Transcriptomic Evidence of a Link between Cell Wall Biogenesis, Pathogenesis, and Vigor in Walnut Root and Trunk Diseases.

Crown gall disease (), crown/root rot disease ( spp.), root lesion disease () and tree vigor are key traits affecting the productivity and quality of walnuts in California. Unchallenged hybrid rootstocks were analyzed by RNA-seq to examine pre-formed factors affecting these traits.

Characterization of Oomycete Species Associated With Root and Crown Rot of English Walnut in Chile.

English (Persian) walnut (Juglans regia) trees affected by root and crown rot were surveyed in five regions of central Chile between 2015 and 2017. In each region, nine orchards, ranging from 1 to 21 years old, were randomly selected and inspected for incidence and severity of tree decline associated with crown and root rot. Soil and symptomatic crown and root tissues were collected and cultured in PARP semiselective medium to isolate potential oomycete pathogens, which were identified through morphology and molecularly using ITS sequences in the rDNA gene and beta tubulin gene.

Temporal Occurrence and Niche Preferences of Phytophthora spp. Causing Brown Rot of Citrus in the Central Valley of California.

Brown rot of citrus fruit is caused by several species of Phytophthora and is currently of serious concern for the California citrus industry. Two species, Phytophthora syringae and P. hibernalis, are quarantine pathogens in China, a major export market for California citrus.