A Comparison of the Effect of High Temperature on Grain Development in Wheat and Rice

Grain weight at maturity of the wheat cultivar Banks was reducedby about 5% for each 1 °C rise in daily mean post-anthesistemperature in the range from 17.7 to 32.7 °C, using grainweight at 17.7 °C as the base. In contrast, the rice cultivarCalrose had a stable grain weight up to 26.7 °C and abovethat showed a 4.4% drop in weight per 1 °C increase in meanpost-anthesis temperatures up to 35.7 °C, using grain weightat 26.7 °C as the base. In both wheat and rice there wasa reduction in the duration of grain growth with increasingtemperature up to a mean of 26.7 °C. In this range rice,but not wheat, showed a compensating increase in the rate ofdry-matter accumulation. Above 26.7 °C the rate of dry-matteraccumulation fell in both species, although this was more stablein rice than in wheat. In wheat the duration of grain growthcontinued to decrease at temperatures above 26.7 °C, butshowed little change in rice up to 35.7°C, the maximum tested.These data are discussed in relation to the physiological, biochemicaland physical constraints that may act to regulate grain developmentin wheat and rice at high temperature. Triticum aestivum, oryza sativa, grain development, high temperature effects     

黑龙江省水稻空壳率与孕穗期低温的关系

对黑龙江省6个主要水稻品种(龙稻3号、垦稻12号、空育131、龙稻7号、龙粳16号和松粳6号)进行孕穗期低温(处理温度分别为15℃、17℃、19℃,低温持续时间分别为2、4、6和8d)处理,采用线性内插和统计回归方法,分析了水稻单穗空壳率与孕穗期低温的关系.结果表明:研究区敏感性水稻品种和耐冷性较强水稻品种的障碍型冷害临界温度分别为17℃和16℃;孕穗期水稻对低温最敏感的时期为抽穗前14～18d.15℃低温处理8d时,松粳6号、垦稻12号的空壳率明显增加,空育131空壳率小幅升高,表明松粳6号和垦稻12号对低温反应较敏感、耐冷性较弱,而空育131对低温反应迟钝,耐冷性较强;垦稻12号、龙粳16号、空育131的冷积温与空壳率存在显著的相关关系(P0.01),随着冷积温的增加,水稻空壳率明显升高,但品种间的增幅不同.     

Different effects of night versus day high temperature on rice quality and accumulation profiling of rice grain proteins during grain filling

High temperature has adverse effects on rice yield and quality. The different influences of night high temperature (NHT) and day high temperature (DHT) on rice quality and seed protein accumulation profiles during grain filling in indica rice ‘9311’ were studied in this research. The treatment temperatures of the control, NHT, and DHT were 28°C/20°C, 27°C/35°C, and 35°C/27°C, respectively, and all the treatments were maintained for 20 days. The result of rice quality analysis indicated that compared with DHT, NHT exerted less effect on head rice rate and chalkiness, whereas greater effect on grain weight. Moreover, the dynamic accumulation change profiles of 61 protein spots, differentially accumulated and successfully identified under NHT and DHT conditions, were performed by proteomic approach. The results also showed that the different suppressed extent of accumulation amount of cyPPDKB might result in different grain chalkiness between NHT and DHT. Most identified isoforms of proteins, such as PPDK and pullulanase, displayed different accumulation change patterns between NHT and DHT. In addition, compared with DHT, NHT resulted in the unique accumulation patterns of stress and defense proteins. Taken together, the mechanisms of seed protein accumulation profiles induced by NHT and DHT during grain filling should be different in rice, and the potential molecular basis is discussed in this study.     

Influence of day length and temperature on number of main stem leaves and time to flowering in lupin

A growth chamber experiment was carried out to investigate the influence of day length and temperature on the development of flowering in eight varieties of the three grain lupin species Lupinus albus (Wat and C3396), L. angustifolius (Gungurru, Polonez and W26) and L. luteus, (Juno, Radames and Teo). The plants were grown at two temperatures, 10°C and 18°C, in combination with five daylength regimes: 10, 14, 18, 24 h day at full light intensity and 10 h full light extended with 8 h low intensity light. Increased daylength decreased days from sowing to flowering in all varieties, but had little effect on thermal time to flowering in most varieties. However, C3396, W26 and Radames had a significantly longer thermal time to flowering at high, non‐vernalising temperature (18°C) at short daylengths. Low light intensity daylength extension did not significantly influence thermal time to flowering. For flower initiation, measured as number of leaves on the main stem three types of response were found. All varieties formed fewer leaves on the main stem at 10°C than at 18°C, although the two thermo‐neutral varieties of L. luteus, Juno and Teo, gave only a small response to temperature and daylength. In Polonez, Gungurru and Wat, low temperature decreased leaf number, but there was only a small response to changes in daylength. Three varieties, C3396, W26 and Radames, showed longer thermal time to flowering at 18°C with short daylengths. This could be explained by a greater number of main stem leaves formed at short daylength at non‐vernalising temperatures. Increased daylength decreased leaf number in these varieties, but never to a smaller number than for plants grown at 10°C. In these varieties, low intensity extension of the daylength had a similar (W26, Radames) or decreased (C3396) effect compared to full light extension. The hastening of time to flowering by long days could be separated into two effects: a high light energy effect hastened development by increasing the rate of leaf appearance in all varieties, while low light energy in thermo‐sensitive varieties was able to substitute for vernalisation by decreasing leaf number.     

Sensitivity of the common bean (Phaseolus vulgaris L.) symbiosis to high soil temperature

Summary Experiments were done to test whether N fixation is more sensitive to high soil temperatures in common bean than in cowpea or soybean. Greenhouse experiments compared nodulation, nitrogenase activity, growth and nitrogen accumulation of several host/strain combinations of common bean with the other grain legumes and with N-fertilization, at various root temperatures. Field experiments compared relative N-accumulation (in symbiotic relative to N-fertilized plants) of common bean with cowpea under different soil thermal regimes. N-fertilized beans were unaffected by the higher temperatures, but nitrogen accumulation by symbiotic beans was always more sensitive to high root temperatures (33°C, 33/28°C, 34/28°C compared with 28°C) than were cowpea and soybean symbiosis. Healthy bean nodules that had developed at low temperatures functioned normally in acetylene reduction tests done at 35°C. High temperatures caused little or no suppression of nodule number. However, bean nodules produced at high temperatures were small and had low specific activity. ForP. vulgaris some tolerance to high temperature was observed among rhizobium strains (e.g., CIAT 899 was tolerant) but not among host cultivars. Heat tolerance ofP. acutifolius andP. lunatus symbioses was similar to that of cowpea and soybean. In the field, high surface soil temperatures did not reduce N accumulation in symbiotic beans more than in cowpea, probably because of compensatory nodulation in the deeper and cooler parts of the soil.     

Effects of Asymmetric Heat on Grain Quality During the Panicle Initiation Stage in Contrasting Rice Genotypes

Heat stress during the panicle initiation stage hinders the formation of rice grains. It is speculated that heat exposure during the panicle initiation stage could influence grain quality in rice. To obtain preliminary knowledge on the effects of asymmetric heat on rice grain quality during the panicle initiation stage, four rice genotypes (Shanyou63, Liangyoupeijiu, Huanghuazhan, and Nagina22) were subjected to three heat treatments, i.e., high daytime temperature (HDT; 37.9 °C/24.5 °C), high nighttime temperature (HNT; 30.9 °C/30.5 °C), the combination of high daytime and nighttime temperature (HDNT; 38.5 °C/31.0 °C), and a control (CK, 31.5 °C/24.0 °C) in temperature-controlled greenhouses for 15 days during the panicle initiation stage. The milling and appearance qualities, which are crucial for commercial value, were studied. Heat treatments significantly reduced the amounts of brown rice, milled rice, and head rice and the grain length, grain width, chalky grain amount, and grain chalkiness in the rice genotypes Liangyoupeijiu, Nagina22, and Huanghuazhan during the panicle initiation stage, and the largest reductions in grain quality were frequently observed under HDNT treatment. The milling and appearance qualities in genotype Shanyou63 were negligibly affected by heat treatments and thus were regarded as tolerant to heat, and the rice genotypes Liangyoupeijiu, Huanghuazhan, and especially Nagina22 were susceptible to heat during the panicle initiation stage. We concluded that heat stress during panicle initiation impacted the milling and appearance qualities in rice, and differences existed among rice genotypes. The underlying mechanisms of the effects of heat on rice grain quality need further study.

     

Responses of carbon and oxygen stable isotopes in rice grain (Oryza sativa L.) to an increase in air temperature during grain filling in the Japanese archipelago

Stable isotopic compositions of carbon (δ¹³C) and oxygen (δ¹⁸O) in plants reflect growth conditions. Therefore, these isotopes might be good indicators of changes in environmental factors, such as variations in air temperature caused by climate change. It is predicted that climate change will lead to a greater increase in minimum air temperatures (primarily during the night) than in maximum air temperatures (primarily during the day) in many parts of Japan. In the present study, we investigated whether the δ¹³C and δ¹⁸O of the rice grain Koshihikari (Oryza sativa L.) from the northern latitudes (30.49°–37.14°) of Japan reflect variations in air temperature during grain filling and are related to the yield and proportion of first-grade rice (<15 % transparency, roundness, and cracking) as an indicator of quality. We revealed that rice δ¹³C was not correlated with mean maximum or minimum air temperatures for each prefecture. By contrast, rice δ¹⁸O was positively correlated with mean minimum air temperature, suggesting that rice δ¹⁸O reflects changes in night air temperature. We further showed that an increase in the mean minimum air temperature during grain filling had a negative effect on rice yield and quality. Our findings indicate that the δ¹⁸O of rice grain may be a good indicator of physiological changes in response to minimum air temperatures during grain filling.     

Environmental induction of larval diapause and life-history consequences of post-diapause development in the Large Copper butterfly,Lycaena dispar (Lepidoptera: Lycaenidae)

Many insects in temperate zones withstand the adverse conditions of winter through entering diapause and the two most important environmental stimuli that induce diapause are photoperiod and ambient temperature. The Large Copper butterfly, Lycaena dispar Haworth (Lepidoptera: Lycaenidae), is a Palearctic butterfly that hibernates as larvae. Since this butterfly is a near threatened species in some regions, there has been a growing need for a standardized protocol for mass rearing of this butterfly based on the adequate knowledge of its ecology. In the present study, we first identified that L. dispar larvae were sensitive to the photoperiodic induction of diapause during their first larval instar. We then investigated to what extent the diapause-inducing effects of photoperiod could be modified by ambient temperatures in L. dispar larvae by exposing them to the range of day-lengths (L:D 14:10, 12:12, 10:14 and 8:16) at three different temperatures (15, 20 and 25 °C). All larvae were induced to enter diapause at low ambient temperature (15 °C) regardless of photoperiod, whereas most of them (86 %) exhibited direct development when temperature was high (25 °C). The photoperiodic induction of diapause was evident when day-length was shorter than 14 h at intermediate temperature (20 °C). Pre-diapause development was prolonged at low temperatures. Finally, we found that post-diapause development of L. dispar larvae was determined by both the chilling temperature experienced by diapausing larvae and the duration of larval diapause. Adult emergence was enhanced when larvae were chilled at 8 °C and when they had been under the state of diapause for 20 days before they were treated to terminate diapause.     

Differential responses of Arabidopsis ecotypes to cold, chilling and freezing temperatures

Arabidopsis plants show an increase in freezing tolerance in response to exposure to low nonfreezing temperatures, a phenomenon known as cold acclimation. In the present study, we evaluated the physiological and morphological responses of various Arabidopsis ecotypes to continuous growth under chilling (14°C) and cold (6°C) temperatures and evaluated their basal freezing tolerance levels. Seedlings of Arabidopsis plants were extremely sensitive to low growth temperatures: the hypocotyls and petioles were much longer and the angles of the second pair of true leaves were much greater in plants grown at 14°C than in those grown at 22°C, whereas just intermediate responses were observed under the cold temperature of 6°C. Flowering time was also markedly delayed at low growth temperatures and, interestingly, lower growth temperatures were accompanied by longer inflorescences. Other marked responses to low temperatures were changes in pigmentation, which appeared to be both ecotype specific and temperature dependent and resulted in various visual phenotypes such as chlorosis, necrosis or enhanced accumulation of anthocyanins. The observed decreases in chlorophyll contents and accumulation of anthocyanins were much more prominent in plants grown at 6°C than in those grown at 14°C. Among the various ecotypes tested, Mt‐0 plants markedly accumulated the highest levels of anthocyanins upon growth at 6°C. Freezing tolerance examination revealed that among 10 ecotypes tested, only C24 plants were significantly more sensitive to subzero temperatures. In conclusion, Arabidopsis ecotypes responded differentially to cold (6°C), chilling (14°C) and freezing temperatures, with specific ecotypes being more sensitive in particular traits to each low temperature.     

Tree leaf out response to temperature: comparing field observations,remote sensing,and a warming experiment

Leaf out time is a widely used indicator of climate change and represents a critical transition point of annual seasonality in most temperate ecosystems. We compared three sources of data to determine the effect of spring temperature on tree leaf out: field observations, remotely sensed satellite data, and experimental warming. All three methods recorded earlier leaf out with warmer spring temperatures. However, leaf out timing was more than twice as sensitive to temperature in the field study (advancing at a rate of 6.1 days/°C), as under experimental warming (2.1 days/°C), with remote sensing intermediate (3.7 days/°C). Researchers need to be aware of the currently unexplained differences among methodologies when using phenological data to parameterize or benchmark models that represent ecosystem processes. The mechanisms behind these discrepancies must be better understood if we are to confidently predict responses of leaf out timing to future climates.     

Effects of temperature and nutrients on microscopic stages of the bull kelp (Nereocystis luetkeana,Phaeophyceae)

Warming ocean temperatures have been linked to kelp forest declines worldwide, and elevated temperatures can act synergistically with other local stressors to exacerbate kelp loss. The bull kelp Nereocystis luetkeana is the primary canopy-forming kelp species in the Salish Sea, where it is declining in areas with elevated summer water temperatures and low nutrient concentrations. To determine the interactive effects of these two stressors on microscopic stages of N. luetkeana, we cultured gametophytes and microscopic sporophytes from seven different Salish Sea populations across seven different temperatures (10–22°C) and two nitrogen concentrations. The thermal tolerance of microscopic gametophytes and sporophytes was similar across populations, and high temperatures were more stressful than low nitrogen levels. Additional nitrogen did not improve gametophyte or sporophyte survival at high temperatures. Gametophyte densities were highest between 10 and 16°C and declined sharply at 18°C, and temperatures of 20 and 22°C were lethal. The window for successful sporophyte production was narrower, peaking at 10–14°C. Across all populations, the warmest temperature at which sporophytes were produced was 16 or 18°C, but sporophyte densities were 78% lower at 16°C and 95% lower at 18°C compared to cooler temperatures. In the field, bottom temperatures revealed that the thermal limits of gametophyte growth (18°C) and sporophyte production (16–18°C) were reached during the summer at multiple sites. Prolonged exposure of bull kelp gametophytes to temperatures of 16°C and above could limit reproduction, and therefore recruitment, of adult kelp sporophytes.     

Growth and mortality of Arctic charr and European whitefish reared at low temperatures

This comparative study explores how low temperatures affect the mortality and growth of first generation hatchery-reared progeny of subarctic populations of Arctic charr (Salvelinus alpinus L.) and European whitefish (Coregonus lavaretus L.). Replicate fish groups where held under simulated natural light regimes (70°N) at three constant temperatures (1, 3 and 6°C). The mortality of Arctic charr was low (≤1.4%) at all temperature treatments, whereas the mortality of whitefish increased with decreasing temperature from 6% at 6°C to 33% at 1°C. The Arctic charr exhibited higher growth rates than whitefish at all three temperature regimes. All groups of Arctic charr increased in weight, whereas whitefish held at 1°C did not gain weight throughout the experimental period of 133 days. Arctic charr exhibited a large intraspecific variability in growth leading to large variations in size-structure, whereas whitefish in contrast showed very homogenous growth and size-structure patterns; a dissimilarity probably related to species-specific differences in antagonistic behaviour. Evidently, Arctic charr are more cold water adapted than whitefish and are able to maintain growth at extremely low temperatures. Arctic charr thus appear to be the most suitable species for aquaculture at low water temperatures.     

Mutation of the rice TCM12 gene encoding 2,3‐bisphosphoglycerate‐independent phosphoglycerate mutase affects chlorophyll synthesis,photosynthesis and chloroplast development at seedling stage at low temperatures

• Glycolysis is a central metabolic pathway that provides energy and products of primary metabolites. 2,3‐Biphosphoglycerate‐independent phosphoglycerate mutase (iPGAM) is a key enzyme that catalyses the reversible interconversion of 3‐phosphoglycerate (3‐PGA) to 2‐phosphoglycerate (2‐PGA) in glycolysis. Low temperature is a common abiotic stress in rice production. However, the mechanism for rice iPGAM genes is not fully understood at low temperature.
• In this study, the rice mutant tcm12, with chlorosis, malformed chloroplasts and impaired photosynthesis, was grown at a low temperature (<20 °C) to the three‐leaf stage, while the normal phenotype at 32 °C was used. Chlorophyll fluorescence analysis and transmission electron microscopy were used to examine features of the tcm12 mutant. The inheritance behaviour and function of TCM12 were then analysed thorough map‐based cloning, transgenic complementation and subcellular localisation.
• The thermo‐sensitive chlorosis phenotype was caused by a single nucleotide mutation (T→C) on the fifth exon of TCM12 (LOC_Os12g35040) encoding iPGAM, localised to both nucleus and membranes. In addition, TCM12 was constitutively expressed, and its disruption resulted in down‐regulation of some genes associated with chlorophyll biosynthesis and photosynthesis at low temperatures (20 °C).
• This is the first report of the involvement of rice iPGAM gene in chlorophyll synthesis, photosynthesis and chloroplast development, providing new insights into the mechanisms underlying early growth of rice at low temperatures.

     

Leaf senescence and grain filling affected by post-anthesis high temperatures in two different wheat cultivars

High temperature is a major factor affecting grain yield and plant senescence in wheat growing regions of central and east China. In this study, two different wheat cultivars, Yangmai 9 with low-grain protein concentration and Xuzhou 26 with high-grain protein concentration, were exposed to different temperature regimes in growth chambers during grain filling. Four day/night temperature regimes of 34°C/22°C, 32°C/24°C, 26°C/14°C, and 24°C/16°C were established to obtain two daily temperatures of 28 and 20°C, and two diurnal day/night temperature differences of 12 and 8°C. Concentration of a lipid peroxidation product malondialdehyde (MDA), activities of the antioxidants superoxide dismutase (SOD) and catalase (CAT), chlorophyll concentration (SPAD) in flag leaves and kernel weight were determined. Results show that activities of SOD and CAT in leaves increased markedly on 14 days after anthesis (DAA) for the high-temperature treatment (34°C/22°C) and then declined. As a result, MDA concentration in leaves increased significantly under high temperature (34°C/22°C and 32°C/24°C). Compared with optimum temperature treatment, high temperature reduced the concentration of soluble protein and SPAD values in flag leaves. Grain-filling rate increased slightly initially, but decreased significantly during late grain filling under high temperature. As a result, final grain weight was reduced markedly under high temperature. Decreases in the activities of SOD and CAT and increases in MDA concentration in leaves were more pronounced with a 12°C of day/night temperature difference when under high temperatures. Kernel weight was higher under 12°C of day/night temperature difference under optimum temperatures (24°C/16°C and 26°C/14°C). The responses to high-temperature regimes appeared to differ between the two wheat cultivars with different grain protein concentrations. It is concluded that a larger diurnal temperature difference hastened the senescence of flag leaves under high-temperature conditions, but retarded senescence under optimum temperature treatments of 26°C/14°C and 24°C/16°C.     

Physiological performance of the cold-water coral Dendrophyllia cornigera reveals its preference for temperate environments

Cold-water corals (CWCs) are key ecosystem engineers in deep-sea benthic communities around the world. Their distribution patterns are related to several abiotic and biotic factors, of which seawater temperature is arguably one of the most important due to its role in coral physiological processes. The CWC Dendrophyllia cornigera has the particular ability to thrive in several locations in which temperatures range from 11 to 17 °C, but to be apparently absent from most CWC reefs at temperatures constantly below 11 °C. This study thus aimed to assess the thermal tolerance of this CWC species, collected in the Mediterranean Sea at 12 °C, and grown at the three relevant temperatures of 8, 12, and 16 °C. This species displayed thermal tolerance to the large range of seawater temperatures investigated, but growth, calcification, respiration, and total organic carbon (TOC) fluxes severely decreased at 8 °C compared to the in situ temperature of 12 °C. Conversely, no significant differences in calcification, respiration, and TOC fluxes were observed between corals maintained at 12 and 16 °C, suggesting that the fitness of this CWC is higher in temperate rather than cold environments. The capacity to maintain physiological functions between 12 and 16 °C allows D. cornigera to be the most abundant CWC species in deep-sea ecosystems where temperatures are too warm for other CWC species (e.g., Canary Islands). This study also shows that not all CWC species occurring in the Mediterranean Sea (at deep-water temperatures of 12–14 °C) are currently living at their upper thermal tolerance limit.     

How different rearing temperatures affect growth and stress status of Siberian sturgeon Acipenser baerii larvae

Environmental temperature is one of the critical factors affecting fish development. The aim of this study was to examine the impact of three different rearing temperatures (16, 19 and 22°C) throughout the endogenous feeding phase of the Siberian sturgeon Acipenser baerii. This was performed by assessing (a) larval survival and growth; (b) immunofluorescence localization and expression of genes involved in muscle development and growth – myog and Igf1; and (c) stress status through the expression of thermal stress genes – Hsp70, Hsp90α and Hsp90β – and whole body cortisol. Overall survival rate and larval weight did not differ significantly across temperatures. Larvae subjected to 22°C showed faster absorption of the yolk-sac than larvae subjected to 19 or 16°C. Both at schooling and at the end of the trial, larvae reared at 16°C showed significantly lower levels of cortisol than those reared at 19 or 22°C. IGF-1 immunopositivity was particularly evident in red muscle at schooling stage in all temperatures. The expression of all Hsps as well as the myog and Igf1 genes was statistically higher in larvae reared at 16°C but limited to the schooling stage. Cortisol levels were higher in larvae at 22°C, probably because of the higher metabolism demand rather than a stress response. The observed apparent incongruity between Hsps gene expression and cortisol levels could be due to the lack of a mature system. Further studies are necessary, especially regarding the exogenous feeding phase, in order to better understand if this species is actually sensitive to thermal stress.     

HtpG Plays a Role in Cold Acclimation in Cyanobacteria

The heat shock protein HtpG is homologous to members of the Hsp90 protein family of eukaryotes and is essential for basal and acquired thermotolerances in cyanobacteria. In this study we have examined the role of HtpG in the cyanobacterium, Synechococcus sp. PCC 7942, in the acclimation to low temperatures. The inactivation of the htpG gene resulted in severe inhibition of cell growth and of the photosynthetic activity when the htpG mutant was shifted to 16°C from 30°C. Wild-type cells were able to resume growth without a lag period when shifted to 30°C after 5 days at 16°C, while the mutant displayed a detectable lag. The HtpG protein was induced in the wild-type cells at 16°C. Electrophoresis in the absence of sodium dodecyl sulfate (SDS) showed that a novel, high-molecular-weight complex containing GroEL and DnaK accumulated at 16°C, but the accumulation was strongly inhibited in the htpG mutant. Our results demonstrate that the HtpG protein contributes significantly to the ability of cyanobacteria to acclimate to low temperatures. Received: 16 July 2001/Accepted: 15 August 2001     

Response of rice plants to constant and cyclic submerged soil temperature regimes

Summary An experiment was conducted in controlled temperature water baths to compare the response of rice plant of variety Taichung (Native) 1 to cyclic soil temperature regime of 32°C/20°C and constant soil temperature regime of 26°C. These temperature regimes are reported to be highly favourable for rice growth and therefore selected for comparison. The plants growing at 32°C/20°C showed some superiority over those growing at 26°C in respect of root growth and tiller development. The grain yield at 32°C/20°C was higher which resulted from larger number of tillers and panicles than at 26°C, although the difference in other yield characteristics was not appreciable. NPK content of grains, straw and roots did not vary appreciably between 32°C/20°C and 26°C but the total uptake of these nutrients varied because of the difference in total dry matter production. The results suggest that the development of rice plants, particularly in reproductive phase, is practically as good at 26°C as at 32°C/20°C and there seems to be no sufficient ground for generalising the phenomenon of diurnal thermoperiodicity for rice plants.     

Effects of temperature on fitness costs in chlorpyrifos‐resistant brown planthopper,Nilaparvata lugens (Hemiptera: Delphacidae)

Insecticide resistance is inevitable if an insecticide is widely used to control insect pests. Fortunately, the resistance‐associated fitness costs often give chances to manage resistances. In most cases, the fitness cost in resistant insects is often evaluated under laboratory conditions for insect development, which limits its practical application in pest control in the field. In a laboratory population R9 with 253‐fold resistance to chlorpyrifos after nine‐generation selection with chlorpyrifos, the relative fitness was only 0.206 under laboratory conditions (25°C, humidity 70%–80% and 16 h light/8 h dark photoperiod), when compared to S9, a susceptible counterpart (resistance ratio = 2.25‐fold) from the same origin as R9 but without any selection with insecticides. Temperatures varied the resistance‐associated fitness costs, with enhanced costs at high temperatures and reduced costs at low temperatures, such as 0.174 at 32°C and 0.527 at 18°C. The copulation rate and fecundity were two key factors for the reduced costs at low temperatures. Another finding was that R9 individuals needed much more time to recover from heat shock than that of S9, but R9 and S9 individuals were similarly sensitive to cold shock. The low fitness cost at low temperatures would increase the overwintering population, which might further increase risks of rapid development and widespread distribution of chlorpyrifos resistance in Nilaparvata lugens.     

The progeny production of a hymenopterous parasitoid,Apanteles sp. groupultor,as affected by temperature

Adults of the parasiteApanteles sp. groupultor were held unter constant temperatures (15, 20, 26, 30°C) each within ±1°C. Total progeny production was significantly greater at 26°C, averaging 85 per female and decreased at 15°C and 30°C. Mating behavior showed that both sexes were a polygamous. The range of constant temperature did not greatly alter the progeny sex ratio when female parent had been mated. At 15°C, male activity was adversely affected when both sexes were exposed to it without previous mating, resulting in a higher number of male progeny. A temperature of 26°C was the most appropriate for normal sex ratio.