|11-866 Project Manager: D. C. Jones|
GENETIC DISSECTION OF HETEROTIC EFFECTS IN UPLAND COTTON
Todd Campbell, USDA-ARS
Previous research suggests a large and consistent yield heterotic effect in Upland cotton. Since the primary methods used in cotton breeding are based on capitalizing additive gene action, attempts to capitalize on the non-additive genetic effects responsible for heterosis have not been realized in cotton. Knowledge of the genetic architecture and chromosomal location of putative genes or quantitative trait loci (QTL) responsible for heterotic effects would facilitate the exploitation of heterosis as a strategy to increase lint yields in contemporary cotton breeding programs. As such, the objective of this project was to genetically characterize yield heterotic effects in an elite Upland x elite Upland cross. In preparation for this project, a cross was made between Georgia King and FM 966 and F1 seed increased in the Cotton Winter Nursery during 2009 to produce copious amounts of F2 seed. During 2010, 300 F2 seeds were distributed to six collaborators on this project. Each collaborator planted their 50 F2 seeds and attempted to make reciprocal crosses involving each F2 plant crossed to Georgia King and FM 966 following a NC Design III mating scheme. Each collaborator also extracted DNA from each F2 plant and shipped the DNA to a central location in New Orleans, LA for DNA marker analysis. Following the 2010 field season, a total of 578 F2BC1 crosses representing 289 F2 plants (F2BC1) were consolidated and seed increased in Maricopa, AZ during 2011. In early 2012, 720 seed lots consisting of F2BC1F2 hybrids, parental lines, and repeating checks were acid de-linted. Following, we determined there were 480 F2BC1F2 seed lots of sufficient size for 2012 and 2013 field tests in SC, LA, and AZ. The 480 represent reciprocal hybrids from 240 original F2 plants.
A single replicate alpha lattice in sets design was constructed and planted at each location in May. Following planting, each location reported poor emergence resulting in less than 50% stands for most plots. After these reports, the quality of the source seed was investigated in SC. Unfortunately, it was determined that seed quality was negatively affected because of insufficient drying of seed following de-linting followed by storing seed in airtight plastic bags. High moisture content in seeds resulted in microbial growth that quickly deteriorated seed quality of all most seed units planted at each location.
As a result of this unfortunate event, the research team determined an alternate research plan moving forward. For the 2012 field trials, the team decided to hand-harvest 25-boll samples from each plot so that yield components (lint percent, boll weight, seed index, etc.) and HVI fiber quality could be measured. Because of variable stands, total plot yield was not collected. By December, each field cooperator (Campbell, Gore, Myers) reported completed 25-boll harvest. Boll samples are currently being ginned at each location and lint fiber samples will be sent to the Fiber Testing Laboratory at Cotton Incorporated. Yield components will be calculated from the 25-boll samples.
In concert with the project report of Dr. David Fang (2012 Final Report Project #12-188), DNA marker genotyping has progressed nicely and a preliminary linkage map should be constructed during the first quarter of 2013. In total, 567 SSR and SNP markers have been genotyped on the Georgia King x FM 966 F2 population. The linkage map will be used in combination with the yield component and HVI fiber quality data collected in the 2012 field trial to identify genomic regions harboring QTL for these traits.
For 2013 and beyond, the research team determined an alternate approach to meet the project objectives moving forward. As noted in previous reports during 2012, recombinant inbred lines (RIL) derived from the same Georgia King x FM 966 F2 plants cross are nearing completion. Approximately 200 RILs should be derived in early 2013. These RILs will be used in place of the original F2 population to construct a new NC Design III genetic population.
We will construct a preliminary F2 linkage map and identify QTL associated with the yield component and HVI fiber quality data collected during 2012. A RIL population derived from the same F2 population will be seed increased, genotyped, and used to develop a new NC Design III genetic population. The RIL population will be phenotyped and used in concert with the Georgia King x FM 966 intraspecific linkage map to identify genomic regions harboring QTL for yield, yield component, and fiber quality traits. This population will be registered and made available to the research community. In addition, the new NC Design III population will be phenotyped and used in concert with the Georgia King x FM 966 intraspecific linkage map to identify genomic regions harboring QTL responsible for yield heterosis.
|Project Year: 2012|
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