Late Heat Stress Research Articles

Antioxidants status and physiological responses to early and late heat stress in two rabbit breeds.

Early life heat stress negatively affects rabbit production and well-being. However, the physiological response to acute heat stress in later life is not clearly defined. The present study aims to investigate the effects of early and late heat stress at 36°C on some blood constituents, antioxidant enzymes activity in the blood, and muscle in New Zealand white and Baladi Black rabbits. A total of sixty post-weaning rabbits of each breed were randomly divided into two groups; control groups (NZWC and BBC) and early heat-stressed groups for six hours at 36 ± 1°C and 62% relative humidity (RH) (NZWT and BBT groups). After heat stress, six rabbits from each group were slaughtered for blood and muscle tissue collection. The surviving rabbits were kept at 28 ± 1°C and 40% RH till 13 weeks of age. At the end of 13 weeks, all rabbits were exposed to late heat stress as precious described to perform four groups: single late stressed groups; NZWC2, BBC2, and double stressed groups; NZWT2 and BBT2. After late heat stress, six rabbits from each group were slaughtered for blood and muscle tissue collection. The early and late heat stress caused a significant reduction in the blood creatine kinase, lactate dehydrogenase, and high-density lipoprotein and antioxidant enzymes' activity in blood and muscle of both NZW and BB rabbits compared with the control groups. While, the blood total cholesterol, triglycerides, total lipids levels, and lipid peroxidation activity in blood and muscle were significantly increased due to the early and late heat-stressed both breeds compared with the control groups. It could be concluded that the early heat stress at 36°C has negative effects on several physiological indicators and antioxidant activities in the blood and muscle of NZW and BB rabbits.

Genetic Variability, Correlation and Path Analysis of Bread Wheat (Triticum aestivum L.) Genotypes under Terminal Heat Stress

Present study investigated the genetic variability, correlation and path analysis on various yield attributing traits of forty nine bread wheat (Triticum aestivum L.) genotypes grown at Kalyani, Nadia, West Bengal during rabi season for two consecutive years 2013–2014 and 2014–2015 enduring with terminal heat stress. Wide spectrum variability was revealed for all the characters studied which could provide scope for improvement through selection. High Phenotypic Coefficient of Variation (PCV), Genotypic Coefficient of Variation (GCV), heritability, Genetic advance (GA), GA (%) of mean was observed in the characters viz., proline content, no. of tillers plant−1, no. of spikes plant−1, no. of grains spike−1 and yield plant−1 under late heat stress condition. The genotypes viz. GW 2011-403, WSM 135, GW 2008-153, RAJ 4358, RAJ 4362, J-07-47 & UP 2783 were found to be high yielders may exploit towards heat tolerance. Yield plant−1 was found to have significant positive association with plant height, no. of tillers plant−1, no. of spikes plant−1, spike length, no. of spikelets spike−1, no. of florets spike−1, no. of grains spike−1, floret fertility and grain weight spike−1 at both genotypic and phenotypic levels; while a significant negative correlation was observed with chlorophyll-a and total chlorophyll content at both the levels and chlorophyll-b at genotypic level only. Considering path coefficient analysis, no. of tillers plant−1, spike length, no. of florets spike−1 and floret fertility were mentioned as selection criteria under late heat stress.

Canopy Temperature as a Selection Parameter for Grain Yield and Its Components in Durum Wheat Under Terminal Heat Stress in Late Sown Conditions

Relationship of canopy temperature (CT) with grain yield and its components were evaluated under terminal heat stress conditions, in Central India, during 2010–2013 growth season, in which 102 durum wheat genotypes were tested under late and very late sown conditions. The genotypes in late sown conditions showed higher grain yield/plant, biomass/plant, harvest index and test grain weight compared to very late sown conditions. The mean grain yield/plant and biomass yield/plant were 18.8 and 55.9 g, respectively, under late sown conditions, compared to 15.1 and 48.9 g under very late sown conditions. Genotypes MACS 3125, HI 8627, HI 8638, HI 8498, WH 896 and HI 8691 showed stable performance under both late and very late sown conditions over the years and hence exhibited high degree of tolerance to terminal heat. CT ranged from 21.0 to 24.7 and 20.2 to 24.9 °C under late and very late sown conditions, respectively. CT showed significant and negative correlation with grain yield/plant and biomass/plant under late and very late conditions and number of grains/spike and 1000 grain weight under very late sown conditions and hence can be successfully used as an important selection parameter in breeding programme at field. The study suggests that CT can be used as one of the important criteria for the selection of stable genotypes under late heat and very late heat stress conditions and can help in improving production and productivity of durum wheat under terminal heat stress conditions.

Evaluation of growth, yield, relative performance and heat susceptibility of eight wheat (Triticum aestivum L.) genotypes grown under heat stress

Eight spring wheat cultivars were evaluated under three heat stress conditions (early, late and very late) in order to identify suitable cultivars to develop heattolerant genotypes resistant to future global warming. Results from the study indicate that stress did not negatively affect flag leaf area in ‘Prodip’ and ‘Sufi’, flag leaf dry matter partitioning in ‘Prodip’, ‘BARI Gom-26’ and ‘Shatabdi’, above-ground dry matter partitioning in ‘Shatabdi’ and ‘BARI Gom-26’, seedling emergence in ‘Sufi’ and ‘BARI Gom-26’, or tiller production in ‘Sufi’ and ‘BARI Gom-26’. With respect to lower yield reduction, relative performance and heat susceptibility index (HSI), ‘Sufi’ was highly heat stress-tolerant, followed by ‘BARI Gom-26’ and ‘Shatabdi’. On the basis of HSI values in early heat stress and extremely late heat stress (corresponding to early and extremely late sowing), ‘BARI Gom-26’ (HSI=0.10, 0.65) and ‘Shatabdi’ (0.22, 0.62) were highly tolerant to early heat stress and moderately tolerant to extremely late heat stress while ‘Sufi’ was highly tolerant (0.35) to extremely late heat stress and moderately tolerant (0.51) to early heat stress. All other genotypes were susceptible to heat stress, among which ‘Gourab’ (2.19, 1.46) was the most susceptible followed by ‘Sourav’ (1.19, 1.42), ‘Prodip’ (1.03, 1.23), ‘BARI Gom-25’ (1.61, 0.89) and ‘Bijoy’ (1.04, 1.28). Thus, ‘BARI Gom-26’, ‘Shatabdi’ and ‘Sufi’ have the greatest potential to be used as high-yielding wheat genotypes under warm to hot environments and could be used in a breeding programme to develop heat-tolerant wheat.

Effect of Temperature on Yield and Some Agronomic Characters of Spring Wheat (Triticum aestivum L.) Genotypes

Eight modern wheat varieties (viz., Sourav, Gourab, Shatabdi, Sufi, Bijoy, Prodip, BARI Gom-25 and BARI Gom-26) were evaluated to find out the suitable variety for optimum and late sown condition, to find out heat tolerant and heat sensitive variety and to find out the optimum sowing time for a specific variety. The experiment was conducted in the research farm of Wheat Research Center (25°38´ N, 88°41´ E and 38.20 m above sea level.), Bangladesh, under eight sowing times (viz., 8 Nov., 15 Nov., 22 Nov., 29 Nov., 6 Dec., 13 Dec., 20 Dec. and 27 Dec.). Results showed that wheat sown in November 22 to December 20 was significantly better compared to November 08, 15 and December 27, from the studied aspects of yield and yield components. Considering overall sowing performance of all genotypes Shatabdi is the best, followed by BARI Gom-26 (2nd), Sourav (3rd), Prodip (4th), Bijoy (5th), Gourab (6th), Sufi (7th) and BARI Gom-25 (least). In extremely heat stress (November 08 and December 27) condition Prodip was found to be heat sensitive genotype (yield reduction 41.18 and 28.92%), followed by BARI Gom-26 (yield reduction 41.15 and 22.73%). Both in too early and very late heat stress conditions, genotypes Sourav and BARI Gom-25 were found to be heat tolerant. In very early (November 08), variety Sourav (yield reduction 20.47%) is recommended, followed by BARI Gom-25 (yield reduction 27.91%) and in very late (December 27), Sufi is the best (yield reduction 8.60%), followed by Bijoy (yield reduction 11.05%). DOI: http://dx.doi.org/10.3329/ijarit.v1i1-2.13932 Int. J. Agril. Res. Innov. & Tech. 1 (1&2): 44-54, December, 2011

Multiple heat and drought events affect grain yield and accumulations of high molecular weight glutenin subunits and glutenin macropolymers in wheat

Spring wheat plants were subjected to water deficit and/or high temperature episodes at spikelet initiation, anthesis or both stages. The stresses modified the early dough stage and maturity, shortened the kernel desiccation period and caused grain yield loss. Plants subjected to stress at the early growth stages had higher grain yields than the non-early-stressed plants when stress reoccurred at anthesis. Concentrations of high molecular weight glutenin subunits in grain were up-regulated by the single early drought, the early drought combined with late heat and the double drought stress treatments, but was down-regulated by the early heat and double heat stress events. Concentration of glutenin macropolymers was increased by the single early drought episode, the single late drought and heat events, as well as the early drought combined with the late heat stress, but was reduced by the early heat stress and double heat events.

Phenology, Growth and Yield of Three Wheat (Triticum aestivum L.) Varieties as Affected by High Temperature Stress

Wheat is the most important cereal in the world. However, due to an increasing trend of rising temperatures around the world, wheat may be exposed to greater thermal stress in the near future. Therefore, the identification and development of suitable wheat varieties is an important step to resolve this threat to production and to achieve high yield, even under high temperature stress. In this context, phenology, growth and yield of three elite varieties of wheat (‘Gourab’, ‘BARI Gom-25’ and ‘BARI Gom-26’) were evaluated under two sowing conditions: optimum (sown on November 15) and late heat stress condition (sown on December 27). All wheat varieties, when sown late, faced severe temperature stress that significantly affected phenology, growth and finally yield. Taking into consideration phenological variation, dry matter (fresh and dry weight) partitioning and grain yield, variety ‘BARI Gom-26’ performed better both in optimum and late heat stress, followed by ‘BARI Gom-25’; ‘Gourab’ performed the least. On the basis of heat tolerance parameters [relative performance (RP) and heat susceptibility index (HSI)], ‘BARI Gom-25’ (RP-79%; HSI-0.7) was the best performing variety followed by ‘BARI Gom-26’ (RP-74%; HSI-0.9) under heat stress while ‘Gourab’ (RP-61%; HSI-1.3) was sensitive to heat.

Gas Exchange of Five Warm‐Season Grain Legumes and their Susceptibility to Heat Stress

AbstractObjective of this study was to compare the heat stress performance of four pulses from dry and hot areas (mungbeans, limabeans, and teparybeans and cowpeas) with that of soybeans. Two experiments were conducted in growth chambers, and data were pooled because results of both experiments were similar. Plants were raised up to flowering at 24/17 °C (day/night) and were then either exposed to these temperatures until maturity or stressed with 33/24 °C for 2 weeks starting at day 1 or 15 after onset of flowering (early vs. late stress). Before, during and after these stress intervals, gas exchange of representative upper leaves was examined; additionally, immediate effects of increasing leaf temperatures from 24 to 32 or 40 °C on chlorophyll fluorescence were assessed. Without heat stress rates of photosynthesis (Pn), and of transpiration (TR), stomatal and mesophyll conductance (gs, gm) and intrinsic transpiration efficiency (iTE) differed significantly among the five crops at each date. However, because of crop‐specific time‐courses ranking among unstressed crops was instable with time, so values were integrated or averaged over time. This procedure revealed high Pn potentials in mung‐ and teparybeans and high iTE values in limabeans compared to the other crops. Heat stress lowered Pn and gs considerably, but increased TR in all five crops. Relative lowering of Pn during heat stress displayed a crop‐specific pattern with limabeans being least susceptible to both early and late heat stress, while cowpeas were highly susceptible to early stress. Effects on Pn were mainly attributable to lowering of gs and only in part to gm. The latter was supported by very small changes (<10 %) of various chlorophyll fluorescence signals shortly after raising leaf temperature to 32 °C in all species. However, in limabeans, a decreased electron transport rate (e‐rate, −18 %) and an increased non‐photochemical quenching (QN, +16 %) pointed to an adaptive mechanism to avoid oxidative strains under heat. Leaf temperatures of 40 °C immediately provoked stronger changes in all fluorescence signals than 32 °C; substantial damages at 40 °C were indicated by effective quantum yield, photochemical quenching and ratio of fluorescence decrease in mungbeans and low ones in cowpeas and soybeans. Nevertheless, some adaptive responses of e‐rates and QN were observed in all crops and were most expressed in limabeans.