Location: Genetic Improvement for Fruits & Vegetables Laboratory
2018 Annual Report
Objectives
Objective 1: Develop potato germplasm with improved levels of resistance to
biotic stressors, particularly late blight, common scab, and soft rot. [NP301, C1, PS1A, 1B; C2, PS2A].
Objective 2: Develop potato germplasm with improved levels of resistance to abiotic stressors, particularly for heat tolerance and reduced nitrogen input. [NP301, C1, PS 1A, 1B].
Objective 3: Use existing knowledge of the gene conservation between tomato and pepper to identify and develop markers for tomato anthracnose resistance in pepper, develop and implement effective marker assisted selection within Capsicum, and release new anthracnose resistant pepper germplasm. [NP301, C1, PS1A and PS1B]
Objective 4: Characterize the inheritance of resistance to tomato chlorotic spot virus in Capsicum, and develop and release adapted breeding lines suitable for breeding resistant hybrids. [NP301, C1, PS1A and PS1B]
Objective 5: Develop and release pepper breeding lines and cultivars with improved quality attributes for the culinary, culinary/ornamental, and minimally processed fresh-cut market. [NP301, C1, PS1B]
Objective 6: Discover pathogen gene function through use of functional genomics techniques. [NP303, C2, PS2A]
Objective 7: Characterize underlying mechanisms of resistance in solanaceous hosts in response to pathogen infection. [NP303, C2, PS2B]
Objective 8: Develop novel strategies for genetic improvement to manage disease in solanaceous crops. [NP303, C3, PS3A]
Approach
Late blight resistance genes in diploid and tetraploid potato will be identified via single nucleotide polymorphisms and incorporated into tetraploid germplasm. Tetraploid germplasm resistant to common scab will be identified via field testing and introgressed into commercial quality germplasm. A tissue culture assay using thaxtomin will be developed to identify scab resistance early in the breeding program at the seedling stage. Diploid germplasm with resistance to soft rot and blackleg will be identified via inoculations with the main bacterial species causing the disease. Resistance will be introgressed into advanced lines for varietal release. Diploids from cultivated and wild potato species will be evaluated for heat tolerance via tissue culture and validated in field tests. Wild species segregating for nitrogen uptake efficiency have been crossed into cultivated diploids. Progeny will be evaluated for nitrogen uptake efficiency and tuberization. Genotype by sequencing will be used to map anthracnose resistance loci in tomato using a recombinant inbred line population that we developed. Genetic stocks with resistance loci will be released. Tomato markers will be used to identify resistance homologues in pepper. Additional loci may be identified via linkage disequilibrium mapping of Capsicum baccatum accessions that we previously characterized. Loci will be transferred to C. annuum using bridge lines. Tomato chlorotic spot virus resistant lines identified in initial screening of C. chinense will be field tested, inheritance characterized, and resistance introgressed into C. annuum. Selection for high-value specialty peppers has combined desirable fruit and plant attributes for culinary/ornamental and strict culinary use. Breeding is required to refine/stabilize selections and conduct multi-location trials. Diverse bell and jalapeno Capsicum germplasm we selected for fresh-cut attributes will be used to develop a selection index. Combining ability will identify superior backcross lines for release. Functional genomics will be used to discern pathogen gene function for glycosyl hydrolase enzymes having multiple roles in initiation of plant disease. Genes encoding glycosyl hydrolases from Alternaria and Streptomyces will be identified in infected hosts via RNA-seq based gene expression profiling. Candidate genes will be cloned and tested via transient expression. Functionality will be further evaluated via RNAi suppression. Nitrogen treatments will be tested to generate RNA-seq host/pathogen expression profiles and identify means to reduce Alternaria infection. To reduce common scab severity, auxin analogues will be applied to potato foliage followed by host/Streptomyces gene expression profiling to identify gene targets for reduced susceptibility. We will evaluate methods for weakening Phytophthora and Alternaria cell walls to reduce pathogen ability to colonize hosts. Enzymes for protoplast generation, plant defense, and enzymes the pathogen uses to alter its own cell wall will be evaluated using Agrobacterium-mediated expression and tissue inoculations.
Progress Report
A diploid mapping population for high specific gravity was evaluated for specific gravity in Oregon and Maine. A tetraploid mapping population was evaluated for late blight and early blight in Pennsylvania and yield, maturity and chipping ability in Maine. Seed from a diploid mapping population for late blight resistance was increased in Maine. High carotenoid diploid clones were evaluated in Florida, North Carolina, Pennsylvania, and Maine. Botanical seed of phu-stn x heat tolerant wild species was started in tissue culture and rapidly micropropagated to generate minitubers for planting in 2019.
Accomplishments
