Photosynthetic efficiency, temperature induction response, carbon isotope discrimination correlate with expression profiling in Indian wheat cultivars

In the backdrop of global warming and increase in temperatures, wheat productivity worldwide would be limited. This study was therefore undertaken to analyze the heat stress response in 12 different cultivars of Indian wheat. Three developmental stages were used i.e. germination stage, seedling stage and anthesis stage, to characterize thermotolerant and thermosusceptible cultivars on the basis of different physiological and molecular parameters. Lethal temperature stress on germinating seeds showed a clear reduction in percentage germination. At the seedling stage, higher decrease in Fv/Fm, total chlorophyll content, membrane injury and carbon isotope discrimination was observed in thermosusceptible cultivars. Results similar to seedling stage were obtained at anthesis stage. PSII efficiency of late-sown cultivars and timely-sown cultivars also indicated that thermosusceptible cultivars are more prone to terminal heat stress than thermotolerant cultivars. Heat Susceptibility Index (HSI) was calculated on the basis of physiological parameters. Based on HSI, thermotolerant and thermosusceptible cultivars were identified. HSI revealed comparatively low heat susceptibility in <i>K7903, CBW12</i> and <i>C306</i> and high heat susceptibility in <i>PBW343, HD2329</i> and <i>HD2428</i>. On the basis of HSI, expression analysis of stress induced genes was performed between 2 tolerant cultivars <i>C306</i> and <i>K7903</i> along with 2 susceptible cultivars, <i>HD2329</i> and <i>PBW343</i>. Higher expression of stress induced genes was observed in the 2 thermotolerant cultivars <i>C306</i> and <i>K7903</i> as compared to the 2 thermosusceptible cultivars <i>HD2329</i> and <i>PBW343</i>. Thus further reconfirms that stress inducible genes can be employed for categorizing cultivars into susceptible and tolerant groups.

在全球变暖和气温升高的背景下，全球小麦生产力将受到限制。为此本研究旨在分析12个不同印度小麦品种的热胁迫响应机制。本研究选取萌发期、苗期及扬花期三个发育阶段，基于不同生理及分子参数对耐热型与热敏感型小麦品种进行鉴定表征。对萌发种子施加致死温度胁迫后，种子萌发率显著降低。在苗期，热敏感型品种的Fv/Fm、总叶绿素含量、膜损伤程度及碳同位素判别率均出现更为显著的下降。扬花期的检测结果与苗期一致。晚播与适播品种的光系统II（PSII）效率同样表明，相较于耐热型品种，热敏感型品种更易受生育后期热胁迫影响。本研究基于生理参数计算了热敏感指数（Heat Susceptibility Index, HSI），并据此划分出耐热型与热敏感型小麦品种。HSI结果显示，K7903、CBW12及C306的热敏感性相对较低，而PBW343、HD2329与HD2428的热敏感性较高。基于HSI分类结果，本研究对2个耐热品种C306、K7903与2个热敏感品种HD2329、PBW343进行了胁迫诱导基因的表达分析。相较于2个热敏感品种HD2329与PBW343，2个耐热品种C306与K7903的胁迫诱导基因表达量更高。该结果进一步证实，胁迫诱导基因可用于将小麦品种划分为敏感型与耐受型两类。