherophorin-like protein which plays a role in cell wall structure | Simões-Araújo et al. (2002) |
| VuNSR11 | Positive regulation of Xylan endohydrolase which plays a role in cell wall structure | Simões-Araújo et al. (2002) | |
| Physiological traits | |||
| Transpiration rate | Qe.ccshau-4A | Increased activity | Sangwan et al. (2019) |
| Membrane stability index | CaCMS_NS4.1 | Increased activity | Jha et al. (2021) |
| Chlorophyll content | QLCCHR.nri-4A | Increased activity | Maulana et al. (2018) |
| CaCHL_NS4.3 | Reduced activity | Jha et al. (2021) | |
| Stomatal conductance | RAN1/HMA7 | Reduced activity | Chen and Chen (2002) |
| Stomatal development | HSP90s | HSP90s interact with YODA cascade, affects phosphorylation of SPEECHLESS (SPCH) and MPK6 to modulate stomatal development | Samakovli et al. (2020) |
| Canopy temperature depression (CTD) | QCtdh.tam-3B | Comparatively higher activity in heat tolerant genotypes | Mason et al. (2013) |
| Photosynthetic rate | Qpn.ccshau-2.1D | Comparatively higher activity in heat tolerant genotypes | Sangwan et al. (2019) |
| Leaf senescence | Ca_12767 | Comparatively lower activity in heat tolerant genotypes | Jha et al. (2021) |
| Biochemical traits | |||
| Late embryogenesis abundant (LEA) proteins | VrLEA-2, VrLEA-40, VrLEA-47, and VrLEA-55 | Higher expression in heat tolerant genotypes | Singh et al. (2022) |
| hydrogen peroxide | Ca_17121 | Reduced activity | Jha et al. (2021) |
| Superoxide dismutase | Cu/Zn SOD | Increased activity | Paul et al. (2018) |
| Catalase | CAT1 | Increased activity | Ara et al. (2013) |
| Gluathathione reductase | Zm00001d027769 | Increased activity | Sheoran et al. (2022) |
| Ascorbate peroxidase (APX) | CaAPX | Increased activity | Wang et al. (2017) |
| Peroxidase | Zm00001d028347 | Increased activity | Sheoran et al. (2022) |