Negative Effects Of High Temperature Research Articles

Effect of elevated CO2 and temperature on spikelet sterility in rice

Increase in the concentration of greenhouse gases (GHGs) led to global climate change has both direct and indirect effects on crop production. An experiment was conducted in IARI farm, New Delhi during the kharif season of year 2017 to quantify the effect of elevated CO2 and temperature on yield attributes as well as spikelet sterility of rice crop. Rice seedlings were transplanted in crates placed inside open top chambers (OTC) subjected to two different CO2 concentrations i.e. ambient (400 ppm) and elevated (550 ± 25 ppm) and also two different temperature levels i.e. ambient and elevated (+2°C). Nitrogen (N) was applied in five doses i.e., 0%, 75%, 100% and 125% of recommended N dose. Elevated CO2 increased panicle number in rice which was further increased with increase in N doses. High temperature significantly decreased grain number per panicle but elevated CO2level was able to increase this yield attribute. Spikelet sterility increased in high temperature treatment (18.9%) due to poor grain filling than chamber control treatment (12.4%). But more biomass accumulation resulted in more grain filling and less spikelet sterility under elevated CO2 level. The study showed thatelevated CO2 level will be able to alleviate the negative effect of high temperature on certain yield attributes in rice.

Can Future CO2 Concentrations Mitigate the Negative Effects of High Temperature and Longer Droughts on Forest Growth?

(1) Background: Climate change may subject forests to climate conditions to which they are not adapted. Elevated temperatures can potentially reduce net photosynthesis by increasing respiration rates and increasingly long droughts dramatically increase morbidity. While CO2 enrichment enhances productivity, it is not clear to what extent CO2 enrichment can offset the negative effects of elevated temperatures and longer droughts; (2) Methods: We used a mechanistic landscape model to conduct controlled simulation experiments manipulating CO2 concentration, temperature, drought length and soil water capacity; (3) Results: We found that elevated CO2 stimulates productivity such that it dwarfs the negative effect caused by elevated temperature. Energy reserves were not as strongly mitigated by elevated CO2, and the mortality of less competitive cohorts increased. Drought length had a surprisingly small effect on productivity measures, but longer droughts increased the risk of mortality; (4) Conclusions: Elevated CO2 compensated for the negative effect of longer droughts in terms of productivity measures, but not survival measures.

The consequences of change in management practices on maize yield under climate warming in Iran

The potential impacts of climate warming on grain yield, water, and nitrogen consumptions of maize have been repeatedly assessed across different regions of the world. However, to date, there is no comprehensive, large-scale evaluation on the effects of climate warming on the cropping systems of Iran. The objective of the current study was to quantify the effects of climate warming on the length of the growing period and grain yield of maize. We also tested the potential of changes in irrigation, nitrogen application rate, and using late maturity cultivars of maize to offset the negative impact of climate warming in order to maintain the current levels of grain yield (4 to 10 t ha−1 depending upon the province) in Iran. The crop modeling framework SIMPLACE was used to evaluate the effects of the warming temperatures, nitrogen application rate, and changes in thermal requirements of the cultivar scenario combinations on grain yield of maize in Iran. The climate, soil, and management inputs of the crop model were obtained from global datasets as grid cells at 0.5° × 0.5° resolution, and the outputs of the crop model were aggregated to the province level. Results of the grain yield projections showed a decline (− 0.1 to − 22%) in maize, especially in the Southern provinces (Khuzestan, Fars, and Kerman) under different warming scenarios by + 0.5 to + 2 °C, an increase from the baseline. The grain yield decline appeared to be mainly driven by a shortening of the length of the growing season and extreme heat stress during anthesis, the most sensitive period of crop growth. Increasing temperatures during the growing season lead to a marginal increase of absolute irrigation requirements over the maize growing areas. For all provinces, application of 10–25% more nitrogen than the current rate (170 kg N/ha-1) was able to offset the negative effects of higher temperatures (+ 0.5 and + 1.0 °C) during the growing season. However, the increased nitrogen application rates were not able to maintain the baseline level of grain yield under the + 1.5 and + 2.0 °C warming scenarios. Introducing late maturity cultivars, which required 20% more temperature sum than current cultivars to reach maturity, improved the grain yield in the cooler provinces by up to 10%. In conclusion, the grain yield baseline level may not be maintained under the highest magnitude of warming by increasing nitrogen application rates or using late maturity cultivars. Furthermore, more water is needed to produce a unit of grain under a warming climate. This study also suggests that combined adaptation strategies should be considered by policymakers in order to mitigate the negative impact of climate warming on the cropping systems of Iran.

Thermal Sensitivity of Gypsy Moth (Lepidoptera: Erebidae) During Larval and Pupal Development.

As global temperatures rise, thermal limits play an increasingly important role in determining the persistence and spread of invasive species. Gypsy moth (Lymantria dispar L. Lepidoptera: Erebidae) in North America provides an ideal system for studying the effect of high temperatures on invasive species performance. Here, we used fluctuating temperature regimes and exposed gypsy moth at specific points in development (first-fourth instar, pupa) to cycles of favorable (22-28°C) or high-temperature treatments (30-36°C, 32-38°C, 34-40°C) for either 2 or 7 d. We measured survival, growth, and prolonged effects of exposure on development time and pupal mass. Survival generally decreased as the experimental temperature treatment and duration of exposure increased for all instars and pupae, with a narrow threshold for lethal effects. In response to increasing temperature and magnified by longer exposure times, growth abruptly declined for third instars and development time increased for pupae. For those surviving the 2-d exposure treatment, development time to pupation increased for all instars, but we did not find consistent effects on final pupal mass. These negative effects of high temperature provide important data on the susceptibility of gypsy moth to heat at different points in development. This work improves our understanding of thermal limits to growth and development in gypsy moth and can aid in determining invasion potential under current and future climates.

Increase in CO2 concentration could alter the response of Hedera helix to climate change.

Increasing CO 2 concentration ([CO 2]) is likely to affect future species distributions, in interaction with other climate change drivers. However, current modeling approaches still seldom consider interactions between climatic factors and the importance of these interactions therefore remains mostly unexplored. Here, we combined dendrochronological and modeling approaches to study the interactive effects of increasing [CO 2] and temperature on the distribution of one of the main European liana species, Hedera helix. We combined a classical continent‐wide species distribution modeling approach with a case study using H. helix and Quercus cerris tree rings, where we explored the long‐term influence of a variety of climate drivers, including increasing [CO 2], and their interactions, on secondary growth. Finally, we explored how our findings could influence the model predictions. Climate‐only model predictions showed a small decrease in habitat suitability for H. helix in Europe; however, this was accompanied by a strong shift in the distribution toward the north and east. Our growth ring data suggested that H. helix can benefit from high [CO 2] under warm conditions, more than its tree hosts, which showed a weaker response to [CO 2] coupled with higher cavitation risk under high temperature. Increasing [CO 2] might therefore offset the negative effects of high temperatures on H. helix, and we illustrate how this might translate into maintenance of H. helix in warmer areas. Our results highlight the need to consider carbon fertilization and interactions between climate variables in ecological modeling. Combining dendrochronological analyses with spatial distribution modeling may provide opportunities to refine predictions of how climate change will affect species distributions.

Effect of Future Climate Change on Wheat Yield and Water Use Efficiency Under Semi-arid Conditions as Predicted by APSIM-Wheat Model

Any change in environmental conditions will affect crop growth and development and have an effect on crop productivity. The objective of the current study was to investigate the effect of climate change on irrigated wheat production and water use efficiency in Fars province in Iran. Accordingly, a general circulation model (HadCM3) was applied for two emission scenarios (A1B and A2) for three periods (2011–30, 2046–65 and 2080–2099) at nine locations in Fars province in central Iran. The APSIM (Agricultural Production Systems sIMulator) crop model was used to simulate growth and development of wheat as well as water use efficiency under future climate scenarios. The results indicated that the increase in CO2 concentration to 674 ppm in 2099 under A1B neutralized the negative effects of high temperature during the growing season and improved crop yield. The results indicate that, by the end of the century under the A2 emission scenario 10–15% of Fars province will have a grain yield of more than 10 t ha−1 and about 65% will have a grain yield of 8–10 t ha−1. Averaged across locations, scenarios and periods, water use efficiency increased by 3.56 kg ha−1 mm−1 in the future scenarios over baseline. Overall, the improved water use efficiency under future climate change was largely the result of a significant increase in yield (from 6989.5 kg ha−1 at baseline to 8416.5 kg ha−1 in all future scenarios) and decreased evapotranspiration (from 506.8 mm at baseline to 478 mm in all future scenarios).

Effects of high temperature on in vitro tuberization and accumulation of stress-responsive proteins in potato

Potato (Solanum tuberosum L.) plants are highly vulnerable to heat stress. Even moderately elevated temperatures can disturb the process of tuberization in this important crop, causing a decline in tuber initiation, a reduction in tuber bulking, and tuber disorders. In the present study, we investigated the effects of heat stress on tuberization in two potato cultivars, the heat-sensitive cultivar Desiree and the heat-tolerant cultivar Festival, using an in vitro system. A temperature of 29 °C reduced tuber initiation and tuber bulking, and stimulated shoot elongation in cv. Desiree, while this temperature treatment did not significantly alter tuberization or shoot elongation in cv. Festival. In addition, high temperature interfered with the onset of microtuber dormancy and promoted growth of tuber apical buds during the tuber bulking stage in both cultivars. Stress-responsive proteins HSP17.6-CI, HSP101, and eEF1A showed heat-induced accumulation patterns in shoots and microtubers of these two cultivars, with the exception of a decline in the abundance of eEF1A in cv. Desiree microtubers under heat stress. High levels of HSP17.6-CI in microtubers of cv. Desiree did not ameliorate the effects of heat stress on tuberization of this relatively heat-sensitive cultivar. Conversely, a higher level of eEF1A under heat stress in microtubers of the heat-tolerant cv. Festival indicated a possible function of this protein in alleviating the negative effects of high temperature on potato tuberization. This study suggested that analysis of stress-responsive proteins in potato microtubers combined with assessment of tuberization parameters in vitro may represent a useful screening procedure for selection of heat-tolerant potato genotypes.

Boron application improves yield of rice cultivars under high temperature stress during vegetative and reproductive stages.

It is reported that high temperatures (HT) would cause a marked decrease in world rice production. In tropical regions, high temperatures are a constraint to rice production and the most damaging effect is on spikelet sterility. Boron (B) plays a very important role in the cell wall formation, sugar translocation, and reproduction of the rice crop and could play an important role in alleviating high temperature stress. A pot culture experiment was conducted to study the effect of B application on high temperature tolerance of rice cultivars in B-deficient soil. The treatments comprised of four boron application treatments viz. control (B0), soil application of 1kg B ha-1 (B1), soil application of 2kg B ha-1 (B2), and foliar spray of 0.2% B (Bfs); three rice cultivars viz. Annapurna (HT stress tolerant), Naveen, and Shatabdi (both HT stress susceptible); and three temperature regimes viz. ambient (AT), HT at vegetative stage (HTV), and HT at reproductive stage (HTR). The results revealed that high temperature stress during vegetative or flowering stage reduced grain yield of rice cultivars mainly because of low pollen viability and spikelet fertility. The effects of high temperature on the spikelet fertility and grain filling varied among cultivars and the growth stages of plant when exposed to the high temperature stress. Under high temperature stress, the tolerant cultivar displays higher cell membrane stability, less accumulation of osmolytes, more antioxidant enzyme activities, and higher pollen viability and spikelet fertility than the susceptible cultivars. In the present work, soil application of boron was effective in reducing the negative effects of high temperature both at vegetative and reproductive stages. Application of B results into higher grain yield under both ambient and high temperature condition over control for all the three cultivars; however, more increase was observed for the susceptible cultivar over the tolerant one. The results suggest that the exogenous application of boron had a substantial effect on cell membrane stability, sugar mobilization, pollen viability, and spikelet fertility, hence the yield. The cultivars due to their variation in the tolerance level for high temperature stress behaved differently, and at high temperature stress, more response of the application of boron was seen in susceptible cultivars.

Differential effects of abiotic conditions on fitness-related parameters of two Euseius species inhabiting avocado agro-ecosystems

Temperature and relative humidity are important factors in shaping the structure and dynamics of communities composed of ectothermic species, as they directly affect fitness-related parameters and biotic interactions. In a climate change context, increased warming and dryness will likely affect arthropod communities of agro-ecosystems managed by biological pest control. In this work, we compare, at the individual level, the functional relation between temperature and relative humidity and different life-history parameters in two sister predatory mite species that inhabit Spanish avocado crops, Euseius stipulatus and E. scutalis (Athias-Henriot) (Acari: Phytoseiidae). We found that negative effects of high temperature and low relative humidity were stronger in E. stipulatus than in E. scutalis. That E. scutalis tolerates very well hot and dry environments makes the species a good candidate to be considered in the future as a biocontrol agent against pests in subtropical and Mediterranean orchards.

Yield of forage, grain and biomass in eight hybrids of maize with different sowing dates and environmental conditions

The aim was to evaluate yield of forage, grain and biomass and fibre content of eight hybrids of maize (Rio-Grande, Arrayan, Genex 778, Narro 2010, Advance 2203, DAS 2358, P4082W and HT9150W) during two sowing seasons (spring/summer) for two consecutive years at La Laguna in Torreon, Mexico. Once the grain progression of the kernel milk line was ⅓, green forage yield (GFY), dry matter (DM), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined. When the corncobs were fully mature, grain yield (GY) and biomass production (TBP) were determined. Weather conditions were recorded during the experiment. The results indicated that maximum temperature was higher and rainfall lower in the summer sowing and second year. Spring sowing had significantly higher yields of GFY, DM, GY and TBP compared to summer sowing. The first year of study showed significantly higher yields regarding GFY, GY and TBP, but FDN, FDA, DM content compared to the second year. The best hybrid for GFY and DM was Rio-Grande; for FDN and FDA was Advance 2203; for GY was HT9150W and finally for TBP was Arrayan. Regardless of the hybrid used and the sowing season, production of maize depended on external factors such as maximum temperature and rainfall; therefore, producers need to consider sowing in spring to avoid the negative effect of high temperatures on plant development.

Interactive effects of increased temperature, pCO2 and the synthetic progestin levonorgestrel on the fitness and breeding of the amphipod Gammarus locusta.

Given the lack of knowledge regarding climate change-chemical exposure interactions, it is vital to evaluate how these two drivers jointly impact aquatic species. Thus, for the first time, we aimed at investigating the combined effects of increased temperature, pCO2 and the synthetic progestin levonorgestrel on survival, growth, consumption rate and reproduction of the amphipod Gammarus locusta. For that, a full factorial design manipulating temperature [ambient temperature and warming (+4°C)], pCO2 [normocapnia and hypercapnia (Δ pH 0.5 units)] and the progestin levonorgestrel (LNG: L1 - 10ngLL-1 and L2 - 1000ngLL-1, control - no progestin and solvent control - vehicle ethanol (0.01%)) was implemented for 21 days. G.locusta was strongly negatively affected by warming, experiencing higher mortality rates (50-80%) than in any other treatments. Instead, growth rates were significantly affected by interactions of LNG with temperature and pCO2. It was observed, in the short-term (7d) that under ambient temperature (18°C) and hypercapnic conditions (pH 7.6), the LNG presence promoted the amphipod's growth, while in the medium-term (21d) this response was not observed. Relative consumption rates (RCRs), during the first week were higher than in the third week. Furthermore, in the first week, RCRs were negatively affected by higher temperature while in the third week, RCRs were negatively affected by acidification. Furthermore, it was observed a negative effect of higher temperature and acidification on G.locusta fecundity, contrarily to LNG. Concluding, the impact of increased temperature and pCO2 was clearly more adverse for the species than exposure to the synthetic progestin, however, some interactions between the progestin and the climate factors were observed. Thus, in a future scenario of global change, the presence of LNG (and other progestins alike) may modulate to a certain level the effects of climate drivers (and vice-versa) on the gammarids fitness and reproduction.

Higher temperatures during development reduce body size in the zebra finch in the laboratory and in the wild

The most commonly documented morphological response across many taxa to climatic variation across their range follows Bergmann's rule, which predicts larger body size in colder climates. In observational data from wild zebra finches breeding across a range of temperatures in the spring and summer, we show that this relationship appears to be driven by the negative effect of high temperatures during development. This idea was then experimentally tested on zebra finches breeding in temperature-controlled climates in the laboratory. These experiments confirmed that those individualso produced in a hot environment (30°C) were smaller than those produced in cool conditions (18°C). Our results suggest a proximate causal link between temperature and body size and suggest that a hotter climate during breeding periods could drive significant changes in morphology within and between populations. This effect could account for much of the variation in body size that drives the well-observed patterns first described by Bergmann and that is still largely attributed to selection on adult body size during cold winters. The climate-dependent developmental plasticity that we have demonstrated is an important component in understanding how endotherms may be affected by climate change.

Effect of high temperature on yield associated parameters and vascular bundle development in five potato cultivars

High temperature is one of the major abiotic stresses affecting performance of crop plants including potato yield. To gain an insight into whether high temperature effects tuber yield and its relation to translocation of photoassimilates in potato, a comparative study was conducted using five (Kufri jyoti, Kufri megha, Kufri pokraj, Rangpuria, and Badami) potato cultivars for two consecutive years. These cultivars were sown early in the season (mid August–November) when the temperature was high and normal growing season (ambient condition) (mid October–mid January) in an open field along in a polyhouse where the temperature was high. Early season planting experienced highest temperature (30–35°C) and temperature in the polyhouse was 2–4°C higher than the ambient condition. Leaf net CO2 assimilation rate, stem anatomy, xylem size, sugar-starch ratio, activity of sucrose phosphate synthase, tuber bulking rate and tuber yield were evaluated under all three conditions (early season, ambient condition and polyhouse conditions). Overall, compared to ambient conditions, under early season and polyhouse conditions, the net photosynthesis rate was significantly reduced but sugar starch ratio was significantly enhanced in all tested cultivars. Under both early planting and polyhouse conditions, the xylem cells were abnormally enlarged and deformed in all potato cultivars, however, the effects were minimal in case of cultivar Kufri megha (high yielding cultivar) and Rangpuria (local cultivar) which was correlated with the minimal yield reduction. Overall, the temperature induced abnormalities in vascular tissues appears to be critical for tuber bulking rate and tuber yield (42–55% in the high yielding cultivars and 44–54% in the local cultivars). The cultivars that could maintain xylem size and phloem structure tended to minimize the negative effects of high temperature on tuber yield.

Peso al nacimiento y al destete y crecimiento de corderos Merinos y cruzados con Merino Precoz y Ile de France: Análisis de algunos factores de variación

El objetivo de este experimento fue estudiar el efecto del tipo genético, sexo, tipo de nacimiento y estación y año de nacimiento sobre el peso al nacimiento y al destete y crecimiento de corderos durante la lactación. Se controló el peso al nacimiento de 170 corderos según tipo genético. sexo y tipo de nacimiento y estación y año de nacimiento. estudiándose los datos obtenidos mediante análisis de varianza. El cruzamiento industrial de ovejas de raza Merina con machos Merino Precoz o Ile de France no incrementó el peso de los corderos al nacimiento. Los machos pesaron al nacimiento más que las hembras y los corderos de parto simple más que los de parto doble. Los corderos nacidos en la primavera (abril y mayo) pesaron significativamente más al nacimiento que los nacidos en verano (agosto y septiembre). El año no tuvo efecto significativo sobre el peso de los corderos al nacimiento. Durante la lactación entre el nacimiento y 45 días (edad al destete) 157 corderos fueron controlados. estudiándose los datos obtenidos mediante análisis de varianza. covarianza y regresión simple. Los corderos Ile de France x Merino crecieron y pesaron más al destete que los otros dos tipos genéticos estudiados Merino Precoz x Merino y Merino x Merino). Entre machos y hembras no se obtuvieron diferencias significativas de crecimiento durante la lactancia y de peso al destete. Los corderos simples crecieron más que los dobles durante el amamantamiento y pesaron más al destete. Los factores fijos estación y año de nacimiento no afectaron significativamente al crecimiento diario durante la lactación ni al peso al destete. El peso de los corderos al nacimiento explicó el 40 y 43 % de la variabilidad del peso de los corderos a los 30 y 45 días de edad respectivamente. Se concluye que es necesaria una modulación adecuada de la alimentación de las ovejas durante el último tercio de la gestación para paliar el efecto de las altas temperaturas sobre el peso de los corderos al nacimiento. Así mismo. el cruzamiento de ovejas Merino con machos Ile de France es interesante para los ovinocultores.

Negative Effects of High Temperatures During Development on Immediate Post-Fledging Survival in Great TitsParus major

We analyzed the effect of nest temperatures, fledging date, age at fledging, fledgling mass and size on postfledging survival of Great Tits Parus major in eastern Spain. We manipulated temperature during nestling development in 26 nests (average temperature was 39.8, 34.6 and 26.4 °C for heated, control and cooled nest-boxes, respectively), and used radio-telemetry to monitor the survival of 48 nestlings (16 heated, 18 cooled, 14 controls) during the first 15 days after fledging. Heated chicks were lighter than control and cooled chicks. Estimated survival of heated fledglings was lower than that of controls. Additionally, survival of control fledglings increased with size, but this relationship was reversed for heated fledglings. Our results suggest that high temperatures experienced in the nest could have negative consequences on immediate post-fledging survival, and that smaller nestlings may deal more effectively with temperatures surpassing their optimal thermal range.

Influence of shading and sprinkling water on milk production and physiological responses of dairy cows

Countless studies attest to the negative effects of high temperatures on milk production. So, many environmental modifications can be introduced in order to decrease the temperature of the animals and, consequently, reduce heat stress, helping so, in the comfort of dairy cows confined. The aim of this review was to approach the effects of shading and sprinkling water on milk production and physiological responses in dairy cows. Several methods have been employed, such as natural or artificial shading, ventilation, cooling air from the application of water droplets, water spray on the animal accompanied by ventilation and air conditioning. In intensive production systems, coupled with the shading, the use of evaporative cooling systems in proportion to the animals an environment with warmer temperatures, avoiding situations of heat stress and increasing milk production. In pastures, the providing shade, either natural or artificial, it is necessary for dairy cows in order to reduce the excess heat received by direct solar radiation, especially during the hottest hours of the day and in regions near the line of Ecuador.

Photovoltaic system assessment considering temperature and overcast conditions: Light load efficiency enhancement technique

Currently, there is an ongoing trend to promote photovoltaic systems as they are a sustainable option for power generation. However, the efficiency conversion of solar energy into electric energy can diminish due to adverse environmental conditions and the performance of power processing circuits. Several approaches have been proposed to mitigate the negative effects of high temperatures and light load operation on power converters. Nonetheless, in areas with hot climates and overcast conditions, the efficiency consequences must be specifically evaluated. In this paper, the assessment of an approach to enhance the converter efficiency at low power levels is presented. The approach employs hybrid-switches within a transformerless converter topology, in such a way that, under light-load operational conditions, soft-switching is achieved. The technique is evaluated for ten specific sites from which there is ample meteorological data available. Results indicate that a 1.35 percent increase in overall efficiency can be obtained with the proposed approach, with an annual surplus energy of 7220Wh for a 1kW system.

Responses of Rapid Viscoanalyzer Profile and Other Rice Grain Qualities to Exogenously Applied Plant Growth Regulators under High Day and High Night Temperatures.

High-temperature stress degrades the grain quality of rice; nevertheless, the exogenous application of plant growth regulators (PGRs) might alleviate the negative effects of high temperatures. In the present study, we investigated the responses of rice grain quality to exogenously applied PGRs under high day temperatures (HDT) and high night temperatures (HNT) under controlled conditions. Four different combinations of ascorbic acid (Vc), alpha-tocopherol (Ve), brassinosteroids (Br), methyl jasmonates (MeJA) and triazoles (Tr) were exogenously applied to two rice cultivars (IR-64 and Huanghuazhan) prior to the high-temperature treatment. A Nothing applied Control (NAC) was included for comparison. The results demonstrated that high-temperature stress was detrimental for grain appearance and milling qualities and that both HDT and HNT reduced the grain length, grain width, grain area, head rice percentage and milled rice percentage but increased the chalkiness percentage and percent area of endosperm chalkiness in both cultivars compared with ambient temperature (AT). Significantly higher grain breakdown, set back, consistence viscosity and gelatinization temperature, and significantly lower peak, trough and final viscosities were observed under high-temperature stress compared with AT. Thus, HNT was more devastating for grain quality than HDT. The exogenous application of PGRs ameliorated the adverse effects of high temperature in both rice cultivars, and Vc+Ve+MejA+Br was the best combination for both cultivars under high temperature stress.

Expression of OsMYB55 in maize activates stress-responsive genes and enhances heat and drought tolerance.

BackgroundPlant response mechanisms to heat and drought stresses have been considered in strategies for generating stress tolerant genotypes, but with limited success. Here, we analyzed the transcriptome and improved tolerance to heat stress and drought of maize plants over-expressing the OsMYB55 gene.ResultsOver-expression of OsMYB55 in maize decreased the negative effects of high temperature and drought resulting in improved plant growth and performance under these conditions. This was evidenced by the higher plant biomass and reduced leaf damage exhibited by the transgenic lines compared to wild type when plants were subjected to individual or combined stresses and during or after recovery from stress. A global transcriptomic analysis using RNA sequencing revealed that several genes induced by heat stress in wild type plants are constitutively up-regulated in OsMYB55 transgenic maize. In addition, a significant number of genes up-regulated in OsMYB55 transgenic maize under control or heat treatments have been associated with responses to abiotic stresses including high temperature, dehydration and oxidative stress. The latter is a common and major consequence of imposed heat and drought conditions, suggesting that this altered gene expression may be associated with the improved stress tolerance in these transgenic lines. Functional annotation and enrichment analysis of the transcriptome also pinpoint the relevance of specific biological processes for stress responses.ConclusionsOur results show that expression of OsMYB55 can improve tolerance to heat stress and drought in maize plants. Enhanced expression of stress-associated genes may be involved in OsMYB55-mediated stress tolerance. Possible implications for the improved tolerance to heat stress and drought of OsMYB55 transgenic maize are discussed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2659-5) contains supplementary material, which is available to authorized users.

Passive heat treatment of sweet basil crops suppressesPeronospora belbahriidowny mildew

Sweet basil (Ocimum basilicum) is an annual herb crop grown in polyethylene-covered structures in Israel. It is Israel's leading herb crop, grown in warm regions of the country. Downy mildew (caused by Peronospora belbahrii) is a severe disease in Israel and in many other crop-growing regions worldwide. Experiments were carried out to identify potential climate-management techniques for suppression of this disease on basil in non-heated greenhouses. Disease severity was evaluated under commercial-like conditions in three experiments, with 8–10 walk-in tunnels at each location. Pathogen inoculum was introduced into all walk-in tunnels. Regression analysis was performed between the disease values and air temperature, relative humidity (RH) and soil temperature. Downy mildew severity was negatively related to high (>25°C) air temperature, RH in the range of 65–85% and high (>21°C) soil temperature. The increase in air temperature did not result in a significant increase in leaf temperature; canopy surface median temperatures only reached 30°C. Symptomless plants from relatively warmer tunnels (peak temperatures of 45–48°C) that were transferred to conditions that promote downy mildew (22 ± 2°C, RH > 95%) became severely diseased, showing sporulation of P. belbahrii, suggesting that infection occurred but at the high temperatures symptom expression/tissue colonisation was suppressed. Pot experiments in which aerial and subterranean plant organs were differentially heated revealed that treating the roots with a high temperature (26–31°C), similar to the soil temperatures in the warmer greenhouses, while maintaining the upper plant parts at ambient temperature (20°C), suppresses canopy downy mildew. The effect lasted for 1–2 weeks after the plants were removed from the heated soil treatments and maintained under optimal conditions for pathogen development. Furthermore, oospores were found in the symptomatic leaves. Oospores are minimally affected by high temperature, and therefore the high temperature presumably did not affect pathogen survival. In conclusion, the effect of high greenhouse temperature on basil downy mildew may not result from a direct negative effect of high temperature on the pathogen but from an indirect high-temperature effect on the host, rendering it less susceptible to pathogen development.