Effect of cold stress on polyamine metabolism and antioxidant responses in chickpea.

Metabolic and genomic characteristics of polyamines (PAs) may be associated with the induction of cold tolerance (CT) responses in plants. Characteristics of PAs encoding genes in chickpea (Cicer arietinum L.) and their function under cold stress (CS) are currently unknown. In this study, the potential role of PAs along with the antioxidative defense systems were assessed in two chickpea genotypes (Sel96th11439, cold-tolerant and ILC533, cold-sensitive) under CS conditions. Six days after exposure to CS, the leaf H2O2 content and electrolyte leakage index increased in the sensitive genotype by 47.7 and 59 %, respectively, while these values decreased or remained unchanged, respectively, in the tolerant genotype. In tolerant genotype, the enhanced activity of superoxide dismutase (SOD) (by 50 %) was accompanied by unchanged activities of ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and catalase (CAT) as well as the accumulation of glutathione (GSH) (by 43 %) on the sixth day of CS. Higher levels of putrescine (Put) (322 %), spermidine (Spd) (45 %), spermine (Spm) (69 %) and the highest ratio of Put/(Spd + Spm) were observed in tolerant genotype compared to the sensitive one on the sixth day of CS. Gamma-aminobutyric acid (GABA) accumulation was 74 % higher in tolerant genotype compared to the sensitive one on the sixth day of CS. During CS, the activity of diamine oxidase (DAO) and polyamine oxidase (PAO) increased in tolerant (by 3.02- and 2.46-fold) and sensitive (by 2.51- and 2.8-fold) genotypes, respectively, in comparison with the respective non-stressed plants (normal conditions). The highest activity of DAO and PAO in the tolerant genotype was accompanied by PAs decomposition and a peak in GABA content on the sixth day of CS. The analysis of chickpea genome revealed the presence of five PAs biosynthetic genes, their chromosomal locations, and cis-regulatory elements. A significant increase in transcript levels of arginine decarboxylase (ADC) (24.26- and 7.96-fold), spermidine synthase 1 (SPDS1) (3.03- and 1.53-fold), SPDS2 (5.5- and 1.62-fold) and spermine synthase (SPMS) (3.92- and 1.65-fold) genes was detected in tolerant and sensitive genotypes, respectively, whereas the expression of ornithine decarboxylase (ODC) genes decreased significantly under CS conditions in both genotypes. Leaf chlorophyll and carotenoid contents exhibited declining trends in the sensitive genotype, while these photosynthetic pigments were stable in the tolerant genotype due to the superior performance of defensive processes under CS conditions. Overall, these results suggested the specific roles of putative PAs genes and PAs metabolism in development of effective CT responses in chickpea.

The influence of breeding history, origin and growth type on population structure of barley as revealed by SSR markers.

Natural and mass selection during domestication and cultivation favored particular traits of interest in barley. In the present study, population structure, and genetic relationships among 144 accessions of barley landraces and breeding materials from various countries were studied using a set of 77 and 72 EST-SSR and gSSR markers, respectively distributed on seven chromosomes of barley. In total, 262 and 429 alleles were amplified in 77 EST-SSRs and 72 gSSR loci, respectively. Out of which, 185 private/group-specific alleles were identified in the landraces compared with 14 in "cultivar and advanced breeding lines", indicating the possibility to introgress favorite alleles from landraces into breeding materials. Comparative analysis of genetic variation among breeding materials, Iranian landraces, and exotic landraces revealed higher genetic diversity in Iranian landraces compared with others. A total of 37, 15, and 14 private/group-specific alleles were identified in Iranian landraces, exotic landraces, and breeding materials, respectively. The most likely groups for 144 barley genotypes were three as inferred using model- and distance-based clustering as well as principal coordinate analysis which assigned the landraces and breeding materials into separate groups. The distribution of alleles was found to be correlated with population structure, domestication history and eco-geographical factors. The high allelic richness in the studied set of barley genotype provides insights into the available diversity and allows the construction of core groups based on maximizing allelic diversity for use in barley breeding programs.

Evaluation of drought tolerance indices for barley landraces under irrigated and dry conditions / Avaliação de índices de tolerância seca para terraços de cevada em condições irrigadas e secas

Barley cultivation for drought areas requires a reliable assessment of drought tolerance variability among the breeding germplasms. Hence, 121 barley landraces, advanced breeding lines, and varieties were evaluated under both moisture non-stress and stress field conditions using a lattice square (11×11) design with two replications for each set of the trials. Twelve drought tolerance indices (SSI, TOL, MP, GMP, STI, YI, YSI, HM, SDI, DI, RDI, and SSPI) were used based on grain yield under normal (Yp) and drought (Ys) conditions. Analysis of variance showed a significant genetic variation among genotypes for all indices except for TOL and SSPI indices. Yp had a very strong association with Ys (r = 0.92**) that indicates high yield potential under non-stress can predict better yield under stress conditions. Yp and Ys were positively and significantly correlated with MP, GMP, STI, YI, HM, and DI indices, whereas they were negatively correlated with SSI and SDI. In principal component analysis (PCA), the first PC explained 64% of total variation with Yp, Ys, MP, GMP, STI, YI, HM, and DI. The second PC explained 35.6% of the total variation and had a positive correlation with SSI, TOL, SDI, and SSPI. It can be concluded that MP, GMP, STI, YI, HM and DI indices with the most positive and significant correlation with the yield at both non-stress and stress environments would be better indices to screen barley genotypes, although none of the indices could undoubtedly identify high yield genotypes under both conditions.

O cultivo de cevada para áreas secas exige uma avaliação confiável da variabilidade da tolerância à seca entre os germoplasmas reprodutores. Assim, 121 linhagens crioulas de cevada (linhas de reprodução avançada e variedades) foram avaliadas em campo sob condições sem estresse e com estresse de umidade do solo, utilizando-se para isso um arranjo experimental de malha quadrada (11×11), com duas repetições para cada conjunto de ensaios. Foram utilizados 12 índices de tolerância à seca (SSI, TOL, MP, GMP, STI, YI, YSI, HM, SDI, DI, RDI e SSPI), com base no rendimento de grãos sob condições normais sem estresse (Yp) e com estresse de seca (Ys). A análise de variância mostrou uma variação genética significativa entre os genótipos para todos os índices, com exceção dos índices TOL e SSPI. Yp teve uma associação muito forte com Ys (r = 0,92**), o que indica que o potencial de alto rendimento sob condições sem estresse pode prever melhor rendimento sob condições de estresse. Yp e Ys foram positivamente e significativamente correlacionados com os índices MP, GMP, STI, YI, HM e DI, enquanto, foram correlacionados negativamente com os índices SSI e SDI. Na análise de componentes principais (PCA), o primeiro PC explicou 64% da variação total com Yp, Ys, MP, GMP, STI, YI, HM e DI. O segundo PC explicou 35,6% da variação total e apresentou correlação positiva com SSI, TOL, SDI e SSPI. Pode-se concluir que, os índices MP, GMP, STI, YI, HM e DI com a correlação mais positiva e significativa com a produção nos ambientes sem estresse e com estresse seriam melhores índices para a seleção de genótipos de cevada, embora nenhum dos índices pudesse concretamente identificar genótipos de alto rendimento sob ambas as condições.

Genetic Mapping of Quantitative Trait Loci for Yield-Affecting Traits in a Barley Doubled Haploid Population Derived from Clipper × Sahara 3771.

Many traits play essential roles in determining crop yield. Wide variation for morphological traits exists in Hordeum vulgare L., but the genetic basis of this morphological variation is largely unknown. To understand genetic basis controlling morphological traits affecting yield, a barley doubled haploid population (146 individuals) derived from Clipper × Sahara 3771 was used to map chromosome regions underlying days to awn appearance, plant height, fertile spike number, flag leaf length, spike length, harvest index, seed number per plant, thousands kernel weight, and grain yield. Twenty-seven QTLs for nine traits were mapped to the barley genome that described 3-69% of phenotypic variations; and some genomic regions harbor a given QTL for more than one trait. Out of 27 QTLs identified, 19 QTLs were novel. Chromosomal regions on 1H, 2H, 4H, and 6H associated with seed grain yield, and chromosome regions on 2H and 6H had major effects on grain yield (GY). One major QTL for seed number per plant was flanked by marker VRS1-KSUF15 on chromosome 2H. This QTL was also associated with GY. Some loci controlling thousands kernel weight (TKW), fertile spike number (FSN), and GY were the same. The major grain yield QTL detected on linkage PSR167 co-localized with TAM10. Two major QTLs controlling TKW and FSN were also mapped at this locus. Eight QTLs on chromosomes 1H, 2H, 3H, 4H, 5H, 6H, and 7H consistently affected spike characteristics. One major QTL (ANIONT1A-TACMD) on 4H affected both spike length (SL) and spike number explained 9 and 5% of the variation of SL and FSN, respectively. In conclusion, this study could cast some light on the genetic basis of the studied pivotal traits. Moreover, fine mapping of the identified major effect markers may facilitate the application of molecular markers in barley breeding programs.