Plant responses to high temperature vary with plant species and phenological stages (Wahid et al. 2007). Reproductive processes are markedly affected by high temperatures in most plants, which leads to reduced crop yield. For example, both grain weight and grain number appeared to be sensitive to high-temperature stress in wheat, as the number of grains per head at maturity declined with increasing temperature (Ferris et al. 1998). Vara Prasad et al. (2000) investigated the effects of day- time soil and air temperature of 28 and 38 C, from start of flowering to maturity of groundnut, and reported 50 % reduction in pod yield at high temperatures. These authors observed that day temperature above 34 C decreased fruit-set and resulted in fewer numbers of pods. However, Greenberg et al. (1992) and Ndunguru et al. (1995) reported that varieties grown by farmers in the Sahel yielded well in the hot months prior to the onset of the rains, and this has been attributed to their ability to maintain partitioning to pods above that in normal tem- peratures. Here, we test the range of genotypic variation in pod yield under hot conditions, using a large and rep- resentative set of genotypes.
The study has clearly indicated the scope of using RAPD markers for varietal differentiation and diversity assessment at molecular level. Genotype specific amplification profiles observed with specific primers would help in the identification of the genotypes resistant to biotic, abiotic stress and agronomically important characters. Development of tolerant genotypes is one of the important approaches to overcome the problem associated with the droughtstress. The current study reveals the appropriate optimized concentration of PEG for screening the groundnut genotypes which could be useful further physiological studies. The results highlight the importance of the PEG as an artificial stress inducer for quick and efficient screening in the laboratory conditions for identification of drought tolerant genotypes for breeding programs in groundnut.
Our findings on RDW, RL, RV, and RD showed significant decrease due to WS. Reference  reported significant root traits decrease underdroughtstress. In addition to leaf area decrease and stomatal closure, RDW, RL, RV, and RD decrease contributed to TTW reduction under WS. Our findings showed also that RDW and RV were nega- tively correlated with pod weight but positively correlated with haulm weight (data not shown). These results suggest that negative impact of droughtstress on root parameters will affect more haulm production than pod yield. How- ever, the roles of root traits in pods yield underdrought conditions are diversely interpreted. For instance, authors [4, 15, 32] have shown that high RDW was positive to maintain high TE and improve yield component and can be used as selection criterion for improving drought resis- tance in groundnut, while  reported that RDW alone may not determine the pod yield and other factors are involved.
A variety GW322 (Table S1) and its improved NILs were utilized for validation of expression of m-QTL26 region. GW322 is high yielding bread wheat cultivar (41–45 qtls/ha) with very high breeder seed indent. The variety is widely adapted for timely sown, irrigated conditions of Peninsular and Central zone of India, however, this variety is susceptible to droughtstress. To improve its tolerance to drought, GW322 NILs were developed by introgressing favorable allele of QTL linked SSR marker Xbarc68- Xbarc101 from a suitable donor (HI1500) through a backcross breeding program in an earlier work in our laboratory (Todkar 2016). In a previous study, QTLs linked to Xbarc68-Xbarc101 markers were identified in C306/HUW206 population (Kumar et al. 2012) and GW322/HI1500 population (Manu 2017). Hence, both C306 and HI1500 are used as donors for transfer of QTL linked to Xbarc68-Xbarc101 in breeding programmes. The SSR marker region Xbarc68-Xbarc101, co-localize with m-QTL26 region on 3B chromosome (Acuña-Galindo et al. 2015) and therefore was used to validate the expres- sion of m-QTL in the present study.
Abstract Climate change is projected to intensify drought and heatstress in groundnut (Arachis hypogaea L.) crop in rainfed regions. This will require developing high yielding groundnut cultivars that are both drought and heat tolerant. The crop growth simulation model for groundnut (CROPGRO-Groundnut model) was used to quantify the potential benefits of incorporating drought and heat tolerance and yield-enhancing traits into the commonly grown cultivar types at two sites each in India (Anantapur and Junagadh) and West Africa (Samanko, Mali and Sadore, Niger). Increasing crop maturity by 10 % increased yields up to 14 % at Anantapur, 19 % at Samanko and sustained the yields at Sadore. However at Junagadh, the current maturity of the cultivar holds well under future climate. Increasing yield potential of the crop by increasing leaf photosynthesis rate, partitioning to pods and seed-filling duration each by 10 % increased pod yield by 9 to 14 % over the baseline yields across the four sites. Under current climates of Anantapur, Junagadh and Sadore, the yield gains were larger by incorporating drought tolerance than heat tolerance. Under climate change the yield gains from incorporating both drought and heat tolerance increased to 13 % at Anantapur, 12 % at Junagadh and 31 % at Sadore. At the Samanko site, the yield gains from drought or heat tolerance were negligible. It is concluded that different combination of traits will be needed to increase and sustain the productivity of groundnutunder climate change at the target sites and the CROPGRO-Groundnut model can be used for evaluating such traits.
when humidity and precipitation decreased or when temperature increased and precipitation decreased under climate change in the central parts of the USA (Brown and Rosenberg, 1997). The economy and food security of the rural communities in the semi-arid regions of Niger are strongly dependent on rainfed agriculture (Marteau et al., 2011). Pearl millet (Pennisetum glaucum [L.]) is one of the most important crops growing on more than 65% (7.5 million ha-1) of the cultivated land of Niger (Mariac et al., 2006). Different reports showed significant impacts of climate change on crop production in West Africa which is, according to the Global Hunger Index, one of the regions with the most severe hunger in the world (Von Grebmer et al., 2008). (Mohamed et al., 2002; Van Duivenbooden et al., 2002) predicted that 10% increase in average temperature may cause a 13% decrease in millet production by using an empirical method for Niger. Furthermore, (Tingem and Rivington, 2009) estimated 14% and 39% decrease in maize and sorghum yield under SRES-A2 emission scenario in Cameron. In general, 11% decrease in crop production under climate change was expected for the whole of West Africa (Roudier et al., 2011). Most climate change assessment studies did not account for differences in crop management and little is known on the interaction between climate and crop nutrition. Poor soil fertility management, high evapotranspiration demand and the low native soil fertility limit pearl millet production in Niger (Bationo et al., 1993). Changes in climate may cause larger (or smaller) losses of nitrogen through leaching and gaseous losses or changes in the demand for fertilizer, e.g. by changes in temperature and precipitation amount and pattern (Olesen and Bindi, 2002; Porter et al., 1995). (Sivakumar and Salaam, 1999) showed that the effectiveness of fertilizer application in this region depends on midseason precipitation. Average or above average midseason precipitation and high application rates of Nitrogen fertilizer resulted in highest yields of pearl millet while lower precipitation eliminated the advantage of nitrogen application. However, this study was a short term experiment (4 years) and only considered mineral fertilizer application as fertilization practice.
Olthof, 1976; Szakasits et al., 2009). However, the experiment still provides a valid model for multiple stress response, as in field conditions different environmental stresses would also occur in differing intensities. A further limitation of the experiment results from the necessity to initiate the two stresses sequentially rather than simultaneously. The lifestyle of plant-parasitic nematodes means that nematodes require several days to migrate through the root and establish feeding cells before eliciting the maximum stress response from the plant (Wyss and Grundler, 1992). To harvest tissue on the first day of nematode invasion would reveal mainly wound responses from the plant (Gheysen and Fenoll, 2002). Therefore in order to study these two stresses in combination it was essential to apply the nematodes before the droughtstress. It is possible that nematode-infected plants may therefore have been ‘primed’ defensively and thus react differently to dehydration stress (Voelckel and Baldwin, 2004; Bruce and Pickett, 2007; Rouhier and Jacquot, 2008). A similar predicament was experienced by Rizhsky et al. (2004) when imposing ‘simultaneous’ drought and heatstress, whereby the drought had to be initiated in advance of the heatstress so that the water content of the leaves had time to reduce to the stipulated level. Sequential stress initiation may thus be a necessary compromise. It should be noted that the microarray experiment here was limited to a single time point, and that a more comprehensive picture may be revealed by more detailed analysis over an extended period of time throughout the development of both stresses (Swindell, 2006; Kilian et al., 2007; Klink et al., 2007). Another possible reason for the observed down-regulation of the nematode response that occurred when both stresses were applied together is the antagonistic crosstalk between biotic and abiotic signalling pathways, a process controlled largely by the hormones ABA, salicylic acid and jasmonic acid (Anderson et al., 2004; Asselbergh et al., 2008b; Yasuda et al., 2008; Ton et al., 2009). As described in Section 2.4.1, the induction of ABA during abiotic stress may down-regulate defence pathways including the SAR, known to be induced by nematode invasion (Wubben et al., 2008; Yasuda et al., 2008). These observations may explain why nematodes could invade drought-stressed roots more easily (Section 2.4.1 and Figure 2.7), whilst combined dehydration and nematode stress caused the transcriptomic repression of nematode-induced genes.
Heatstress is the result of the combined effects of environment, metabolic rate, and protective clothing [Havenith 1999]. It can result in a spectrum of disorders known as heat- related illness, which can include mild health conditions such as heat rashes and heat cramps; or more complicated events such as heat exhaustion and heat stroke [CDC 2008]. Heat exposure is a recognized occupational hazard that is present in many work environments [NIOSH 2013, OSHA 2015]. It induces physiological strain [Kjellström, et al. 2009], decreases work capacity [Kjellström, et al. 2009, Sahu, et al. 2013], jeopardizes worker’s health [Arbury, et al. 2014, Spector, et al. 2014], and increase the risk to work related injury [Fogleman, et al. 2005, Ramsey, et al. 1983]. Environmental contributions to heatstress should include at least temperature and humidity. For this reason, the National Weather Service Heat Index and the wet bulb globe temperature (WBGT) are frequently used indices.
Combined ANOVA showed non-significant G × E interactions for pod yield and other physiological parameters (Table 2 ), suggesting that genotypes responded in different ways in three different environments. The same was evident from the performance of the genotypes, wherein some genotypes showed a reduction in pod yield underheatstress, while others were either stable or recorded an increased pod yield. The observation suggests scope to identify groundnut genotypes that perform well in normal as well as heat-stress environments. Genotypic variation for pod yield [ 30 – 32 ] for harvest index [ 33 ] under high temperature among groundnut genotypes was associated with differences in botanical type. Our study involved two botanical types, var. hypogaea (Virginia market class) and var. vulgaris (Spanish market type) of Arachis hypogaea subsp. fastigiata but did show such an association.
Damage to the plants caused by exposure to high temperature differs from crop to crop, and depends on growth stage and type of plant tissue. Some growth stages are more sensitive to high stress than others. In pearl millet, for example, the seedlings are most vulnerable to heat during emergence, because of the rise of soil surface temperature (Klueva et al., 2001). Heatstress can reduce crop yield or change quality. Heatstress can be severe or moderate, and usually when the term high temperature is used, it refers to rise in temperature which stresses the crop (Stone, 2001). Agonga (2006) indicated that the heatstress delays pod formation in bambara groundnut. McDonald and Paulsen (1997) studied the response of Alaska pea to elevated temperature during flowering, where one week after start of flowering, the plants were exposed to 20/15 or 30/25 °C day/night temperature for 7 days, after exposure to high temperature, plants were transferred to 20/15 °C until physiological maturity. They found that high temperature reduced plant height by 15% , TDM by 49%, seed yield by 54% and HI by 8%. During flowering, pollen development, fertilization and asynchrony of stamen are sensitive to temperature stress. The loss of pollen or stigma viability underheatstress might be the main reason for lowered number of seeds produced in the legumes (Thuzar et al., 2010).
Global climate change in the form of rising temperatures and increasingly variable rainfall patterns, along with heightened competition for scarce natural resources, potentially threatens the sustainability of cotton cropping systems. Thus, future cotton production is likely to occur under an increased prevalence of multiple abiotic stresses, including extreme and prolonged high temperatures and water deficits. Therefore, it is of increasing relevance that the combined effects of heat and drought stresses on cotton productiv- ity are more comprehensively examined under field conditions. This article reviews the separate influences of heat and droughtstress on cotton, outlines known effects of the combination of high temperature and water deficit on cotton and model plant species, discusses the genetic dissec- tion of heat or droughtstress tolerance traits in cotton, investigates the potential of field-based phenotyping methods for evaluating the response of cotton plants to heat and drought stresses, and, finally, offers perspectives on the development of stress-resilient cotton germplasm. Importantly, the integration of approaches from several dis- ciplines is needed to allow cotton breeders to efficiently develop superior cultivars for optimal stress resilience in a farmer’s field.
The assessment of these phytochemicals using in vitro methods has gained current research interest because these approaches are simple, fast and less expensive than in vivo trials (Rodriguez-Roque et al., 2013). In vitro gastrointestinal digestion is designed to mimic the human digestive system and is a useful tool to assess the bio-accessibility or bioactivity of compounds (Rodriguez-Amay, 2010). Cilla et al. (2013) suggested that in vitro studies are unrealistic if they involved only a single compound at high concentrations far above the concentrations detected in in vivo and, therefore, bioactivity might be overestimated. However, using whole food samples or plant extracts instead of bioactive constituents to measure bioactivities can provide information close to real-life physiological situations (Cilla et al., 2013). These in vitro gastrointestinal digestion studies have been used in conjunction with Caucasian Colon Adenocarcinoma Cell (Caco-2 cell) culture systems. Caco-2 cell cultures can be used to provide an estimation not only to monitor nutrient uptake and transport of supplements and whole food samples but also to determine in digested plant-based foods have bioprotective capacity against oxidative damage (Aherne et al., 2007; Etcheverry et al., 2012; Kopsell & Kopsell, 2006). There has been no previous study that investigated the biological activity of water stressed tomato fruits using these methods.
Gossypium hirsutum L. (Upland) and G. bar- badense L. (Pima) are the most important fiber crops grown worldwide in more than 50 countries. However, rising temperatures, variable rainfall pat- terns, and increasing drought affect areas because of climate change and threaten cotton production on a global scale. Drought and high temperatures are the main limiting factors on plant growth and photosynthesis in cotton production areas. These two abiotic stresses often occur simultaneously; however, the combined effects of both factors have not been thoroughly dissected at the physiological level (Xu and Zhou 2006).
It is indicative of a substantial stress, not yet too severe.
During the crop growing period, soil temperature at 5 and 10 cm at the hottest period of the day (1 to 3 O’clock PM), the maximum (Max) and minimum (Min) air temperatures and the relative humidity were recorded daily from a meteo- rological station located close to the experimental field. In the moderate temperature season, temperatures were measured on soil covered by vegetation. But this vegetation was dried in high temperature season. The air temperature and relative humidity were used to determine the vapor pressure deficit (VPD) (Prenger and Ling, 2001). Time of emergence and time to flowering (50 % of the plants started flowering) were recorded before water stress application. The SPAD chlorophyll meter reading (SCMR) was measured on the third leaf (from the top of the plant) using a Minolta SPAD-502 meter (Tokyo, Japan) in the MT09 and HT10
New crop cultivars will be required for a changing climate characterised by increased summer drought and heatstress in Europe. However, the uncertainty in climate predictions poses a challenge to crop scientists and breeders who have limited time and resources and must select the most appropriate traits for improvement. Modelling is a powerful tool to quantify future threats to crops and hence identify targets for improvement. We have used a wheat simulation model combined with local-scale climate scenarios to predict impacts of heatstress and drought on winter wheat in Europe. Despite the lower summer precipitation projected for 2050s across Europe, relative yield losses from drought is predicted to be smaller in the future, because wheat will mature earlier avoiding severe drought. By contrast, the risk of heatstress around flowering will increase, potentially resulting in substantial yield losses for heat sensitive cultivars commonly grown in northern Europe.
Increasing temperatures are highly likely to result in large yield losses in maize production in SSA (Jones and Thornton, 2003; Lobell et al. 2008; Rowhani et al. 2011). Compared to other abiotic stresses associated with climate change (droughtstress and water- logging), relatively little research has been conducted on heatstress in maize. The vast majority of studies have focussed on biochemical and molecular responses using only a limited number of genotypes with stress applied in vitro as a single and rapid heatstress event, rather than in response to heatunder field conditions (Cairns et al. 2012b). The current study has shown large genetic variation in grain yield underheatstress in sub-tropical and tropical maize germplasm in the field. To date there has been no extensive breeding effort that targets specifically heatstress in tropical and sub-tropical maize. Several potential donors with tolerance to heatstress were identified in this study, however further trials are needed to confirm these results. Combineddrought and heatstress is likely to become an increasing constraint to maize production in SSA, particularly in the drought-prone lowlands of southern Africa (Cairns et al. 2012b). Our results indicate that current maize germplasm developed for drought tolerance may not perform well underdroughtstress at elevated temperatures. Thus maize breeding for tolerance to droughtstressunder elevated temperatures must include screening under the combined effect of drought and heat rather than the individual stresses.
Abstract: Superoxide dismutase (SOD) is one of the major classes of antioxidant enzymes, which protects the cellular and subcellular components against harmful reactive oxygen species. In maize, three types of SODs are present based on their constituent metal ions, namely Cu/Zn-SOD, Mn-SOD and Fe-SOD. We investigated the effect of water stress on SOD isozymes in two contrast maize genotypes, tolerant and susceptible. We found Mn-SOD and Fe-SOD with production of more transcriptomes in the tolerant genotype than susceptible. Cytosolic SOD had heightened expression levels in the tolerant genotype. The expression analyses of cytosolic SOD, Mn-SOD and Fe-SOD would be used as candidate genes for the development of drought tolerant maize.
Leaf area index is the most important growth indicator in sunflower because sunflower plants perform maximum photosynthesis with reaching the highest leaf area if there is not any stress . In any water stress during these growing stages, crop growth rate could reduce because of decreasing in leaf area with falling leaves and with rapid aging of leaf especially after flowering stage , . Especially in earlier growing period of sunflower (4 to 8 leaves), droughtstress rapidly leads reduction of number and size of leaves, less leaf area index and less absorption at maturity stage, also shorter plants and lower plant dry matter. These earlier water stresses reduce leaf growth rate and leaf number among vegetative phase then it results initiating of decreases leaf area index after that , , . Fereres et al. (1983) found that leaf area was decreased rapidly by droughtstress and affected grain yield negatively and Goksoy et al. (2004) observed that restricted irrigations reduced leaf area due to yellowing and falling leaves too.
According to the above results, we could find: compared with other groups, 65 w, 15 min processing wheat seedling had highly ability in growth, but not necessarily the optimal dose and time, which still can was selected as the experimental conditions. Then, the control group and 65 w, 15 min processing wheat seedling were in droughtstress at the same time , and measured corresponding physiological indexes to study the dose of ultra- sonic effect on wheat seedling underdroughtstress .