Heat Tolerance Index Research Articles

Evaluation of a new method for quantification of heat tolerance in different wheat cultivars

Heat stress seriously affects wheat production in many regions of the world. At present, heat tolerance research remains one of the least understood fields in wheat genetics and breeding and there is a lack of effective methods to quantify heat stress and heat tolerance in different wheat cultivars. The objective of this study was to use various wheat cultivars to evaluate stress intensity (δ) and a new method for quantification of heat tolerance and compare this technique with three other currently utilized methods. This new parameter for heat tolerance quantification is referred to as the heat tolerance index (HTI) and is an indicator of both yield potential and yield stability. Heat treatments were applied in a controlled setting when anthesis had been reached for 80% of the wheat. The stress intensity evaluation indicated heat shock was the main factor associated with kernel weight reduction while grain yield reduction was mainly associated with chronic high temperature. The methods evaluation showed that a temperature difference of 5°C from natural temperatures was a suitable heat treatment to compare to the untreated controls. HTI was positively correlated with yield under heat stress (r=0.8657, δ2010=0.15, in 2009–2010; r=0.8418, δ2011=0.20, in 2010–2011; P<0.01), and negatively correlated with yield reduction rate (r=–0.8344, in 2009–2010; r=–0.7158, in 2010–2011; P<0.01). The results of this study validated the use of HTI and temperature difference control for quantifying wheat heat tolerance that included the yield potential and the stability of different wheat cultivars under heat stress. Additionally, 10 wheat cultivars showed high HTI and should be further tested for their heat confirming characteristics for use in wheat heat tolerance breeding.

Evaluation of chickpea (Cicer arietinum L.) genotypes for heat tolerance: a physiological assessment

A field experiment was carried out in factorial randomized block design to evaluate 56 chickpea (Cicer arietinum L.) genotypes for high temperature tolerance. High temperature was imposed by delaying sowing dates i.e. normal (9th November) and late sowing (19th December). Under late sown condition, high temperature was experienced by crop starting from flowering stage to crop maturity (during this period maximum temperature ranged from 25 to 40 °C). Chickpea genotypes were assessed based on various physiological tests. A significant genotypic variability was recorded in relative water content, membrane stability index, canopy temperature depression (CTD), photosynthetic pigments, photosynthetic rate (PN), canopy photosynthesis, growth, and yield based indices. In general, late sown high temperature stress condition significantly reduced all the physiological, growth and yield parameters except CTD. For each trait promising genotypes under late sown (high temperature) condition were identified. Furthermore, photosynthetic pigment profile under late sown high temperature condition at podding stage was analyzed using thin layer chromatography and that also revealed the genotypic variations. Tolerant genotypes in general maintained darker bands and also showed more number of photosynthetic pigments than relatively sensitive ones. In addition to this, total carotenoids content, under late sown condition at podding stage exhibited significant positive association with heat tolerance index (HTI), CTD, rate of photosynthesis and total chlorophyll content. That in turn indicated that higher level of total carotenoids played important role to maintain heat tolerance under late sown high temperature condition by protecting the photosynthetic machinery. In general, genotypes identified for high temperature tolerance based on HTI, heat susceptibility index (HSI) and heat yield stability index (HYSI), also had better physiological performance as evident from higher values of almost all physiological parameters recorded during the present study. Further, on the basis of all over performance, eight genotypes Pusa 1103, Pusa 1003, KWR 108, BGM 408, BG 240, PG 95333, JG 14, BG 1077 proved to be high temperature tolerant (HSI ≤ 0.9, HTI ≥ 0.59 and HYSI ≥ 50%).

Evaluation for heat stress tolerance in durum wheat genotypes using stress tolerance indices

ABSTRACTHeat stress is a major environmental stress limiting wheat productivity in most cereal growing areas of the world. The objective of this study was to evaluate heat stress tolerance in durum wheat (Triticum turgidum var. durum) genotypes. For this purpose, 45 genotypes were grown during two growing seasons (2012–2013 and 2013–2014) under non-stress (normal sowing) and heat-stress (late sowing) conditions. The heat tolerance indices were calculated based on grain yield under normal sowing (Yp) and late sowing (Ys) conditions. Results of combined analysis of variance showed the significant influences of heat stress on grain yield as well as significant differences among genotypes for grain yield and the indices. Results of correlation coefficients and multivariate analyses revealed that the stress tolerance index (STI), geometric mean productivity and mean productivity (MP) indices were the most profitable criteria for selection of heat tolerant and high yielding genotypes. Using STI, GMP and MP, the genotypes G29, G41 and G10 were found to be the best genotypes with relatively high yield and suitable for both normal and heat stressed conditions. Based on biplot analysis using Yp, Ys and the indices, it was possible to identify superior genotypes across the conditions.

English

Wheat is the most popular and staple food for millions of people. It is severely affected by heat stress in many countries. Vegetative growth and reproductive phases in wheat differ in their sensitivity to temperature. Heat tolerant (GW-190) and Heat susceptible (J-2010-11) genotypes grown up to tillering and grain filling stages and Heat treatments (40°C and 45°C for 2h and 4h) were given using Heating House. After heat treatment samples were collected, the biochemical and physiological analysis such as Protein, Proline, Glycine betaine, Membrane stability, Relative water content, Germination percent, Seed vigour and Heat tolerant index were performed. Protein, proline and glycine betaine were found significantly highest 34.06 mg/g Fr. Wt., 13.70 mg% and 902.24 µg/F. wt respectively in heat tolerant genotype GW-190 at 45°C for 4 h at tillering stage. Membrane stability and relative water content were found significantly highest 56.83% and 86.15 % respectively in heat tolerant genotype GW-190 at tillering stage. Germination percent, Seed vigor and Heat tolerance index were found higher in control group of Heat tolerant GW-190 genotypes. Where, all the biochemical and physiological contents were found lower in heat susceptible J-2010-11 genotype. From the above results it was concluded that GW-190 was heat tolerant genotypes which is suitable for grown in area of high temperature and J-2010-11 was found heat susceptible. Key words: Relative water content, membrane stability, seed index, heat tolerant index, correlation.

Vacas F1 Holandês x Zebu no terço final de gestação apresentam adaptação fisiológica quando criadas no ambiente semiárido

This study aimed to verify the adaptability of F1 Holstein x Zebu cows in the late pregnancy third, raised in the semiarid region of Minas Gerais, by means of physiological responses. A total of ten cows were used, all in fourth pregnancy. To characterize the climatic environment, daily collections of air temperature, air relative humidity and wind speed were carried out to enable the calculation of the Globe Temperature and Humidity Index (GTHI) and Radiant Thermal Load (RTL). The physiological parameters analyzed were: respiratory frequency, rectal temperature and surface body temperature, at 10 am and 3 pm. The adaptability tests used were Heat Tolerance Index (HTI) and Heat Tolerance Coefficient (HTC). The climatic environment was out of thermal comfort in the afternoon. There were significant differences (P <0.05) for the values of the physiological parameters. However, these responses were within the comfort range recommended for crossbred animals. The adaptability tests confirmed that the animals show adaptation to the semiarid environment of Minas Gerais, showing differences (P <0.05) on HTC between 10 am (2.52) and 3 pm (2.64), and the HTI showed an average of 9.64, a value that is very close to the index 10. It is concluded that the F1 Holstein x Zebu cows in the late pregnancy third are adapted to the climate in the semiarid region of Minas Gerais, for not altering their physiological behavior in face of the adversities of the climatic environment.

Sulfhydral compounds mitigate the adverse effect of high temperature stress in contrasting wheat genotypes

Sulfhydral Compounds Mitigate the Adverse Effect of High Temperature Stress in Contrasting Wheat Genotypes The experiment was conducted to investigate the role of foliar sprays of thiourea (500,1000 ppm), thioglycolic acid (100,200 ppm) and dithiothreitol (25,50 ppm) under high temperature stress on physiology, growth and productivity of heat tolerant (Raj 4083) and heat susceptible (PBW 373) wheat genotypes. These genotypes were sown on 15th November (normal) and 15th December (heat stress) in field conditions under standard package and practices. The sulfhydral compounds were sprayed at jointing (45 DAS) and anthesis (60 DAS) stages. Results showed that photosynthetic parameters, water status, membrane stability index, pigment contents and yield reduced significantly under temperature stress conditions in both the genotypes. The foliar application of thiourea, thioglycolic acid and dithiothreitol increased or maintained these parameters efficiently in tolerant as well as susceptible genotypes. The heat susceptibility index decreased whereas heat tolerance index increased on account of sulfhydral spray. It is concluded that the foliar application of thiourea, thioglycolicacid and dithiothreitol improved the production potential of wheat genotypes under stress conditions; however, the application of dithiothreitol 50 ppm performed the best for mitigating the adverse effects of high temperature stress in wheat....

Heat tolerance in Brazilian hair sheep.

ObjectiveThe aim of this study was to evaluate heat tolerance using heat tolerance indices, physiological, physical, thermographic, and hematological parameters in Santa Ines and Morada Nova sheep breeds in the Federal District, Brazil.MethodsTwenty-six adult hair sheep, one and a half years old, from two genetic groups (Santa Ines: 12 males and 4 females; Morada Nova: 7 males and 3 females) were used and data (rectal temperature, respiratory rate, heart rate, skin temperatures; hematological parameters) were collected during three consecutive days, twice a day (morning and afternoon), with a total of six repetitions. Also physical parameters (biometric measurements, skin and hair traits) and heat tolerance indices (temperature-humidity index, Iberia and Benezra) were evaluated. The analyses included analyses of variance, correlation, and principal components with a significance level of 5%.ResultsThe environmental indices, in general, indicate a situation of thermal discomfort for the animals during the afternoon. Breed significantly influenced (p<0.001) physiological and physical characteristics of skin, hair, biometric measurements and Iberia and Benezra heat tolerance indices. Santa Ines animals were bigger and had longer, greater number and darker hair, thicker skin, greater respiratory rate and Benezra index and lower Iberia index compared with Morada Nova breed.ConclusionAlthough both breeds can be considered adapted to the environmental conditions of the region, Morada Nova breed is most suitable for farming in the Midwest region. The positive correlation found between the thermographic temperatures and physiological parameters indicates that this technique can be used to evaluate thermal comfort. Also, it has the advantage that animals do not have to be handled, which favors animal welfare.

Evaluation of heat tolerance indices in bread wheat (Triticum aestivum L.) genotypes based on physiological, biochemical and molecular markers

An experiment was carried out to examine wheat seed germination, vigor index, biochemical indices and genetic diversity associated with heat tolerance, using ISSR markers, under heat stress, viz., 22 ± 1, 25 ± 1, 30 ± 1 and 35 ± 1 °C referred as T0, T1, T2 and T3, respectively, in bread wheat genotypes. Wheat genotypes were categorized as heat tolerant and susceptible based on heat tolerance index (HTI). The germination percentage and seedling vigor index were positively correlated with HTI. The HTI was found higher in tolerant cv. GW-190, followed by GW-496, J-2010-02 and J-2010-10 genotypes under T3. Leaf proline content correlated positively with HTI. Sugars, free amino acids and protein content in leaf correlated positively with each other during heat stress. Total 24 ISSR primers were used to generate 124 bands across 10 wheat genotypes, of which 76 bands were polymorphic with an average of 3.16 bands per marker. The ISSR markers distinguished two clusters of wheat genotypes and out grouped heat tolerant genotype (GW-190 and GW-496) and heat sensitive genotype (J-2010-05) with minimum 68 % similarity. The jaccard similarity coefficient ranged from 0.68 to 0.89. The UBC-811 amplified unique markers distinguished tolerant GW-190 (152 bp) and sensitive J-2010-10 (110 bp) genotypes.

Expediency of using heat tolerance index of bread winter wheat seeds

Aim. To study the dependence of heat tolerance index of bread winter wheat seeds on the varietal characteristics, abiotic and anthropogenic factors.Methods. Laboratory (determining seed vigor and laboratory germination), mathematical statistics (for assessing the reliability of research results).Results. The highest heat tolerance index of seeds was marked in varieties: Podolianka, Pereiaslavka, Remeslivna, Myronivska rannostyhla, Natalka, Myrliena, Myronivska storichna, Yuviliar Myronivskyi, Oberih Myronivskyi, Horlytsia myronivska, Berehynia myronivska, Hospodynia myronivska.The seeds being grown with no mineral fertilizer after predecessors black fallow, peas, and perennial grasses had high heat tolerance index (79, 72, and 66%), and after predecessors silage corn and winter wheat their heat tolerance index increased by 8 and 12% when applying fertilizers at dose N120P80K80.When warming seeds, high indices of seed vigor and laboratory germination were noted in the variants of application plant protection products and micronutrient fertilizers during spring-summer period, as compared to untreated variants.Conclusions. Experimentally it was established that heat tolerance of winter wheat seeds depends on the varietal characteristics and the influence of abiotic and anthropogenic factors. These data indicate the possibility of using thermo-testing method for a more objective assessment of sowing qualities. As we consider, it is necessary to carry out comprehensive studies on seeds grown in various soil and climatic zones by common methods, thus making it possible to obtain vast experimental material for studying development and productivity of plants derived from various quality seeds and to develop a test system of forecasting yield properties of seeds.

Effect of the C.–1 388 A>G polymorphism in chicken heat shock transcription factor 3 gene on heat tolerance

Heat stress is one of the main factors that influence poultry production. Heat shock proteins (HSPs) are known to affect heat tolerance. The formation of HSPs is regulated by heat shock transcription factor 3 (HSF3) in chicken. A DNA pool was established for identifying single nucleotide polymorphisms (SNPs) of the chicken HSF3, and 13 SNPs were detected. The bioinformatic analysis showed that 8 SNPs had the capacity to alter the transcription activity of HSF3. The dual luciferase report gene assay showed that there was a significant difference (P<0.01) in the Firefly luciferase/Renilla luciferase ratio (F/R) of C.–1 703 A>G (S1) and C.–1 388 A>G (S4) sites at the 5′-untranslated region (UTR) of chicken HSF3. The electrophoretic mobility shift assay showed that the S4 site was a transcription binding factor. The analysis of the association of the S1 and S4 sites with heat tolerance index revealed that the S4 site was significantly correlated with the CD3+ T cell, corticosterone, and T3 levels in Lingshan chickens and with the heterophil/lymphocyte value in White Recessive Rock. These results showed that the S4 site at the 5′ UTR of chicken HSF3 might have an impact on heat tolerance in summer and could be used as a potential marker for the selection of chicken with heat tolerance in the future.

Indices and their Applicability under High Temperature in Potato (&lt;i&gt;Solanum tuberosum&lt;/i&gt; L.) Cultivars

The increasing temperature is going to be more vulnerable for cool season crops like potato which requires an optimum productivity temperature of 18 to 20 °C. Thus, breeding for heat tolerance has become very important. Therefore, some previously used indices for abiotic stress tolerance have been used in our study for screening of high temperature stress tolerance in potato. Three high yielding (Kufri jyoti, Kufri megha and Kufri pokraj) and two local (Rangpuria and Badami) commonly grown potato cultivars were selected for our experiment. Potato cultivars were sown under normal condition and two high temperature conditions (polyhouse and early season) and indices such as HSI (heat susceptibility index), HTI (heat tolerance index), GM (geometric mean) and HII (heat intensity index) were used to evaluate the performance of the cultivars under all the three temperature conditions. The positive and significant correlation between HTI (heat tolerance index), and GM (geometric mean) as well as with tuber yield under all the conditions revealed that these indices were efficient in selecting the high temperature tolerant potato cultivars. We recorded the equal applicability of these two indices for both high yielding and local group of potato cultivars. Our study revealed that cultivar Kufri megha and Rangpuria showed higher heat tolerance between high yielding and local cultivars respectively.

Infrared Thermography to Evaluate Heat Tolerance in Different Genetic Groups of Lambs

Heat stress is considered a limiting factor for sheep production. We used information from physiological characteristics linked to heat tolerance to determine whether infrared thermography temperatures were able to separate groups of animals and determine the most important variables in this differentiation. Forty-eight four-month-old male lambs from eight genetic groups were used. Physiological (rectal temperature–RT, heart rate–HR, respiratory rate–RR) and blood traits, infrared thermography temperatures, heat tolerance indices, body measurements, weight and carcass traits were measured. Statistical analyses included variance, correlations, factor, discrimination and regression. Observing the correlations between physiological characteristics (RT, RR and HR) with temperatures measured by infrared thermography, regions for further studies should include the mean temperature of flank, nose and rump. Results show that there are strong relationships between thermograph measurements and RR, RT and HR in lambs, which are suggested to be directly correlated with heat tolerance capacity of the different genetic groups evaluated in this study. The assessment of body surface temperature measured by the thermograph could be used as a noninvasive tool to assess heat tolerance of the animals.

Indices and their Applicability under High Temperature in Potato (&lt;i&gt;Solanum tuberosum&lt;/i&gt; L.) Cultivars

The increasing temperature is going to be more vulnerable for cool season crops like potato which requires an optimum productivity temperature of 18 to 20 °C. Thus, breeding for heat tolerance has become very important. Therefore, some previously used indices for abiotic stress tolerance have been used in our study for screening of high temperature stress tolerance in potato. Three high yielding (Kufri jyoti, Kufri megha and Kufri pokraj) and two local (Rangpuria and Badami) commonly grown potato cultivars were selected for our experiment. Potato cultivars were sown under normal condition and two high temperature conditions (polyhouse and early season) and indices such as HSI (heat susceptibility index), HTI (heat tolerance index), GM (geometric mean) and HII (heat intensity index) were used to evaluate the performance of the cultivars under all the three temperature conditions. The positive and significant correlation between HTI (heat tolerance index), and GM (geometric mean) as well as with tuber yield under all the conditions revealed that these indices were efficient in selecting the high temperature tolerant potato cultivars. We recorded the equal applicability of these two indices for both high yielding and local group of potato cultivars. Our study revealed that cultivar Kufri megha and Rangpuria showed higher heat tolerance between high yielding and local cultivars respectively.

Thermal comfort indices of female Murrah buffaloes reared in the Eastern Amazon.

The study aimed to develop new and more specific thermal comfort indices for buffaloes reared in the Amazon region. Twenty female Murrah buffaloes were studied for a year. The animals were fed in pasture with drinking water and mineral supplementation ad libitum. The following parameters were measured twice a week in the morning (7 AM) and afternoon (1 PM): air temperature (AT), relative air humidity (RH), dew point temperature (DPT), wet bulb temperature (WBT), black globe temperature (BGT), rectal temperature (RT), respiratory rate (RR), and body surface temperature (BST). The temperature and humidity index (THI), globe temperature and humidity index (GTHI), Benezra's comfort index (BTCI), and Ibéria's heat tolerance index (IHTI) were calculated so they could be compared to the new indices. Multivariate regression analyses were carried out using the canonical correlation model, and all indices were correlated with the physiological and climatic variables. Three pairs of indices (general, effective, and practical) were determined comprising the buffalo comfort climatic condition index (BCCCI) and the buffalo environmental comfort index (BECI). The indices were validated and a great agreement was found among the BCCCIs (general, effective, and practical), with 98.3 % between general and effective a.nd 92.6 % between general and practical. A significant correlation (P < 0.01) was found between the new indices and the physiological and climatic variables, which indicated that these may be used in pairs to diagnose thermal stress in buffaloes reared in the Amazon.

Field response of chickpea (Cicer arietinum L.) to high temperature

High temperature is an important factor affecting chickpea growth, development and grain yield. Understanding the plant response to high temperature is a key strategy in breeding for heat tolerance in chickpea (Cicer arietinum L.). This study assessed genetic variability for heat tolerance in chickpea and identified sources of heat tolerance that could be used for crop improvement. One hundred and sixty-seven genotypes were grown in two environments (heat stressed/late sown and non-stressed/optimal sowing time) in 2 years (2009–2010 and 2010–2011) at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, India. Large genetic variation was observed for phenology, growth, yield components and grain yield. While phenology (assessed as days to first flower, days to 50% flowering and days to first pod) was negatively correlated with grain yield at high temperature; plant biomass, pod number, filled pod number and seed number per plant were positively correlated. Genotypes were classified into short and long duration groups based on their maturity. Days to first flowering (DFF) of long duration genotypes were negatively associated with grain yield under stressed conditions in both years compared with medium to short duration genotypes. However, genotypes varied in their heat sensitivity and temperatures ≥35°C produced yield losses up to 39%. A heat tolerance index (HTI) classified the genotypes into five groups: (i) stable heat tolerant (>0.5), (ii) moderately heat tolerant (0.1–0.49), (iii) stable heat sensitive (−ve values), (iv) heat tolerant to moderately sensitive (−0.10 to 1) and (v) heat sensitive to moderately tolerant (−0.5 to 0.4). Pod characteristics, including days to first pod and pod number per plant, were correlated with grain yield whereas canopy temperature depression (CTD) was generally not correlated. Heat tolerant genotypes in a range of maturities were identified that could be used to improve the heat tolerance of chickpea.

Tolerância ao calor em bovinos das raças Nelore branco, Nelore vermelho e Pantaneira

A identificação de parâmetros/ métricas associados à adaptação ambiental é uma das principais tendências e desafios da pecuária mundial. Desta forma, o objetivo deste trabalho foi avaliar as características de tolerância ao calor de bovinos da raça Nelore e Pantaneiro no ecossistema do Pantanal matogrossense no pico de calor da região. Estes animais foram mantidos por duas horas à sombra (8:00h às 10:00h) e em seguida uma hora ao sol (10:00h às 11:00h). Após a exposição foram analisados parâmetros de frequência cardíaca (FC), frequência respiratória (FR), temperatura retal (TR), temperatura superficial da costela (TSC), temperatura superficial do pescoço (TSP) e temperatura superficial da garupa (TSG). Também foram avaliados a taxa de sudação (TXS), comprimento e densidade de pelos e calculados o índice de tolerância ao calor (ITC). No período estudado, a temperatura ambiental variou de 29,0 a 40,0ºC e a média para umidade relativa foi de 75%. O ambiente teve influência marcante sobre as variáveis fisiológicas, com exceção da FR. A TR e a TXS diferiram significativamente entre os grupos genéticos, sendo da raça Nelore mais elevada em relação à Pantaneira, mas todas dentro dos limites fisiológicos. A análise multivariada mostrou a importância de variáveis como taxa de sudação e comprimento de pelos para adaptação de bovinos na região. Apesar do Nelore vermelho estar separado dos outros dois grupos, foi possível concluir que ambas as raças analisadas apresentaram capacidade de adaptação e tolerância ao calor às condições climáticas do Pantanal e podem ser produzidas de modo sustentável na região.

Tolerância ao Calor em Ovinos de Pelames Claro e Escuro Submetidos ao Estresse Térmico

The aim of this research was to evaluate heat tolerance of thirty crossbred sheep (Santa Ines with Dorper) with white and black coat under heat stress. The experiment was conducted in September and October of 2012 and a completely randomized design was used. Before and after one hour exposure to solar radiation (14h00 - 15h00), rectal temperature, respiratory rate and surface temperature of the animals were measured. The Black Globe Temperature Humidity Index, the Heat Tolerance Index and the Heat Tolerance Coefficient were calculated. The values found for the Black Globe Temperature Humidity Index in the sun and in the shade were 89.08 and 82.81 respectively. Animals coat coloring did not influence on their rectal temperature and there was no difference on the heat tolerance index. It was verified the effect of coat coloring on the respiratory rate in dark colored hair coat sheep (P < 0.05) and the effect of the environment and coat coloring on the surface temperature and on the heat tolerance coefficient under the sun. Dark colored hair coat sheep presented lower heat tolerance.

Screening of Pearl Millet F1Hybrids for Heat Tolerance at Early Seedling Stage

Ten pearl millet genotypes selected on the basis of response to supra-optimal temperature tolerance were crossed in a half-diallel mating system. The 45F1hybrids produced were tested along with parents for heat tolerance and related traits at seedling stage. Field screening and laboratory screening techniques were simultaneously used for the evaluation ofF1hybrids and their parents. Heat tolerance was measured as seedling thermotolerance index (STI) and seed to seedling thermotolerance index (SSTI) under field conditions, but membrane thermostability (MTS) in the laboratory. The hybrid H77/29-2×CVJ-2-5-3-1-3 showed highest STI value followed by H77/833-2×96AC-93. The genotype H77/833-2×96AC-93 had the highest worth for SSTI. These three indices were highly correlated among themselves. STI values were invariably high, whereas SSTI has lower values, as it also covers the effect of under soil mortality (USM). It was seen that the heat tolerance indices STI and SSTI were not showing any perceptible pooled correlation with developmental traits except germination and emergence rate. Based on our results, it could be suggested that membrane thermostability (MTS) may be used for screening large number of genotypes. Field based indices STI and SSTI may be used for evaluation of hybrids and varieties before they are released.

&lt;b&gt;Heat tolerance index, food intake and weight gain of Santa Ines sheep in the agreste region of Pernambuco State, Brazil&lt;/b&gt; - doi: 10.4025/actascianimsci.v35i3.18466

This study evaluated the influence of coat color on the heat tolerance and performance of 21 Santa Inês lambs, non-pregnant, non-lactating, seven animals of each coat color: black, brown and white, with an average initial weight of 25.71, 24.85 and 25.00 kg, for white, brown and black animals, respectively, and 12 months of age. The study was conducted during summer in the agreste region of Pernambuco State, Brazil. Twenty-one sheeps were assigned to a completely randomized design with three treatments and seven replicates. The heat tolerance index and the animal performance were evaluated once a week for eight weeks. White sheep were slightly superior in heat tolerance to brown and black sheep, 88.3, 85.5 and 86.6 respectively, but this was not reflected in the growth performance of the animals, which showed average daily weight gain of 170.10, 193.69 and 199.50 g for animals white, brown and black, respectively.

Approach to Screen Coconut Varieties for High Temperature Tolerance by in-vitro Pollen Germination

Successful fruit set in coconut depends on several reproductive processes including pollen quality, pollen germination percentage (%PG) and pollen tube growth processes. Three preliminary experiments were conducted at the Coconut Research Institute, Lunuwila, Sri Lanka to quantify the response of in vitro pollen germination in coconut to time of incubation, the response of in vitro pollen germination and pollen tube growth to temperature and to determine the cardinal temperatures (Tmin, Topt, Tmax) of coconut varieties for in vitro pollen germination. Pollen was collected from palms of six cultivars / varieties expressing variable tolerance to abiotic stresses. Pollen germination and pollen tube length were recorded after incubation in artificial growth media at the respective treatments. For pollen collected during October / November periods, cultivars differed for in- vitro pollen germination percentage with a mean values of 23%. The mean cardinal temperatures (Tmin, Topt, Tmax) averaged over cultivars were 20.0 ºC, 28.0 ºC, and 38.8 ºC, respectively, for pollen germination. The information generated in this study will be tested in different seasons of the year for consistency and used to develop a heat tolerance index for coconut. This index will be used to identify coconut varieties suitable for high-temperature prone areas. In addition, the identified cardinal temperatures and response functions could be incorporated into process-based coconut models to increase prediction accuracy under current extreme and projected future climates. DOI: http://dx.doi.org/10.4038/cocos.v19i1.4748