|Campbell, Benjamin - Todd|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2007
Publication Date: 3/15/2008
Citation: Campbell, B.T., Bowman, D.T., Weaver, D.B. 2008. Heterotic effects in topcrosses of modern and obsolete cotton cultivars. Crop Science 48:593-600. Interpretive Summary: Hybrid cotton production systems present an intriguing opportunity to increase lint yield potential through hybrid vigor or heterosis. Increasing lint yield potential through heterosis is dependent on non-additive type gene action and the development of F1 or F2 hybrids. Over the last 50 years, cotton breeders have used primarily re-selection, mass selection, and pedigree breeding techniques to develop pure line cotton cultivars. These breeding techniques have likely accumulated additive gene action and not capitalized on the non-additive gene action involved in heterosis. The objective of this study was to determine if more heterosis exists in hybrids derived from obsolete varieties as opposed to hybrids derived from modern varieties. Results demonstrated obsolete hybrids produced larger heterosis for yield. This study demonstrates that increased yield, derived from non-additive gene effects, may be attained from using obsolete cultivars in parental line development for a hybrid production system.
Technical Abstract: Historically, re-selection, pedigree, and mass selection breeding methods have been used to develop open-pollinated cultivars of cotton (Gossypium hirsutum L.). As a result, modern cotton cultivars should have accumulated additive genetic effects over time, while also possessing fewer non-additive gene effects than obsolete cultivars. Breeders wishing to capitalize on the effects of hybrid vigor or heterosis should carefully consider their selection of parental lines for use in hybrid breeding efforts so that non-additive effects can be maximized. A topcross test was conducted to compare the heterotic effects of obsolete and modern cultivars for yield, yield components, and fiber quality. Significant differences were detected between heterosis values for the modern and obsolete cultivar groups for seed cotton yield, lint yield, lint percent, and boll weight. No significant heterotic effects were detected for fiber quality. The obsolete group of cultivars showed average lint yield heterosis values of 34% compared to 23% for the modern cultivars. Both cultivar groups displayed significant, but similar heterosis values for the number of bolls m-2 (17 and 15%, respectively). The major yield component associated with lint yield heterosis for both groups was bolls m-2, although boll weight heterosis also contributed to lint yield heterosis for the obsolete cultivars. Although modern cultivars produced considerable heterotic effects for yield, this study demonstrates that obsolete cultivars may provide an additional source of non-additive genetic effects that can be exploited in a hybrid production system.