Project Summaries

12-186  Project Manager: D. C. Jones


Michael A. Gore, USDA-ARS

The increased performance of hybrid offspring over that of one or both parents or hybrid vigor is one of the least understood biological phenomena that have been exploited by plant breeders to increase crop yields over the last century. While continuing to be the foundation of commercial hybrid corn breeding programs, significant strides have been made towards revealing the genetic basis of hybrid vigor in corn. Combined with its largely self-pollinating nature and absence of suitable methods for efficient hybrid production, upland cotton has been virtually unexploited for its hybrid vigor relative to corn in the United States. Not unlike corn, however, higher lint yield is consistently observed for the hybrid progeny of certain upland cotton cultivars, but the genetic factors responsible for the higher yield of hybrids relative to one or both of their parents are virtually unassessed with modern molecular and statistical genetics methods. In the present study, we constructed an experimental population by using a complex mating design that enables the separation of the hybrid vigor phenomenon into individual genetic effects. Specifically, the constructed experimental population will be used to identify chromosomal regions that are responsible for hybrid vigor of yield and fiber quality traits. The findings from this study could potentially enhance existing efforts to increase lint yield and fiber quality in commercial upland cotton breeding programs.

This is a collaborative proposal entitled "Genetic Dissection of Heterotic Effects in Upland Cotton" of Dr. Todd Campbell. In this related proposal, the specific objectives are (i) to measure yield and its components and fiber quality in an experimental upland cotton population, and (ii) to identify chromosomal regions in the cotton genome that are responsible for improved lint yield and fiber quality in hybrid upland cotton.

Constructed by backcrossing distinct F2 individuals to both parental lines, the North Carolina design III is used to estimate the average degree of dominance for QTL controlling polygenic traits scored on the backcross progeny. In this study, the NCIII is based on the backcross of 240 F2 individuals to GA King and FM 966-the two parental inbred lines from which they were derived. The NCIII population of 480 F2BC1F2 lines was evaluated across three locations (Arizona, Louisiana, and South Carolina) in 2012. Within a location, the experimental design was a sets design, in which each set contained all lines of a family. Each set was randomized across environments as a 12 × 20 incomplete block α-lattice design. The α-lattice design was augmented by including the two parents and two checks within each incomplete block. The order of the 16 entries in each incomplete block was randomized. Experimental units were 2-row plots of 10.67-m at each location. In Maricopa, Arizona, inter-row spacing was 1.02-m with a 3.05-m alley at the end of each plot. We planted Set 1 (240 F2BC1F2 lines with BC parent FM966 plus 80 checks) on Wednesday, 2 May, and planted Set 2 (240 F2BC1F2 lines with BC parent Georgia King plus 80 checks) on Thursday, 3 May. Plots of a conventional cotton line were planted as border on all sides of the experiment. All plots were grown with standard cultivation and pest control methods. The average plant stand count for these plots was only 20% of the targeted three plants per foot. Given such a low seed germination rate, we only hand-harvested 25-boll samples from each of the two-row plots. The collected seedcotton samples are in the process of being ginned on a laboratory 10-saw gin to allow for the measurement of yield component and fiber quality traits. Fiber samples were sent to Cotton Incorporated for HVI analysis.


Project Year: 2012

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