Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 3, 2000
Publication Date: June 5, 2001
Interpretive Summary: A study was undertaken to determine the genomic locations of genes affecting several traits in pepper, including fruit shape, color & size. To assess the significance of genotype versus environment in determining pepper fruit characteristics, most traits were analysed in two subsequent years. A final objective was to compare the position of genes identified in npepper with those of fruit-related genes in tomato, a closely related species with a very similar genetic map. A total of 55 genes were identified for the 15 traits examined. Of these genes 18 were identified in only a single year. For traits known to be strongly influenced by environmental conditions (e.g. ripening date), different genes were detected in the two years. For traits with higher heritability (e.g. fruit shape), the same genes were identified in both years. On four different chromosomes, genes controlling several related traits (e.g. fruit diameter, ,fruit weight, thickness of flesh, & stem diameter) were found in the same position. It is unknown whether several genes in close proximity are controlling the related traits. Comparison revealed that genes controlling identical traits in tomato & pepper were often found in the same regions of the same chromosomes. This may indicate that genes involved in fruit development in tomato & pepper are evolutionarily related & function in similar ways. The results from this study provide basic information for geneticists seeking to use molecular markers to select genotypes with desirable fruit characteristics, & also provide clues about the degree to which information obtained for one vegetable species can be applied to another.
Technical Abstract: QTL analysis of pepper fruit characters was performed in an F3 population derived from a cross between two Capsicum annuum gentoypes, the bell-type cultivar 'Maor' & the Indian small-fruited line 'Perennial'. RFLP, AFLP, RAPD & morphological markers (a total of 177) were used to construct a comparative pepper-tomato genetic map for this cross & fourteen quantitatively inheritance traits were evaluated in 180 F3 families. A total of 55 QTL were identified by interval analysis using LOD 3.0 as the theshold for QTL detection. QTL for several traits including fruit diameter & weight, pericarp thickness & pedicel diameter were often located in similar chromosomal regions reflecting high genetic correlations among these traits. A major QTL that accounts for more than 60% of the phentoypic variation for fruit shape (ratio of fruit length to fruit diameter) was detected in chromosome 3. This chromosome also contained QTL for most of the traits scored in the populations. Markers in linkage groups 2, 3, 8 & 10 were associated with QTL for multiple traits; suggesting their importance as loci that control developmental processes in pepper. Several QTL in pepper appeared to correspond to positions in tomato for loci controlling the same traits, suggesting the hypothesis that these QTL may be orthologous in the two species.