Resistance to fungicides is a concern with cucumber downy mildew, Pseudoperonospora cubensis clade 2. These fungicides still suppressed downy mildew well enough that yields of marketable-sized fruit of a susceptible slicing cucumber were much better than not spraying.
Cucurbit downy mildew (CDM), is an economically significant disease of cucurbitaceous crops in the Eastern United States (US). Cucumbers are particularly susceptible and as a result, disease management of this pathogen relies heavily on fungicide use.
Watermelon production in the U.S. and around the world faces serious threats by viral diseases, including aphid-transmitted potyviruses: papaya ringspot virus (PRSV) and zucchini yellow mosaic virus (ZYMV). In a recent study, a CucCAP team examined expression of anti-microbial/anti-viral, ribosome-inactivating proteins (RIPs) in watermelons in response to inoculation with PRSV. The PRSV-resistant citron watermelon (Citrullus amarus) exhibited high RIP expression, versus low expression in plants of the susceptible, cultivated “Charleston Gray” watermelon. This finding may offer additional genetic and genomic resources for improving potyvirus-resistance in watermelon cultivars.
Stated preference surveys are a relatively new approach to measuring specialty crop producers’ valuation of breeding traits.
Powdery mildew is one of the most important diseases of melon. CucCAP researchers used a densely genotyped melon population to identify QTL associated with resistance in multiple plant tissues.
Scientists at the University of Florida led by Geoffrey Meru characterized resistance to Phytophthora crown rot in PI 181761 and identified a major QTL on chromsome 13. Several SNP markers were designed to target this QTL for marker-assisted selection.
CucCAP researchers developed 5 Phytophthora fruit rot resistant watermelon germplasm lines with high levels of resistance against a broad range of diverse P. capsici isolates collected from across the United States.
Researchers in Dr. Mary Hausbeck’s group at MSU have developed a highly sensitive DNA-based protocol to genetically distinguish between spores of cucumber downy mildew and hop downy mildew from spore trap samples. The enhanced sensitivity enables detection 5-10 days before symptoms appear in cucumber fields, providing a broader window for initiation of chemical control.