Hot pepper is the most important worldwide grown and consumed spice and vegetable crop. Though hybrid breeding has been proposed for genetic improvement in the crop, but there is lack of information on heterosis in crosses among crop genotypes in Ethiopia. Twelve genotypes (nine Asian and three Ethiopian parents) of hot pepper were crossed in 2003 cropping season in a half-diallel fashion to fit Griffing's fixed effect model analysis. An open field experiment was conducted in 2004/ 2005 to investigate heterosis for fourteen traits in 66 F 1 hybrids grown together with their 12 selfed parents. Highly significant genotypic differences were observed for all the traits except for leaf area. Variance component due to specific combining ability (dominance) were larger than that due to general combining ability (additive) for each of the studied traits with few exceptions. Broad sense heritability (H b 2 ) for fruit traits were more than 60% and with wide gap from narrow sense heritability (h n 2 ) for most of the important traits like number of fruit per plant (H b 2 = 88.3% and h n 2 = 46.0%), days to maturity (H b 2 = 87.2% and h n 2 = 23.1%) and dry fruit yield per plant (H b 2 = 72.6% and h n 2 = 14.6%). Maximum heterosis over mid-parent and betterparent, and economic superiority of hybrid over standard check were recorded, respectively for dry fruit yield per plant (163.8, 161.8 and 92.1%), number of fruits per plant (104.4, 79.6 and 136.4%) and days to maturity (-29.8, -31.5 and -23.6%).

Introduction: Onion is an important cash crop for smallholder farmers in the Central Rift Valley of Ethiopia. However, the yield of the crop is low owing to a number of constraints out of which soil nutrient depletion and inappropriate soil fertility management practices are the most important ones. Methods and Materials: A field experiment was carried out for two consecutive years of 2011 and 2012 using irrigation at Melkassa, Central Rift Valley Region of Ethiopia, to assess the response of onion to different levels of nitrogen and phosphorus fertilizers and to identify economical rates of the fertilizers for optimizing the yield and quality of the crop. The treatments consisted of five levels of nitrogen (0, 34.5, 69, 103.5 and 138 kg ha-1) and four levels of phosphorus (0, 46, 92, and 138 kg P2O5 ha-1). The experiment was carried out as a randomized complete block design in a factorial arrangement with three replications. Results: The results of the study revealed that the main effect of nitrogen significantly (P≤0.05) affected most of the growth parameters and bulb characters which all attained maximum values at 138 kg N ha-1. The main effect of P significantly (P ≤ 0.05) influenced leaf number, leaf length, and bulb diameter. Nitrogen and phosphorus interacted to influence total and marketable bulb yields. Application of N at the rate of 103.5 kg N ha-1 combined with 138 kg ha-1 P2O5 led to the production of the highest total and marketable bulb yield of onion. However, results of the economic analysis revealed that application of N at the rate of 103.5 kg ha-1 and P2O5 at 92 kg ha-1 led to the highest net return.

The productivity and marketable quality of hot pepper (Capsicum annuum var. annuum L.) are low in tropical regions mainly due to virus infections and lack of effective virus management strategies. The absence of effective virus management strategies could be attributed to lack of information on virus vectors and host resistance. Parental (P 1 and P 2 ) and progeny (F 1 , B 1 , B 2 and F 2 ) generations of five hot pepper crosses were grown in Ethiopia at three sites (Bako, Hawasa and Melkasa) to monitor number and species of potential aphid vectors, disease incidence levels with regards to natural infections by Potato virus Y (PVY) and Ethiopian pepper mottle virus (EPMV) complex, and to determine genetic tolerance of the crop to the viruses. Disease incidence was assessed before the flowering stage of the crop plants using visible disease symptoms due to infections by PVY and EPMV. The serological tests revealed presence of symptomless genotypes of the crop to the virus infections. Aphid species potentially transmitting the viruses, such as Acyrthosiphon pisum (Harris), Aphis fabae (Scopoli), and Myzus persicae (Sulzer), were identified from specimens caught by yellow water traps. The highest number of aphids from yellow water traps was recorded at a dense foliage growth stage of the crop at Melkasa. Highly significant variation was observed among generations of the five crosses in response to infections by PVY and EPMV complex. The most susceptible parents had the levels of disease incidences ranging from 80 to 90%, whereas their progenies had only below 30% incidence levels. The most tolerant parent remained symptomless to the natural infections of PVY-and EPMV-complex. Incidence levels in progenies of a cross from the most susceptible and tolerant parents remained below 20%. Based on serological test, the proportion of PVY-positive plants ranged from 0 to 75% and of EPMV-positive plants from 0 to 25%, with 0 to 17% co-infection by the two viruses. Availability of virus sources in the vicinity, efficiency of aphids in vectoring, weather conditions during the growth period, genetic tolerance and the growth stage of the crop affected natural infection by PVY-and EPMV-complex. Exploitation of the genetic potential of introduced elite genotypes and their progenies along with breeding elite local cultivars for resistance Electronic supplementary material The online version of this article (and excluding aphid vectors at young (seedling) stage of the crop plants could be helpful for minimizing losses in yield and quality of hot pepper due to infections by PVY-and EPMV-complex.

Fifteen onion genotypes (one standard check and 14 exotic cultivars) were evaluated in RCBD with 3 replications at Melkassa Research Center during the 1999/2000 growing season (Aug.-Feb.). The objective of the study was to understand the association of characters with seed yield.The genotypic correlation coefficients were greater in magnitude than the phenotypic ones. Seed yield/plant had a high, significant correlation with number of flower stalks/plant, number of seeds and flowers/umbel and umbel size. Bolting and flowering period had a significant negative correlation with seed yield/plant. From the path analysis results, the number of flower stalks/plant, bolting period, thousand seed weight, flower stalk diameter and umbel size had a high direct positive effect on seed yield/plant. Since the direct and indirect effects through these components on seed yield are high and positive, selection should concentrate on these traits for high seed yield in onion cultivars. Since these components were found to affect seed yield they could be used for developing varieties for the growing onion industry in the country.

The combining ability of four tomato genotypes (Lycopersicon esculentum Mill.) for salt tolerance was determined by investigating the progeny from a 4 × 4 diallel cross. Sixteen progenies (F 1 s, selfs and reciprocals) were evaluated at three levels of salinity (0%, 1.0%, 1.5%) in a complete block design with four replications under greenhouse conditions. The analysis of the genetic component revealed that the mode of inheritance of salt tolerance appeared to be different to that of plant characters and salinity levels as measured by plant height and fruit yield components. However, the fruit count was consistently controlled by additive gene effects. The specific crosses Moneymaker (MM) × Red Alert (RA) and Ailsa Craig (AC) × Gardener's Delight (GD) produced the highest yield. The small-fruited parents, Red Alert and Gardener's Delight, had higher general combining ability value for salt tolerance than the large-fruited, Ailsa Craig and Moneymaker, for fruit yield components. RA and GD were superior parents in transmitting salt tolerance. The study revealed that plant selection could be used to improve varietal performance for salt tolerance. It is also suggested that the potential variation in commercial cultivars could be exploited to improve adaptability to more saline growing conditions till resistant cultivars are developed through crosses with the wild species or genetic transformation with optimum management practices.