Combining Ability for Nodes above White Bloom

T.P. Wallace and C.E. Watson


 
ABSTRACT

Nodes above white bloom (NAWB) is a measurement which can be used to monitor in season progression of the vegetative/fruiting relationship in cotton. As flowering approaches the mainstem terminal, a point is reached at which cut-out is imminent and further growth.in terms of branching and flowering is negligible. Defining the critical point or range in terms of NAWB at which the cut-out stage begins, and characterizing different cultivars and environmental effects on NAWB, will improve the potential application of NAWB for use as a management tool.

As a measure of approaching cut-out, NAWB can also be used as a measure of relative maturity or degree of determinacy when making comparisons among different cultivars. The potential application of this measurement for use as selection criteria in a breeding program has already been suggested. The measurement would provide a quick and easy way to compare different breeding lines during the flowering period to determine which lines will cut-out earliest in the season.

A study was undertaken to investigate the genetic components of the NAWB measurement. Six parents consisting of two early, two medium, and two late maturing cultivars were utilized in a half-diallel mating system, and the F1's were evaluated in replicated one row plots in the field for NAWB on five different dates during July and August of 1991. Means for ten plants from each plot were evaluated using Griffing's Model I Method 4 combining ability analysis. Results indicated significant differences among cultivars for NAWB. General combining ability for NAWB was significant for each date indicating a significant additive genetic component controlling the expression of this trait. Conversely, a lack of significant specific combining ability indicated the absence of significant non-additive genetic variance.

Results from the set of parents utilized in this study suggests that selection in either direction for NAWB in a breeding program would be effective and not complicated by non-additive gene action.



Reprinted from 1992 Proceedings Beltwide Cotton Conferences pg. 612
©National Cotton Council, Memphis TN

[Main TOC] | [TOC] | [TOC by Section] | [Search] | [Help]
Previous Page [Previous] [Next] Next Page
 
Document last modified Sunday, Dec 6 1998