2007 Annual Report 1a.Objectives (from AD-416) Develop control strategies that will minimize yield and fiber quality losses caused by nematodes and microbial pathogens that are emerging as significant impediments to sustained profitability by cotton producers. Of particular concern is the spread of the reniform nematode in the southern U.S. and south Texas, the emergence of a new disease called South Carolina seed rot in the southeast, the introduction of a particularly virulent isolate of Fusarium oxysporum f. sp. vasinfectum that was inadvertently imported from Australia on cottonseed and that could adversely affect 50% of U.S. cotton production, and the identification of race 4 of F.o.v. for the first time in the U.S. To address these emerging diseases we will:. 1)Complete the introgression of reniform nematode (Rotylenchulus reniformis) resistance from Gossypium longicalyx and G. barbadense into Upland cotton (G. hirsutum) and develop markers for the trait suitable for marker-assisted selection; 2) Describe mechanisms of pathogenesis and identify virulence genes in the bacterial pathogen(s) causing the disease known as South Carolina seed and boll rot; and develop detection methods for the pathogen(s); and. 3)Determine whether fusaric acid contributes to differences in virulence among races and biotypes of Fusarium oxysporum f. sp. vasinfectum to provide a basis for developing strategies for controlling Fusarium wilt of cotton. 1b.Approach (from AD-416) 1) Introgression of Reniform Nematode Resistance: Standard procedures for cotton flower emasculation and pollen transfer will be followed for backcross breeding. After each cross, progeny will be bioassayed for resistance to the reniform nematode, and the most highly resistant progeny will be retained for subsequent crossing, self seed generation, and DNA extraction for marker development. Plants will be grown under field conditions and evaluated for agronomic performance. Standard techniques and commercially available technology will be used for cotton DNA extraction. PCR amplification, electrophoresis, and fragment size detection will be utilized to identify molecular markers. . 2)South Carolina Seed and Boll Rot: A mutagenesis system will be used to identify genes involved in production, regulation, and/or secretion of factors that cause boll rot. Based on these results, a set of predicted gene sequences associated with pathogenicity will be used to develop a PCR based method for detecting seed and boll rotting bacteria in field samples. Bolls from greenhouse grown plants will be used in initial testing to determine the efficacy of the developed amplification system. . 3)Relation of Fusaric Acid to Virulence of Fusarium oxysporum f. sp. vasinfectum (F.o.v.): Biotypes of F.o.v. will be monitored for their ability to produce high levels of phytotoxins, and virulence of biotypes will be determined. The biosynthesis of those phytotoxins that correlate with virulence will be determined by feeding labeled substrates to the pathogens. Genes involved in the biosynthesis of these phytotoxins will be identified. Knock-out mutants will be generated to assess the role of specific phytotoxins in virulence and pathogenicity. 4.Accomplishments Reniform Nematode-Resistant Upland Cotton Germplasm Released to Breeders and Researchers: Upland cottons are the primary cotton types grown in the U.S.; these cottons are highly susceptible to damage by the reniform nematode, and development of reniform nematode-resistant Upland cottons will be a major benefit to U.S. cotton producers. Scientists in the Cotton Pathology Research Unit at the Southern Plains Agricultural Research Center, College Station, TX, in cooperation with scientists at Texas A&M University, have previously developed reniform-resistant cotton plants. Seed of these reniform-resistant plants were distributed to more than 30 industry and University breeders and scientists for their use in developing commercial cottons carrying the resistance character. This accomplishment is important because it has quickly disseminated to users important new cotton germplasm that will be used to develop new, nematode-resistant cotton varieties for U.S. farmers. Preliminary field observations indicate that reniform nematode populations in heavily infested fields have been substantially reduced where the resistant plants are being grown. (NP 303, Component 3, Problem Statement 3B) Molecular Markers to Identify Reniform Nematode Resistance in Cotton: The reniform nematode costs the U.S. cotton industry in excess of $400 million annually in lost production and crop damage; effective exploitation of newly-developed nematode-resistant cotton germplasm will largely stop these losses. Scientists in the Cotton Pathology Research Unit at the Southern Plains Agricultural Research Center, College Station, TX, in collaboration with scientists at Texas A&M University, identified molecular markers for resistance to the reniform nematode inherited from the wild cotton species, Gossypium longicalyx. These molecular markers will allow cotton breeders and other researchers to more efficiently track the resistance trait as they conduct work to develop commercial, agronomically superior, and nematode-resistant new cotton varieties. This accomplishment is important because it will greatly facilitate breeding work and will significantly speed up the development process for new cotton varieties that will allow productive and profitable utilization of lands that are at present not amenable to cotton production due to reniform nematode infestation. (NP 303, Component 3, Problem Statement 3B) Immunity of Cotton Bolls to Stink Bug-Vectored Bacterial Infections: A bacterial boll disease has recently emerged as an important obstacle to efficient cotton production in the southeastern U.S. cotton belt; cotton fields affected by this seed and boll rot disease have had significant yield losses ranging from 10 to 15 percent. Scientists in the Cotton Pathology Research Unit at the Southern Plains Agricultural Research Center, College Station, TX, established that cotton bolls three weeks after flower drop are not damaged by the southern green stink bug (SGSB), which has previously been shown by Unit scientists to "vector" the disease through the bug’s piercing/sucking feeding behavior. The work established that, although feeding behavior by SGSB facilitates development of the disease in young cotton bolls, the bolls become essentially immune to SGSB damage as they age. This accomplishment is important because it documents the timeline of cotton boll susceptibility/resistance and will facilitate efforts to manage the disease, via appropriate insect control strategies, to assure disease control effectiveness while avoiding unnecessary and expensive control measures. (NP 303, Component 2, Problem Statement 2B) 5.Significant Activities that Support Special Target Populations This project has established and maintains productive lines of research with Village Botanica, Waller, TX (a small, woman-owned business); the project also interacts productively with Our Lady of the Lake University, San Antonio, TX (a Hispanic serving institution), with some Unit support to the University being made via a Specific Cooperative Agreement. 6.Technology Transfer Number of new CRADAs and MTAs 3 Number of non-peer reviewed presentations and proceedings 7 Number of newspaper articles and other presentations for non-science audiences 1 Review Publications Golubinko, Z., Akhunov, A., Beresneva, Y., Khashimova, N., Mustakimoval, E., Ibragimov, F., Abdurashidova, N., Stipanovic, R.D. 2007. Induction of peroxidase as a disease resistance response in resistant (Hibiscus trionum) and susceptible (Althea armeniaca) species in the family Malvaceae. Phytoparasitica. 35:401-413. Howell, C.R. 2006. Effect of seed quality and fungicide/Trichoderma spp. seed treatments on pre- and post-emergence damping-off in cotton. Phytopathology. 97:66-71. Robinson, A.F. 2007. Nematode management in cotton: Biology and management strategies in major production regions. In: Ciancio, A., Mukerji, K.G., editors. Integrated Management and Biocontrol of Vegetable and Grain Crop Nematodes. Berlin: Springer Press. p. 141-174. Robinson, A.F. 2007. Reniform in U.S. cotton: When, where, why, and some remedies. Annual Review of Phytopathology. 45:263-288. Sunilkumar, G., Campbell, L.M., Puckhaber, L.S., Stipanovic, R.D., Rathore, K. 2006. Engineering cottonseed for use in human nutrition by tissue-specific reduction of toxic gossypol. Proceedings of the National Academy of Sciences. 103:18054-18059.