Project Summaries

10-704  Project Manager: D. C. Jones

INTEGRATION OF THE GOSSYPOL-FREE TRAIT IN ELITE GERMPLASM

Steven S. Hague, Texas AgriLife Research

Researchers in the lab of Keerti Rathore at Texas A&M University developed a transgenic upland cotton (Gossypium hirsutum) cv. 'Coker 312' line with ultra-low gossypol levels in the seed while maintaining normal gossypol levels in the rest of the plant.  This research team achieved this by transformation with a gene silencing RNAi construct using the Agrobacterium tumefaciens system. This construct contained a sequence encoding a hairpin RNA of the delta-cadinene synthase, a key enzyme involved in the gossypol synthesis pathway. The transgenic 'Coker 312' lines were stable and showed no detrimental effect due to the expression gene silencing construct. For this reason the need of a backcross breeding project was established to introgress the valuable Ultra-Low Gossypol Cottonseed (ULGCS) trait into other cotton lines.

Through backcrossing, one or a few genes of interest can be transferred from a donor parent that contains the gene or genes of interest in an otherwise undesirable genetic background into adapted or elite materials (recurrent parent) with desirable characteristics that lack the gene or genes of interest. In every cycle of backcrossing, the selected progeny containing the gene of interest is crossed to the recurrent parent so that at the end of the process the recurrent parent's genetic background is recovered. In this case, 'Coker 312' was used as the donor parent of the ULGCS trait and six upland cotton lines were chosen as recurrent parents.  A rapid and non-destructive system to identify the ULGCS trait was sought. Seed chipping, which is popular for corn and soybean was attempted with poor results. The seeds were chipped and DNA analyzed with PCR. While this method was highly accurate in identifying seeds containing the ULGCS trait, the seeds were generally damaged to the point of compromising seed germination.  Alternative methods involving flouroglucinol assays and near-infrared assays were tested on cottonseed.  While the two methods had similar results and showed a high-degree of accuracy, for breeding purposes with this trait to assure gene purity at a near 100% confidence level was needed. Neither of these procedures provided such accuracy.

Recurrent parents and transgenic backcross versions of the lines were evaluated in field trials. The yield potential of transgenic lines was similar or in some cases better than the recurrent parents. The fiber quality of the transgenic lines were almost always either similar or significantly better than that of the recurrent parent. Data suggests no ill-effects associated with ULGCS in terms of yield or fiber quality performance. From this project, we concluded the ULGCS trait could be manipulated within a breeding program with high efficiency. The ULGCS trait appeared to have no linkage drag on yield or fiber quality and transgenic lines appear to have normal responses to pests in comparison to conventional glanded upland cotton. Through the course of this project one PhD student received their degree, six abstracts/proceedings were made, and two manuscripts are under development for publication in referred journals. The seed from these populations will be stored until there is further interest in commercialization.

 

Project Year: 2012
 

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