Objective 1. Develop molecular tools to rapidly identify and detect presence of cotton boll rot pathogens in plants and insects. (NP303, C1, PS1A, PS1B) Objective 2. Improve the understanding of insect vector/pathogen interactions and pathogen reservoirs to reduce the spread of cotton diseases. (NP303, C2, PS2C, PS2D) Objective 3. Identify fungal and host genes that can be targeted for disease suppression, and develop cotton germplasm resistant to FOV and nematodes. (NP303, C2, PS2A, PS2B; C3, PS3A, PS3B) Objective 4. Evaluate national and international sorghum germplasm resources, and determine the inheritance and allelic relationships of host plant resistance to anthracnose, grain mold, head smut, and downy mildew diseases. (NP303, C3, PS3A; C2, PS2A) Objective 5. Determine the population structure of diverse anthracnose (Colletotrichum sublineolum) and head smut (Sporisorium reilianum) isolates and phenotypic expression patterns of virulence on host differentials. (NP303, C2, PS2A)
Boll rots, nematodes, and fungal pathogens continue to pose the greatest threat to U.S. cotton production. To address boll rots, we previously sequenced the genome of several bacterial boll rot pathogens vectored by cotton fleahoppers, stink bugs, and verde plant bugs to identify pathogenicity genes involved in boll rot disease. In this project, we will confirm whether Lygus spp. and stink bugs vector boll rot and Fusarium wilt pathogens, respectively, and identify pathogenicity genes common to all bacterial boll rot pathogens with the long-term goal of developing a PCR-based kit that can be used in the field to rapidly detect insects harboring pathogens. The ability to rapidly detect boll rot pathogens within insects and plants, along with an improved understanding of insect vector and pathogen interactions, are both critically needed to develop sound management strategies for cotton diseases and respective insect vectors. A strain of Fusarium oxysporum f. sp. vasinfectum, known as race 4 (FOV4), was recently detected in several cotton fields in West Texas and New Mexico. This strain was initially detected and confined to cotton fields in California. Unlike other FOVs, race 4 does not require the presence of nematodes to cause severe disease of plants; however, the interaction between root knot nematodes and FOV4 pathogenicity remains unclear. Spread of FOV4 in the United States could be catastrophic because there are currently no feasible control options once this pathogen is established in a field. The development of resistant germplasms is widely deemed the most practical and long-term solution for managing this disease. To this end, we will identify and test sources of resistance to FOV4 and develop respective markers which will be incorporated into previously developed nematode-resistant germplasm to facilitate our breeding efforts to produce cotton lines that are resistant to both FOV4 and nematodes.
This is a new project that replaced 3091-22000-035-000D and which is continuing and expanding upon the work of the precursor project. In fiscal year 2022 work under Objective 1, progress was made in further characterizing genes that are responsible for causing boll rot disease in cotton. Under Objective 3, work focused on identifying genes that can be exploited for Fusarium and nematode suppression/control; preliminary data are being analyzed. In sorghum pathology research under Objective 4, significant progress was made in identifying resistant germplasm that can be exploited to control head smut and downy mildew in production environments. The work under this new project, as it progresses, will develop foundational new knowledge and technology that will help U.S. farmers produce cotton and sorghum more productively and profitably.