Effect of Heat Stress on Growth and Physiological Traits of Alfalfa (Medicago sativa L.) and a Comprehensive Evaluation for Heat Tolerance

Abstract

Alfalfa (Medicago sativa L.) is a valuable forage legume, but its production is largely affected by high temperature. In this study, we investigated the effect of heat stress on 15 alfalfa cultivars to identify heat-tolerant and -sensitive cultivars. Seedlings were exposed to 38/35 °C day/night temperature for 7 days and various parameters were measured. Heat stress significantly reduced the biomass, relative water content (RWC), chlorophyll content, and increased the electrolyte leakage (EL) and malondialdehyde (MDA) content of heat-sensitive alfalfa cultivars. However, heat-tolerant cultivars showed higher soluble sugar (SS) and soluble protein (SP) content. The heat tolerance of each cultivar was comprehensively evaluated based on membership function value. Cultivars with higher mean membership function value of 0.86 (Bara310SC) and 0.80 (Magna995) were heat tolerant, and Gibraltar and WL712 with lower membership function value (0.24) were heat sensitive. The heat tolerance of the above four cultivars were further evaluated by chlorophyll a fluorescence analysis. Heat stress significantly affected the photosynthetic activity of heat-sensitive cultivars. The overall results indicate that Bara310SC and WL712 are heat-tolerant and heat-sensitive cultivars, respectively. This study provides basic information for understanding the effect of heat stress on growth and productivity of alfalfa.

Identification and Characterization of Contrasting Genotypes/Cultivars for Developing Heat Tolerance in Agricultural Crops: Current Status and Prospects

“…Heat stress (>32/20 • C) significantly reduced chickpea biomass by 22-30%, relative to those grown under normal temperatures; heat stress had a smaller effect on the biomass of heat-tolerant genotypes (ICC15614 and ICCV92944) than heat-sensitive genotypes (ICC5912, ICC10685) (Kaushal et al, 2013). Similarly, in a field experiment on alfalfa (Medicago sativa), heat stress (38/35 • C) reduced plant biomass, relative to the control (25 • C), more so in heatsensitive Wl712 than heat-tolerant Bara310SC (Wassie et al, 2019). Field studies on lentil revealed that heat stress (>32/20 • C) significantly reduced plant biomass, relative to the control (Sita et al, 2017a); genotypes IG3263, IG2507, IG3297, IG3312, IGG3327, IG3330, IG3546, IG3745, IG4258, and FLIP2009 retained more biomass (termed heat-tolerant) than genotypes IG2519, IG2802, IG2506, IG2849, IG2821, IG2878, IG3326, IG3290, IG3973, IG3964, IG4242, DPL15, DP315, IG4221, and IG3568 (termed heat-sensitive).…”

“…Barghi et al (2013) reported the highest CMT in genotype Qazvin (98.13%) and regarded it as heat-tolerant, whereas genotype B4400 (33.19%) had the lowest CMT (heat-sensitive). Under high temperature (38/35 • C), screening of 15 Medicago cultivars for CMT identified Bara310SC and WL712 as heat-tolerant (24.07%) and heat-sensitive (53.2%) cultivars, respectively, having minimum and maximum electrolyte leakage, respectively (Wassie et al, 2019).…”

Stomatal and Photosynthetic Traits Are Associated with Investigating Sodium Chloride Tolerance of Brassica napus L. Cultivars

“…The 200 mM was more harmful compared to the 100 mM of NaCl. Under high salinity level, analysis of results showed that the highest reduction in Pn, Tr, and Gs was achieved in Zhongshuang11 (67, 69, and 65%, respectively) whereas the lowest minimizing (35,31, and 36%, respectively) was found in Hua6919 ( Figure S5). However, the salt tolerance coefficient of all cultivars referred that, Hua6919 had the highest values based on Pn, Tr, and Gs (75.6, 74.7, and 67.3%, respectively), while Zhongshuang11, Xiangyouza553, and Zhongshuang11 (43.6, 42.9, and 32.2%, respectively) had the minimum values (Table 3).…”

“…Various screening methods of salinity tolerance have been developed in rapeseed based on multi-index results [10,23,31,32]. The membership function value (MFV) is an appreciate screening method for different stress conditions; drought stress [33,34], heat stress [35], nitrogen stress [36], and salt stress [31]. Wu et al [31] evaluated the salt tolerance of B. napus germplasm using the MFV method in the germination stage but an effective screening method in the seedling stage not presented.…”

Comparative transcriptome analysis of genes involved in the drought stress response of two peanut (Arachis hypogaeaL.) varieties

“…The relative drought tolerance of peanuts was determined by the method of average "membership function" method [70].…”