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%).

Two separate field experiments were conducted on hot pepper in which the genetic, heritability and environmental components of variation for seven plant and fruit traits in 78 genotypes and gene effects for four fruit traits in six generations of five crosses were estimated. The objectives were to determine the variation and effects of genes controlling inheritance of plant and fruit traits, and to propose efficient breeding procedures for improving the crop. Analysis of variance in half‐diallel crosses revealed the presence of total genetic variability for seven traits among the 78 experimental entries with an excess of over‐dominance genes. The presence of unequal distributions of dominant genes with positive and negative effects was observed among the parents and indicated the need to be cautious while selecting hot pepper parents for breeding purposes. Significant variability was also revealed in environmental sensitivity among the 78 experimental entries for some traits along with high heritability, which could be an advantage for a plant breeder but provides less clear opportunities for an agronomist to achieve better plant and fruit traits. Progeny generations (F1, F2, B1 and B2) were found to perform better for fruit traits than their parents (P1 and P2). The presence of significant gene interactions indicated a polygenic inheritance of the fruit traits studied and the possibility of pyramiding favorable alleles in the required directions at different levels of progeny generations. Heterosis, backcrossing, multiple crossing and pedigree breeding methods with recurrent selection may facilitate simultaneous exploitation of the genetic components and gene effects obtained. Nevertheless, it is doubtful whether selection efforts within the current set of hot pepper parents would be beneficial to achieve superior fruit traits for developing new varieties.

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.

Lack of availability/scarcity of genetic information has limited improvement work on hot pepper (Capsicum annuum L. var. annuum) in Ethiopia. However, information regarding the types and relative importance of gene actions can be generated using combining ability analysis and utilized in the selection of suitable genotypes for hybridization and for obtaining promising hybrids. This study aimed to generate useful information with respect to combining ability and gene action from p(p + 1)/2 half-diallel crossing pattern using twelve selected hot pepper genotypes of Ethiopian and Asian origins. Twelve parental lines and their 66 F1s were tested in randomized complete block design with three replications at Melkasa Agricultural Research Center, Ethiopia, in 2004/2005 cropping season. Significant GCA and SCA effects were obtained for dry fruit yield per plant and related traits. The results showed the importance of both additive and non-additive gene actions with the predominance of the non-additive variances for dry fruit yield per plant and related traits, except for plant height and fruit length. An efficient breeding strategy for hot pepper could, therefore, be based on recurrent selection, inbred-derived hybrids or multiple crossing using genetically diverse hot pepper genotypes.