HYBRID SUNFLOWER OFFTYPES RESULTING FROM POLLINATION BY INSECTS OF THE TEXAS ROLLING PLAINS by SERGIO N. MALDONADO, B.S. A THESIS IN ENTOMOLOGY Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE August, 1993 ACKNOWLEDGEMENTS My appreciation is extended to Dr. Sherman A. Phillips, Jr., chairperson of my committee, for his assistance, confidence, and support during the completion of my studies at Texas Tech University. I thank Drs. Norman Hopper and Ellen B. Peffley for their suggestions during distinct phases of my research. I thank Chris A. Wimmer (Sunflower Field Crop Manager) and Richard Larsen (Regional Manager) of Cargill Hybrid Seeds for allowing my use of their fields. Thank you all. Also, thanks to Amadou Ba, Dr. Arturo Olivarez, Clinton Smith, Hail Shannag, He Li, Rafael Jusino-Atresino, Sergio Sanchez-Pena, and Stacy Mackenzie for their support and help on certain aspects of this work. I thank Drs. George Bohart and Terry Griswold for verification of native bee identifications. I am grateful to Mary Peek and to Shirley Jerden of the Department of Agronomy, Horticulture, and Entomology for their help in reviewing parts of this thesis and to my parents, Beatriz N. and Sergio Maldonado for all their support and encouragement during my studies at Texas Tech University. I thank my brothers Victor, Javier, Salvador, Gustavo, David, my sister Adriana, and my grandmothers Celia and Margarita, for their support. Finally, I dedicate this thesis to my wife Rosana C. Maldonado for her encouragement, help, patience and support. Gracias a todos. ii TABLE OF CON1ENTS A CK:N' 0 'WI...EIX:J-~ ............................••.............•........................................•.i i ABS1R.ACI'.............................................................................................................. i v TABLES ................................................. ·-································································ vi FlG'URES .................................................................................................................. xi CHAPIER I. IN1R.ODUCTION .................................................................................. ! II. MA 1ERIALS AND METIIODS ......................................................... 1 0 Study Site: 1991 .......................................................................... 1 0 Data Collection and Analyses: 1991. .................................. .! 2 Study Site: 1992 .......................................................................... 1 3 Data Collection and Analyses: 1992 ................................... .1 4 Offlypes from Testing Fields ................................................ 1 9 III. RESUL TS ................. -............................................................................. 2 0 Data Collection: 1991 .................................................................2 0 Data Collection: 1992 .................................................................2 7 Analyses of Data from Testing Fields ............................... .4 1 IV. DISCUSSION ·····················-··································································4 6 v. CONQUSIONS ..................................................................................... 5 0 RE'FEREN CES CllE-D ............................................................................................. 5 2 APPEND IX .............................................................................................................. 5 7 iii ABSlRACf 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 . IV 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. v TABLES 1 . Planting dates and field size for hybrid sunflower parental lines (Lubbock Co., Texas: Summer 1991 ) .................. 1 1 2. Planting dates and field size for hybrid sunflower parental lines (Lubbock Co., Texas: Summer 1992) .................. 15 3. Insects collected from five hybrid sunflower seed production fields in male-restorer lines and cytoplasmic male-sterile lines during four consecutive days (Lubbock Co., Texas: July 1991) .............................................. 2 1 4. Percent of most abundant insect families collected from sunflower male-restorer lines and cytoplasmic male-sterile lines (parentals) during daytime and nighttime sampling periods (Lubbock Co., Texas: July 1991) .....................................................................................................2 4 5. Chi-square analysis (df = 1) of four most abundant insect families collected from sunflower male­ restorer lines and cytoplasmic male-sterile lines (parentals) during daytime and nighttime sampling periods (Lubbock Co., Texas: July 1991) .................... 25 6. Percent of native bees collected during four consectutive days from five hybrid sunflower seed production fields (Lubbock Co., Texas: July 1991) ..........2 6 7. Chi-square analysis (df = 1) of honey bees and native bees foraging in five hybrid sunflower seed production fields (Lubbock Co., Texas: July 1991) ........................................... 2 9 . VI 8. Mean number of honey bees and native bees (x ± SE) for four sampling dates obtained from parental lines in five hybrid sunflower seed production fields (Lubbock Co., Texas: July 1991) ..................................................................................... 3 0 9. Insects collected every other day for four weeks in five hybrid sunflower seed production fields (Lubbock Co., Texas: July 1992) ..................................................................................... 3 1 1 0. Mean number of honey bees and native bees (x ± SE) for nine sampling dates obtained from parental lines in five hybrid sunflower seed production fields (Lubbock Co., Texas: July 1992) ..................................................................................... 3 7 11. Mean number of honey bees and native bees per 100 flowers (x + SE) for nine sampling dates from male­ restorer lines and cytoplasmic male-sterile lines in five hybrid sunflower seed production fields (Lubbock Co., Texas: July 1992) ............................................................................. 3 8 12. Mean number of honey bees (x ± SE) per 100 flowers each of cytoplasmic male-sterile and male-restorer lines within three areas of hybrid sunflower seed production fields (Lubbock, Co., Texas: July 1992) ........................................................ .3 9 13. Mean number of native bees (x + SE) per 100 flowers each of cytoplasmic male-sterile and male-restorer lines within three areas of hybrid sunflower seed production fields (Lubbock Co., Texas: July 1992) ......................4 0 14. Native bee species and number of specimens collected from five hybrid sunflower seed production fields (Lubbock Co., Texas: July 1992) ........................................................ .4 2 .. Vll 15. Analysis of variance for honey bee visitation in five hybrid sunflower seed production fields (Lubbock Co., Texas: July 1992) ..................................................................................... 58 16. Analysis of variance for honey bee visitation