2010 Annual Report
1a.Objectives (from AD-416)
The objective of the Western Integrated Cropping Systems Research Unit is to develop new materials and methods for sustainable production of high quality cotton and other crops grown in the irrigated western United States. Specifically, research on integrated management of insects, identification and management of invasive plant pathogens and development of novel germplasm should enable efficient and profitable crop production with limited impact on the environment.
1b.Approach (from AD-416)
An interdisciplinary team consisting of an entomologist, geneticist, ecologist and plant pathologist will work together with Federal, State, and University collaborators to solve the major problems facing sustainable production of irrigated crops in the context of environmental stewardship. Efforts focus on discovering and developing new pest insect controls based on parasites and pathogens that impact only pest insects. Determination of overwintering locations and movement of pest insects will allow for more accurate prediction of future pest infestations and to identify release points of parasites. A process for rapid identification of race 4 Fusarium oxysporum vasinfectum (FOV), a disease new to the US will be developed and used to determine the extent of the infestation and to measure plant responses to remediation attempts. Conventional breeding techniques in combination with modern molecular techniques will lead to cotton germplasm with improved yield and fiber qualities and increased resistance to insects and diseases. “Replacing 5303-21220-002-00D (5/05)."
This is the final report for the project 5303-21220-003-00D terminated in May 2010. Substantial progress was made in cotton cultivar improvement and in understanding the dominant disease and insect pest problems of cotton in the semi-arid western US. Cotton germplasm with improved fiber, tolerance to heat stress, or resistance to the fungus causing Fusarium wilt (race 4 of Fusarium oxysporum f. sp. vasinfectum, FOV) were released. These materials increase the genetic diversity available to breeders addressing the problems of California cotton. Candidate genes controlling fiber quality and resistance to races 1 and 4 of FOV, and the root-knot nematode, were identified. Analyses provided insights into the interactions of genes from resistant and susceptible cultivars, as well as molecular markers for assisting breeding. Field assays identified a Pima cultivar with resistance to race 4 of FOV. The identified cultivar has since become the dominant Pima cultivar grown in California. A molecular assay for race 4 of FOV was developed to provide a rapid diagnostic tool to facilitate research on this devastating disease. Additional studies identified novel strains of FOV from archived specimens across the US cottonbelt. Observed virulence of the novel strains justifies an ongoing survey of FOV in the US. Documentation of natural infection of cottonseed by race 4 of FOV provided information critical to efforts by the seed industry to limit spread of FOV. Efforts to improve methods of managing race 4 of FOV identified commercially available detergents with good efficacy against FOV spores. These materials provide non-corrosive alternatives to household bleach for disinfesting field equipment. Field studies indicated that solarization was as effective as available chemical fumigants against soilborne FOV spores. This finding provides an environmentally friendly method of spot-treating severe infestations of FOV. Hot water treatment was identified as a means of disinfesting seed of race 4 of FOV, and may facilitate development of a commercial procedure to minimize the potential for spread of the disease in planted seed. Efforts to facilitate ecologically-based management of Lygus bugs through simulation of population dynamics and dispersal were unsuccessful, and emphasis switched to better understanding sampling methods and Lygus-cotton interactions. Procedures for calibrating the sweep net sampling method were developed, validated, and used to demonstrate the lack of differences in population estimates by different trained samplers. These results are key to the development of robust treatment decision rules. Video-monitored assays of Lygus feeding behavior demonstrated major differences among Lygus genders and adult age groups that will be critical to the accurate characterization of injury to cotton. Corresponding results from ongoing greenhouse and field studies are consistent with the conclusion of Lygus age- and gender-specific injury rates to cotton. These results will facilitate improved understanding of Lygus-cotton interactions and development of improved treatment decision rules.
Identification of a gene and molecular markers associated with Fusarium wilt resistance in cotton. Fusarium wilt is an important disease of cotton caused by a fungus (Fusarium oxysporum f. sp. vasinfectum) that can survive for long periods in the soil. An ARS researcher in Shafter, CA collaborated with University scientists to study inheritance of Fusarium resistance in Upland and Pima cottons. A major resistance gene for race 1 of F. oxysporum f. sp. vasinfectum was identified and analyses of molecular markers suggested genetic interactions and the mechanism of resistance. Identified markers should be useful for breeding Fusarium wilt resistance into elite cotton cultivars by marker-assisted selection.
Diminished diapause response of Lygus hesperus with laboratory rearing. Understanding of the diapause phenomenon in Lygus hesperus is important to the development of ecologically-based management tactics, but results of previous studies using laboratory-reared insects were inconsistent. ARS researchers at Shafter, CA and Maricopa, AZ examined the incidence of diapause exhibited by field-collected and laboratory-reared Lygus under controlled conditions. The diapause response of Lygus originating from established laboratory colonies was substantially reduced compared with that of Lygus originating from the field. These results identify serious artifacts of earlier studies and indicate a sound understanding of diapause in Lygus will necessitate re-examination of this phenomenon using insects more typical of field populations.
Age- and gender-based differences in feeding behavior of adult Lygus hesperus. Lygus species constitute the most important pest complex of US cotton but mechanisms of injury to cotton are poorly understood. ARS researchers at Shafter, CA used video-based assays to document differences in feeding behaviors among selected classes of Lygus adults. Young adults of both genders and recently mated older males fed more often and for longer periods than older females. Recognition of the heterogeneity of feeding behaviors among Lygus adults provides key information to reduce or eliminate previously unexplained variability in studies to quantify Lygus-induced crop losses.
Ulloa, M., Percy, R.G., Hutmacher, R.B., Zhang, J. 2009. The Future of Cotton Breeding in the Western United States. J. Cotton Sci. 13(4):246-255.
Spurgeon, D.W. 2009. Using Marked Lygus hesperus (Knight) (Hemiptera: Miridae) Adults to Evaluate Sweepnet Sampling in Cotton. Journal of Cotton Science. 13: 196-205.
Holmes, E.A., Bennett, R.S., Spurgeon, D.W., Colyer, P.D., Davis, R.M. 2009. New Genotypes of Fusarium oxysporum f. sp. vasinfectum from the Southeastern United States. Plant Disease. 93:1298-1304.
Cooper, W.R., Dillwith, J.W., Puterka, G.J. 2010. Salivary proteins of Russian wheat aphid (Hempitera: Aphididae). Environmental Entomology. 39(1):223-231.
Cooper, W.R., Rieske, L.K. 2010. Gall structure affects ecological associations of Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae). Environ. Entomol. 39(3): 787-797.
Cooper, W.R., Puterka, G.J., Glenn, D.M. 2010. Relative attractiveness of colour traps to pear psylla in relation to seasonal changes in pear phenology. The Canadian Entomologist. 142(2):188-191.
Spurgeon, D.W. and C.P.-C. Suh. 2009. Pheromone Production by the Boll Weevil (Coleoptera: Curculionidae) Fed Cotton Squares and Bolls. Journal of Entomological Science. 44:209-221.
Spurgeon, D.W. 2010. Efficacy of Beauveria bassiana against Lygus hesperus (Hemiptera: Miridae) at Low Temperatures. J.Entomol. Sci. 45: 211-219.
Roberts, P.A., Ulloa, M. 2010. Introgression of root-knot nematode resistance into tetraploid cottons. Crop Sci. 50 (3):940-951.