Barrier analysis detected genetic discontinuity among Ethiopian barley (Hordeum vulgare L.) landraces due to landscape and human mobility on gene flow

The rate of gene flow is greatly affected by the ability of a species to move from one location to another. In Ethiopia the presence of diverse agro-ecological zones, climatic features, rugged mountains and isolated valleys affected the seed-mediated gene flow among regions. Hence, this study was aimed at investigating and detecting presence of any gene barriers and genetic differentiation among regions. Thus, the study was proposed to test whether the high genetic diversity of barley in Ethiopia was due to a reduced gene flow resulting from geographic barriers and/or effects of human activities. A total of 199 barley landraces collected from 10 different geographic regions and altitudes of Ethiopia were analyzed for 15 molecular markers. A barrier analysis was conducted to identify any geographic areas with pronounced genetic discontinuity between the regions that can be interpreted as barriers to gene flow. The result obtained from analysis of molecular variances indicated high genetic variation within regions rather than between regions. Despite high gene flow among regions, we were able to detect genetic discontinuity due to landscape and human mobility for certain barley growing areas. Hence, it was postulated that these barriers have to be considered in genetic resource sampling strategies.     

Genetic diversity and population structure of Guinea yams and their wild relatives in South and South West Ethiopia as revealed by microsatellite markers

Genetic diversity and population structure of Guinea yams and their wild relatives collected from south and south west Ethiopia were assessed using microsatellite markers. The total number of alleles amplified for the 7 loci studied was found to be 60, with an average of 8.6 alleles per locus. The average expected heterozygosity for the entire population was found to be 64 % indicating that Guinea yams and their wild relatives in the study area display a high level of genetic diversity. Using allelic richness as a measure of genetic diversity the wild forms exhibited greater allelic diversity than the cultigens. Contrary to what is expected in vegetatively propagated crops, none of the seven loci studied showed a significant excess of heterozygotes. In all the comparisons made, a low mean F_ST (but significant) has been observed, indicating that the majority of microsatellite diversity in the populations under study was found within rather than between populations.     

Diversity, composition and density of trees and shrubs in agroforestry homegardens in Southern Ethiopia

Diversity of trees and shrubs in agricultural systems contributes to provision of wood and non-wood products, and protects the environment, thereby, enhancing socioeconomic and ecological sustainability of the systems. This study characterizes the diversity, density and composition of trees in the agroforestry homegardens of Sidama Zone, Southern Ethiopia, and analyses physical and socioeconomic factors influencing diversity and composition of trees in the systems. A total of 144 homegardens were surveyed from 12 sites. In total, 120 species of trees and shrubs were recorded of which, 74.2 % were native to the area. The mean number of tree species per farm was 21. Density of trees varied between sites with mean values ranging from 86 to 1,082, and the overall average was 475 trees ha^?1. Four different crop-based enset (Enset ventricosum (Welw.) Cheesman)-coffee homegarden types were recognized and they differed not only in the composition of major crops but also in the diversity, density and composition of trees. The composition, diversity and density of trees is influenced by physical and socioeconomic factors. The major physical factors were geographical distance between sites and differences in altitude of farms. The most important socioeconomic factors were farm size and access to roads. Tree species richness and density increased with farm size. Increased road access facilitated marketing opportunities to agricultural products including trees, and lead to a decline in the basic components of the system, enset, coffee and trees. In the road-access sites, the native trees have also been largely replaced with fast growing exotic species, mainly eucalypts. The decrease in diversity of trees and perennial components of the system, and its gradual replacement with new cash and annual food crops could jeopardize the integrity and complexity of the system, which has been responsible for its sustenance.     

Supplementation with linseed (<Emphasis Type="Italic">Linum usitatissimum</Emphasis>) cake and/or wheat bran on feed utilization and carcass characteristics of Arsi-Bale sheep

Thirty yearling male intact Arsi-Bale sheep with initial body weight (BW) of 15.5 ± 0.21 kg (mean ± SD) were used in 90 days feeding trial, 10 days digestibility trial followed by evaluation of carcass parameters at Bokoji, Ethiopia. The objectives were to evaluate effects of supplementation with linseed (Linum usitatissimum) cake (LSC), wheat bran (WB), and their mixtures at 2:1 and 1:2, respectively on feed intake, digestibility, daily BW gain, and carcass parameters. The five treatments included ad libitum feeding of natural pasture hay (control) and with daily supplementation of 300 g dry matter (DM) sole LSC, 2LSC:1WB mix, 1LSC:2WB mix, and sole WB. Six sheep were randomly assigned to each treatment using randomized complete-block design. Four sheep in each treatment were randomly selected and used for determination of digestibility and carcass characteristics using a completely randomized design. The intake of hay DM was higher (P < 0.001) for the non-supplemented sheep compared with the supplemented ones, but the contrary was true for total DM intake. Sheep in the control treatment lost BW (−1.5 g/day), while the supplemented ones gained 69.0–104.1 g BW/head/day. Digestibility of CP was higher (P < 0.001) for supplemented sheep as a result of higher (P < 0.001) CP intake. Slaughter weight, empty BW, and hot carcass weight were lower (P < 0.001) for sheep in the control treatment compared with the rest. Sheep supplemented with LSC and its mixtures with WB had better (P < 0.001) performance in daily BW gain than sole WB supplemented ones indicating the advantages of using supplements as mixed rations. Moreover, supplementation proved to be profitable, whereas feeding hay alone led to economic loss.     

昆虫嗅觉相关蛋白及嗅觉识别机理研究概述

嗅觉是昆虫产生行为的基础之一,在长期进化的过程中昆虫形成了复杂的嗅觉系统,完成这一过程,需要有多种与嗅觉相关的蛋白参与,包括气味结合蛋白、化学感受蛋白、气味受体和感觉神经元膜蛋白等。了解昆虫感受外界信息的嗅觉机制可以帮助我们更好地理解昆虫识别配偶、天敌及寻找食物来源、产卵场地等行为特征,为进一步调控昆虫的行为、防控害虫侵袭、保护和利用有益昆虫奠定基础。本文综述了昆虫嗅觉相关的几类重要蛋白的生化特性和生理功能,并对昆虫气味分子的识别机制、气味分子在昆虫体内运输机制的最新研究进展进行了概述。     

Accruing genetic gain in pro-vitamin A enrichment from harnessing diverse maize germplasm

Maize has been targeted as one of the major crops for provitamin enrichment and delivery because it is an inexpensive and easily available source of food for millions of people in sub-Saharan Africa. Although tropical-adapted yellow maize contains provitamin-A carotenoids that can be converted into vitamin A in the human body, they represent less than 25% of the total carotenoids in most widely grown and consumed maize cultivars in Africa. Novel genes conditioning high concentration of β-carotene and other carotenoids were then continually introduced from the temperate zone and tropics to boost provitamin A in tropical-adapted maize. Several promising inbred lines developed from backcrosses involving diverse exotic donor lines displayed provitamin A concentrations that match or surpass the current breeding target of 15 μg g^?1. Some of these lines attained high provitamin A content by accumulating mainly high β-carotene while others contained high provitamin A by promoting accumulation of high levels of both carotenes and xanthophylls. Several inbred lines with intermediate to high levels of provitamin A have already been used to develop hybrids and synthetics without compromising grain yield and other adaptive traits that are required to profitably cultivate maize by farmers in West and Central Africa.     

Hypothalamic-pituitary-adrenal axis responsiveness to insulin-induced hypoglycaemia is modified by trypanosome infection in Boran (Bos indicus) cattle.

Ten Boran (Bos indicus) cattle were used to study the stress responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis during trypanosome infection. Five cattle were infected with Trypanosoma congolense IL 1180 by tsetse challenge and five cattle served as controls. All infected animals developed acute trypanosomiasis. Insulin-induced hypoglycaemia (50 per cent of pre-insulin glucose concentration) was used as a stress factor. Acute hypoglycaemia was observed in three infected and three control animals after insulin challenge. Two animals from each group either did not respond or responded slowly. Hypoglycaemia in infected animals completely failed to induce an HPA axis response, while in control animals an HPA axis response was indicated by a significant increase in plasma adrenocorticotrophic hormone (ACTH) and cortisol concentrations (P less than 0.01). The results show that trypanosomiasis in Boran cattle can cause a decrease in the stress responsiveness of the HPA axis as indicated by a blunted ACTH/cortisol response to insulin-induced hypoglycaemia.