Importance of pre‐anthesis anther sink strength for maintenance of grain number during reproductive stage water stress in wheat

Reproductive stage water stress leads to spikelet sterility in wheat. Whereas drought stress at anthesis affects mainly grain size, stress at the young microspore stage of pollen development is characterized by abortion of pollen development and reduction in grain number. We identified genetic variability for drought tolerance at the reproductive stage. Drought‐tolerant wheat germplasm is able to maintain carbohydrate accumulation in the reproductive organs throughout the stress treatment. Starch depletion in the ovary of drought‐sensitive wheat is reversible upon re‐watering and cross‐pollination experiments indicate that the ovary is more resilient than the anther. The effect on anthers and pollen fertility is irreversible, suggesting that pollen sterility is the main cause of grain loss during drought conditions in wheat. The difference in storage carbohydrate accumulation in drought‐sensitive and drought‐tolerant wheat is correlated with differences in sugar profiles, cell wall invertase gene expression and expression of fructan biosynthesis genes in anther and ovary (sucrose : sucrose 1‐fructosyl‐transferase, 1‐SST; sucrose : fructan 6‐fructosyl‐transferase, 6‐SFT). Our results indicate that the ability to control and maintain sink strength and carbohydrate supply to anthers may be the key to maintaining pollen fertility and grain number in wheat and this mechanism may also provide protection against other abiotic stresses.     

The effect of heat stress on tomato pollen characteristics is associated with changes in carbohydrate concentration in the developing anthers

Continuous exposure of tomato 'Trust' to high temperatures (day/night temperatures of 32/26 degrees C) markedly reduced the number of pollen grains per flower and decreased viability. The effect of heat stress on pollen viability was associated with alterations in carbohydrate metabolism in various parts of the anther during its development. Under control, favourable temperature conditions (28/22 degrees C), starch accumulated in the pollen grains, where it reached a maximum value 3 d before anthesis; it then diminished towards anthesis. During anther development, the concentration of total soluble sugars gradually increased in the anther walls and in the pollen grains (but not in the locular fluid), reaching a maximum at anthesis. Continuous exposure of the plants to high temperatures (32/26 degrees C) prevented the transient increase in starch concentration and led to decreases in the concentrations of soluble sugars in the anther walls and the pollen grains. In the locular fluid, however, a higher soluble sugar concentration was detected under the high-temperature regime throughout anther development. These results suggest that a major effect of heat stress on pollen development is a decrease in starch concentration 3 d before anthesis, which results in a decreased sugar concentration in the mature pollen grains. These events possibly contribute to the decreased pollen viability in tomato.     

Deterioration of ovary plays a key role in heat stress-induced spikelet sterility in sorghum

In sorghum (Sorghum bicolor [L.] Moench), the impact of heat stress during flowering on seed set is known, but mechanisms that lead to tolerance are not known. A diverse set of sorghum genotypes was tested under controlled environment and field conditions to ascertain the impact of heat stress on time-of-day of flowering, pollen viability, and ovarian tissue. A highly conserved early morning flowering was observed, wherein >90% of spikelets completed flowering within 30 min after dawn, both in inbreds and hybrids. A strong quantitative impact of heat stress was recorded before pollination (reduced pollen viability) and post pollination (reduced pollen tube growth and linear decline in fertility). Although viable pollen tube did reach the micropylar region, 100% spikelet sterility was recorded under 40/22°C (day/night temperatures), even in the tolerant genotype Macia. Heat stress induced significant damage to the ovarian tissue near the micropylar region, leading to highly condensed cytoplasmic contents and disintegrated nucleolus and nucleus in the susceptible genotype RTx430. Whereas, relatively less damages to ovarian cell organelles were observed in the tolerant genotype Macia under heat stress. Integrating higher tolerance in female reproductive organ will help in effective utilization of the early morning flowering mechanism to enhance sorghum productivity under current and future hotter climate.     

HEAT INJURY DURING FLORAL DEVELOPMENT IN COWPEA (VIGNA UNGUICULATA,FABACEAE)

High night temperatures during floral development induce male sterility in cowpea (Vigna unguiculata [L.] Walp.). The objectives of this study were to determine: the possible causes of the male sterility; the stage of floral development when damage due to heat stress occurs; and whether specific tissues are damaged during the period of sensitivity to heat. Plants were grown under controlled temperatures in both greenhouses and growth chambers in separate experiments. Floral development was normal under a night temperature of 20 C, whereas flowers developed under high night temperature (30 C) set no pods due to low pollen viability and anther indehiscence. Anthers developed under 33/30 C day/night temperatures did not exhibit endothecial formation, whereas anthers developed under 33/20 C day/night temperatures exhibited normal development of the endothecial layer. Reciprocal transfers of plants between chambers with high or optimum night temperature demonstrated that the stage of floral development most sensitive to heat stress occurs 9 to 7 d before anthesis. Anthers developed under either optimal or high night temperatures were compared cytologically. Development was similar through meiosis, but after tetrad release, which occurred 8 d before anthesis, the tapetal layer degenerated prematurely under high night temperature. Premature degeneration of the tapetal layer and lack of endothecial development may be responsible for the low pollen viability, low anther dehiscence, and low pod set under high night temperatures.     

Physiological factors limit fruit set of tomato (Lycopersicon esculentum Mill.) under chronic, mild heat stress

The effects of chronic, mild heat stress on fruit set, fruit production, release of pollen grains, photosynthesis, night respiration and anther dehiscence were examined in tomatoes (Lycopersicon esculentum Mill.) differing in high‐temperature sensitivity. Plants were grown under three temperature regimes: (1) 28/22 or 26/22 °C (optimal temperature); (2) 32/26 °C (high temperature); and (3) 32/26 °C day/night temperatures relieved at 28/22 °C for 10 d before anthesis, then returned to 32/26 °C (relieving treatment). FLA 7156 was the only cultivar with fruit set at 32/26 °C. All five cultivars, however, had fruit set under the relieving treatment (RT). The longer the relief, the higher the percentage of fruit set. Longer periods of relief also increased the number of pollen grains released, and linear regression analysis showed a significant relationship between the number of pollen grains released and the percentage of fruit set. Germination of pollen grains was also lowered in high‐temperature‐grown plants. The number of pollen grains produced, photosynthesis and night respiration did not limit fruit set under chronic, mild heat stress, however. This suggested that cultivar differences in pollen release and germination under heat stress are the most important factors determining their ability to set fruit.     

Response of in vitro pollen germination and pollen tube growth of groundnut (Arachis hypogaea L.) genotypes to temperature

Air temperatures of greater than 35 °C are frequently encountered in groundnut‐growing regions, especially in the semi‐arid tropics. Such extreme temperatures are likely to increase in frequency under future predicted climates. High air temperatures result in failure of peg and pod set due to lower pollen viability. The response of pollen germination and pollen tube growth to temperature was quantified in order to identify differences in pollen tolerance to temperature among 21 groundnut genotypes. Plants were grown from sowing to harvest in a poly‐tunnel under an optimum temperature of 28/22 °C (day/night). Pollen was collected at anther dehiscence and was exposed to temperatures from 10° to 47·5 °C at 2·5 °C intervals. The results showed that a modified bilinear model most accurately described the response to temperature of percentage pollen germination and maximum pollen tube length. Genotypes were found to range from most tolerant to most susceptible based on both pollen characters and membrane thermostability. Mean cardinal temperatures (T_min, T_opt and T_max) averaged over 21 genotypes were 14·1, 30·1 and 43·0 °C for percentage pollen germination and 14·6, 34·4 and 43·4 °C for maximum pollen tube length. The genotypes 55‐437, ICG 1236, TMV 2 and ICGS 11 can be grouped as tolerant to high temperature and genotypes Kadiri 3, ICGV 92116 and ICGV 92118 as susceptible genotypes, based on the cardinal temperatures. The principal component analysis identified maximum percentage pollen germination and pollen tube length of the genotypes, and T_max for the two processes as the most important pollen parameters in describing a genotypic tolerance to high temperature. The T_min and T_opt for pollen germination and tube growth, rate of pollen tube growth were less predictive in discriminating genotypes for high temperature tolerance. Genotypic differences in heat tolerance‐based on pollen response were poorly related (R² = 0·334, P = 0·006) to relative injury as determined by membrane thermostability.     

An overview of heat stress in tomato (Solanum lycopersicum L.)

Heat stress has been defined as the rise of temperature for a period of time higher than a threshold level, thereby permanently affecting the plant growth and development. Day or night temperature is considered as the major limiting factor for plant growth. Earlier studies reported that night temperature is an important factor in the heat reaction of the plants. Tomato cultivars capable of setting viable fruits under night temperatures above 21 °C are considered as heat-tolerant cultivars. The development of breeding objectives is generally summarized in four points: (a) cultivars with higher yield, (b) disease resistant varieties in the 1970s, (c) long shelf-life in 1980s, and (d) nutritive and taste quality during 1990s. Some unique varieties like the dwarf “Micro-Tom”, and the first transgenic tomato (FlavrSavr) were developed through breeding; they were distributed late in the 1980s.High temperature significantly affects seed, pollen viability and root expansion. Researchers have employed different parameters to evaluate the tolerance to heat stress, including membrane thermo stability, floral characteristics (Stigma exertion and antheridia cone splitting), flower number, and fruit yield per plant. Reports on pollen viability and fruit set/plant under heat stress by comparing the pollen growth and tube development in heat-treated and non-heat-stressed conditions are available in literature. The electrical conductivity (EC) have been used to evaluate the tolerance of some tomato cultivars in vitro under heat stress conditions as an indication of cell damage due to electrolyte leakage; they classified the cultivars into three groups: (a) heat tolerant, (b) moderately heat tolerant, and (c) heat sensitive.It is important to determine the range in genetic diversity for heat tolerance in tomatoes. Heat stress experiments under field conditions offer breeders information to identify the potentially heat tolerant germplasm.     

Influence of drought and heat stress,applied independently or in combination during seed development,on qualitative and quantitative aspects of seeds of lentil (Lens culinaris Medikus) genotypes,differing in drought sensitivity

Terminal droughts, along with high temperatures, are becoming more frequent to strongly influence the seed development in cool‐season pulses like lentil. In the present study, the lentil plants growing outdoors under natural environment were subjected to following treatments at the time of seed filling till maturity: (a) 28/23 °C day/night temperature as controls; (b) drought stressed, plants maintained at 50% field capacity, under the same growth conditions as in a; (c) heat stressed, 33/28 °C day/night temperature, under the same growth conditions as in a; and (d) drought + heat stressed, plants at 50% field capacity, 33/28 °C day/night temperature, under the same growth conditions as in (a). Both heat and drought resulted in marked reduction in the rate and duration of seed filling to decrease the final seed size; drought resulted in more damage than heat stress; combined stresses accentuated the damage to seed starch, storage proteins and their fractions, minerals, and several amino acids. Comparison of a drought‐tolerant and a drought‐sensitive genotype indicated the former type showed significantly less damage to various components of seeds, under drought as well as heat stress suggesting a cross tolerance, which was linked to its (drought tolerant) better capacity to retain more water in leaves and hence more photo‐assimilation ability, compared with drought‐sensitive genotype.     

Effect of high temperature and water stress on pollen germination and spikelet fertility in rice

In future climates, rice could more frequently be subjected to simultaneous high temperature and water stress during sensitive developmental stages such as flowering. In this study, five rice genotypes were exposed to high temperature, water stress and combined high temperature and water stress during flowering to quantify their response through spikelet fertility. Microscopic analyses revealed significant differences in anther dehiscence between treatments and genotypes, with a moderately high association with the number of germinated pollen grains on the stigma. There was a strong relationship between spikelet fertility and the number of germinated pollen on stigmas. Although, all three stress treatments resulted in spikelet sterility, high-temperature stress caused the highest sterility in all five genotypes. A cumulative linear decline in spikelet fertility with increasing duration of independent high-temperature stress and in combination with water stress was quantified. Better anther dehiscence, higher in vivo pollen germination, and higher spikelet fertility were observed in both the N22 accessions compared with IR64, Apo and Moroberekan under high temperature, water stress and combined stress, indicating its ability to tolerate multiple abiotic stresses.     

Differential responses of BA injection on yield and specific grain growth in contrasting genotypes of wheat (Triticum aestivum L.)

The effect of exogenous cytokinin (benzyladenine) was investigated on location specific grains in three contrasting wheat genotypes tolerant or susceptible to post anthesis high temperature conditions. Seeds were sown in earthen pots under natural environment in November and January for normal and late sowings, respectively. Grain weight was increased by the application of benzyladenine at anthesis under late sown stress only in those genotypes, which are known, to posses temperature tolerance in developing grains. However, under normal sowing conditions BA application was effective irrespective of genotype response to late sown stress. The effect was most visible in distal spikelets in the spike and distal grains in the spikelet which resulted in higher increment in weight of younger grains (c and d) as compared to older grains (a and b). It has been suggested that the responsiveness of the genotype to BA application under late sown stress is important and may be developed as an indicator to screen wheat genotypes for relative tolerance to late sown stress under irrigated conditions.     

Germination profiling of lentil genotypes subjected to salinity stress

• Salinity is one of the most severe environmental stresses, negatively affecting productivity of salt‐sensitive crop species. Given that germination is the most critical phase in the plant life cycle, the present study aimed to determine seed germination potential and associated traits under salt stress conditions as a simple approach to identify salt‐tolerant lentil genotypes.
• The genetic material consisted of six lentil genotypes whose adaptation to various agroclimatic conditions is not well elucidated. Salinity stress was applied by addition of NaCl at three different levels of stress, while non‐stressed plants were included as controls. Evaluation of tolerance was performed on the basis of germination percentage, seed water absorbance, root and shoot length, seedling water content, seedling vigour index and number of seedlings with an abnormal phenotype.
• Overall, our findings revealed that salinity stress substantially affects all traits associated with germination and early seedling growth, with the effect of salinity being dependent on the level of stress applied. It is noteworthy, however, that genotypes responded differently to the varying salinity levels. In this context, Samos proved the most salt‐tolerant genotype, indicating its possible use for cultivation under stress conditions.
• In conclusion, the determination of seed germination and early growth potential may be exploited as an efficient strategy to reveal genetic variation in lentil germplasm of unknown tolerance to salinity stress. This approach allows selection of desirable genotypes at early growth stages, thus enabling more efficient application of various breeding methods to achieve stress‐tolerant lentil genotypes.

     

Anatomical differences on development of fertile and sterile pollen grains of Prunus salicina Lindl.

Anatomical changes occurring during the microsporogenic development of P. salicina Lindl. were studied in male fertile and male sterile genotypes. Male fertile pollen grains showed three well determined pore regions, without ektexine. Intine was thick and surrounded the vegetative cell. Vegetative cells enclosed the generative cells; their cytoplasm was rich in plastids, abundant RER and active mitochondria. Development of sterile pollen was different from the meiosis step. Microspores did not show germination pores and ektexine was continuous around the whole grain. Pollen grains showed an atypical shape. The tapetum persisted after the tetrad stage and showed hypertrophy and vacuole development, resulting in abnormal microspore development. Only a few pollen grains and rudiments of collapsed microspores close to the anther wall were formed at anthesis.     

Anther response to high-temperature stress during development and pollen thermotolerance heterosis as revealed by pollen tube growth and in vitro pollen vigor analysis in upland cotton

Main conclusion

Pollen tube growth in styles was strongly inhibited by temperature above 35 °C, and the yield of cotton decreased because of the adverse effect of high temperatures during square development. High-temperature stress during flowering influences the square development of upland cotton (Gossypium hirsutum L.) and cotton yield. Although it is well known that square development is sensitive to high temperature, high-temperature sensitive stages of square development and the effects of high temperature on pollen tube growth in the styles are unknown. The effect of high temperature on anther development corresponding to pollen vigor is unknown during anther development. The objectives of this study were to identify the stages of square development that are sensitive to high temperatures (37/30 and 40/34 °C), to determine whether the abnormal development of squares influenced by high temperature is responsible for the variation in the in vitro germination percent of pollen grains at anthesis, to identify the effect of high temperature on pollen germination in the styles, and to determine pollen thermotolerance heterosis. Our results show that the stages from the sporogenous cell to tetrad stage (square length <6.0 mm) were the most sensitive to high temperature, and the corresponding pollen viability at anthesis was consistent with the changes in the square development stage. Pollen tube growth in the styles was strongly inhibited by temperature above 35 °C, and the yield of cotton decreased because of the effect of high temperature during square development. The thermotolerance of hybrid F₁ pollen showed heterosis, and pollen viability could be used as a criterion for screening for high-temperature tolerance cultivars. These results can be used in breeding to develop new cotton cultivars that can withstand high-temperature conditions, particularly in a future warmer climate.

     

Soybean (Glycine max) pollen germination characteristics, flower and pollen morphology in response to enhanced ultraviolet-B radiation

BACKGROUND AND AIMS: Ultraviolet-B (UV-B) radiation effect on reproductive parts of the plants has received little attention. We studied the influence of UV-B radiation on flower and pollen morphology, pollen production and in vitro pollen germination and tube growth of six genotypes of soybean (Glycine max). METHODS: Soybean genotypes were investigated by growing them under four levels of biologically effective UV-B radiation of 0 (control), 5, 10 and 15 kJ m(-2) d(-1) in sunlit controlled-environment chambers. KEY RESULTS: Reductions in lengths of flower, standard petal, and staminal column along with reduced pollen production, germination and tube growth were observed in all genotypes with increasing UV-B radiation. Combined response index (CRI), the sum of percentage relative responses in flower size, pollen production, pollen germination and tube growth due to UV-B radiation varied with UV-B dosage: -67 to -152 with 5 kJ m(-2) d(-1), -90 to -212 with 10 kJ m(-2) d(-1), and -118 to -248 with 15 kJ m(-2) d(-1) of UV-B compared to controls. Genotypes were classified based on the UV-B sensitivity index (USI) calculated as CRI per unit UV-B, where D 90-9216, DG 5630RR and D 88-5320 were classified as tolerant (USI > -7.43), and DP 4933RR, Stalwart III and PI 471938 were sensitive (USI < -7.43) in their response to UV-B radiation. Pollen grains produced in plants grown at 15 kJ m(-2) d(-1) UV-B radiation were shrivelled and lacked apertures compared to control and other UV-B treatments in both sensitive and tolerant genotypes, and the differences were more conspicuous in the sensitive genotype (PI 471938) than in the tolerant genotype (D 90-9216). The number of columellae heads of the exine was reduced with increasing UV-B radiation. CONCLUSIONS: Soybean genotypes varied in their reproductive response to UV-B radiation. The identified UV-B tolerant genotypes could be used in future breeding programmes.     

Small temporal differences in water uptake among varieties of pearl millet (Pennisetum glaucum (L.) R. Br.) are critical for grain yield under terminal drought

Background and aim

Intuitively, access to water from the soil at key phenological stages is important for adaptation to drought. This study aimed to assess the temporal pattern of water extraction under terminal drought stress.

Methods

Pearl millet genotypes with varying levels of terminal drought tolerance were grown in a lysimetric system with a soil volume and plant spacing similar to field conditions. Water extraction was monitored until maturity under differing water regimes.

Results

The yield did not differ among genotypes under well-watered (WW) conditions, and the water extraction profile of WW plants was similar across all genotypes. In contrast, the yield of sensitive genotypes was 30–100 % lower than that of tolerant lines under water stress (WS). The total volumes of water extracted by tolerant and sensitive genotypes were similar under WS; however, tolerant genotypes extracted less water prior to anthesis, and more water after anthesis. Grain yield was positively related to the amount of water extracted during week three after panicle emergence. Increased water extraction after anthesis benefitted the tillers more than the main culm and was correlated with higher staygreen scores.

Conclusion

Increased water uptake after anthesis, which results from earlier water conservation during pre-anthesis, increases yield under terminal drought in pearl millet.     

Pollen development at high temperature and role of carbon and nitrogen metabolites

Fruit and seed crop production heavily relies on successful stigma pollination, pollen tube growth, and fertilization of female gametes. These processes depend on production of viable pollen grains, a process sensitive to high‐temperature stress. Therefore, rising global temperatures threaten worldwide crop production. Close observation of plant development shows that high‐temperature stress causes morpho‐anatomical changes in male reproductive tissues that contribute to reproductive failure. These changes include early tapetum degradation, anther indehiscence, and deformity of pollen grains, all of which are contributing factors to pollen fertility. At the molecular level, reactive oxygen species (ROS) accumulate when plants are subjected to high temperatures. ROS is a signalling molecule that can be beneficial or detrimental for plant cells depending on its balance with the endogenous cellular antioxidant system. Many metabolites have been linked with ROS over the years acting as direct scavengers or molecular stabilizers that promote antioxidant enzyme activity. This review highlights recent advances in research on anther and pollen development and how these might explain the aberrations seen during high‐temperature stress; recent work on the role of nitrogen and carbon metabolites in anther and pollen development is discussed including their potential role at high temperature.     

外源硅对花期高温胁迫下杂交水稻授粉结实特性的影响

以杂交中熟籼稻品种金优63、汕优63为供试材料,采用盆栽试验,在水稻生长前期连续喷施3次硅酸钠(Na₂SiO₃·9H₂O),于人工气候箱内在水稻开花期进行常温(日均温26.6 ℃,日最高温度29.4 ℃)和高温(日均温33.2 ℃,日最高温度40.1 ℃)处理5 d,研究施硅在花期高温胁迫下对杂交水稻剑叶叶绿素含量、光合性能、抗氧化酶活性、丙二醛(MDA)含量、花粉活力、花药酸性转化酶活性、柱头授粉性能和结实率等的影响.结果表明: 与对照相比,施硅可显著提高高温胁迫下水稻剑叶叶绿素含量,提高净光合速率和气孔导度,减少胞间CO₂浓度,增强叶片光合作用,减少MDA含量,提高超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性;提高花药中可溶性酸性转化酶活性和花粉活力,增加花粉囊基部裂口宽度,提高水稻每柱头上授粉总数、萌发数、花粉萌发率和萌发数大于10粒者所占的比例,降低花粉总数小于20粒者所占的比例;使金优63、汕优63结实率的降低分别减轻13.4%、14.1%.因此,在水稻生长前期喷施外源硅,可减轻水稻在开花期结实率的降低,提高杂交水稻的抗热性.     

Comparative response of two wucai (<Emphasis Type="Italic">Brassica campestris</Emphasis> L.) genotypes to heat stress on antioxidative system and cell ultrastructure in root

The effects on root growth, root antioxidant capacity, and cellular ultrastructure were investigated using two wucai genotypes (heat-tolerant WS-1 and heat-sensitive WS-6) under heat stress (40/30 °C) for 5 days. Heat stress caused decreases in root biomass, relative water content (RWC), root vigor, and root traits of two wucai genotypes. In addition, it resulted in reactive oxygen species (ROS) accumulation and increased hydrogen peroxide (H₂O₂) content, superoxide anion (O₂ ^?) formation rate, and malondialdehyde (MDA) content, but the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were inhibited to different extents in two genotype wucai roots. However, these data indicated that the decline extent of WS-1 (heat tolerant) in root growth and antioxidant capacity was significantly lower than that of WS-6 (Heat sensitive). Microscopic analyses revealed that WS-1 (heat tolerant) showed a better cellular shape than WS-6 under heat stress and slightly oxidative damage; nuclear and mitochondria in WS-1 were of a better intact shape and clear bilayer membrane. Most importantly, the thicker root cell wall in heat-tolerant wucai genotype responding to heat stress was first reported. These results suggested that the ability of heat-tolerant wucai genotype to minimize the heat stress depended upon the higher self-regulation capacity and effectiveness of the antioxidant metabolism.     

Characterisation of plant growth‐promoting rhizobacteria from rhizosphere soil of heat‐stressed and unstressed wheat and their use as bio‐inoculant

• High temperature induces several proteins in plants that enhance tolerance to high temperature shock. The fate of proteins synthesised in microbial cells or secreted into culture media by interacting microbes has not been fully elucidated. The present investigation aimed to characterise plant growth‐promoting rhizobacteria (PGPR) isolated from the rhizosphere of wheat genotypes (differing in tolerance to high temperature stress) and evaluate their performance as bioinoculant for use in wheat.
• Four bacterial strains, viz. Pseudomonas brassicacearum, Bacillus thuringiensis, Bacillus cereus strain W6 and Bacillus subtilis, were isolated from the rhizosphere of heat‐stressed and unstressed wheat genotypes. The wheat genotypes were exposed to high temperature stress at 45 °C for 10 days (3 h daily) at pre‐anthesis phase. Isolates were identified on the basis of morphology and biochemical characteristics, 16S rRNA gene sequencing and whole cell protein profiles. Results were further complemented by size exclusion chromatography (SEC) with fast protein liquid chromatography (FPLC) and SDS PAGE of 80% ammonium sulphate precipitates of the cell‐free supernatants.
• Isolates were positive for catalase, oxidases and antimicrobial activity . P. brassicacearum from the rhizosphere of the heat‐tolerant genotype was more efficient in phosphate solubilisation, bacteriocin production, antifungal and antibacterial activity against Helminthosporium sativum, Fusarium moniliforme and Klebsiella pneumonia, respectively. The inoculated seedlings had significantly higher root and shoot fresh weight, enhanced activity of antioxidant enzymes, proline and protein content. Total profiling of the culture with SDS‐PAGE indicated expression of new protein bands in 95 kDa in P. brassicacearum.
• Temperature‐induced changes in PGPR isolates are similar to those in the host plant. P. brassicacearum may be a good candidate for use in biofertiliser production for plants exposed to high temperature stress.