Disease Resistance of Cotton Hybrids with Different Level of Total and Different Ratios of (+)- to (-)-Gossypol in Seeds

The presence of gossypol in glands of cotton helps protect the plant from pests. However, there is very limited information on how ratio of (+)- and (‑)‑gossypol enantiomers affected resistance to insects and pathogens. We are interested in developing cotton plants that produce seed with a low level of (‑)‑gossypol in the seed, since it may be possible to feed this seed to non-ruminant animals.  To understand how the level of total gossypol, and the (+)- to (‑)‑gossypol ratio in flower petals and seeds influence resistance to insects and pathogens we initiated greenhouse and field studies in which we compared commercial Uzbek varieties with new cotton lines derived from crosses with lines exhibiting the high (+)‑gossypol seed trait.  Thus, different cotton varieties and progenies were evaluated for resistance to insects (Helicoverpa armigera, and Tetranychus urtical) and to the major  pathogens affecting cotton production in Uzbekistan including Verticillium dahliae, Thelaviopsis bazicola and Rhizoctonia solani.  Results from our research showed that the level of (+)-gossypol in flower petals and seeds does not affect resistance to these insects and pathogens.  Thus, it should be possible to develop breeding material with good resistance to insects and diseases, but that also exhibit the high ratio of (+)- to (-)-gossypol in seeds.