Economic impact of Wheat streak mosaic virus in the Texas High Plains

Wheat streak mosaic virus, vectored by the wheat curl mite Aceria tosichella Keifer, is a major limiting factor in wheat production in the Texas Panhandle. It is the most frequently encountered virus in the region, affecting both shoot and root biomass, and consequently it can drastically reduce both forage and grain yield, and water-use efficiency of the plant. In light of the continuing decline of water levels in the Ogallala Aquifer, its effect on water-use efficiency has significant implications for irrigated fields, especially with regard to energy costs for pumping water. This article estimates the potential economic losses from the virus infection. To achieve this objective, partial budgeting techniques, based primarily on data from field experiments, were used. Results indicate that Wheat streak mosaic virus causes grain and forage yield losses that significantly affect profits from wheat production. In addition, irrigated wheat producers are more negatively affected by the disease due to the economic losses from reduced water-use efficiency of infected plants. The economic insights from this article provide important implications for wheat management and research priority-setting.     

Studies on seed transmission of “Candidatus Liberibacter solanacearum” in pepper and its impact on plant emergence

“ Candidatus Liberibacter solanacearum” (Lso), transmitted by the potato psyllid (Bactericera cockerelli), is the causal agent of potato zebra chip, but can also infect other solanaceous plants, including peppers. Studies were conducted to investigate whether Lso could be transmitted to the next generation of plants through seeds from infected pepper plants. In 2014, jalapeno pepper plants were infested with psyllids carrying a mixture of Lso A and B (AB) at the AgriLife Research Station at Bushland. The study was again conducted in 2019 and pepper plants were infested with psyllids carrying Lso B or Lso AB. In each of the studies, noninfested plants served as controls. At harvest, fruits were collected and tested for the presence of Lso using quantitative PCR. Seeds from infected fruits were then tested for Lso. Overall, the percentage of seeds that tested positive for Lso ranged from 33% to 70%. However, Lso detection in embryos ranged only from 0% to 8%. Seed samples from Lso-positive fruits were planted in the greenhouse to determine the impact of Lso on emergence and the incidence of Lso in emerged plants. Although plant emergence differed between some of the seeds obtained from Lso-positive and -negative fruits, the overall impact of Lso on plant emergence was not consistent. However, of the 182 plants that emerged from seeds collected from infected fruits, none was positive for Lso, suggesting that seeds are unlikely to serve as sources for new Lso infections and their impact on disease epidemiology is negligible.     

Genetic diversity of the African wild rice (Oryza longistaminata Chev. et Roehr) from Ethiopia as revealed by SSR markers

Data from microsatellite markers have been extensively used for both in situ and ex situ conservation strategies by determining the level of genetic diversity of natural populations that can widen the gene pool of cultivated plants. Such conservation practices are based on understanding of the between and within population genetic variations and partitioning populations on the basis of geographic origin. Therefore, the objective of this study was to assess the genetic diversity of Oryza longistaminata Chev. et Roehr and how this variation is partitioned within and between the eight O. longistaminata populations found in the different geographic regions of Ethiopia using simple sequence repeat markers. Five microsatellite markers in 320 samples generated 64 alleles that revealed the presence of large amount of genetic variability (Ho = 0.225; He = 0.768; Na = 7.375; Ne = 6.565 and P = 0.744). The F-statistics detected by the microsatellite loci showed Fst = 0.064 and Fis = 0.743 and there was no population in Hardy–Weinberg equilibrium. The genetic diversity results obtained from this data indicated that there are high levels of genetic diversity in the populations of O. longistaminata studied and it is higher within than between populations. Among the eight populations sampled, five populations were identified as priorities for conservation strategies. Thus, national collection and conservation strategies need to consider these populations.     

Potential of feed-food double-cropping in central highlands of Ethiopia

The potential of feed-food double-cropping was evaluated at Ginchi, Ethiopia, for two years with the objective of evaluating herbage yields of fodder crops and the subsequent effects on grain yields of chickpea and grass pea. Early maturing oat (79Ab382 (TX) (80SA95); 79CP84 (Coker SR. res) 80SA130; SRCP X 80Ab2806; C7512/SRCP X 80Ab 2252 and CO X SRCP X 80Ab2291) and common vetch (Acc. No. 2490; Acc. No. 2742) were selected and planted on lands reserved for chickpea/grass pea at the start of the main rainy season. Following forage harvest, chickpea and grass pea were planted on all plots and control fallow plot (farmers’ practice). A randomized complete block design with three replicates was used. Vigor (potential growth), plant height, herbage yield of forage crops, and grain yields of chickpea and grass pea varied across years. Higher average herbage yield (3.36 t ha^–1) was obtained from oat–common vetch mixtures compared to a fallow system (1.11 t ha^–1). Moreover, grain yields of chickpea and grass pea grown as a double-crop following oat–common vetch were more or less similar to yields obtained under a fallow system except in the case of chickpea following T6 (oat SRCP X 80Ab2806 × Vicia sativa acc. No. 2742). From this study, it was concluded that double-cropping of early-maturing, improved forage crops and residual soil moisture-based planting of chickpea and grass pea could improve feed availability, and labor and land productivity.     

Genetic diversity of Ethiopian <Emphasis Type="Italic">Xanthosoma sagittifolium</Emphasis> (L.) Schott accessions assessed with AFLPs

Xanthosoma sagittifolium (L.) Schott originated from the American tropics. Domestication may have occurred in various places as this Araceae species is an important food source. It has been cultivated for many decades. In this study, Amplified Fragments Length Polymorphism (AFLP) markers were used to analyze the genetic relationships among 78 Ethiopian X. sagittifolium accessions, for conservation purpose. Cormels were collected from Bench-Maji, Kefa, Dawuro and Wolaita zones, representing four populations. The accessions belonged to either green (G) or purple (P) colored leaf and petiole accessions. Three different AFLP primer combinations resulted in 478 scorable bands, of which 99.2% were polymorphic. The mean Nei’s gene diversity (He) within populations was 0.35 while the G accessions featured higher He (0.38) than the P ones (0.35). The Nei’s gene diversity (He) at entire collection level was 0.38. The detected high genetic diversity may indicate the X. sagittifolium plants growing in the country may derive from diverse parental genotype stock elsewhere and/or there may be multiple introductions to the country. Low levels of genetic differentiation were detected among populations (Gst?=?0.07) and between the G and P accessions (Gst?=?0.02). Insignificant genetic and geographic correlation was revealed by Mantel test. Clustering analysis grouped 91% of the accessions together. Conservation and management of X. sagittifolium in the country should concentrate on maintaining high level genetic diversity within each population as well as at entire collection level through both ex situ and in situ conservation actions.     

Leaf and seed yield of jute mallow (Corchorus olitorius L.) accessions under field conditions for two consecutive growing seasons

Jute mallow is a nutritious leafy vegetable used by many people in Africa. The purpose of this study was to select accessions with high leaf yield and seed yield. We investigated seven agronomic traits that are related to leaf yield and seed yield and how they correlate with each other. The results indicated significant differences among the accessions in all traits. Leaf fresh weight ranged from 18.3 to 121.3 g/plant in accessions TOT 6747 and TOT 8532, respectively. The highest variability between the accessions was also observed in seed yield. It ranged from 1.0 g/plant in accession TOT 7980 to 35.5 g/plant in TOT 7866. Eight other accessions had a seed yield of 1.0 g/plant. Significant and positive correlations were observed between leaf fresh weight and leaf dry weight (r = 0.84), leaf area (r = 0.33), and number of leaves (r = 0.40). A significant correlation was observed in seed yield and weight of pods per plant (r = 0.83). The evaluation of these agronomic traits for leaf and seed yield in this germplasm has revealed useful information for breeders in their efforts to improve the yield as well as selection of accessions with good agronomic traits.     

Evaluation of accessions of vetch species for agronomic performance under nitosol and vertisol conditions in the central highlands of Ethiopia

Journal of Crop Science and Biotechnology - Vetch is an annual forage legume and accessions of its species performed differently under different soil conditions. Twenty accessions of five vetch...     

Analysis of genetic diversity in the endangered tropical tree species <Emphasis Type="Italic">Hagenia abyssinica</Emphasis> using ISSR markers

Genetic diversity within and among 12 populations of the dioecious tropical tree species Hagenia abyssinica (Bruce) J.F. Gmel. in Ethiopia was examined with eight inter simple sequence repeat (ISSR) primers. A total of 104 clearly scorable bands were generated, among which 84 (81%) were polymorphic. Jaccard similarity coefficient was calculated for pairwise comparisons among all 120 individuals and ranged from 0.30 to 0.88 while average within-population similarity ranged from 0.53 to 0.66. Within-population variability was estimated as percentage polymorphic loci (ranging from 52% to 87%), Shannon’s information index (0.30–0.50) and Nei’s genetic diversity (0.21–0.35). The highest variability values were obtained for one recently planted population and for one wild population growing in an undisturbed primary forest area. Significant overall differentiation among populations was detected by both Shannon’s information index (0.26) and G _ST (0.25). Relatedness among samples was estimated with a principal coordinate analysis, and relatedness among populations was estimated with a cluster analysis (UPGMA). A Mantel test indicated a significant association between genetic and geographic distances, and an autocorrelation analysis showed significant evidence of gene flow over distances up to 30 km. This study is the first of its kind for H. abyssinica, which has decreased recently in Ethiopia and now must be regarded as an endangered species. Both within-population and between-population diversity estimates are typical of outcrossing, longlived and late successional species, suggesting that recent anthropogenic disturbances have not yet had much impact on population genetic parameters. DNA marker data can, however, be used to identify the most suitable sites for in situ conservation and for collection of material for establishment of genebanks and plant improvement programs.