Acquired Thermo‐Tolerance and Trans‐Generational Heat Stress Response at Flowering in Rice

In rice, pre‐exposure to sublethal treatment followed by harsh lethal treatment is known to improve tolerance of different abiotic stresses at the vegetative stage within and across generations. Our major aim was to test the phenomenon of thermo‐tolerance at flowering across (trans)‐generations and within generation using rice cultivars contrasting for heat stress tolerance at flowering. To test trans‐generational response, plants were exposed to higher temperature at flowering stage and seeds obtained from previous generations were exposed to heat stress during flowering, which recorded significantly lower fertility when exposed to the same degree of stress in their subsequent generations. A pre‐acclimation to moderately high acclimating temperatures imposed over three different durations during the vegetative and initial reproductive stage showed positive response in the tolerant N22, particularly under severe heat stress (40 °C). This finding indicates the possibility of acquiring ameliorative thermo‐tolerant mechanisms at anthesis, restricted to tolerant genetic backgrounds to combat subsequent harsh conditions within the same generation. However, trans‐generational memory was ineffective in mitigating spikelet sterility losses in both tolerant and susceptible backgrounds. Rice is extremely sensitive to heat stress during flowering; hence, similar exercise across other crops of interest needs to be carried out before generalizing conclusions.     

Drought Priming at Vegetative Growth Stage Enhances Nitrogen‐Use Efficiency Under Post‐Anthesis Drought and Heat Stress in Wheat

To study the effects of early drought priming at 5th‐leaf stage on grain yield and nitrogen‐use efficiency in wheat (Triticum aestivum L.) under post‐anthesis drought and heat stress, wheat plants were first exposed to moderate drought stress (drought priming; that is, the leaf water potential reached ca. ?0.9 MP a) at the 5th‐leaf stage for 11 days, and leaf water relations and gas exchange rates, grain yield and yield components, and agronomic nitrogen‐use efficiency (ANUE ) of the primed and non‐primed plants under post‐anthesis drought and heat stress were investigated. Compared with the non‐primed plants, the drought‐primed plants possessed higher leaf water potential and chlorophyll content, and consequently a higher photosynthetic rate during post‐anthesis drought and heat stress. Drought priming also resulted in higher grain yield and ANUE in wheat under post‐anthesis drought and heat stress. Drought priming at vegetative stage improves carbon assimilation and ANUE under post‐anthesis drought and heat stress and their combination in wheat, which might be used as a field management tool to enhance stress tolerance of wheat crops to multiple abiotic stresses in a future drier and warmer climate.     

Application of natural plant extracts improves the tolerance against combined terminal heat and drought stresses in bread wheat

Drought and heat are among the main abiotic stresses causing severe damage to the cereal productivity when occur at reproductive stages. In this study, ten wheat cultivars were screened for combined heat and drought tolerance imposed at booting, heading, anthesis and post‐anthesis stages, and role of the foliage applied plant extracts was evaluated in improving the performance of differentially responding wheat cultivars under terminal heat and drought stresses. During both years, wheat crop was raised under ambient temperature and 70% water holding capacity (WHC) till leaf boot stage. The plant extracts (3% each) of sorghum, brassica, sunflower and moringa were foliage applied at booting, anthesis and post‐anthesis stage; and after one week of application of these plant extracts, combined heat and drought was imposed at each respective stage. Heat and drought stresses were imposed at each respective stage by placing pots in glass canopies with temperature of 4 ± 2°C above than the ambient temperature in combination with drought stress (35% WHC) until maturity. Combination of drought and heat stresses significantly reduced the performance of tested wheat cultivars; however, stress at the booting and heading stages was more damaging than the anthesis and post‐anthesis stages. Cultivars Mairaj‐2008 and Chakwal‐50 remained green with extended duration for grain filling, resulting in the maintenance of number of grains per spike and 100‐grain weight under stress conditions and thus had better grain yield and water‐use efficiency. However, in cultivars Fsd‐2008, and Shafaq‐2006, the combined imposition of drought and heat accelerated the grain filling rate with decrease in grain filling duration, grain weight and grain yield. Foliar application of all the plant extracts improved the wheat performance under terminal heat and drought stress; however, brassica extract was the most effective. This improvement in grain yield, water‐use efficiency and transpiration efficiency due to foliage applied plant extracts, under terminal heat and drought stress, was owing to better stay‐green character and accumulation of more soluble phenolics, which imparted stress tolerance as indicated by relatively stable grain weight and grain number. In crux, growing of stay‐green wheat cultivars with better grain filling and foliage application of plant extracts may help improving the performance of bread wheat under combined heat and drought stresses.     

Expression analysis of the genes involved in osmotic adjustment in bread wheat (Triticum aestivum L.) cultivars under terminal drought stress conditions

Osmotic adjustment is the main component for physiological machinery of wheat drought tolerance. Some of parameters implicated in osmotic adjustment in 15 bread wheat cultivars were evaluated at soil water deficits (50% FC) and FC as the control in the greenhouse. For the physiological traits, analysis of variance showed that there are highly significant differences between treatments, i.e. water stress levels and wheat cultivars. Shahpasand and Marvdasht as sensitive wheat cultivars had significantly lower osmotic adjustment, relative water content, K+ content, soluble sugar, proline, and glycine betaine levels than the rest of the cultivars. The results of cluster analysis revealed that all cultivars were grouped into three distinct clusters. Dez, Kavir, Pishtaz, and Maron cultivars which have the highest osmoregulation activity were in cluster I, whereas clusters II (Pishgam, Aflak, Hirmand, Zagros, and Vee/Nac) and III (Ws-89-2, Sardari, Azar2, Shapasand, and Marvdasht) had intermediate activity and the lowest capacities for osmoregulation, respectively. In addition, in wheat flag leaf during the reproductive stage under drought conditions, the changes in gene expression of two key genes namely P5CS (D-Pyrroline-5-carboxylate synthetase) and BADH (Betaine Aldehyde Dehydrogenase) in two selected cultivars including Dez and Marvdasht revealed that water stress can increase the expression level of the genes P5CS and BADH in the resistant cultivar, Dez, compared with Marvdasht, the sensitive one. In general, it seemed that application of the all cultivars in cluster I would enable breeders to acquire more reliable achievements under drought conditions.     

Alterations in Photochemical and Physiological Activities of Chickpea (Cicer arietinum L.) Cultivars under Drought Stress

In this study, some morphological, physiological and biochemical parameters of two chickpea cultivars, cv. Gökçe and Canıtez, were analysed to understand their tolerance to drought stress. Twenty-day-old plants were subjected to three different regimes of drought stress by withholding water for 3, 5 or 7 days, and then rewatering for 2 days after the initial 7 days of drought stress. Drought treatments only reduced shoot elongation in the Canıtez cultivar. Leaf production and fresh biomass decreased in both cultivars under all drought treatments, however to a greater extent in Canıtez. In both cultivars, malondialdehyde, proline and anthocyanin accumulation increased significantly, whereas relative water content declined under drought stress. The total chlorophyll and carotenoid contents of Gökçe were not affected by drought stress, whereas the chlorophyll content of Canıtez increased greatly at the end of the treatments. Using chlorophyll a fluorescence measurements, we found that extended drought treatment caused photoinhibition of PSII activity in both cultivars. However, this was greater in Canıtez, especially under severe drought stress. Although Canıtez recovered quickly from drought stress and exhibited a good ability to overcome drought stress, via activation of many protection mechanisms such as increasing antioxidant enzymes and proline and anthocyanin accumulation during vegetative stage, our results show that Canıtez is less drought tolerant than Gökçe.     

Long‐Term Field Drought Affects Leaf Protein Pattern and Chloroplast Ultrastructure of Winter Wheat in a Cultivar‐Specific Manner

Recurrent drought periods of varying duration often cause extensive crop damage and affect wheat production in Southern Europe. This study compares biochemical and ultrastructural responses of four wheat (Triticum aestivum L.) cultivars to long‐term field drought, and their contribution to final grain yield. Gel electrophoresis and immunoblotting analyses combined with transmission electron microscopy and grain yield evaluation were employed to assess drought susceptibility of the wheat cultivars. Two of them behaved as drought‐tolerant, the other two presented as drought sensitive. Enhanced degradation of Rubisco large subunit (RLS), Rubisco small subunit (RSS) and Rubisco activase (RA) accompanied by an increased protease activity and reduced levels of heat shock proteins (HSP70) and dehydrins (DHNs) were associated with drought sensitivity. Drought tolerance coincided with relatively stable or increased HSP70 and DHN contents, and unchanged/higher levels of RLS, RSS and RA. Sensitive cultivars were more vulnerable to ultrastructural damages, showing obvious degradation of chloroplast membrane systems and depletion of leaf starch reserves. These drought responses affected yield potential, as tolerant cultivars gave higher yield under intense drought. Thus, our results provide additional insights into the complexity of plant drought responses, identifying multiple interacting traits that may serve as indirect selection criteria for wheat drought tolerance.     

水稻苗期抗旱性指标的筛选

为探索水稻苗期抗旱性形态和生理机制，筛选苗期抗旱性指标，以15个水稻品种为试验材料，在干旱棚内系统研究了水、旱条件下苗期形态和生理指标的变化。结果表明，叶龄、心叶下倒数第1叶叶面积、叶鲜重、根长4个指标的相对值与反复干旱存活率显著或极显著相关，可作为苗期抗旱性的形态指标；超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）活性，氨基酸（AA）、抗坏血酸（AsA）、还原性谷甘肽（GSH）、可溶性蛋白质、丙二醛（MDA）含量8个指标的相对值与反复干旱存活率显著或极显著相关，可作为苗期抗旱性的生理指标。通过主成分分析确立了SOD酶活性、GSH含量、叶鲜重和叶龄4个指标相对值为水稻苗期抗旱性的综合指标，以反复干旱存活率为因变量，4个综合指标为自变量建立的回归方程对供试品种的抗旱性进行预测效果较好。     

Contrasting rice backcross inbred lines (BILs) for grain yield and heading under lowland reproductive stage moisture stress

Identification and understanding the role of physio-morphological drought responsive mechanisms leading to grain yield enhancement under water stress is a critical insight for designing appropriate strategies to breed drought-tolerant cultivars for any drought prone ecology. In this study, three pairs of contrasting BILs with varied maturity were characterized for several agronomical, physiological and morphological traits across a wide range of moisture stress environments at reproductive stage during 2012–2014. Within each group, BILs differ significantly for grain yield, heading, biomass and harvest index under drought stress, but showed similar yield potential, phenology and other traits under control condition. The most tolerant BIL, S-15 out yielded all BILs and standard checks under both conditions. Apart from superior agronomic performance, drought tolerant BILs maintained significantly higher assimilation rate, transpiration rate and transpiration efficiency compared to susceptible BILs under stress in all three groups. In addition, most tolerant BIL (S-15) showed significantly higher stomatal conductance than susceptible BIL (S-55) in early group. Among root traits, significant differences under stress was observed for root dry weight between contrasting BILs in each group, even though tolerant BILs had higher root length and root volume compared to susceptible BILs, which is non-significant. Hence, consideration of root traits an important strategy for drought avoidance in case of rice may not always contributes to significant yield improvement under moisture stress condition. Further, tolerant BILs also recorded significantly higher shoot dry weight and drought recovery score at seedling stage under stress. Our findings suggest that genotypes with higher photosynthetic efficiency and better plant water status are able to produce higher grain yield under drought stress environments.     

Morphological attributes associated with early-season drought tolerance in spring durum wheat in a mediterranean environment

Impacts of drought during the reproductive development phase of wheat have been thoroughly investigated, while studies of the early-season drought effects are lacking. Field experiments were conducted to study the effect of duration of drought stress during the period from emergence to the end of tillering on the growth and performance of different wheat cultivars, and to identify traits that could be associated with the resistance to early season drought. Experiments were conducted on a Vertic Calcixerol soil in the semiarid cereal-growing region of Morocco in 1995 and 1996. Six spring durum wheat (Triticum durum Desf.) cultivars selected on the basis of variation in morphology, phenology, and zone of adaptation were subjected to four water regimes, including a well-irrigated control. The three water stress treatments were imposed by withholding water during the period from emergence to either the onset, middle, or the end of tillering. Subsequent irrigations provided adequate soil moisture for the remainder of the growing season. Results from both years were generally consistent. The differential responses of the six cultivars was mainly due to differences in numbers of kernels produced. High yields under early-season drought were attributed to high leaf area index under stress and, upon recovery, and to high tiller survival rate. The consistency observed over years in the relationships between grain yield and those traits that proved to be most associated with the resistance to early-season drought, would suggest the usefulness of these traits as selection criteria for breeding for improved drought resistance in a Mediterranean climate type of North Africa. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reproductive response of two morphologically different pea cultivars to drought

Water use by semi-leafless peas (Pisum sativum L.) is usually less than that of conventional peas because of their reduced surface leaf area, suggesting that semi-leafless peas would be less sensitive to drought because drought develops later. This work aimed to study the reproductive response of peas cv. Solara (semi-leafless) and cv. Frilene (conventional) subjected to similar controlled soil drought during the critical period occurring between flowering and initial seed filling. Plants were subjected to drought by watering with a fraction of water used in the evapotranspiration of control plants. Soil, pod and seed water contents, leaf water status parameters, dry matter (DM) partitioning, seed yield, yield components and water use efficiency (WUE) were measured. Although soil water content decreased in a similar way in both cultivars, leaf Ψ_w and RWC only decreased significantly in Solara. Well-watered Frilene plants produced higher shoot and pod DM, but lower seed DM. Well-watered Solara plants produced lower pod DM and higher seed DM than Frilene. Under drought, Frilene increased partitioning of total plant DM to vegetative organs, particularly roots, and decreased DM allocation to pods and seeds increasing flower abortion. By contrast, droughted Solara interrupted vegetative growth and increased leaf senescence but maintained similar partitioning of total plant DM to pods and seeds as in well-watered conditions. For both cultivars there was a close relationship between the percentage of total DM partitioned into seeds and WUE_y (water use efficiency on seed yield basis). Results demonstrate that when plants suffered the same level of drought in the soil, the reproductive response of the two cultivars was linked to differences in their WUE.     

Effect of Water Stress on Physiological Attributes and their Relationship with Growth and Yield of Wheat Cultivars at Different Stages

The effects of water stress on physiological attributes of drought‐sensitive (Kalyansona) and drought‐tolerant (C‐306) wheat cultivars were studied in a pot experiment. Water stress was imposed by withholding irrigation at boot and anthesis stages. Leaf water potential, leaf osmotic potential and leaf turgor potential (measured with pressure chamber and osmometer), as well as leaf diffusive resistance, leaf transpiration rate and leaf‐to‐air transpiration gradient (measured with a steady‐state porometer) were measured diurnally. Growth and yield parameters were recorded after harvesting of the crop. Triplicate data were analysed using a completely randomized design and correlations amongst these parameters were computed. Water stress was found to reduce diurnal leaf water potential and leaf osmotic potential in both the genotypes but leaf osmotic potential was significantly higher in the drought‐tolerant cultivar C‐306 than in the drought‐sensitive cultivar Kalyansona. Positive turgor was recorded in both the genotypes under water stress and non‐stress conditions. Water‐stressed plants showed significantly lower turgor potential than control plants. In diurnal observations, water‐stressed plants exhibited significantly higher leaf diffusive resistance in both genotypes at both stages. The diffusive resistance of C‐306 was predominantly higher than that of Kalyansona. Water stress decreased leaf transpiration rate at both stages but the reduction was higher at the anthesis stage. The leaf‐to‐air temperature gradient was much higher in C‐306 than in Kalyansona at the boot stage but at the anthesis stage genotypic variation was non‐significant. The capacity to maintain cooler foliage was lower at the anthesis stage than at the boot stage in both the cultivars. Shoot dry weight, number of grains, test weight, grain yield, biological yield and harvest index decreased to a greater extent when water stress was imposed at the anthesis stage, while imposition of water stress at the boot stage caused a greater reduction in plant height and number of tillers. Similarly, water stress caused a smaller reduction in growth, yield and yield attributes in C‐306 than in Kalyansona. In general, the correlation coefficient of grain and biological yield with water potential and its components was positive and highly significant. Similarly, turgor potential was also correlated positively and significantly with grain yield at both the stages, but with biological yield it was significant only at the anthesis stage. A negative and significant correlation was obtained for diffusive resistance and leaf‐to‐air temperature gradient with grain yield at the boot and anthesis stages. The rate of transpiration was also positively and significantly correlated to grain and biological yields at both the stages. Amongst the yield attributes, number of leaves and number of tillers were positively correlated at the anthesis stage, whereas leaf area and shoot dry weight were significantly correlated with grain and biological yields at both the stages.     

Drought priming effects on alleviating the photosynthetic limitations of wheat cultivars (Triticum aestivum L.) with contrasting tolerance to abiotic stresses

Abiotic stress tolerance in plants is said to be induced by pre-stress events (priming) during the vegetative phase. We aimed to test whether drought priming could improve the heat and drought tolerance in wheat cultivars. Two wheat cultivars “Gladius” and “Paragon” were grown in a fully controlled gravimetric platform and subjected to either no stress or two drought cycles during the tillering stage. At anthesis, both batches were either subjected to high temperature stress, drought stress or kept as control. No alleviation of grain yield reduction due to priming was observed. Higher CO₂ assimilation rates were achieved due to priming under drought stress. Yield results showed that priming was not damage cumulative to wheat. Priming was responsible to alleviated biochemical photosynthetic limitations under drought stress and sustained photochemical utilization under heat stress in “Paragon.” Priming as a strategy in abiotic stress alleviation was better evidenced in the stress susceptible cultivar “Paragon” than tolerant cultivar “Gladius”; therefore, the type of response to priming appears to be cultivar dependable, and thus phenotypical variation should be expected when studying the effects of abiotic priming.     

Water Deficit Reduced Fertility of Young Microspores Resulting in a Decline of Viable Mature Pollen and Grain Set in Rice

Pollen formation in rice ( Oryza sativa L.) is highly vulnerable to environmental stresses such as heat, chilling and drought. In rice plants exposed to drought during male reproductive development, the most obvious damage often observed is a decline in the number of engorged pollen and grain set. This has been well characterized in rice under chilling and to a lesser extent under drought stress. Moreover, detailed literature on the immediate effects of drought on developing young microspores in rice is still limited. Here, we report findings from experiments on rice plants exposed to water deficit for three consecutive days during early stages of anther development. When the osmotic potential of the growing medium was equal to or less than −0.5 MPa, as induced by polyethylene glycol, the leaf water potential was significantly lowered and grain set was reduced. A strong correlation between grain set and viable young microspores (P < 0.001, r² = 0.8223) indicates that water deficit immediately reduced fertility of rice plants at the time of exposure. This result suggests a new underlying mechanism of water deficit-induced pollen abortion in rice.     

水稻开花期抗旱性鉴定指标的筛选

水稻抗旱性鉴定指标的筛选已成为水稻抗旱性研究课题的热点之一。本文利用10个水、旱稻品种（组合）,在开花期水分胁迫条件下,测定了剑叶叶绿素、脯氨酸、丙二醛、可溶性糖含量,叶片相对含水量,株高,叶面积及光合速率等10项与抗旱性有关的形态和生理指标,进行了主成分分析和逐步回归分析。结果表明,水稻开花期叶片脯氨酸含量、叶片相对含水量、气孔导度、叶面积等4项指标对水稻的抗旱性有显著影响,可作为水稻开花期抗旱性鉴定指标。利用所建立的最优回归方程对供试品种（组合）进行了抗旱性预测,结果与它们在田间表现基本一致, 表明用这4个指标在开花期对水稻抗旱性进行鉴定是可行的。     

土壤水分胁迫下小麦叶片的渗透调节与膨压维持

两年的试验结果表明,在土壤缓慢脱水和长期水分胁迫下,四个小麦品种叶片均产生渗透调节,孕穗期和灌浆期渗透调节能力较强,渗透调节的幅度为0.40～0.64MPa,抗旱性强的品种大于抗旱性弱的品种.由于渗透调节在土壤含水量60%左右或轻度胁迫下,叶片膨压基本不变.五个生育期四个处理水平叶水势与膨压回归分析,从水势每下降一个单位,膨压降低的单位数看,昌乐5号(0.146)<山农587(0.151)<烟农15(0.162)<济南13(0.240),抗旱性强的品种由于渗透调节能力强,膨压降低的单位数小,维持膨压的程度高.     

Heat Shock Protein in Developing Grains in Relation to Thermotolerance for Grain Growth in Wheat

Wheat ( Triticum aestivum L.) cvs DL 153-2 and HD 2285 (relatively tolerant), HD 2329 and WH 542 (relatively susceptible), were grown under normal (27 November) and late (28 December) sown conditions. In another experiment, these cultivars were grown under normal sowing and at anthesis stage, they were transferred to control (C) and heated (H) open top chambers (OTCs). Under late sowing, wheat cultivars were exposed to a mean maximum temperature of up to 3.6 °C higher than normal sowing and in H-OTCs, mean maximum temperature was 3.2 °C higher than C-OTCs during grain growth period. Heat susceptibility index (S) for grain growth and grain yield was determined at maturity in both the experiments. The level of heat shock protein (HSP 18) in the developing grains was determined in C- and H-OTC grown plants and in normal and late sown plants by Western blot analysis. The moderately high temperature exposure increased the accumulation of HSP 18 in the developing grains. The relatively tolerant cultivars, as also revealed from S , showed a greater increase in HSP 18 compared with susceptible types in response to moderate heat stress. An association of HSP 18 with thermotolerance for grain growth in wheat was indicated.     

Effect of intermittent drought on grain yield and quality of rice (Oryza sativa L.) grown in Rwanda

The climate change will contribute drought and temperature extremes to rice growing systems, especially when cultivated in equatorial regions. To evaluate opportunities to cultivate and breed drought-tolerant rice, seven rice cultivars were evaluated in Rwanda for recurring morphological drought scores, grain yield and components, and quality characteristics. The cultivation conditions, that is site and drought treatment, impacted morphological drought scores, growth and yield attributes, while cultivar affected quality attributes. Thus, site showed a higher impact on grain yield and components than drought and cultivar, with generally a reduced grain yield at the low-temperature site, as a result of low spikelet fertility. Morphological drought scores were generally increased by drought, while drought at the reproductive stage at the high-temperature site was negative for yield and its components. The cultivars “Intsindagirabigega” and “Jyambere” were adapted to high-temperature site conditions. The cultivar “Intsindagirabigega” had the highest amylose content, and “Mpembuke,” the highest antioxidant capacity. Thus, climate change with increased temperature and drought extremes may increase rice productivity in cool areas, while especially drought at reproductive stage will be detrimental in low altitude areas with high temperature. Cultivar variation indicated opportunities for selection and breeding of climate change tolerant rice cultivars which should be of immediate priority.     

Exogenous application of allelopathic water extracts helps improving tolerance against terminal heat and drought stresses in bread wheat (Triticum aestivum L. Em. Thell.)

The allelopathic water extracts (AWEs) may help improve the tolerance of crop plants against abiotic stresses owing to the presence of the secondary metabolites (i.e., allelochemicals). We conducted four independent experiments to evaluate the influence of exogenous application of AWEs (applied through seed priming or foliage spray) in improving the terminal heat and drought tolerance in bread wheat. In all the experiments, two wheat cultivars, viz. Mairaj‐2008 (drought and heat tolerant) and Faisalabad‐2008 (drought and heat sensitive), were raised in pots. Both wheat cultivars were raised under ambient conditions in the wire house till leaf boot stage (booting) by maintaining the pots at 75% water‐holding capacity (WHC). Then, managed drought and heat stresses were imposed by maintaining the pots at 35% WHC, or shifting the pots inside the glass canopies (at 75% WHC), at booting, anthesis and the grain filling stages. Drought stress reduced the grain yield of wheat by 39%–49%. Foliar application of AWEs improved the grain yield of wheat by 26%–31%, while seed priming with AWEs improved the grain yield by 18%–26%, respectively, than drought stress. Terminal heat stress reduced the grain yield of wheat by 38%. Seed priming with AWEs improved the grain yield by 21%–27%; while foliar application of AWEs improved the grain yield by 25%–29% than the heat stress treatment. In conclusion, the exogenous application of AWEs improved the stay green, accumulation of proline, soluble phenolics and glycine betaine, which helped to stabilize the biological membranes and improved the tolerance against terminal drought and heat stresses.     

大豆根区逆境耐性的种质鉴定及其与根系性状的关系

依根系类型从黄淮海和长江中下游地区301份代表性材料中选取62份，以株高、叶龄、地上部干物重、地下部干物重为指标，采用平均隶属函数值方法鉴定了苗期耐旱性、苗期耐铝毒性，加上主茎节数、分枝数、单株荚数、单株粒数、百粒重等性状鉴定了后期耐旱性，并通过钒钼黄比色法测定植株P含量鉴定了苗期耐低磷性。筛选出1级苗期     

Two Soybean Plant Introductions Display Slow Leaf Wilting and Reduced Yield Loss under Drought

Due to high costs of irrigation, limited availability of irrigation water in many locations and/or lack of irrigation capabilities, genetic improvement for drought tolerance is an effective method to reduce yield loss in soybean [Glycine max (L.) Merr.]. Slow wilting and minimal yield reduction under drought are important traits in evaluating drought tolerance. Two maturity group III soybean plant introductions (PIs, PI 567690 and PI 567731) and two elite cultivars (DKB38‐52 and Pana) were evaluated with and without irrigation on a sandy soil. Drought was imposed by withholding irrigation at full bloom and continued until moderate wilting was shown by the fast leaf wilting in the check cultivar, Pana. Then, irrigation was resumed until maturity. Genotypes were scored for leaf wilting during the stress period, and yields were assessed at the end of the growing season and used to calculate a drought index. Yields of the exotic PIs were lower than those of the checks under both drought and well‐watered conditions. However, the PIs exhibited significantly lower wilting and less yield loss under drought (higher drought index) than check cultivars. The two PIs may have useful genes to develop drought‐tolerant germplasm and cultivars and maybe useful in genetic and physiological studies to decipher mechanisms responsible for improving yield under limited water availability.