Project Summaries

09-576NC  Project Manager: D. C. Jones

BREEDING COTTON VARIETIES FOR NORTH CAROLINA

Vasu Kuraparthy, North Carolina State University

Cotton (Gossypium hirsutum L.) acreage in North Carolina has fluctuated in recent years from nearly 1,000,000 acres in 2002 with an annual crop value of nearly 400 million dollars to 550,000 acres in 2012. While improving cotton lint yield continues to be the primary focus of the cotton breeding programs, increasing emphasis is now placed on improving the fiber quality to make the US cotton competitive in international markets. Specific problems encountered by growers include boll rot, weak seedling vigor - a frequent problem resulting in occasional poor stand and replanting, Columbia lance, reniform, root knot and sting nematode damage, and susceptibility to insects such as thrips.  Earliness is also an important sought after trait by growers who typically want to follow winter crops after cotton. Improving the genetic architecture is the best method to enhance the cotton productivity at minimal cost to both growers and the ecosystem. Genetic variation for flowering time and maturity can be used to develop earliness in cotton cultivars.

Our objectives in 2012 were to 1) continue to screen and develop cotton germplasm for earliness, 2) develop superior germplasm with improved yield and fiber quality through conventional breeding,  3) evaluate inbreds of random mating population for improved yield and fiber quality, and 4) evaluate lines developed by the program in the recent past.

By using the previous breeder's advanced breeding lines and Regional Breeders Testing Network (RBTN) entries as germplasm base, new and adapted lines with improved fiber yield and quality will be developed.  Biparental and three-way crosses were made using introductions from several RBTN entries and early flowering TAMCOT introductions. Segregating populations derived from these cross combinations were grown at Clayton, NC for early generation selections and further backcrosses. By evaluating random mating population (RMP) in summer 2011 we identified a few lines that have better fiber quality parameters. These selections were crossed with introductions and our in-house germplasms to introgress fiber quality into elite backgrounds. A total of twenty inbreds from RM populations with better fiber quality are crossed with germplasm introductions PD05069, LA06307025, MD25-26ne AU3111, ARK0309-31 and Acala 1517-08. These F1s will be intercrossed to develop four-way cross seed.  Progenies of all the above crosses will be evaluated for earliness and fiber quality during initial generations, and yield and fiber quality traits during advanced generations.

About 750 lines of the random mating (RM) population are advanced through single seed descent method to obtain F5 lines. However, enough seed was obtained through manual selfing for only about 450 lines for field-testing. Four hundred and fifty unreplicated entries were tested at three NC locations (Rocky Mount, Lewiston, and Plymouth) for lint yield and fiber quality in the summer of 2012. In each location these F5:6 inbred lines were tested with 3 checks (one main check and two sub checks) using modified augmented type-2 design. Each entry was planted in a two-row plot at approximately 3.25 seed/ft. Plot lengths were 35 ft long with 12 ft alleys and interrow spacing varied from 36 inches to 38 inches. All the test plots at all three locations were harvested using a two-row cotton picker. Seed cotton samples were collected for fiber quality and yield component analysis.  Once the ginning and sample weights are completed the fiber samples will be sent to Cotton Incorporated for fiber quality analysis. Changes in correlations between traits among parents and inbred populations of different cycles of random mating will be analyzed to identify inbreds with superior yield and fiber quality.

Main emphasis of this part of the research is to develop improved germplasm by combining parents with specific morphological traits. These include sub okra, nectariless, laciniate, okra, and smooth leaf lines (NC05AZ06, NC05AZ20, NC05AZ23, NC06AZ16, NC06AZ20, GUMBO 500, FM832, DP451, JAJO 8067, NC05ST31) that were grown at the Central Crops Research Station, Clayton.  Several of the above lines have a combination of these traits.  A few have been tested for a couple of years.  Among these germplasm lines NC05-11 and NC05AZ21 with normal leaf and okra leaf shapes, respectively, were found to have improved yield and fiber quality and Fusarium wilt resistance and are in the process of releasing as new germplasm. A manuscript on germplasm registration submitted to the Journal of Plant Registrations is nearly complete.  This will describe NC05AZ21 and NC05-11 which were developed in the Department of Crop Science at North Carolina State University to supply improved germplasm to the cotton breeding community.

 

Project Year: 2012
 

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