|Coffey, Michael - UC, RIVERSIDE|
Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: April 15, 2007
Publication Date: July 1, 2007
Citation: Mccreight, J.D., Coffey, M.D. 2007. Resistance to a new race of the cucurbit powdery mildew present in Arizona and California. HortScience. 42:1013. Technical Abstract: A new strain of the powdery mildew fungus Podosphaera xanthii, designated race S, was first detected on melon (Cucumis melo L.) in the lower desert areas of Yuma, Ariz. and Imperial Valley, Calif. in 2003 when it caused economic losses in some fields. Race S overcomes resistance in 19 reported melon powdery mildew race differentials. Melon PI 313970 exhibited resistance, as indicated by absence of both visible mycelia and sporulation, to race S in naturally infected field tests in 2003, 2005 and 2006 in Yuma and Imperial Valley, and repeated, controlled-inoculation greenhouse and laboratory assays in Riverside, Calif. using typed, single spore-derived strains. In 2005, a naturally infected, field test with seven replications of ‘Top Mark’, PI 313970 and their F1, F2, and respective backcross progenies was evaluated for resistance to race S in Imperial Valley. Total number of plants per entry in the seven replications ranged from 15 for ‘Top Mark’ to 159 for the F2 family. Powdery mildew infection was evaluated on 22 May, 8 June and 22 June. PI 313970 was resistant to race S, but exhibited resistant blister type reactions, similar to its responses to race 1 and race 2. A single recessive gene controlled resistance and two recessive genes controlled the resistant blister reaction to race S in PI 313970.