Characterization of some bread wheat genotypes using molecular markers for drought tolerance

Because of its wide geographical adaptation and importance in human nutrition, wheat is one of the most important crops in the world. However, wheat yield has reduced due to drought stress posing threat to sustainability and world food security in agricultural production. The first stage of drought tolerant variety breeding occurs on the molecular and biochemical characterization and classification of wheat genotypes. The aim of the present study is characterization of widely grown bread wheat cultivars and breeding lines for drought tolerance so as to be adapted to different regions in Turkey. The genotypes were screened with molecular markers for the presence of QTLs mapped to different chromosomes. Results of the molecular studies identified and detected 15 polymorphic SSR markers which gave the clearest PCR bands among the control genotypes. At the end of the research, bread wheat genotypes which were classified for tolerance or sensitivity to drought and the genetic similarity within control varieties were determined by molecular markers. According to SSR based dendrogram, two main groups were obtained for drought tolerance. At end of the molecular screening with SSR primers, genetic similarity coefficients were obtained that ranged from 0.14 to 0.71. The ones numbered 8 and 11 were the closest genotypes to drought tolerant cultivar Gerek 79 and the furthest genotypes from this cultivar were number 16 and to drought sensitive cultivar Sultan 95. The genotypes as drought tolerance due to their SSR markers scores are expected to provide useful information for drought related molecular breeding studies.     

The characterization of wheat genotypes for salinity tolerance using morpho-physiological indices under hydroponic conditions

Salinity affects plant growth, development, yield, and is a big challenge for wheat growth across the globe. Possible feasible solution is creation of salt-tolerant material, genetic variation is a criterion to developing genetically superior individuals. To assess the genetic variation for salt tolerance, nationally and internationally-derived 81 wheat genotypes were selected and evaluated in 0- and 150-mM salt in nutritional culture at seedling stage. Results indicate that salinity levels reveal significant (p ≤ 0.01) differences for fresh root weight (RW), shoot length (SL), fresh shoot weight (SW), total plant length (TL), total fresh weight (TW), root/shoot weight ratio (RSWR), root/shoot length ratio (RSLR), and relative growth rate for weight (RGR-Wt). While, there was no difference for root length (RL). Hierarchical Clustering and Pairwise correlation analysis showed TW, RGR-Wt, SL, SW, and RW were positively correlated among themselves, whereas RL had poor correlations with all the traits except TL and RSLR. Hence, selection of SL can improve the performance of other parameters. Based on PCA analysis, SW and RGR-Wt were the major discriminative components for wheat genotypes. Present study explained that shoot related parameters could be used as a selection criterion to categorize salt-tolerant genotypes. Outperforming genotypes 1104 and 1106 in saline conditions could be used as parents in creation of salt-tolerant wheat genotypes, and parameters such as SL, SW, TW, and RGR-Wt for early screening will be important for creating salt-tolerant and high yielding wheat genotypes.     

Freezing tolerance of chickpea: biochemical and molecular changes at vegetative stage

The aim of this study was to find a correlation between the freezing tolerance of three chickpea (Cicer arietinum L.) cultivars (?nci, I??k-05, and Sar?-98) and their wild relative C. echinospermum and physiological responses. Chickpea plants (15-d-old) were subjected to cold acclimation (CA) (10 °C for 7 d), freezing (-3 or -5 °C for 2 h), and subsequent rewarming (25 °C for 7 d). In two separate experiments with three replications, we determined growth, water status, photosystem 2 photochemical activity, photosynthetic pigments, H₂O₂, malondialdehyde, and proline content, relative leakage ratio, antioxidant enzyme activities, and gene expressions in cultivars different in freezing tolerance. Freezing temperatures adversely affected all the physiological parameters of all cultivars. Rewarming did not lead to complete recovery. The cultivar ?nci was more tolerant to the freezing temperatures than others.     

Higher salinity tolerance cultivars of winter wheat relieved senescence at reproductive stage

In order to probe into the potential of relieving senescence in the new cultivars, we have compared gas exchanges and related physiological parameters of two cultivars of winter wheat (DK961, salt-tolerant; JN17, salt-sensitive) under a series of NaCl concentrations. Through out the whole reproductive period, it was noted that net photosynthetic rate, stomatal conductance, pigment contents, ions contents, leaf area index, leaf area duration, leaf relative water content and dry matter accumulation of spikes decreased in both cultivars with saline concentrations increasing. However, the salt-tolerant cultivars showed none significant reductions in those parameters compared with control under 0.3% and 0.5% salt concentrations, with only considerable decrease happening when soil salt concentration exceeded to 0.7%. Sharply contrast to salt-tolerant cultivars, the salt-sensitive cultivars appeared linear reductions in physiological parameters under a series of salt concentrations (0.3%, 0.5% and 0.7%), with the photosynthetic duration being evidently shorter. Significantly positive correlations among K⁺/Na⁺, reproductive growth period and total growth period were noted in salt-sensitive cultivars, however, none significant relations appeared among those parameters in salt-tolerant cultivars, indicating a strong tolerant behavior happened. Our result suggested that higher salinity tolerance cultivars of winter wheat could relieve senescence at the reproductive stage.     

Evaluation of Pakistan wheat germplasms for stripe rust resistance using molecular markers

Wheat production in Pakistan is seriously constrained due to rust diseases and stripe rust (yellow) caused by Puccinia striiformis f. sp. tritici, which could limit yields. Thus development and cultivation of genetically diverse and resistant varieties is the most sustainable solution to overcome these diseases. The first objective of the present study was to evaluate 100 Pakistan wheat cultivars that have been grown over the past 60 years. These cultivars were inoculated at the seedling stage with two virulent stripe rust isolates from the United States and two from Pakistan. None of the wheat cultivars were resistant to all tested stripe rust isolates, and 16% of cultivars were susceptible to the four isolates at the seedling stage. The data indicated that none of the Pakistan wheat cultivars contained either Yr5 or Yr15 genes that were considered to be effective against most P. striiformis f. sp. tritici isolates from around the world. Several Pakistan wheat cultivars may have gene Yr10, which is effective against isolate PST-127 but ineffective against PST-116. It is also possible that these cultivars may have other previously unidentified genes or gene combinations. The second objective was to evaluate the 100 Pakistan wheat cultivars for stripe rust resistance during natural epidemics in Pakistan and Washington State, USA. It was found that a higher frequency of resistance was present under field conditions compared with greenhouse conditions. Thirty genotypes (30% of germplasms) were found to have a potentially high temperature adult plant (HTAP) resistance. The third objective was to determine the genetic diversity in Pakistan wheat germplasms using molecular markers. This study was based on DNA fingerprinting using resistance gene analog polymorphism (RGAP) marker analysis. The highest polymorphism detected with RGAP primer pairs was 40%, 50% and 57% with a mean polymorphism of 36%. A total of 22 RGAP markers were obtained in this study. RGAP, simple sequence repeat (SSR) and sequence tagged site (STS) markers were used to determine the presence and absence of some important stripe rust resistance genes, such as Yr5, Yr8, Yr9, Yr15 and Yr18. Of the 60 cultivars analyzed, 17% of cultivars showed a RGAP marker band for Yr9 and 12% of cultivars exhibited the Yr18 marker band. No marker band was detected for Yr5, Yr8 and Yr15, indicating a likely absence of these genes in the tested Pakistan wheat cultivars. Cluster analysis based on molecular and stripe rust reaction data is useful in identifying considerable genetic diversity among Pakistan wheat cultivars. The resistant germplasms identified with 22 RGAP markers and from the resistance evaluations should be useful in developing new wheat cultivars with stripe rust resistance.     

Evaluating stripe rust resistance in Indian wheat genotypes and breeding lines using molecular markers

Stripe rust (yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is a serious disease of wheat worldwide, including India. Growing resistant cultivars is the most cost-effective and eco-friendly approach to manage the disease. In this study, 70 publically available molecular markers were used to identify the distribution of 35 Yr genes in 68 wheat genotypes. Out of 35 Yr genes, 25 genes amplified the loci associated with Yr genes. Of the 35, 18 were all-stage resistance ASR (All-stage resistance) genes and 7 (Yr16, Yr18, Yr29, Yr30, Yr36, Yr46 & Yr59) were APR (Adult-plant resistance) genes. In the field tests, evaluation for stripe rust was carried out under artificial inoculation of Pst. Fifty-three wheat genotypes were found resistant to yellow rust (ITs 0), accounting for 77.94% of total entries. Coefficients of infection ranged from 0 to 60 among all wheat genotypes. Two genotypes (VL 1099 & VL 3002) were identified with maximum 15 Yr genes followed by 14 genes in VL 3010 and HI8759, respectively. Maximum number of all-stage resistance genes were identified in RKD 292 (11) followed by ten genes in DBW 216, WH 1184 and VL 3002. Maximum number of adult-plant resistance gene was identified in VL 3009 (6), HI 8759 (5) and Lassik (4) respectively. Genes Yr26 (69.2%), Yr2 (69.1%), Yr64 (61.7%), Yr24 (58.9%), Yr7 (52.9%), Yr10 (50%) and Yr 48 (48.5%) showed high frequency among selected wheat genotypes, while Yr9 (2.94%), Yr36 (2.94%), Yr60 (1.47%) and Yr32 (8.8%) were least frequent in wheat genotypes. In future breeding programs, race specific genes and non-race specific genes should be utilised to pyramid with other effective genes to develop improved wheat cultivars with high-level and durable resistance to stripe rust. Proper deployment of Yr genes and utilizing the positive interactions will be helpful for resistance breeding in wheat.     

粳稻孕穗期耐冷性NILs的形态评价和分子验证

2004年在海拔1916m昆明两种冷害（水温19.5±0.7℃,低田温冷泉水温17.8±1.1℃)、阿子营冷害(海拔2150m,水温18.2±0.22℃)条件下对5个亲本及其25个近等基因系进行耐冷性鉴定,用Statistica对17个农艺性状进行形态聚类和SSR分子标记聚类分析。结果表明：(1)已培育的穗期耐冷性NILs与轮回亲本十和田的形态极为相似,但与耐冷性相关的性状(穗颈长、实粒数、结实率、花药长和花药体积)有明显的差异;(2)从78个SSR标记筛选出了7个标记在十和田和NILs间存在多态性, 其中RM7452标记与耐冷基因连锁,各个近等基因系间遗传背景相似,但与十和田耐冷性差异大,证明了这些NILs是水稻穗期耐冷基因精细定位和克隆的理想材料。     

小麦种质芽期和苗期的耐盐性鉴定评价

【目的】研究不同来源小麦种质资源的耐盐性差异,筛选耐盐性较好的品种（系）,探索不同生育期小麦耐盐性鉴定的适合盐浓度,为小麦耐盐鉴定及耐盐小麦品种选育提供参考。【方法】对来源不同的293份小麦种质,在1.5%NaCl盐溶液下进行盐胁迫处理,调查各种质的芽期相对盐害指数;选择芽期相对耐盐指数小于40%的24份小麦资源,在苗期进行不同盐浓度胁迫鉴定,测量不同处理的根长及苗高相对生长率。【结果】筛选出16份芽期相对盐害指数小于20%的高耐盐种质和42份芽期相对盐害指数20-40%耐盐的小麦种质;苗期鉴定表明1.0% NaCl盐浓度为合适的筛选浓度、根长相对生长率为适合的苗期耐盐性鉴定指标,以此为鉴定技术筛选出了Marmin-Minhardi譎44-Minturki和花树蒲两份芽期及苗期均表现耐盐的优异小麦种质;【结论】来源不同的小麦资源中芽期综合耐盐性大小依次为地方品种>国外引进品种>中间试验品系;Marmin-Minhardi譎44-Minturki和花树蒲两份耐盐小麦种质可作为小麦耐盐育种新种质。     

Identification and registration of corn genotypes using molecular markers

In plant genetics and breeding, second-generation molecular markers allow detailed characterization of plant genotypes. Unique genotypes at ten simple sequence repeat (SSR) loci were established for 40 maize accessions by means of PCR. For every locus, SSR analysis revealed heterozygotes among simple hybrids, which made it possible to identify the parental forms with a high probability of exclusion of nonparental forms. A system was proposed for registration of maize genotypes in the form of genetic formulas reflecting the allelic state of microsatellite loci, in order to catalog, preserve, and effectively employ the existing maize gene pool in breeding.     

Phytosiderophore release by wheat genotypes differing in zinc deficiency tolerance grown with Zn-free nutrient solution as affected by salinity

There is limited information concerning the effect of salinity on phytosiderophores exudation from wheat roots. The aim of this hydroponic experiment was to investigate the effect of salinity on phytosiderophore release by roots of three bread wheat genotypes differing in Zn efficiency (Triticum aestivum L. cvs. Rushan, Kavir, and Cross) under Zn deficiency conditions. Wheat seedlings were transferred to Zn-free nutrient solutions and exposed to three salinity levels (0, 60, and 120 mM NaCl). The results indicated that Cross and Rushan genotypes exuded more phytosiderophore than did the Kavir genotype. Our findings suggest that the adaptive capacity of Zn-efficient ‘Cross’ and ‘Rushan’ wheat genotypes to Zn deficiency is due partly to the higher amounts of phytosiderophore release. Only 15 days of Zn deficiency stress was sufficient to distinguish between Zn-efficient (Rushan and Cross) and Zn-inefficient (Kavir) genotypes, with the former genotypes exuding more phytosiderophore than the latter. Higher phytosiderophore exudation under Zn deficiency conditions was accompanied by greater Fe transport from root to shoot. The maximum amount of phytosiderophore was exuded at the third week in ‘Cross’ and at the fourth week in ‘Kavir’ and ‘Rushan’. For all three wheat genotypes, salinity stress resulted in higher amounts of phytosiderophore exuded by the roots. In general, for ‘Kavir’, the largest amount of phytosiderophore was exuded from the roots at the highest salinity level (120 mM NaCl), while for ‘Cross’ and ‘Rushan’, no significant difference was found in phytosiderophore exudation between the 60 and 120 mM NaCl treatments. More investigation is needed to fully understand the physiology of elevated phytosiderophore release by Zn-deficient wheat plants under salinity conditions.     

Conferring drought-tolerant wheat genotypes through morpho-physiological and chlorophyll indices at seedling stage

The decrease in water resources due to the excessive use of water for irrigation purpose and climatic changes represents a serious world-wide threat to food security. In this regards, 50 wheat accessions were analyzed, using completely random factorial design at the seedlings stage under normal and drought stress conditions. Significant variation was detected among all accessions under both conditions. All characters studied showed variations in the mean values in water deficit environments in studied gemplasm at seedling stage. As seedling fresh weight, dry weight, relative water content, cell membrane thermo-stability, chlorophyll a & b were positively associated among themselves under drought conditions which showed the significance of these attribute for water deficit areas in future wheat breeding programs. Based on their performance, five accessions namely Aas-11, Chakwal-86, Pasban-90, Chakwal-97 and Kohistan-97 were selected as drought tolerant and three accessions namely Mairaj-08, Lasani-2008 and Gomal-2008 were selected as drought susceptible genotypes. The choice of wheat accessions based on the characteristics of the seedlings is informal, low-priced and less hassle. Likewise, the seedlings attributes exhibit moderate to high variation with an additive genetics effects on the environments. Best performance accessions under water deficit environment will be beneficial in future wheat breeding schemes and early screening for the attributes suggested in current experiment will be useful for producing best-yielded and drought-tolerance wheat genotypes to sustainable food security.     

Effect of paclobutrazol on wheat salt tolerance at pollination stage

The effects of paclobutrazol (PBZ) (0, 30, 60, and 90 ppm) and NaCl (0, 75, 150, and 225 mM) treatments on a salt-tolerant (Karchia-65) cultivar of wheat (Triticum aestivum L.) at the pollination stage were studied. Salt stress decreased plant height, the length and area of the flag leaf, fresh and dry weights of the shoot, roots, and flag leaf, and water content. On the background of salinity, PBZ treatment further suppressed plant height. Although plants growth was suppressed in PBZ-treated plants, PBZ treatment moderated the negative effect of salinity on some growth parameters. Under PBZ treatments, plants tissues accumulated more watersoluble carbohydrates and reducing sugars than control plants, with the exception of water-soluble carbohydrates in the roots. The Na⁺ content in roots significantly (p ≤ 0.05) increased at 150 and 225 mM NaCl, but PBZ treatment moderated the harmful effect of the highest levels of salinity. Salinity with or without PBZ treatment improved the K⁺, P, and N contents in plants. It is reasonably to suggest that the protection and increasing salt tolerance caused by PBZ was due to the mechanism nearly similar to the salt-tolerant cultivar physiological systems. These observations suggest that PBZ treatment has the potential to increase salt tolerance with a limiting damage caused by salt stress even in salt-tolerant plants. This text was submitted by the authors in English. Published in Russian in Fiziologiya Rastenii, 2009, Vol. 56, No. 2, pp. 278–284.     

Analysis of emergence stage facilitates the evaluation of chickpea (Cicer arietinum L.) genotypes for salinity tolerance imparted by mycorrhizal colonization

Salinity is an ever-increasing constraint limiting crop production in arid and semi-arid regions. Arbuscular mycorrhiza (AM) helps host plant to cope with detrimental effects of salinity. Experiments were aimed to examine the hypothesis that emergence is a better stage to determine salt tolerance of chickpea genotypes than germination and genotypic variability in their tolerance ability at emergence and subsequent vegetative growth is the manifestation of differential benefits imparted by mycorrhiza. Investigations were carried out at germination and emergence stage of genotypes (PBG 5, GPF 2, PBG 1, BG 1053, L 550) at 0, 40, 60, 80 mM NaCl. Significant genotypic variations in salt tolerance were observed at emergence rather than germination because of greater inhibitory effects on seedling emergence. Percent mycorrhizal colonization (MC) and its resulting impact on respiration rate (RR) and salt tolerance index (STI) at emergence indicated that PBG 5, with lowest RR, highest STI and mycorrhiza benefit percentage was the most tolerant whereas, L 550 the most sensitive genotype. Genotypic variability recorded at 30 days was consistent with that at emergence stage. Superior salt tolerance of PBG 5 than L 550 could be attributed to higher correlation between MC and physio-biochemical traits (RWC, chlorophyll a/b, proline accumulation, antioxidant activities). The study supported the hypothesis that both emergence stage and mycorrhizal effectiveness are important determinants of salt tolerance in chickpea genotypes. Evaluation of genotypes for relative adaptation to salinity should include estimation of their differential salt tolerance at different growth stages and symbiotic effectiveness of AM .     

Diversity analysis of selected rice landraces from West Bengal and their linked molecular markers for salinity tolerance

Study of genetic diversity in crop plants is essential for the selection of appropriate germplasm for crop improvement. As salinity posses a serious environmental challenge to rice production globally and especially in India, it is imperative that the study of large collections of germplasms be undertaken to search for salt tolerant stocks. In the present study, 64 indica germplasms were collected from different agro-climatic zones of West Bengal, India, from the Himalayan foothills in the northern part down to the southern saline belt of the state keeping in view the soil characteristics and other edaphic factors prevailing in the region. Salt tolerance parameters were used to screen the large set of germplasms in terms of root-shoot length, fresh-dry weight, chlorophyll content, Na+/K+ ratio and germination potential in presence of salt. Standard evaluation score or SES was calculated to find out tolerant to sensitive cultivar. Twenty-one SSR markers, some associated with the Saltol QTL and others being candidate gene based SSR (cgSSR) were used to study the polymorphism of collected germplasm. A wide diversity was detected among the collected germplasms at the phenotypic as well as molecular level. Of the 21 SSR markers, 15 markers were found to be polymorphic with 88 alleles. Based on phenotypic and biochemical results, 21 genotypes were identified as salinity tolerant, whereas 40 genotypes turned out to be salt susceptible. The present study shows that apart from the established salt tolerant lines, several other landraces like Bonkanta, Morisal, Ghiosh, Patni may be the source of salt tolerant donor in future breeding programs.     

Assessment of molecular diversity at QTLs for preharvest sprouting resistance in wheat using microsatellite markers.

Breeding for preharvest sprouting (PHS) resistance is of great interest in wheat-growing areas where high rainfall occurs during grain ripening and harvest. We have characterized 32 wheat accessions using 33 microsatellite markers flanking PHS quantitative trait loci (QTLs) previously identified on group 3, 4, 5, and 6 chromosomes of hexaploid wheat. A total of 229 alleles, with an average of 6.94 alleles per marker, were observed among the 32 wheat lines. The polymorphic information content (PIC) was estimated and ranged between 0.25 and 0.90, with an average of 0.67. A cluster analysis revealed 3 main clusters and 3 singlet wheat lines, which is in agreement with pedigree-based relationships, seed coat colour, and origin. Canadian wheat accessions were subdivided into 4 sub-clusters based on pedigree and wheat classes. Grouping of preharvest sprouting germplasm into clusters was consistent with cluster-specific allele diversity observed in the PHS-resistant lines AUS1408, Red-RL4137, White-RL4137, and Kenya321. The implications of these findings in white wheat breeding for PHS tolerance are discussed.     

Evaluation of salt tolerance at the seedling stage in rice genotypes by growth performance, ion accumulation, proline and chlorophyll content

Aims

The objectives of this study were to evaluate salt tolerance level of rice genotypes using the well-established screening criteria; the salt injury score, survival percentage and ratio between Na⁺ and K⁺, as well as the contents of proline and chlorophyll, and to identify the relationship between salt tolerance and physiological characters.

Methods

One hundred and six rice genotypes were grown in hydroponic solutions subjected to salt stress and evaluated for salt tolerance ability and the physiological parameters. Multivariate cluster analysis was performed based on salinity tolerance scores (ST scores; score 1 being the most tolerant, score 9 the most sensitive), survival percentage and Na⁺/K⁺ ratio.

Results

ST scores based on salt injury symptoms were negatively correlated with survival percentage and chlorophyll concentration in the stressed seedlings but positively correlated with Na⁺/K⁺ ratio and proline content. Rice genotypes were classified into five salt tolerance groups: tolerant (T), moderately tolerant (MT), moderately sensitive (MS), sensitive (S) and highly sensitive (HS). The means of ST scores were significantly different among the five tolerance groups indicating that the ST score was the most reliable index for identifying salt tolerance. The means of Na⁺/K⁺ ratio and proline content in stressed seedlings were distinctively different between the extreme T and HS groups, but the means among the intermediate groups (MT, MS and S) were not significantly different. Chlorophyll content, on the other hand, was not related to the levels of salt tolerance.

Conclusions

In addition to the commonly used Na⁺/K⁺ ratio, proline content is suggested to be another useful criterion to differentiate salt-tolerant from salt-sensitive rice. This study also identified several Thai improved and local cultivars with the level of salt tolerance and physiological characters comparable to Pokkali, the standard salt-tolerant donor and may be utilized as alternative sources of salt tolerance alleles.     

Plasmon analysis in wheat alloplasmic lines using morphological and chloroplast microsatellite markers

Inheritance of plant traits mainly depends upon nuclear genes, cytoplasmic factors and their interactions. In the present study, 32 alloplasmic lines accompanied by a euplasmic parental line (control) were evaluated using molecular (chloroplast microsatellite) and morpho-physiological traits during 2010–2011 and 2011–2012. The results of combined analysis of variance showed the significant effect of growing seasons on most of the studied traits as well as the significant effect of cytoplasm on plant height, leaf net CO₂ assimilation rate and grain yield per plant. Results of cluster analysis divided the six plasmons based on their phenotypic effects into three groups: (1) R and S^v type, D (Aegilops typica and Ae. ventricosa) and D² type, as well as B-type plasmon (euplasmic line); (2) a single plasmon of M type and three plasmons of B type; (3) all other B-type and a single D-type plasmon (Aegilops cylindrica). Molecular analysis showed that 20 primer pairs out of 26 chloroplastic microsatellite markers (cpSSR) produced polymorphic bands in the alloplasmic lines. A total of 50 alleles were identified with an average of 2.5 alleles per locus. In this study, polymorphism information content (PIC) ranged from 0.05 (WCt17 primer) to 0.49 (WCt9 primer). Cluster analysis of molecular data revealed that the alloplasmic lines belong to two major clusters, in which differentiation of cytoplasmic types belonging to the genus Triticum and Aegilops has been evident. Likewise, analysis of molecular variance showed significant differences between two studied groups (F _ST = 0.67, P < 0.001). Overall, our findings indicated that the cpSSR markers can be valuable resources of polymorphic markers for the analysis of cytoplasm of Triticeae species, with the potential for clear differentiation in close species and genera of this tribe.