Heat Tolerance Traits Research Articles

Molecular basis of heat stress tolerance in wheat

The rise in Earth’s temperature is one of the most alarming climatic issues in the field of agriculture and food production, in the present context. The increase in temperature leads to heat stress, major abiotic stress responsible for a huge decline in the production of crops. Wheat (Triticum aestivum), among many crops, also experiences a significant decline in yield and overall productivity due to extreme heat stress. But Wheat has also developed natural tolerance mechanisms to defend itself from heat damage. The selection of cultivars with a higher degree of tolerance mechanism protects against thermal stress, which minimizes the risk of poor productivity to a greater extent. In this review, we discuss the current works of literature concerning the heat stress tolerance mechanism in wheat plants and also highlight the strategic approaches that improve their heat stress tolerance at the molecular level. The success of these approaches depends on a better understanding of heat tolerance traits, their genomic composition, and molecular responses.

Physiological response of Nigerian locally adapted chickens with different heat shock protein 70 genotypes to acute heat stress

Slow growth rate and acute heat stress are among the major constraints to indigenous chicken production in Nigeria. Characterization of heat-tolerance genes is a requisite for selective breeding of poultry for improved heat-tolerance and productivity. Therefore, this study investigated variation in HSP70 gene and its association with heat-tolerance traits of Nigerian locally adapted chickens. One-day old chicks comprising 118 Yoruba Ecotype Chicken-YEC and 138 FUNAAlpha Chicken-FAC were tagged and fed ad-libitum on starter (0-6 weeks) and grower (7-24 weeks) diets. At week 12, blood was sampled, DNA was extracted, amplified and electrophoresed following standard procedures. HSP70 gene was genotyped using MmeI restriction endonuclease. At week 23, 36 chickens (six chickens per identified HSP70 genotypes) selected from each of YEC and FAC were exposed to 40?1?C for one hour. Cloaca temperature, respiratory rate (RR) and pulse rate (PR) were recorded and heat stress index (HSI) calculated. Data were analysed using descriptive statistics and ANOVA. Alleles A and B with genotypes: AA, AB, and BB were detected. After acute heat-stress, YEC with BB had higher RR value compared to those with AA and AB. The PR value of FAC with genotype BB was significantly higher (p<0.05) than those of AA, but similar to chickens with AB. Within FAC, HSI of BB-HSP70 was lower than AA-HSP70 but similar to AB-HSP70, while within YEC HSI of BB-HSP70 was similar to those of AA-HSP70 and AB-HSP70. The HSP70 gene was polymorphic in the studied chickens and genotype BB-HSP70 was associated with thermo-tolerance.

Identification of genomic regions governing moisture and heat stress tolerance employing association mapping in rice (Oryza sativa L.).

Rice crop is damaged extremely by abiotic stress world-wide. The best approach to enhance drought tolerance in rice varieties is to identify and introgress yield QTLs with major effects. The Association mapping approach helps in the identification of genomic regions governing physiological, yield and yield attributes under moisture and heat stress conditions in diverse collections of crop germplasm, based on historic recombination events and linkage disequilibrium across the genome. The association mapping panel of 110 rice germplasm lines exhibited significant variation for all the traits in both irrigated and moisture stress conditions. The extent of yield reduction ranged to 83% during rabi, 2018-19, 53% in rabi, 2019-20 and 68% in pooled analysis. The genotypes Badami, Badshabhog, Pankaj, Varalu, Vasundhara, Vivekdhan, Krishna and Minghui63 exhibited drought tolerance with least yield penalty under moisture stress conditions. The genotypes Konark, MTU3626, NLR33671, PR118 and Triguna exhibited minimal reduction in heat stress tolerance traits. Association mapping of germplasm using 37808 SNP markers detected a total of 10 major MTA (Marker-trait association) clusters distributed on chromosomes 1, 3, 4 and 11 through mixed linear model (MLM) governing multiple traits from individual data analysis which are consistent across the years and situations. The pooled data generated a total of five MTA clusters located on chromosome 6. In addition, several novel unique MTAs were also identified. Heat stress analysis generated a total of 23 MTAs distributed on chromosomes 1, 5, 6 and 11. Candidate gene analysis detected a total of 53 and 38 genes under individual and pooled data analysis for various yield and yield attributes under control and moisture stress conditions, respectively and a total of 11 candidate genes in heat stress Conditions. The major and novel MTAs identified in the present investigation for various drought and heat tolerant traits can be utilized for breeding climate-resilient rice varieties. The candidate genes predicted for key MTAs are of great value to deploy into the rice breeding after functional characterization.

Pollen viability-based heat susceptibility index (HSIpv): A useful selection criterion for heat-tolerant genotypes in wheat.

Terminal heat stress during reproductive stage in wheat (Triticum aestivum L.) causes pollen grain sterility and has a drastic impact on wheat crop production. Finding genotypes with high pollen viability under heat stress is crucial to cope with the impact of climate change through developing heat-tolerant cultivars. To assess the effect of terminal heat stress on pollen viability in a panel of spring wheat genotypes (N = 200), RCBD (randomized complete block design) field trials were conducted under normal and heat stress conditions for two consecutive years (2020-2021 and 2021-2022). Analysis of variance showed significant variation in genotypes, treatments, and genotype×treatment interaction. Fifty and 46 genotypes were categorized as heat tolerant (HSI pv < 0.5) in the first and second year, respectively. Twelve genotypes, namely, Chenab-70, Pari-73, Pak-81, MH-21, Punjab-76, NIFA-Aman, NUWYT-63, Swabi-1, Nisnan-21, Frontana, Amin-2000, and Pirsabak-2004, were found to be heat tolerant across the years. The violin plot displayed a trend of improvement in heat tolerance (HSI pv < 0.5) over the period of time in many modern wheat varieties. However, some modern wheat varieties released after 2001 such as Janbaz-09 (57%), Ghazi-2019 (57%), and Sindhu-16 (43%) had very low pollen viability under heat stress conditions. The results of phenotypic coefficient of variance (PCV%), genotypic coefficient of variance (GCV%), broad sense heritability (h2 bs), and genetic advance (GA) suggested the major contribution of genetic factors in controlling pollen viability trait. Higher values of h2 bs and GA under heat stress conditions suggested pollen viability as a heat tolerance trait controlled by additive genetic effects. Taken together, these results suggested pollen viability as a useful trait for selection in early generations under elevated temperatures. The genotypes identified as heat tolerant in both years can be used as genetic resources for breeding cultivars with higher pollen viability under elevated temperature conditions.

Deciphering the genetic basis and prediction genomic estimated breeding values of heat tolerance in Zhikong scallop Chlamys farreri

The changes in seawater temperature due to global warming have produced profound influences on the growth, survival and production of aquatic species. Therefore, improving the performance of these species under heat stress is crucial for the sustainable development of aquaculture. Genomic selection, as a method of genetic improvement of economic traits, has great potential and value in cultivation of new strains with adaptation advantages. In present study, 1060 Zhikong scallops Chlamys farreri, an economically important species, were exposed to a gradient heating experiment to obtain individuals with heat tolerance. Among them, 154 individuals died firstly during experiment were considered as heat-sensitive group (HS), and 156 still alive after recovering for 7 days were taken as heat-tolerant group (HT). Then, these 310 individuals were sequenced, and 35,507 single nucleotide polymorphisms (SNPs) of 289 scallops were genotyped for genome wide association study (GWAS) and genomic prediction analysis. The results showed that seven SNPs and two genes (PNC1 and RASD1) were significant associated with heat tolerance trait in C. farreri. In addition, the heat tolerance trait of C. farreri was moderately heritable, and the heritability of survival status and survival time was 0.52 ± 0.04 and 0.24 ± 0.03, respectively. Furthermore, genomic best linear unbiased prediction (GBLUP) and Bayes B models were proved to be more suitable for genomic breeding value predictions of heat tolerance trait in C. farreri. The accuracy of genomic estimated breeding value could be stabilized when the number of markers reached 8 k. Population size could improve the accuracy of breeding value predictions and the accuracy has not reach a plateau yet in our study. Taken together, the findings obtained in this study provide insights into the genetic basis of heat tolerance in C. farreri and contribute to the genetic improvement of scallop and other related species.

Assessing the heat sensitivity of Urdbean (Vigna mungo L. Hepper) genotypes involving physiological, reproductive and yield traits under field and controlled environment.

The rising temperatures are seriously impacting the food crops, including urdbean; hence efforts are needed to identify the sources of heat tolerance in such crops to ensure global food security. In the present study, urdbean genotypes were evaluated for heat tolerance under natural outdoor for two consecutive years (2018, 2019) and subsequently in the controlled environment of the growth chamber to identify high temperature tolerant lines. The genotypes were assessed involving few physiological traits (membrane damage, chlorophyll, photosynthetic efficiency, stomatal conductance, lipid peroxidation), reproductive traits (pollen germination % and pollen viability %) and yield related traits (total number of pods plant-1, total seeds plant-1, single seed weight and seed yield plant-1). Based upon these tested traits, PantU31, Mash114, UTTARA and IPU18-04 genotypes were identified as promising genotypes for both years under heat stress condition. Further confirming heat tolerance, all these four tolerant and four sensitive genotypes were tested under controlled environment under growth chamber condition. All these four genotypes PantU31, Mash114, UTTARA and IPU18-04 showed high chlorophyll content, photosynthetic efficiency, stomatal conductance, leaf area, pods plant-1, total seeds plant-1 and low reduction in pollen germination % and pollen viability under stress heat stress condition. Moreover, yield and yield related traits viz., pods plant-1, seeds plant-1, single seed weight and seed yield plant-1 showed very strong positive correlation with pollen germination and pollen viability except electrolyte leakage and malondialdehyde content. Thus, these genotypes could be potentially used as donors for transferring heat tolerance trait to the elite yet heat-sensitive urdbean cultivars.

Genetic polymorphism in HSPB6 gene and their association with heat tolerance in Sahiwal cattle

Heat shock proteins (HSPs) are known to modulate cellular response during summer stress in dairy cattle. Among different classes of HSPs, heat shock protein 20 (HSPB6) is a member of the small HSP family protein, the role of which has not been fully characterized in the context of heat stress in cattle. This study identified single nucleotide polymorphisms (SNPs) in the HSPB6 gene in Sahiwal cattle and their associations with heat tolerance traits (RR, RT and HTC). Three SNPs (SNP 1-3) were reported, which included two transitions, viz. SNP1-g.436G&gt;A (Intron 1) and SNP2-g.2152A&gt;G (3′-UTR) and one transversion, viz. SNP3-g.2417A&gt;T (3′-UTR). The association analysis revealed that SNPs loci, viz. SNP1-g.436G&gt;A and SNP2-g.2152A&gt;G were significantly associated with heat tolerance traits. The GG genotype of SNP2-g.2152A&gt;G was significantly associated with heat tolerance traits in Sahiwal cattle. The association analysis of four available haplotypes, viz. Hap1 (GGA), Hap2 (AAA), Hap3 (GAA), and Hap4 (AAT) of HSPB6 gene with heat tolerance traits did not differ significantly with any haplotype in Sahiwal cattle. This study provides the first association analyses between the SNPs of HSPB6 gene and heat tolerance traits in Sahiwal cattle, which could be used as effective SNP markers in genetic selection for heat tolerance in cattle breeding programs.

Heritability estimates for gonadal development traits and their genetic correlations with growth and heat tolerance traits in the Fujian Oyster Crassostrea angulata

Improving the progress of breeding is the main purpose of breeders, and shorting the reproductive cycle is one of the ways to improve the breeding progress. Although the reproductive cycle of Crassostrea angulata can be shortened from one year to half a year by selecting precocious individuals, little is known about whether this selection will accelerate their gonadal development or disturb their selection for productive traits. Here, the heritability of gonadal development traits (gametogenic stage and egg diameter) and their genetic correlations with both growth traits (shell height at 4 and 12 months and total body weight at 12 months) and heat tolerance trait were estimated. The heritability for gametogenic stage was low (0.18 ± 0.09), while the egg diameter showed a high heritability (0.78 ± 0.30). These results suggest that selection for precocious individuals has little effect on the rate of gonadal development in the C. angulata, despite the effect may be greater in females than in males. The genetic correlations between gonadal development traits and both growth (-0.02–0.30) and heat tolerance traits (-0.08–0.34) were low and non-significant. These results suggest that selection for precocious individuals has negligible effects on their productive traits. Therefore, it is feasible to double the breeding efficiency of C. angulata by halving their reproductive cycle.

Biogeography of cereal stemborers and their natural enemies: forecasting pest management efficacy under changing climate.

Climate warming presents physiological challenges to insects, manifesting as loss of key life-history fitness traits and survival. For interacting host-parasitoid species, physiological responses to heat stress may vary, thereby potentially uncoupling trophic ecological relationships. Here, we assessed heat tolerance traits and sensitivity to prevailing and future maximum temperatures for the cereal stemborer pests, Chilo partellus, Busseola fusca and Sesamia calamistis and their endo-parasitoids, Cotesia sesamiae and Cotesia flavipes. We further used the machine learning algorithm, Maximum Entropy (MaxEnt), to model current and potential distribution of these species. The mean critical thermal maxima (CTmax ) ranged from 39.5 ± 0.9°C to 44.6 ± 0.6°C and from 46.8 ± 0.7°C to 48.5 ± 0.9°C for parasitoids and stemborers, with C. sesamiae and Ch. partellus exhibiting the lowest and highest CTmax respectively. From the current climate to the 2050s scenario, parasitoids recorded a significant reduction in warming tolerance compared with their hosts. Habitat suitability for all stemborer-parasitoid species was spatially heterogeneous under current and future climatic scenarios. Cotesia sesamiae C. flavipes and B. fusca exhibited significant habitat loss, whereas Ch. partellus and S. calamistis showed a significant habitat gain under future 2050s predictions. Model metrics based on mean area under the curve ranged from 0.72 to 0.84 for all species, indicating a good predictive performance of the models. These results suggest C. sesamiae and C. flavipes may face survival constraints or extirpation compared with their pest hosts when environmental temperature reaches their upper thermal limits earlier, likely reducing pest regulation through density-mediated effects. The results demonstrate potential destabilization of stemborer-parasitoid trophic systems potentially compromising biocontrol efficacy under climate warming. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Identification and Genetic Mapping of Potential QTLs Conferring Heat Tolerance in Cotton (Gossypium hirsutum L.) by Using Micro Satellite Marker’s Approach

High-temperature stress can cause serious abiotic damage that limits the yield and quality of cotton plants. Heat Tolerance (HT) during the different developmental stages of cotton can guarantee a high yield under heat stress. HT is a complex trait that is regulated by multiple quantitative trait loci (QTLs). In this study, the F2 population derived from a cross between MNH-886, a heat-tolerant cultivar, and MNH-814, a heat-sensitive variety, was used to map HT QTLs during different morphological stages in cotton. A genetic map covering 4402.7 cm, with 175 marker loci and 26 linkage groups, was constructed by using this F2 population (94 individuals). This population was evaluated for different 23 morpho-physiological HT contributing traits QTL analysis via composite interval mapping detected 17 QTLs: three QTLs each for Total Number of Sympodes (TNS), Length of Bract (LOB), and Length of Staminal-column (LOS); two QTLs for First Sympodial Node Height (FSH), and one QTL each for Sympodial Node Height (SNH), Percent Boll set on second position along Sympodia (PBS), Total Number of Nodes (TNN), Number of Bolls (NOB), Total Number of Buds (TNB), and Length of Petal (LOP). Individually, the QTLs accounted for 7.76%–36.62% of phenotypic variation. QTLs identified linked with heat tolerance traits can facilitate marker-assisted breeding for heat tolerance in cotton.

Response of Physiological, Reproductive Function and Yield Traits in Cultivated Chickpea (Cicer arietinum L.) Under Heat Stress.

Under global climate change, high-temperature stress is becoming a major threat to crop yields, adversely affecting plant growth, and ultimately resulting in significant yield losses in various crops, including chickpea. Thus, identifying crop genotypes with increased heat stress (HS) tolerance is becoming a priority for chickpea research. Here, we assessed the response of seven physiological traits and four yield and yield-related traits in 39 chickpea genotypes grown in normal-sown and late-sown environments [to expose plants to HS (>32/20°C) at the reproductive stage] for two consecutive years (2017–2018 and 2018–2019). Significant genetic variability for the tested traits occurred under normal and HS conditions in both years. Based on the tested physiological parameters and yield-related traits, GNG2171, GNG1969, GNG1488, PantG186, CSJ515, RSG888, RSG945, RVG202, and GNG469 were identified as promising genotypes under HS. Further, ten heat-tolerant and ten heat-sensitive lines from the set of 39 genotypes were validated for their heat tolerance (32/20°C from flowering to maturity) in a controlled environment of a growth chamber. Of the ten heat-tolerant genotypes, GNG1969, GNG1488, PantG186, RSG888, CSJ315, and GNG1499 exhibited high heat tolerance evidenced by small reductions in pollen viability, pollen germination, and pod set %, high seed yield plant–1 and less damage to membranes, photosynthetic ability, leaf water status, and oxidative processes. In growth chamber, chlorophyll, photosynthetic efficiency, pollen germination, and pollen viability correlated strongly with yield traits. Thus, GNG1969, GNG1488, PantG186, RSG888, CSJ315, and GNG1499 genotypes could be used as candidate donors for transferring heat tolerance traits to high-yielding heat-sensitive varieties to develop heat-resilient chickpea cultivars.

Genomic selection applications can improve the environmental performance of aquatics: A case study on the heat tolerance of abalone.

Aquaculture is one of the world's fastest‐growing and most traded food industries, but it is under the threat of climate‐related risks represented by global warming, marine heatwave (MHW) events, ocean acidification, and deoxygenation. For the sustainable development of aquaculture, selective breeding may be a viable method to obtain aquatic economic species with greater tolerance to environmental stressors. In this study, we estimated the heritability of heat tolerance trait of Pacific abalone Haliotis discus hannai, performed genome‐wide association studies (GWAS) analysis for heat tolerance to detect single nucleotide polymorphisms (SNPs) and candidate genes, and assessed the potential of genomic selection (GS) in the breeding of abalone industry. A total of 1120 individuals were phenotyped for their heat tolerance and genotyped with 64,788 quality‐controlled SNPs. The heritability of heat tolerance was moderate (0.35–0.42) and the predictive accuracy estimated using BayesB (0.55 ± 0.05) was higher than that using GBLUP (0.40 ± 0.01). A total of 11 genome‐wide significant SNPs and 2 suggestive SNPs were associated with heat tolerance of abalone, and 13 candidate genes were identified, including got2,znfx1,l(2)efl, and lrp5. Based on GWAS results, the prediction accuracy using the top 5K SNPs was higher than that using randomly selected SNPs and higher than that using all SNPs. These results suggest that GS is an efficient approach for improving the heat tolerance of abalone and pave the way for abalone selecting breeding programs in rapidly changing oceans.

Context-dependent integrated stress resistance promotes a global invasive pest.

In nature, insects concurrently face multiple environmental stressors, a scenario likely increasing with climate change. Integrated stress resistance (ISR) thus often improves fitness and could drive invasiveness, but how physiological mechanisms influence invasion has lacked examination. Here, we investigated cross-tolerance to abiotic stress factors which may influence range limits in the South American tomato pinworm-a global invader that is an ecologically and socially damaging crop pest. Specifically, we tested the effects of prior rapid cold- and heat-hardening (RCH and RHH), fasting, and desiccation on cold and heat tolerance traits, as well as starvation and desiccation survivability between T. absoluta life stages. Acclimation effects on critical thermal minima (CTmin ) and maxima (CTmax ) were inconsistent, showing significantly deleterious effects of RCH on adult CTmax and CTmin and, conversely, beneficial acclimation effects of RCH on larval CTmin . While no beneficial effects of desiccation acclimation were recorded for desiccation tolerance, fasted individuals had significantly higher survival in adults, whereas fasting negatively affected larval tolerances. Furthermore, fasted and desiccation acclimated adults had significantly higher starvation tolerance, showing strong evidence for cross-tolerance. Our results show context-dependent ISR traits that may promote T. absoluta fitness and competitiveness. Given the frequent overlapping occurrence of these divergent stressors, ISR reported here may thus partly elucidate the observed rapid global spread of T. absoluta into more stressful environments than expected. This information is vital in determining the underpinnings of multistressor responses, which are fundamental in forecasting species responses to changing environments and management responses.

Comprehensive Understanding of Selecting Traits for Heat Tolerance during Vegetative and Reproductive Growth Stages in Tomato

Climate change is an important emerging issue worldwide; the surface temperature of the earth is anticipated to increase by 0.3 °C in every decade. This elevated temperature causes an adverse impact of heat stress (HS) on vegetable crops; this has been considered as a crucial limiting factor for global food security as well as crop production. In tomato plants, HS also causes changes in physiological, morphological, biochemical, and molecular responses during all vegetative and reproductive growth stages, resulting in poor fruit quality and low yield. Thus, to select genotypes and develop tomato cultivars with heat tolerance, feasible and reliable screening strategies are required that can be adopted in breeding programs in both open-field and greenhouse conditions. In this review, we discuss previous and recent studies describing attempts to screen heat-tolerant tomato genotypes under HS that have adopted different HS regimes and threshold temperatures, and the association of heat tolerance with physiological and biochemical traits during vegetative and reproductive growth stages. In addition, we examined the wide variety of parameters to evaluate the tomato’s tolerance to HS, including vegetative growth, such as leaf growth parameters, plant height and stem, as well as reproductive growth in terms of flower number, fruit set and yield, and pollen and ovule development, thereby proposing strategies for the development of heat-tolerant tomato cultivars in response to high temperature.

Genetic diversity and signatures of selection for heat tolerance and immune response in Iranian native chickens

BackgroundUnderstanding how evolutionary forces relating to climate have shaped the patterns of genetic variation within and between species is a fundamental pursuit in biology. Iranian indigenous chickens have evolved genetic adaptations to their local environmental conditions, such as hot and arid regions. In the present study, we provide a population genome landscape of genetic variations in 72 chickens representing nine Iranian indigenous ecotypes (Creeper, Isfahan, Lari, Marand, Mashhad, Naked neck, Sari, Shiraz and Yazd) and two commercial lines (White Leghorn and Arian). We further performed comparative population genomics to evaluate the genetic basis underlying variation in the adaptation to hot climate and immune response in indigenous chicken ecotypes. To detect genomic signatures of adaptation, we applied nucleotide diversity (θπ) and FST statistical measurements, and further analyzed the results to find genomic regions under selection for hot adaptation and immune response-related traits.ResultsWe assessed the relationship between the genetic diversity of indigenous chicken ecotypes and their genetic distances to two different commercial lines. The results of genetic structure analysis revealed clustering of indigenous chickens in agreement with their geographic origin. Among all studied chicken groups, the highest level of linkage disequilibrium (LD) (~ 0.70) was observed in White Leghorn group at marker pairs distance of 1 Kb. The results from admixture analysis demonstrated evidence of shared ancestry between Arian individuals and indigenous chickens, especially those from the north of the country. Our search for potential genomic regions under selection in indigenous chicken ecotypes revealed several immune response and heat shock protein-related genes, such as HSP70, HSPA9, HSPH1, HSP90AB1 and PLCB4 that have been previously unknown to be involved in environmental-adaptive traits. In addition, we found some other candidate loci on different chromosomes probably related with hot adaptation and immune response-related traits.ConclusionsThe work provides crucial insights into the structural variation in the genome of Iranian indigenous chicken ecotypes, which up to now has not been genetically investigated. Several genes were identified as candidates for drought, heat tolerance, immune response and other phenotypic traits. These candidate genes may be helpful targets for understanding of the molecular basis of adaptation to hot environmental climate and as such they should be used in chicken breeding programs to select more efficient breeds for desert climate.

Heterosis in Bread Wheat (Triticum aestivum L.) for Earliness and Heat Tolerant Traits over the Environments

The present study was carried out in 9 diverse parents, their 36 hybrids and 2 checks evaluated during Rabi 2020-21 at Rajasthan College of Agriculture, Mpuat, Udaipur in RBD with three replications in three different environments in wheat for earliness and heat tolerant traits viz., days to 50 per cent flowering, leaf canopy temperature, total protein content in grains, heat injury, proline content and total chlorophyll content on pooled basis. The pooled analysis for above characters revealed that mean squares due to environments, genotypes, parents, crosses as well as parents v/s. crosses were significant indicating presence of overall heterosis for the traits. Out of thirty six crosses 5 crosses viz., GJW 463 x RAJ 4120, DBW 173 x RAJ 4120, GJW 463 x DBW 173, GW 451 x LOK 1 and DBW 173 x RAJ 3777 were found superior with maximum significant heterobeltiosis and economic heterosis for heat tolerant traits and earliness over the environments. These genotypes could be used to maintain transgressive segregants in future breeding programme.

Impedance Flow Cytometry for Selection of Pollen Traits Under High Temperature Stress in Pepper

High temperature stress is a major limiting factor for pepper productivity, which will continue to be a problem under climate change scenarios. Developing heat tolerant cultivars is critical for sustained pepper production, especially in tropical and subtropical regions. In fruiting crops, like pepper, reproductive tissues, especially pollen, are the most sensitive to high temperature stress. Typically, pollen viability and germination are assessed through staining and microscopy, which is tedious and potentially inaccurate. To increase efficiency in assessing pollen traits of pepper, the use of impedance flow cytometry (IFC) has been proposed. We conducted three independent experiments to determine the most effective methodology to use IFC for evaluating pollen traits for heat tolerance in pepper. Seven floral developmental stages were evaluated, and stages 3, 4, and 5 were found to best combine high pollen concentration and activity. Flowers in development stages 3, 4, or 5 were then heat treated at 41, 44, 47, 50, and 55 °C or not heat treated (control). The critical temperature to assess heat tolerance using IFC was found to be 50 °C, with a reduction in pollen activity and concentration occurring at temperatures greater than 47 °C. Twenty-one entries of pepper were then accessed for pollen traits using the staining and IFC methods over 2 months, April (cooler) and June (hotter). Growing environment was found to be the greatest contributor to variability for nearly all pollen traits assessed, with performance during June nearly always being lower. PBC 507 and PBC 831 were identified as being new sources of heat tolerance, based on using IFC for assessing pollen. Pollen viability determined by staining and pollen activity determined using IFC were significantly positively correlated, indicating that IFC is an efficient and accurate method to assess pollen traits in pepper. This work provides a basis for further research in this area and supports more efficient breeding of heat-tolerant cultivars.

Connecting Heat Tolerance and Tenderness in Bos indicus Influenced Cattle.

Simple SummaryBos indicus (also known as zebu or humped) cattle are heat tolerant and parasite resistant, which is advantageous in hot, humid climates. However, Bos indicus cattle are also known for excitable temperaments, slower growth, and variation in meat quality characteristics. The relationships between thermotolerance, temperament, and meat production traits are poorly understood. Due to its contribution to body weight, muscle may play an important role in determining the thermoregulatory capacity of Bos indicus cattle. Ultimately, defining relationships between muscle metabolism and heat tolerance are necessary in order to enhance tenderness, without sacrificing heat tolerance of Bos indicus breeds.Bos indicus cattle are widely utilized in tropical and subtropical climates. Their heat tolerance and parasite resistance are integral for beef production in these regions; however, a reputation for excitable temperaments, slower growth, and variation in tenderness has limited their use in commercial beef production. This suggests that there is antagonism between heat tolerance and meat production traits. Meat quality characteristics are determined by the properties of skeletal muscle as well as conditions during slaughter and processing. Thus, it is possible that adaptations related to heat tolerance in the living animal affect tenderness and other meat quality attributes. Since muscle represents a large proportion of body mass, relatively small changes at the cellular level could impact overall heat production of the animal. Specifically, protein degradation and mitochondria function are aspects of organ and cellular metabolism that may help limit heat production and also have a connection to tenderness. Protein degradation postmortem is critical to structural changes that enhance tenderness whereas mitochondria may influence tenderness through their roles in energy metabolism, calcium regulation, cell death signaling, and oxidative stress. This review explores potential relationships between cellular metabolism in vivo and beef quality development in Bos indicus and Bos indicus influenced cattle.

Multivariate analysis of body weight, morphometric and thermo-physiological traits of indigenous pigs under tropical conditions

The study aimed at describing objectively the interdependence among the morphological and heat tolerance traits of Nigerian indigenous pigs and to predict body weight from conformation traits. Data on body weight, eight linear body measurements (BL, CG, CD, WH, RH, EL, SL and TL) and three thermo-physiological parameters were measured on 150 randomly selected pigs of three growth stages (piglets, growers and finishers) from February to December, 2020. The animals were managed in an extensive system in Plateau State, north central Nigeria. General linear model was used to study growth stage and sex effects including their interaction. Multivariate principal component analysis was used for the size, shape and heat tolerance determination while the animals were classified using canonical discriminant analysis. The stepwise regression was used for body weight prediction. The results showed that finishers had significantly higher (P&lt;0.05) body weight, body length, chest girth, chest depth, withers height, rump height, ear length, snout length and tail length, followed by growers while the least values were recorded in piglets. Pulse rate was not significantly different (P&gt;0.05) between piglets and finishers, although the latter had higher respiratory rate (39.48±0.53 vs. 39.90±0.53 vs. 36.77±0.75). However, rectal temperature was similar (P&gt;0.05) among the three pig categories. With the exception of tail length, sexual dimorphism was observed in all the morphometric traits with higher values recorded for males. However, the three thermo-physiological traits were not affected by sex (P&gt;0.05). BW was highly and positively correlated with most biometric traits (r = 0.80-0.93, 0.66-0.80 and 0.83-0.93; P&lt;0.01 for piglets, growers and finishers, respectively). Three principal components (PC1, PC2 and PC3) were extracted for optimal balance of the animals. Withers height, ear length and body weight were found to be the most discriminating variables to separate the pig categories. Classification results showed that 100% of piglets, 96.7% of growers and 96.7% of finishers were correctly assigned to their distinct populations. The present Information could be exploited in devising appropriate management and breeding programs for tropically adapted pigs in Nigeria.

A novel SNP of TECPR2 gene associated with heat tolerance in Chinese cattle

Heat stress affects the animal production and causes serious economic losses to the husbandry. Tectonin beta-propeller repeat containing 2 (TECPR2) gene plays an important role in autophagy which may affect the temperature sensation in animals. A missense mutation (XM_024981840.1:c.3989 G > A p.Arg1330His) of the transcripts X4 in the bovine TECPR2 gene was identified. In this study, the c.3989 G > A variant in TECPR2 gene was genotyped in a total of 25 cattle breeds (520 individuals). Our results indicated that the frequency of A allele showed a decreasing pattern from southern cattle to northern cattle, while the frequency of G allele showed the opposite pattern, which was consistent with the climate distribution of China. Compared with the GG genotype, southern cattle carried more the AA and AG genotypes. Furthermore, the association results carried out that the frequencies of genotypes (GG, AG, AA) and the value of climate parameters (mean annual temperature (T), relative humidity (RH) and temperature humidity index (THI) were significantly correlated (p < 0.01). Hence, we speculated that the c.3989 G > A variant of TECPR2 gene was associated with the heat tolerance trait in Chinese cattle and the locus may be considered as a molecular marker for Chinese cattle breeding.