Development Of Tolerant Genotypes Research Articles

Screening Iranian endemic coriander genebank germplasm for drought tolerance using a new multivariate statistical method

Drought is one of the serious abiotic factors influencing crop production such as coriander. Development of tolerant genotypes is prevented by the lack of effective selection criterion. Objectives of this study were evaluation of coriander accessions for water deficit stress and introduce a new multivariate method to select drought tolerant genotypes. For investigation of 19 traits, 16 Iranian endemic coriander genotypes were grown in a glasshouse under control and water deficit stress conditions. Shoot dry weight (SDW), fruit weight per plant (FWPP), fruit number per plant (FNPP) and umbel number per plant (UNPP) were decreased (Susceptibility Index>38%) under water deficit stress condition compared with the control condition. While the mean values of root dry weight (RDW) and root to shoot ratio (RTSR) were increased 1.49% and 97.33% under water stress condition, respectively. Because of high inheritance, high expected genetic gain, high genotypic correlation with together, well response to drought stress and high explanation of FWPP variation in regression model, the FWPP, branch number per plant (BNPP), FNPP and SPAD chlorophyll content in grain filing stage (SCCIGFS) traits were selected to screen coriander genotypes for drought tolerance in coriander. The principal component analysis mediated method (PCAMM) indicated as comprehensive criterion to screen drought tolerant genotypes. This method was highly heritabl, able to separate the Fernandez described A, B, C and D groups, no multicollinear and using multiple drought tolerance related traits. The PCAMM results showed that G13, G16, G2 and G12 genotypes belonged to Fernandez described A, B, C and D groups, respectively.

ESTIMATION OF SALT TOLERANCE POTENTIAL OF SYNTHETIC HEXAPLOID WHEAT BASED ON ION DISCRIMINATION

Soil salinity has become a significant problem in agricultural lands making a huge area unavailable for production. Salt affected lands can be exploited effectively by utilization of salt tolerant germplasm for various crops through identification and development of tolerant genotypes. Wheat being a major food crop in many countries come to priority in this regard, and has been subjected to extensive breeding to develop tolerant germplasm. In the quest for novel sources of genes to improve the existing germplasm, several synthetic hexaploids have been developed by exploiting a diploid wheat progenitor, Aegilops tauschii. Some of these synthetic hexaploids were evaluated for their salt tolerance potential using an in vitro test called K+:Na+ discrimination. A total of thirteen genotypes were grown in hydroponics at a salinity level of 75mM NaCl. Eight genotypes showed tolerance by discriminating between Na+ and K+ ions under saline conditions. SH-13 and SH-11 were the most tolerant genotypes with good agronomic characters under salt stress, while SH-3, SH-5, SH-7, SH-8, and SH-12 showed the highest 1000 grain weight and more grains per spike in the field. A positive correlation was found between root and shoot length and K+/Na+ value of the tolerant genotypes. The results suggested that the genes for salt tolerance have been transferred in the synthetics from wild species which can be exploited through their utilization in wheat breeding programs.

Individual and combined effects of drought and heat on antioxidant parameters and growth performance in Buffel grass (Cenchrus ciliaris L.) genotypes

Drought and heat stress are two critical threats to crop growth and sustainable agriculture worldwide. In the last decade, many studies focused on the response of crops to a single stress, nevertheless studying the response of plants to a combination stress may be critical to our understanding of stress tolerance in plants and the development of tolerant genotypes. Buffel grass (Cenchrus ciliaris L.) is a warm-season grass known in arid and semiarid regions for its tolerance to heat and drought stress, productivity, and forage quality. However, in our previous works, several accessions have exhibited different responses to abiotic stresses. Therefore, the objective of this work was to evaluate the effects of combination of drought and heat stresses on biochemical parameters and plant growth and to compare the impacts of the stresses separately and when combined. We found that sensitive genotype exhibited higher lipid peroxidation content, lower total reducing power values and reduced catalase and superoxide dismutase activities than tolerant under drought or heat stress or combination stress. In this study, heat stress had a predominant effect on buffel grass genotypes over drought stress, which explained why simultaneous application of heat and drought revealed similar biochemical and growth responses to the heat stress. Antioxidant metabolism seems to be critical for tolerate abiotic stress. This study may provide useful information to perform a rapid and low-cost characterization in new buffel grass germplasm and to identify genotypes with better growth performance under drought and heat conditions.

SCREENING DROUGHT TOLERANCE IN BREAD WHEAT GENOTYPES (Triticum aestivum L.) USING DROUGHT INDICES AND MULTIVARIATE ANALYSIS

Drought is a wide-spread problem seriously influencing wheat (Triticum aestivum L.) production , but development of tolerant genotypes is hampered by the lack of effective selection criteria. The objective of research study was to evaluate the efficiency of several selection indices to identify drought tolerant genotypes under drought stress conditions. Twenty seven bread wheat genotypes differing in yield performance were grown under drought stress, and normal irrigation during 2014-2015 growing season, were evaluated in split plot design with three replications Significant and high positive correlation was found between grain yield in the stress condition (Ys) and (Yp) with indices STI, GMP, YI, and Significant negative correlation was found between Ys with SSI, SI, SSPI, TOL indices. Principal component analysis (PCA) based on the Spearman’s correlation matrix, indicated that first PCA (80.6%) and second PCA (18.1%) accounted for 98.7% of variations among the indices. The results of PCA revealed that the screening methods were significantly inter-correlated with each other indicating that several of the statistics probably measure similar aspects of drought tolerance. Cluster analysis classified the cultivars into four groups according to drought tolerance. The results showed that MP, GMP and STI were more effective in identifying high yielding genotypes in both drought-stressed and irrigated conditions, identifying G1 and G10 as more tolerant and G25 and G26 as more sensitive genotype to drought stress.

Evaluating the expression of Hv TIP2;3 and Hv TIP4;1 in barley genotypes under different levels of salinity stress

Barley is the most salt tolerant cereal and is grown in a wide range of climatic conditions. To improve the plant tolerance to salinity‚ expression analysis of genes involved in stress tolerance could be effective in identification and development of tolerant genotypes. In this study, for evaluation of salinity effect on expression of HvTIP2;3 and HvTIP4;1 genes (encoding channel proteins in the membrane) in the root of barley, three genotypes viz., Clipper (salt susceptible), Sahara3771 (salt tolerant) and advanced breeding line (a salt tolerant line derived from a cross between Kavir and Sahara genotypes) were planted under 0, 100 and 200 mMNaCl. Analysis of variance revealed non-significant differences among genotypes, salinity levels and sampling stages for HvTIP2;3 and HvTIP4;1 genes expression pattern, whereas genotype x salinity interaction for HvTIP2;3 and genotype x sampling stage interaction were significant for both of the genes studied. The expression of HvTIP 2;3 gene in the 100 mMNaCl, was increased in salt susceptible genotype Clipper and decreased in tolerant genotypes compared with control. Mean comparison of genotype and sampling stage combination showed that the expression level of HvTIP4;1 gene 3 weeks after salinity stress was increased in Sahara and advanced breeding line and decreased in Clipper. The study revealed that these genes are affected under salinity stress‚ and their effective utilization may increase salinity tolerance in plants.

Numerical and graphical assessment of relationships between traits of the Iranian Coriandrum sativum L. core collection by considering genotype × irrigation interaction

Drought is a worldwide problem seriously influencing production of agricultural plants such as coriander, but development of tolerant genotypes is inhibited by a lack of effective selection criteria. The objective of this study was to interpret the relationship between fruit yield and related traits in coriander to evaluate genotype by trait interaction by considering genotype×irrigation interaction. According to this aim, 16 Iranian endemic coriander genotypes were grown in a glasshouse under well watered (WW) and water stressed (WS) conditions. Structural equation modeling (SEM) was used, based on genotypic correlation coefficients and genotypic variance estimates obtained from combined analysis of WW and WS conditions and genotype-trait (GT) biplot analysis. Applying both types of analyze to the multiple trait data revealed that SEM and DC+YPr data based GT biplot results are similar. The GT biplot graphically displayed the interrelationships among traits and facilitated visual comparison of genotypes for selection. Predictors in the causal diagram could explain 70.8%, 80.9%, 100% and 41.7% of the total variation in fruit weight per plant (FWPP), fruit number per plant (FNPP), day to end of flowering (DTEOF) and umbel number per plant (UNPP), respectively. Also, the GT biplots explained 81.2% for WW data, 74% for WS data and 79.7% for DC+YPr data. It was found that selection for high SPAD chlorophyll content in the grain filling stage (SCCIGFS), UNPP, FNPP and branch number per plant (BNPP), and low shoot dry weight per plant (SDWPP) and DTEOF should be considered as priorities in breeding programs for coriander aiming for more productive and drought tolerant genotypes. Furthermore, G13 (TN-59-353) can be used as a drought tolerance donor in breeding programs.

Carbon and nitrogen stoichiometry in Brassica napus L. seedlings after supplementation with Ca2+ and K+ under irrigated and drought stress conditions

Exposure of plants to long periods of water scarcity, mainly in arid and semi-arid regions, is one of the major reasons for over 50% reduction in average yields. Proper management of Brassica napus to enhance its ability to survive under drought and high temperature stress at early growth stages, besides development of tolerant genotypes, could improve its production in the rainfed areas. In the present study, we report the interactive effects of Ca 2+ , K + and N supplementation and water availability on the fresh biomass, N and C content, as well as C/N ratio of crop plants. Exposure to water stress significantly reduced the fresh biomass, Nitrogen (N), Carbon (C) content and the C/N ratio. Ca 2+ and K + supplementation before drought positively affected fresh biomass by stimulating N uptake and C assimilation. However, the C/N ratio was reduced after supplementation with Ca 2+ and K + . The N supplementation before drought imposition, though enhanced the N uptake, but the excessive damage to cell membranes and electrons leakage from Electron Transport Chain (ETC) during photosynthesis resulted in a decrease in C assimilation. Consequently, there was a decrease in the C/N ratio in seedlings exposed to drought after supplementation with N. Key words : Drought, nutrients supplementation, carbon, nitrogen, C/N ratio.

RESPONSE OF SOME EGYPTIANS SWEET MELON (Cucumis melo var. Aegyptiacus L.) CULTIVARS TO WATER STRESS CONDITIONS

Drought is a wide-spread problem seriously influencing sweet melon (Cucumis melo var. Aegyptiacus L.) production and quality. Therefore, the identification or development of tolerant genotypes is of high importance for incorporating in sweet melon production. Hence, two field experiments were conducted in a clay loam soil at Baramoon Experimental Farm, Dakahlia Governorate, Egypt during the two summer seasons of 2009 and 2010, to evaluate five sweet melon cultivars (Shahd El-Dokki, Ananas El-Dokki, Ismaelawi, Kahera-6 improved, Albasosi) under regular irrigation and stress conditions using a split plot design with three replicates. Drought conditions were started after first irrigation and created by reducing the frequency of irrigation by one half compared with regularly irrigated plants, i.e., missing alternate irrigation. Results indicated that exposing the sweet melon cultivars to water stress led to significant decreases in fruit weight, fruit length, fruit width, flesh fruit thickness, total yield per plant and Leaf relative water content in both seasons. Whereas, water deficit caused significant increases in total soluble solids in both seasons. The tested cultivars markedly varied among them in all estimated characters in both seasons. The interaction between irrigation levels and cultivars had significant effects on all traits under study. Cultivars with the highest yield and yield components under non-stress conditions had the highest yield and yield components under stress conditions, and this was true in both seasons. On the basis of the drought resistance indices (drought susceptibility index, relative yield reduction and relative yield values), Kahera-6 improved was relatively stress susceptible, whereas Albasosi was more tolerant and stable cultivar so; this cultivar could be further tested for their drought confirming characteristics.

Drought Tolerance Evaluation of Maize Hybrids using Biplot Method

Drought stress is one of the most important a-biotic stresses influencing performance of crop plants. Therefore, the identification or the development of tolerant genotypes is of high importance for incorporating in maize production. So, in order to find the best drought tolerant hybrids, thirty eight maize hybrids were planted in two separate experiments with normal irrigation and water deficit at grain filling period using a Randomized Complete Block Design (RCBD) with three replications. Drought tolerance indices such as Stress Susceptibility Index (SSI), Mean Productivity (MP), Tolerance (TOL), Geometric Mean Productivity (GMP), Harmonic Mean Productivity (HAR) and Stress Tolerance Index (STI) were used to evaluate susceptibility and tolerance of the hybrids. Hybrids No. 4, 8, 17 and 38 had higher grain yield over the mean of the two conditions. These hybrids located at part of high yield potential and low sensitivity to drought (i.e., in part with up component one and down component two) in biplot. According to YP (grain yield in normal irrigation condition) and YS (grain yield in water deficit condition), hybrid No. 8 (K74/2-2-1-3-1-1-1-1 x K3653/2) was the best hybrid and can be used in future breeding programs to develop commercial hybrid.

The Effects of Drought Stress on Improved Cotton Varieties in Golesatn Province of Iran

Drought stress is one of the most important abiotic stresses influencing performance of crop plants. Therefore, the identification or development of tolerant genotypes is of high importance for incorporating in cotton production. In this study to evaluate the effect of drought stress on some cotton traits, 5 improved cotton varieties were studied in a split plot design with three replications in 2 years (2000-2001) at 2 locations (Hashemabad and Anbaroloom); one with Mediterranean climate and the other with drought-stress condition. Treatments were irrigation as main plot in 3 levels (I0=without irrigation, I1=one time irrigation; that carried out 70 days after sowing, and I2=at least 3 times irrigation) and varieties as subplot in 5 levels (5 genotypes). In the basis of combined variance analysis significant differences were detected among varieties for yield, boll number, boll weight, length and number of sympodial and monopodial branches. Drought stress decreased yield, boll number, boll weight, and induced earliness. With increasing irrigation frequency, earliness lightly reduced in the former climate probably because of inducing vegetative growth and retarding in generative phase. In latter climate increased irrigation frequency had a positive effect on the yield. It seems that water deficiency has reduced yield via decreasing boll number. The number of formed bolls in stressful conditions was less than that of in non-stressful conditions. Stress tolerance index (STI) revealed that Siokra-324 and Tabladila were more tolerant and stable varieties.