Research into two diseases of solanaceous crops in California: 1. Characterization of potato early dying in Kern County, California. 2. Phylogeny, host range and molecular detection of Fusarium solani f.sp. eumartii, causal agent of eumartii wilt in potat

In Kern County, California, potato early dying is associated with seed piece rot and vascular discoloration. Symptomatic plants showed decreased above-ground growth and increased vascular occlusion compared to asymptomatic plants. Pectobacterium spp. and Pseudomonas spp. were found in both asymptomatic and symptomatic stems. Placement of seed pieces in wet and dry conditions significantly impacted seed piece rot, but did not affect expression of above-ground disease symptoms.; The phylogeny of isolates of Fusarium solani f. sp. eumartii (Carp)Wr. from two hosts (Solanum tuberosum L. and Lycopersicon esculentum Mill.) in California was determined based on sequences of four DNA fragments. Isolates of F.s .f. sp eumartii from both hosts comprised a single monophyletic clade separate from other formae speciales of F. solani and mating populations of its teleomorph, Nectria haematococca. Nitrate non-utilizing mutants of representative isolates were paired to determine vegetative compatibility groups (VCG) of the isolates. All isolates from tomato were in one VCG and the isolates from potato were either in that VCG or one other.; Isolates of F.s. f.sp.eumartii from both potatoes and tomatoes caused typical dry rot symptoms on potato tubers and induced root and/or collar rot on four solanaceous species (Solanum tuberosum L., Lycopersicon esculentum Mill., Capsicum anuum L. and Solanum melongena L) in the greenhouse and the field. Although the host range of F. solani f. sp. eumartii has traditionally been limited to potatoes, it includes other solanaceous crops.; Specific primers developed from the elongation factor 1-alpha gene of Fusarium solani f. sp. eumartii amplifed a 550 bp product. No amplification was observed from other Fusarium spp. associated with potato dry rot or from other formae specialis of F. solani. These primers allowed for identification of F.s. f. sp. eumartii in pure culture and detection of the fungus in potato tubers inoculated with F.s. f. sp. eumartii.