Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: 12/28/2015
Publication Date: N/A
Technical Abstract: Gossypol is present in cotton plants in two enantiomeric forms, (+)- and (-)-gossypol. The ratios of these enantiomers vary considerably among Gossypium species and between different plant tissues. Cotton seeds are commonly used as animal feed only for ruminants because (-)-gossypol is highly toxic to non-ruminants, while (+)-gossypol does not have the same degree of toxicity. Consequently, recent breeding efforts have focused on the development of germplasm lines with a high (+)- to (-)-gossypol ratio. Interestingly, a previous study conducted in Uzbekistan reported that boll damage by Helicoverpa armigera was negatively correlated with high levels of the (+)-gossypol enantiomer in plants. USDA recently developed a germplasm line that has a high (+)- to (-)- gossypol ratio, commonly referred to as the G + line. However, uncertainty remains on how manipulation of the (+)- to (-)- gossypol ratio affects the levels of other terpenoid aldehydes (TA), which also may be involved in plant defense against pests. In the current study, we quantified six terpenoid aldehydes (hemigossypolone, gossypol and heliocides H1-H4) and calculated the (+)- to (-)-gossypol ratio in terminal leaves, first position squares and boll carpel wall tissues of the G+ line and its genetically similar (~75%) parent line (SureGrow 747), which served as a control. Additionally, the TA content of a commercially utilized cultivar, DeltaPine 1219 B2RF, was also quantified for comparison. The (+)- to (-)- gossypol ratio in the square tissue of the G+ line was 92:8 compared with a ~3:2 ratio found in the other cultivars. The (+)-gossypol ratio in terminal leaves and boll carpel wall tissues was also higher for the G+ line when compared with the other cultivars, but these differences were not as pronounced as in the square tissue. The levels of hemigossypolone, gossypol and heliocides H1-H4 varied among tissue types and cultivars. The levels of total gossypol in the terminal leaf tissue of the G+ line were significantly higher than those of the other cultivars, but these differences were relatively small. The levels of the other TAs in leaf tissue were similar among cultivars. Regarding square tissue, most of the TA levels in the G+ line were similar to those observed in the other cultivars. Lastly, the total gossypol level in the G+ line was significantly higher than those observed in the other cultivars; however, levels of the other TAs were significantly lower in the G+ line. Given the dynamic changes in TA levels within different plant tissues and among varieties, our data suggests that the susceptibility of the G+ line to herbivory is likely dependent on the plant tissue fed upon by insect pests.