Genetic diversity and population structure analysis of Grass pea (Lathyrus sativus L.) accessions collected from North-Western Ethiopia using SSR markers

Genetic Resources and Crop Evolution - Grass pea (Lathyrus sativus L.) is a legume crop known to be an excellent source of protein, tolerant to drought, waterlogging, and salinity. The crop is used...     

Growth performance and gum arabic production of Acacia senegal in northwest lowlands of Ethiopia

Despite the wide distribution of natural stands of Acacia senegal in Ethiopia, commercial exploitation of gum arabic is constrained by lack of tapping and development techniques. We evaluated the gum arabic yield from natural stands of A. senegal and the growth of 6 provenances in different parts of the country. For the gum yield evaluation from natural stands, four tapping positions and three tapping seasons were tested in a factorial RCB design. The second experiment in Metema evaluated survival and growth of six provenances. A. senegal trees in natural stands respond well to tapping if tapped during the appropriate season and at the correct position on the tree. The mean gum yield did not vary significantly by tapping season (p=0.63). Higher mean yield was, however, collected from trees tapped in October (96 g·tree^?1 per two harvests). The mean yield differed significantly (p=0.009) between the tapping positions. Mean separation (α=0.05) shows that trees tapped at mid stem gave higher yield (160 g·tree^?1 per two harvests). The interaction effect of tapping season and position was not significant. Higher mean yield ((70 ± 112) g·tree^?1) was recorded in mid October-mid stem in two harvests. The second experiment indicated statistically significant difference in mean survival (p=0.0298), height (p=0.000) and root collar diameter (RCD), (p=0.012) between the six provenances. Highest survival, height and root collar diameter growth was observed from Abderafi provenance (100%, (148±11) cm, (38±11) mm, respectively). We recommend October and mid-stem and branches as appropriate tapping season and position. We recommend planting of the Abderafi provenance for the study area due to its superior growth and survival. Our study contributes to the proper selection of provenances for plantation development and improved tapping technology for better production of gum arabic in the country.     

Aluminum inhibits apoplastic flow of high–molecular weight solutes in root apices of Zea mays L.

Using an aluminum (Al)‐sensitive maize cultivar, we investigated the influence of Al on the apoplastic solute bypass flow and its relationship with Al‐induced (1 h, 50 μM) callose formation and root growth. We selected the fluorescent probes 8‐hydroxypyrene‐1,3,6‐trisulfonic acid, trisodium salt (MW 524) (HPTS) and dextran‐Texas Red (TR) conjugates (MW 3,000, 10,000, and 40,000) to monitor their apoplastic transport. Confocal laser–scanning microscopy (CLSM) analysis and spectrofluorometric quantification showed Al‐induced callose formation in peripheral root cells within 1 h. Pretreatment of plants with the callose synthesis inhibitor 2‐deoxy‐D‐glucose (DDG) reduced the callose formation by half. Uptake experiments with both HPTS and dextrans showed uniform dye distribution in control root apices. After Al treatment for 1 or 2 h, which inhibited root growth by 32% or 50%, respectively, the dyes accumulated in the epidermal and outer cortical cell layers, especially in the 1–2 mm apical root zone. Al treatment reduced the export of the dyes out of the apical 1 cm treatment zone. This was due to strong sorption of HPTS but not of dextrans by Al‐loaded cell walls. Aluminum treatment reduced loading into the xylem sap particularly of higher–molecular weight dextrans. Pretreatment of roots with DDG and presence of 50 mM mannitol during the Al treatment partially forestalled the inhibitory effect of Al on the dye transport, but only slightly reduced the Al‐induced growth inhibition. Exudation experiments revealed that xylem water flow remained unaffected by the Al treatment of the root tips. The results with dextran suggest that Al binding in cell walls of the root apex inhibits apoplastic bypass flow of higher–molecular weight solutes, which might contribute to Al‐induced inhibition of root growth.     

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.     

Fungal invasion and mycotoxin contamination of stored sorghum grain as influenced by threshing methods

Sanitation from harvest to storage is a key factor in eliminating sources of infection and reducing levels of mycotoxigenic fungal invasion, and thereby mycotoxin contamination. This study was conducted at Haramaya University, Eastern Ethiopia to investigate the effects of threshing methods on fungal invasion and mycotoxin contamination of sorghum grain. The methods included threshing on bare ground, cow-dung-painted ground, concrete asphalt and canvas. The threshed grain was kept separately in bags in three replications in a completely randomized design and stored for five months. The results revealed that all the sorghum grain samples taken from different threshing methods were contaminated with both Aspergillus and Fusarium species. There were variations in fungal invasion between samples taken immediately after threshing and stored samples. The level of Aspergillus spp. invasion was much higher in the latter in sorghum grain threshed on bare ground. The concentration of aflatoxin B₁ was gradually increased, whereas the total fumonisin concentration was decreased with the storage duration both in 2013 and 2014. On stored sorghum grain, the highest (1.97 µg kg^?1) and the lowest (0.70 µg kg^?1) mean aflatoxin B₁ concentrations were recorded from sorghum grains threshed on bare ground and on canvas, respectively. Sorghum grain obtained from canvas threshing method had significantly lower mean total fumonisin content (142.5, 54.9 µg kg^?1) than grain from the other methods at threshing. The current work clearly demonstrated the effect that threshing might have on fungal invasion and mycotoxin contamination of sorghum grains. .     

NDVI-based estimates of evapotranspiration of winter wheat indicate positive effects of N fertilizer application on agronomic water-use efficiency

Yield increases by fertilizer application impose higher crop water use, as biomass production is positively correlated with transpiration. To quantify effects of N fertilizer supply on evapotranspiration (ET) of winter wheat, a field experiment with three nitrogen rates (N0, N120 and N230) under non-water-limited conditions was performed during 2014 and 2015. Normalized difference vegetation index (NDVI) was used to derive crop coefficients which were used to calculate N effects on bare soil evaporation (E), transpiration, evapotranspiration (ET), grain yield and harvest index (HI). E during the early post-winter growth period was measured with micro-lysimeters and compared with model estimates. N fertilizer supply resulted in lower cumulative E, and increases in grain yield were higher than increases in ET, resulting in a higher agronomic water-use efficiency (WUE_Y). HI of treatment N120 was higher than that of treatment N230 indicating that HI was not the main reason of higher WUE_Y of treatment N230. It is concluded that estimates of ET under variable N supply require consideration of N-induced effects on canopy development which could be successfully monitored by NDVI measurements. N supply increases ET and WUE_Y potentially imposing a trade-off between water conservation and efficiency of water use for crop production.     

The significance of organic‐anion exudation for the aluminum resistance of primary triticale derived from wheat and rye parents differing in aluminum resistance

Eight primary octoploid triticale genotypes (xTriticosecale Wittmack) derived from four wheat cultivars (Triticum aestivum L.) and two rye inbred lines (Secale cereale L.) differing in aluminum (Al) resistance were investigated with respect to their response to Al supply. Aluminum‐induced inhibition of root elongation (48 h, 25 µM Al supply), callose formation, and the accumulation of Al in root tips (4 h, 25 µM Al supply) were used as parameters to assess Al resistance. Using these parameters, the existing information on Al resistance of the wheat and rye cultivars was generally confirmed. The triticale cultivars showed a wide range of Al resistance amongst the Al‐sensitive wheat and the Al‐resistant rye cultivars. The rye parents and the Al‐resistant wheat parent Carazinho were characterized by Al‐induced exudation particularly of citrate but also of malate from whole root systems of 14 d old seedlings (8 h, 50 µM Al supply). Regression analysis revealed that the degree of Al resistance of the triticale genotypes was closely related to the Al‐induced citrate exudation, which was mainly controlled by the Al resistance of the wheat parent.     

Spatial and temporal genetic analyses of Ethiopian barley (Hordeum vulgare L.) landraces reveal the absence of a distinct population structure

Ethiopia is known for its wide topographically induced variation that favours a large amount of plant genetic diversity, and determination of the genetic structure of the germplasm is a crucial step towards exploiting this variation. Accordingly, a study was initiated to determine population structure patterns based on spatial and temporal factors and thereby establish group accessions depending on genetic similarity. To achieve this goal, 15 simple sequence repeats (SSRs) were used for 199 barley landraces collected from ten administrative regions of Ethiopia. The analysis of the spatial genetic structure was performed on the entire data set and on two groups created based on the year of collection. The results obtained from the model-based Bayesian clustering revealed 16 unstructured groups. Furthermore, the grouping of the accessions based on SSR markers resulted in hierarchical chain-type clusters with most of the accessions in the first cluster. The spatial correlations between the genetic and geographical distances revealed a weak population structure for the entire data set, and a weak temporal population structure was also observed for the barley populations from the recent collection. In general, the results indicated the absence of a distinct and consistent population structure among the regions, which could be presumed because of high gene flow. These findings will facilitate parent selection in order to broaden the genetic base of modern cultivars via breeding efforts and also provide information for the planning of an efficient germplasm collection strategy.     

Livestock Feed Marketing in Ethiopia： Challenges and Opportunities for Livestock Development

This paper presents the feed marketing systems of Ethiopia in terms of feed demand and supply, feed quality issues, feed prices and price trends based on qualitative data generated through rapid market appraisal methodology. The results indicate that, the demand for roughages, agro-industrial by-products （AIBP） and compound feeds is showing increasing trend. The use of feed from commercial sources is, however, very limited due to shortage of feed supply and inefficient marketing system. The AIBP mainly from flour and grind mills, oil processing plants and breweries are in short supply and directly marketed to user or through traders. Consequently, most of the exiting feed mixers/processing enterprises are operating under capacity estimated at about 20%-30%. The main marketed roughages, which are mainly cereal straws and baled hay, are also in short supply. Feed prices are increasing from time to time and mainly exacerbated by the increasing trend in export market of AIBP and double taxation in mixed rations. There is no any feed quality control or assurance mechanism in Ethiopia. Precaution needs to be taken in the area of taxation in order to avoid double taxation. Implications to improve the feed marketing systems and opportunities for livestock development are drawn.