Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: August 12, 2012
Publication Date: December 1, 2012
Citation: Stetina, S.R., Molin, W.T. 2012. Gossypium accessions resistant to Rotylenchulus reniformis vary in sensitivity to the herbicide fluometuron. Journal of Nematology. 44:493. Technical Abstract: Reniform nematode (Rotylenchulus reniformis) resistance is being transferred to Upland cotton (Gossypium hirsutum) from its distant relatives. Anecdotal observations of fluometuron damage to LONREN lines with resistance from G. longicalyx raised concerns about introducing herbicide sensitivity from other resistance sources. The research objective was to evaluate fourteen sources of reniform nematode resistance for their reaction to fluometuron in a replicated greenhouse trial: G. herbaceum accessions A1-017 and A1-024; G. arboreum accessions A2-083, A2-100, A2-190, and A2-194; G. barbadense accessions Pima PHY 800, GB 713 and TX 110; G. hirsutum accessions T19, T1347, and T1348; and three G. hirsutum lines with resistance introgressed from G. barbadense (FR-05) or G. longicalyx (LONREN-1 and LONREN-2). The control was G. hirsutum cultivar Deltapine 161 B2RF. Six seeds of each line were planted on top of a mixture of sandy loam soil and sand (3:1 by volume) in 10 cm square pots. Fluometuron added to 100 cm3 additional soil mix (1:1, sandy loam:sand) at rates of 0, 0.34, 0.67, 1.01, 1.34, and 1.68 kg a.i./ha was used to cover the seeds, and care was taken during watering to avoid disturbing soil. Three weeks after planting, each plant was scored for herbicide damage on scale of 0 to 4 where 0 = no damage and 4 = maximum damage observed, and electron transport rates (photosynthesis) in the cotyledons of two plants per pot were measured. Green tissue above the cotyledons was harvested from all plants in each pot and a combined dry weight determined. ANOVA compared accessions, regression determined the nature of the response to the herbicide, and contrasts compared response trends for accessions with the control. Damage ratings were higher on the G. arboreum accessions, while G. barbadense GB 713 and TX 110 showed less damage than the control. Damage increased linearly with increasing herbicide rate for all accessions. Gossypium arboreum A2-083 showed a greater increase in damage in response to increasing herbicide rates than the control, but no other accessions differed. All lines exhibited linear reductions in biomass as herbicide rates increased, but only the G. arboreum accessions and G. herbaceum A1-017 weighed less than the control. Gossypium barbadense GB 713 and Pima PHY 800 showed a greater magnitude in biomass reduction than the control, but no other accessions responded differently. Electron transport rates of all G. herbaceum and G. arboreum accessions and G. barbadense Pima PHY 800 were lower than the control. The relationship between herbicide rate and photosynthetic activity was curvilinear, with similar decreases in photosynthetic activity in response to increasing herbicide concentration for all accessions. Increased sensitivity to fluometuron could be introduced through wide crosses, but with the exception of G. arboreum A2-083, the accessions did not respond to the herbicide differently from the commercial control.