Genetic analysis and phenotypic associations for drought tolerance in Hordeum spontaneum introgression lines using SSR and SNP markers

Associations between markers and drought related traits were investigated on a set of 57 advanced barley breeding lines, carrying various levels of introgression from Hordeum spontaneum lines 41-1 and 41-5, the best sources of drought tolerance in the ICARDA barley breeding program, using 74 simple sequences repeats (SSR) and 20 single nucleotide polymorphism markers. The 57 lines were evaluated for grain yield and drought related traits for three years (2003/04, 2004/05, 2005/06) in nine Mediterranean low rainfall environments. A high level of polymorphism was found with SSR markers, and the mean polymorphism information content and gene diversity values were 0.67 and 0.71, respectively. The number of alleles per locus varied from 2 to 11, with an average of 5.8 alleles per marker. Considering all the 57 lines, the linkage disequilibrium (LD) analysis was significant at a comparison-wise P?<?0.01 level in nearly 9 % of the SSR marker pairs used and a decay of LD was observed to a value of r ²?<?0.2 at a genetic distance of 40?cM. The association analysis revealed a total of 147 significant marker?Ctrait associations for grain yield and drought related traits. A total of 72 (49 %) marker?Ctrait associations showed favorable effects of the exotic germplasm where the H. spontaneum lines contributed to an improvement of the trait under drought stress conditions. The number of significant marker?Ctrait associations per trait were: 12 for growth habit; 2 for growth vigor; 11 for peduncle extrusion; 5 for number of grains per spike; 20 for peduncle length; 16 for days to heading; 20 for plant height; 8 for spike length; 17 for thousand kernel weight; 30 for grain yield; 4 for harvest index and 2 for biological yield. The phenotypic variation explained by individual marker?Ctrait associations ranged from 7.6 % to 36.2 %. The identification of genomic regions associated with grain yield and drought related traits is useful for the genetic improvement of cultivars better adapted to drought stress environments. Thus, the present study is encouraging in identifying significant marker?Ctrait associations through LD based association mapping analysis, which could complement and augment previous quantitative trait loci information for the potential use of Marker Assisted Selection for drought.     

Arbuscular mycorrhizal association of indigenous agroforestry tree species and their infective potential with maize in the rift valley, Ethiopia

Tree species in agroforestry are important source of inoculum for companion agricultural crops. Agroforestry trees can serve as a source of Arbuscular mycorrhiza (AM) inoculants to intercropped annuals. We studied spore abundance, root colonization of Albizia gummifera (J.F. Gmel.) and Croton macrostachyus (Hochst Ex Del.) trees and their effect on colonization of maize. Soil and root samples were collected from field standing trees from under and outside the canopy of trees and maize crops in the main rainy season. The number of spore count was significantly higher under the canopy of A. gummifera (791/100 g of dry soil) and C. macrostachyus (877/100 g of dry soil) trees than outside the canopy (547 and 588/100 g of dry soil, respectively). The level of root colonization of C. macrostachyus (45 %) was higher than A. gummifera (41 %). Root colonization of maize crops grown under the canopy of A. gummifera and C. macrostachyus trees was significantly higher than outside the canopy (P < 0.001). Maize seedlings grown on non-sterilized soils collected under and outside the canopy of A. gummifera and C. macrostachyus trees recorded higher root colonization, plant height, shoot and root dry weight than grown on sterilized soils (P < 0.001). The percentage of AM colonized roots of Zea mays seedlings was significantly positively correlated with the number of spore counts for field soils. The rhizospheres of indigenous agroforestry perennial species are important source of inoculum for annuals. The integration of perennials and annuals in an agroforestry system enhances the maintenance of soil quality in the tropics.     

Risk factors for bovine mastitis with the isolation and identification of Streptococcus agalactiae from farms in and around Haramaya district,eastern Ethiopia

Tropical Animal Health and Production - A cross-sectional study was carried out to determine the prevalence and risk factors of bovine mastitis caused by Streptococcus agalactiae from farms in and...     

The potential contribution of wild barley (Hordeum vulgare ssp. spontaneum) germplasm to drought tolerance of cultivated barley (H. vulgare ssp. vulgare)

Improving drought tolerance has always been an important objective in many crop improvement programs and is becoming more important as one way of adapting crops to climate changes. However, due to its complexity, the genetic mechanisms underlying the expression of drought tolerance in plants are poorly understood and this trait is difficult to characterize and quantify. This study assessed the importance of the wild progenitor of cultivated barley, Hordeum spontaneum C. Koch, in contributing developmental and yield-related traits associated with drought tolerance and therefore its usefulness in breeding for improved adaptation to drought stress conditions. Fifty-seven fixed barley lines derived from crosses with two H. spontaneum lines (41-1 and 41-5) were evaluated in Mediterranean low rainfall environments with 10 improved varieties and three landraces for grain yield, developmental and agronomic traits. The study was conducted for three years (2004–2006) in a total of nine environments (location–year combinations), eight in Syria and one in Jordan, which were eventually reduced to seven due to a large error variance in two of them. There was significant genetic variation among the genotypes for most of the traits measured, as well as differential responses of genotypes across environments. Traits such as peduncle length, peduncle extrusion and plant height were positively correlated with grain yield in the dry environments. Differences in phenology were small and not significantly correlated with differences in grain yield under stress. Performances at the three highest yielding environments were much more closely correlated than those at the four stress environments. The GGE biplot analysis allowed identification of genotypes consistently best adapted to the lowest yielding environments and confirmed the existence of unique environments for identifying better adapted genotypes in the low rainfall environments of Syria. The top yielding lines in the driest of the seven environments derived mostly from crosses with H. spontaneum 41-1, while most of the improved varieties showed a positive genotype by environment (GE) interaction with the highest yielding environments. The results of the field experiments indicated that there was variation for grain yield under drought stress among barley genotypes, and that some of the lines derived from H. spontaneum had consistently superior specific adaptation to the range of severe stress conditions used in this study. The usefulness of H. spontaneum in breeding programs for stress conditions is likely to increase in view of the predicted increase in the occurrence of high temperatures and droughts.     

On-farm tree species diversity and management in semi-arid of Lemo district,Southern Ethiopia

Agroforestry Systems - Despite the emerging and promising of on-farm trees to the biodiversity conservation, economic and ecological importance, there is still a dearth of empirical scientific...     

SSR analysis of introgression of drought tolerance from the genome of Hordeum spontaneum into cultivated barley (Hordeum vulgare ssp vulgare)

Wild barley (Hordeum vulgare ssp. spontaneum) and landraces are important sources of resistance to biotic and abiotic stresses since they possess wide genetic diversity that may be missing in current elite varieties. In this study, we evaluated a set of 57 barley introgression lines divided in groups depending on the expected levels of introgression (50, 25, and 12.5 %) from one Hordeum spontaneum accessions (Hsp 41-1) and on those (50 and 25 %) from a second (Hsp 41-5); in both cases the 25 % level was represented by two groups depending on the other parent. The two H. spontaneum accessions have been used as the best sources of drought tolerance in the ICARDA barley-breeding program. Graphical genotyping and genetic diversity analysis were used to examine the relative contribution of H. spontaneum and the extent of genetic differences among the 57 lines using 74 microsatellite markers that cover 941 cM of the barley genome. The average proportion of the genome containing H. spontaneum alleles in each group was of 44.5 %, group 1; 24.6 %, group 2; 21.6 %, group 3; 45.4 %, group 4; 19 %, group 5; 15.5 %, group 6 and 11.4 %, group 7. Introgression lines in group 1 and 4, with the highest observed introgression with Hsp 41-1 and Hsp 41-5, showed higher grain yield and better agronomic performance under field conditions in Breda and Khanaser, i.e., the two most stressed environments in which the groups were phenotyped, indicating the usefulness of using H. spontaneum as a source of chromosomal linkage blocks important for improved drought tolerance. However, more extensive genome coverage will be needed to identify the specific chromosomal regions associated with superior performance under extreme drought.     

Genotype × environment interaction and yield stability in barley (Hordeum vulgare L.) genotypes in the central highland of Ethiopia

Journal of Crop Science and Biotechnology - Barley is one of the most important cereal crops cultivated over a wider environment in the diverse agro-ecologies in Ethiopia. Study on genotype by...     

Impacts of traditional agroforestry practices,altitudinal gradients and households’ wealth status on perennial plants species composition,diversity, and structure in south-central Ethiopia

Agroforestry Systems - Conspicuous trees and other perennial plants in smallholders’ farms have been acknowledged for their biodiversity conservation values. Impacts of agroforestry...     

The Effect of the Surrounding Landscape and Socioeconomic characteristics on Woody Species Diversity in Homegardens of Shewarobit District,Northeast Ethiopia

Although homegardens are most often suggested as the refuges for biodiversity in human-dominated landscapes, how the surrounding landscape and socioeconomic characteristics affect this diversity in the tropics has received little research attention. Hence, this study has examined how these factors affect woody species diversity in homegardens of northeast Ethiopia. Three landscapes which are similar in agroecology were selected and in total 54 households were used for both a survey and a woody species inventory in respondents’ homegardens. The homegardens were stratified based on their locations in relation to crop fields and natural vegetation using satellite images from Google Earth. The variation in Shannon–Wiener diversity index among homegardens and the effect of the socioeconomic factors including household wealth status, homegarden area and the households’ types of uses of woody plants on species diversity were analyzed using one-way ANOVA. Altogether 53 woody plant species belonging to 35 botanical families were identified. Survey results indicated that the woody species diversity was higher in homegardens situated close to crop land as compared with the diversity in homegardens close to natural vegetation. Higher woody species diversity was recorded in homegardens which are larger in area and where the households’ types of uses of woody plants is higher. Moreover, the woody species diversity was found to be higher in homegardens of the high and medium income households when compared with that of poor households. Overall, results suggest that the concurrent ecological and socioeconomic studies are needed to design conservation strategy and policy for plant biodiversity in agricultural landscapes.     

Farmers’ local knowledge and topsoil properties of agroforestry practices in Sidama,Southern Ethiopia

Based on farmers’ knowledge and laboratory studies, the nutrient accumulation in the topsoil (0–20 cm) under Cordia africana Lam (Cordia), Millettia ferruginea Hochst (Millettia) and Eucalyptus camaldulensis Dehnhardt (Red gum) managed under two agroforestry practices on different farms at three sites was evaluated. The number of these trees on individual farms has increased during the last two decades. The number of stems ha⁻¹ of Red gum was higher on farms of wealthier households than on farms of poor and medium households at two of the sites, but, at one site the number of stems ha⁻¹ on farms of poor households was higher than on farms of wealthier households. Apart from the concentration of Na in the topsoil, there were significant variations in the analysed soil nutrients between the tree species. At all study sites, significantly higher concentration of P was observed under Millettia and Cordia than under Red gum. At one site, concentrations of available P under Cordia were nearly two-fold, and four and half-fold greater than under Millettia and Red gum, respectively. At one site, total N under Red gum was 14% and 24% lower than under Cordia and Millettia, respectively. In contrast, organic C content under Red gum was 11.6% greater than under Millettia and 23.8% greater than under Cordia. The pH under Millettia and Cordia were significantly higher than concentrations under Red gum at one site. Topsoil under Millettia and Cordia also had significantly higher levels of exchangeable Ca and Mg than Red gum.