Hybrid sunflower offtypes resulting from pollination by insects of the Texas rolling plains



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Undesirable hybrid sunflower offtypes have been observed tn testing fields (grow-outs) in Mexico as a result of insect-vectored pollen contamination of parental lines grown on the Texas High Plains. Therefore, this research was designed to investigate if insects originating from the Texas Rolling Plains, immediately adjacent to the High Plains, were contributing to the observance of these offtypes. Insects from five fields in Lubbock County were sampled using plastic bags during the parental-line growing seasons of 1991 and 1992, and the number of honey bees and native bees foraging in fields was recorded. Daytime and nighttime samples were taken during 1991 and only daytime samples were taken during 1992. In addition, native bees were collected and identified to species during both seasons. Results from 1991 show significant differences (P < 0.01) between parental lines and sampling periods regarding the number of insects of the family Dolichopodidae (chi-square analysis). Significant differences (P < 0.05) in honey bee preferences were also detected between parental lines (chi-square analysis). Regression analysis for 1992 showed a high correlation (r2 = 0.82; P < 0.05) between the abundance of insects of the family Anthocoridae and increasing distances from the edge of the Caprock Escarpment. Significant differences (ANOV A; f. < 0.05) were detected for number of native bees among fields and between parental lines, as opposed to the number of honey bees that showed significant differences (ANOV A; £. < 0.05) only between parental lines. In addition, data from grow-out fields in Mexico (parental lines grown on the Texas High Plains) were analyzed using regression analysis (second-order polynomial) to describe the correlation between distance of each field from the Caprock Escarpment and the number of hybrid sunflower offtypes for both seasons. Although no significant difference in correlation (f. > 0.05; r2 = 0.06) was detected for distance of fields froni the Caprock Escarpment and the number of offtypes in 1991, a significant correlation (P < 0.05; r2 = 0.84) was detected for 1992. I conclude that the problem of offtypes is directly related to the large number of native bee species, the presence of non-cultivated sunflowers (Helianthus annuus L.) in the Texas Rolling Plains, and the fact that parental lines are planted too near the Caprock Escarpment to avoid contamination during pollination.



Sunflowers -- Mutation breeding, Sunflowers -- Texas -- Lubbock County -- Field experiments, Sunflowers -- Mexico -- Tamaulipas, Sunflowers -- Mexico -- Jalisco, Pollination by insects -- Texas -- Lubbock County -- Experiments