To clarify the inheritance mode of important quantitative traits of red pepper and to establish an effective breeding program on the basis of the genetic information obtained, heterosis, combining ability and gene actions were estimated with a half-diallel set composed of 8 parents and 28 F₁ hybrids is the field. The same materials grown in the plastic pots and placed in the net house were served for genetic analysis of capsaicin content in the fruits. On the other hand, heritability and genetic advance were estimated with F₂ population originated from a cross combination, ´Taiguk´ x ´Saegochu´. The relationships among the traits in terms of correlation coefficients estimated with parent, F₁ and F₂ populations were reviewed to provide the effective selection criteria in red pepper breeding program.
The results obtained are summarized as follow.
1. Significant heterosis was recorded in most characters studied; dry fruit weight(62.5%), fresh fruit weight (54.1%), fruit powder weight(51.6%), fruit number (22.8%), and fruit length (16.4%).
2. The mean squares of general combining ability(GCA) for all studied characters were highly significant, and those of specific combining ability(SCA) were also significant except that of fruit length.
3. The significant positive GCA effects for fruit number, yield and capsaicin content were shown in ´Taiguk´ and ´Texans´. ´Munbong´ and ´Gimjanggochu´ expressed negative GCA effects for fruit number, dry fruit weight and quality. However, the other characters showed either significant positive or negative GCA effects to the direction of selection.
4. Partial dominance was observed in the characters; days to first flower, fruit length, fruit diameter, percentages of pericarp+placenta and of seed to the total dry fruit weight, percentage of fruit dry matter, capsaicin content and yield components since additive genetic variance was greater than dominant genetic variance.
5. Yield was seemingly controlled by dominant genes is the fashion of overdominance. Overdominance in yield was brought by the variety ´Taiguk´ due to excess of dominant genes, and this was suspected to be the influence of nonallelic gene interaction in fruit number which is the major component of yield.
6. Heritability estimated was very high for capsaicin content, while it was low for capsanthin content.
7. Varieties were classified into 3 types according to changes of capsaicin content in matured fruits at different harvesting dates: type Ⅰ, reaching a peak on Aug. 24, rapidly dropping until Sept. 15 and rising again; type Ⅱ, showing a peak on Aug. 24 and keeping to decrease; type Ⅲ, the same pattern as type Ⅱ with a peak on Sept. 15.
8. Inheritance mode of capsaicin content was significantly different upon the harvesting dates. Partial dominance gene action was observed in the analysis on Aug. 24 by showing lower mean capsaicin content of hybrids than that of parents. In the analysis on Sept. 15, however, overdominance was noticed possibly due to additive action of nonallelic genes. Low capsaicin content was dominant over high content. On July 17 and Oct. 15, most of varieties showed epistasis.
9. ´Texans´ appeared to be a recessive gene carrier over the other parents in the espression of capsaicin content under the favorable conditions, but it showed significant nonallelic gene interaction under the adverse conditions such as low temperature.
10. Plant height and number of lateral branches were positively correlated with days to first flower, capsaicin content, fruit number and yield in parent, F₁ and F₂ populations. Capsaicin content was positively correlated with days to first flower, fruit number and yield in parental as well as F₁ materials, while it was negatively correlated with fruit length and weight per fruit. In the F₂ population capsaicin content showed no relationships with days to first flower, fruit length, weight per fruit, percentages of pericarp+placenta and of seed to the total dry fruit weight.
|