Severe drought and temperature increase are predicted to be the major consequences of climate change. Groundnut is a major crop cultivated in the Sahel zone where water and high temperature stress are serious constraints for its production. Investigating drought and heat effects on physiological traits, yield and its attributes could significantly contribute for improving groundnut productivity and consequently the incomes of farmers. A groundnutgermplasm (268 genotypes) was evaluated in four trials during two years under intermittent drought and fully irrigated conditions. Droughtstress reduced pod yield up to 72 % compared to 55 % at moderate temperature. The haulm yield decrease due to drought was 34 % at high temperature and 42 % under moderate temperature. Haulm yield tended to increase under high temperature. Genotype by environment interaction (GxE) was significant under well-watered (WW) and water stress (WS) treatments. The genotype and genotype by environment (GGE) biplots analyses revealed several mega environments under WW and WS treatments. The GGE biplots analyses revealed also several genotypes with high performance and stability across year and temperature environments under both WW and WS conditions. The regression analyses indicated that among several traits, only the partition rate was significantly correlated to pod yield.
Genome analysis tools provide access to thousands of polymorphism, thus considerably broadening our capacity to monitor genetic diversity (Glaszmann et al., 2010). The molecular characterization provides information related to rare alleles from cultivated and wild accessions for allele mining (Upadhyaya et al., 2010d). ICRISAT in collaboration with Generation Challenge Programme, CIRAD, France, and CAAS, China has developed the composite collections of sorghum, (3,367 accessions) from the world collection (33,100 accessions) and molecularly profiled using 41 SSR markers and a reference set of 384 accessions was developed, which represents 78 per cent (615 of the 789 alleles) of the SSR markers allelic diversity. This reference set could be used for extensive genotyping with additional SSR markers and for phenotyping for biotic and abiotic stress and for agronomic traits. The reduced size of germplasm collections (core, mini core and reference set) had provided ample opportunities to the breeders for their efficient and economic multi-environment evaluation.
Wheat cultivars, which have the ability to produce high production in normal conditions and stable output under environmental constraints are in demand (Yang et al., 2002). The acquisition of thermotolerance is a fundamental objective in wheat breeding (Fokar et al., 1998; Blum et al., 2001). Knowledge of genetics and of the physiology of heat tolerance, and of how to utilise appropriate germplasm and methodologies, will aid in the development of heat tolerant wheat genotypes (Fokar et al., 1998). The evaluation of wheat production under successively higher temperatures in nursery growth is currently the most popular methodology (Blum et al., 2001). Recently, certain studies point out that the warmest summer, which is noticed in the last century in the tropical and subtropical regions could become normal in the end of this century (Battisti and Naylor, 2009).
Abstract: The ability to grow crops under low-water conditions is a significant advantage in relation to global food security. Bambara groundnut is an underutilised crop grown by subsistence farmers in Africa and is known to survive in regions of water deficit. This study focuses on the analysis of the transcriptomic changes in two bambara groundnut landraces in response to dehydration stress. A cross-species hybridisation approach based on the Soybean Affymetrix GeneChip array has been employed. The differential gene expression analysis of a water-limited treatment, however, showed that the two landraces responded with almost completely different sets of genes. Hence, both landraces with very similar genotypes (as assessed by the hybridisation of genomic DNA onto the Soybean Affymetrix GeneChip) showed contrasting transcriptional behaviour in response to dehydration stress. In addition, both genotypes showed a high expression of dehydration-associated genes, even under water-sufficient conditions. Several gene regulators were identified as potentially important. Some are already known, such as WRKY40, but others may also be considered, namely PRR7, ATAUX2-11, CONSTANS-like 1, MYB60, AGL-83, and a Zinc-finger protein. These data provide a basis for drought trait research in the bambara groundnut, which will facilitate functional genomics studies. An analysis of this dataset has identified that both genotypes appear to be in a dehydration-ready state, even in the absence of dehydration stress, and may have adapted in different ways to achieve drought resistance. This will help in understanding the mechanisms underlying the ability of crops to produce viable yields underdrought conditions. In addition, cross-species hybridisation to the soybean microarray has been shown to be informative for investigating the bambara groundnut transcriptome.
A decrease in wheat production severely affects the economy of our country and increases the miseries of the inhabitants (Khan et al., 2011). The popularity of food made from wheat flour creates a large demand for the grains production, even in economies with significant food supplies (Ullah et al., 2011). While Interest in crop response to environmental stresses has increased greatly in recent years because severe losses may result from heat, cold, drought and high concentrations of toxic mineral elements (Blum, 1988). Therefore, it is necessary to investigate genetic diversity in the currently used wheat germplasm against droughtstress (Maqbool et al., 2010).
2.7. Expression Validation of Differentially Expressed Genes Using Real-Time qPCR
Four genes which were potential candidate dehydration-associated genes (based on their functional annotations) with a differential expression level of >2-fold change and FDR corrected p-value ≤ 0.05 from the differential expression analysis, were chosen for quantitative PCR (qPCR) validation. The actin-11 from the available bambara groundnut transcriptome sequence was used as a housekeeping gene. The actin-11 gene is known to be one of the most stable reference genes for gene expression normalisation and has been used in soybean and rice specimens [ 41 , 42 ]. PCR forward and reverse primers were designed using Primer-BLAST [ 43 ] for the chosen genes. The primers were designed in three steps. Firstly, the target gene sequence to which the primers needed to be designed was downloaded from the soybean database. Secondly, the soybean-specific target gene sequence was blasted against a bambara groundnut transcriptome generated from RNA-sequencing data for a low-temperature stress experiment [ 44 ], by creating a BLAST database. Thirdly, the target gene sequence obtained from the bambara groundnut BLAST database was used to search through the BLAST database at NCBI to add weight to the selection of this sequence. Once the gene sequence was identified in the BLAST database, it was utilised to design primers with an appropriate primer size, GC content, and melting temperature (Tm) using Primer-BLAST. PCR was performed to check the quality of all the primers designed for the four dehydration-associated genes. PCR analysis was performed using the 7000 Sequence Detection System (Applied Biosystems, Cheshire, UK). The annealing temperature was set to 60 ◦ C for the primer designed for the genes for PAL1 (Phenylalanine ammonia-lyase 1) and COMT (3-Caffeic acid o methyltransferase), and 58 ◦ C for the Beta-fructofuranosidase and UBC-2 (ubiquitin conjugating enzyme-2) genes. The cycling parameters were set as: 95 ◦ C for 10 min, 40 cycles of denaturing at 95 ◦ C for 30 s, annealing at 60 ◦ C/58 ◦ C for 30 s, and extension at 72 ◦ C for 30 s. First strand cDNA synthesis for all the RNA samples was carried out using a SuperScript III First-Strand Synthesis kit (ThermoFisher Scientific, Lutterworth, UK). The first-strand cDNA was prepared for analysis by qPCR using PerfeCta SYBR Green SuperMix (Quantabio, Beverly, MA, USA) containing 2X reaction buffer (with optimized concentrations of MgCl 2 ), dNTPs (dATP, dCTP, dGTP, dTTP), AccuStart Tag DNA Polymerase (Quantabio, Beverly, MA,
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.
climate scenarios compared with 1960-1990. Because soil water deficit increases towards the end of crop growth, wheat will avoid the most severe droughtstress by maturing early. It is interesting to note (Fig. 1A) that the soil water deficit (SWD) at anthesis does not vary greatly between sites in 6
change and climate projections show closer frequencies of extreme weather events, higher temperatures, and increas- ingly scarce water resources . Intermittent drought in Sahelian zones decreased yield of groundnut up to 52% . To sustainably alleviate the water deficit effects and improve groundnut production in drought-prone environments, it is imperative to develop and release drought-tolerant vari- eties [10, 15]. Groundnut breeding efforts at ICRISAT have recently selected new varieties improved for high yield and resistance to diseases (leaf spots). The release and adoption of these new varieties in Sahelian countries where drought is occurring almost each year requires assessment under water deficit conditions. Therefore, the objectives of this work were to (i) investigate the groundnut elite lines response to droughtstressunder controlled conditions and select tolerant varieties and (ii) identify relevant drought tolerance related traits for groundnut improvement programs in Sahelian environment.
DOI: 10.4236/ajps.2019.108099 1392 American Journal of Plant Sciences hard for peasants to correctly make the solution, and if seed sellers immerse the seeds themselves, the seeds will quickly begin to germinate, creating difficulties for transportation and storage. Based on these reasons, maize seedlings were used as the experimental subject, and the influence of different Calcium solu- tions on maize seedlings underdroughtstress is explored with the goal of find- ing a strategy that works best in real-world situations.
380 ppm for the baseline climate and 530 ppm for the 2050 climate projections (IPCC 2001 ). For both the sites in India, the simulations were initiated on 15 May each year and the soil profile was considered to be at the lower limit (LL) of water availability on that day. Under normal sowing conditions the sowing window was 01 July to 15 August for Anantapur and 15 June to 30 July for Junagadh. The simulated crop was sown on the day when the soil moisture content in the top 30 cm soil depth had reached at least 40 % of the extractable water-holding capacity during the sowing window. Di-ammonium phosphate at 100 kgha −1 was applied at the time of sowing to supply 18 kgN and 20 kg P per ha to the crop. A plant population of 25 plants m −2 and row spacing of 30 cm were considered for simulating groundnut growth. Soil-limited photosynthesis factor (SLPF) of 0.74 was used for Anantapur and 0.87 for Junagadh. Site-specific values of SLPF were calibrated such that a single value of light-saturated leaf photosynthesis (AMAX) from literature accurately predicted biomass and yield over all sites. An SLPF value less than 0.90 represents soil limitations other than N or water. At all the sites the crop was grown rainfed in the model. Simulations were done for 30 years (1973 –2002) for Anantapur and 22 years (1985–2007) for Junagadh.
Haulm weight and pod weight obtained per plot were converted into haulm yield (Hy) and pod yield (Py), expressed in g m −2 and used to determine the total biomass (Bt) given as: Bt = Hy + (Py × 1.65). The pod weight was multiplied by a correction factor of 1.65 to adjust for the differences in the energy requirement for producing pod dry matter compared with vegetative part [ 50 ]. Harvest index (HI) was determined as a ratio of adjusted pod weight to total biomass, given as: HI = (1.65 × Py)/Bt. For each plot, days to 75% flowering, days to maturity, pod yield (kg ha −1 ), kernel yield (kg ha −1 ), hundred kernel weight (g), sound mature kernel (%) and oil content (%) were recorded. Oil content was estimated with near infrared reflectance spectroscopy (NIRS) (model XDS RCA, FOSS Analytical AB, Sweden, Denmark) using whole kernels [ 51 ]. Two physiological parameters, crop growth rate (CGR) (g m −2 day −1 ) and pod growth rate (PGR) (g m −2 day −1 ) were estimated following a modified procedure given by Williams and Saxena [ 52 ]. Stress susceptible and tolerance indices were calculated to identify heat-tolerant genotypes using the following formula:
The identification and use of accessions available in cassava germplasm banks may contribute to improvements in the productivity of fresh roots and starch (Table 4). However, despite the constant need to develop novel and more productive cassava varieties, it is necessary to consider current trends within the food industry, and farmers searching for native starches with special features that could replace chemically modified varieties or open new market opportunities (Leonel, 2007). Therefore, breeding programs should also seek to improve the starch quality produced by new varieties. In this regard, Brazil has a strategic advantage since it is considered the center of genetic diversity of M. esculenta (Olsen, 2004; Isendahl, 2011), and thus has sufficient genetic diversity to meet these demands. As demonstrated, the analysis of genetic relationships among cassava accessions based on root traits and starch granules is an important component of breeding programs, because it provides crucial information required for establishing segregated populations stratified by targeted goals for quality starch.
Fig. 3A shows box plots of DSI95. For all sites except WA, the medians of predicted DSI95 for fifteen GCMs for the 2050(A1B) scenario were lower that the values of DSI95 for the baseline scenario. This means that despite a decrease in precipitation during summer in northern Europe and during the whole growing season in southern Europe (Fig. SI.1), relative yield losses from drought were predicted to be smaller in the future than at present even for currently grown wheat cultivars. Maturity dates are predicted to be 2–3 weeks earlier for the 2055(A1B) scenario compared with 1960–1990 (Fig. 1B). Because soil water deficit (SWD) increases towards the end of crop growth, wheat will avoid the most severe droughtstress by maturing early. It is interesting to note (Fig. 3B) that SWD at anthesis does not vary greatly between southern and northern sites and the median of SWD at anthesis is predicted to stay at about the same level in the future with one exception, CF, where it increased from 50 to 67 mm. Medians of monthly mean maximum temperatures for the 2050(A1B) scenario are predicted to increase between 1.5 and 3.5uC depending on the month and the site (Fig. SI.1). Fig. 4 shows the probability of two events: first, when the maximum daily tem- perature within 3 days of anthesis exceeded a temperature threshold of 27uC or 30uC (Fig. 4A and 4C), and second, when the maximum temperature exceeded thresholds both within 3 days of anthesis and Figure 3 | (A) 95-perccentiles of DSI, and (B) soil water deficit at anthesis.
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 .
Salinity is an increasing concern for the productivity of staple food crop. Crops with improved salt tolerance are highly needed to cultivate saline lands. Groundnut demand is increasing in countries like India, where saline land could be put undergroundnut cultivation. The objective of this study was to identify groundnut genotypes with salinity tolerance for breeding programs. A set of 275 groundnutgermplasm accessions were screened across three different seasons for salinity tolerance. Shoot biomass and seed yield under saline and non-saline conditions were recorded. Shoot biomass under saline conditions showed limited genotypic variation and was not determined as a selection criterion in the subsequent trials. While a six-fold range of variation for pod yield under salinity (10-12.5 dSm -1 NaCl) was observed. Pod weight
The experiment was conducted to evaluate the differences of plant growth as well as sweetener material of two types of Stevia rebaudiana under conditions of absence and presence of droughtstress. In vitro, the experiment was conducted as drought traits using four levels of polyethylene glycol (0.0, 10,000, 20,000, 30,000 ppm). It was observed that survival % and No. of shoots should be considered as the important factors associated with stevioside content in stevia plant. Accord- ing to path coefficient analysis and positive direct effect of studied traits, survival % recorded the highest value (0.5386), whereas No. of shoots recorded the highest value (−0.8827) as negative direct effect in related to stevioside content. The results showed that all traits were affected, espe- cially under 30,000 ppm level of polyethylene glycol. Generally, the most of studies traits exhi- bited a recorded clearly difference between the two types and used drought levels on stevia plants. Therefore, selection based on survival % would be more effective to improving stevioside content of stevia plants in droughtstress conditions.
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.
As a summer crop, sunflower (Helianthus annuus L.) is influences commonly by droughtstress due to growing generally in rain fed regions without irrigation. Drought affects severely not only seed yield both also other important yield traits which plays important roles on yield formation in sunflower. Therefore, drought resistance became one of the most important goals in the sunflower breeding programs in the world. The study was conducted to determine drought tolerance levels of sunflower genotypes under controlled environmental conditions in Edirne which is a border city in Trakya region which is European part of Turkey and has about 50% of Turkish sunflower production areas. Sunflower restores lines which developed in National Project were evaluated foliar responses against droughtstress. Based on study results, the most affected foliar trait was leaf area and it was reduced until 75%. Similarly, leaf number of plants also influenced severely especially from earlier droughts and plants responded about 60% leaf number decreases. On the other hand, on the chlorophyll content of plant leaves, sunflower genotypes responded differently both in earlier (R.3) and later (R.5.1) plant growth stages. While chlorophyll content of sunflower lines increased about 40-50%, some of them decreased about 30%. Similarly, sunflower genotypes responded differently droughtstress in their foliar traits depending on when stress applied early or late. As results, sunflower genotypes had different tolerance to drought and higher tolerant ones will be considered to develop tolerant hybrids and will be used as initial material for further breeding purposes.