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Title: Confirming resistance in bottle gourd germplasm by quantifying powdery mildew conidia using a cellometer

item Kousik, Chandrasekar - Shaker
item Ikerd, Jennifer

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2013
Publication Date: 7/29/2015
Citation: Kousik, C.S., Ikerd, J.L. 2015. Confirming resistance in bottle gourd germplasm by quantifying powdery mildew conidia using a cellometer. Phytopathology. 103(Suppl. 2):S2.75.

Interpretive Summary: N/A

Technical Abstract: Powdery mildew (PM) caused by Podosphaera xanthii, an important foliar disease affecting cucurbit crops grown in the United States, commonly occurs on foliage, petioles, and stems. We have developed two highly resistant bottle gourd (Lagenaria siceraria) germplasm (USVL351 and USVL482) for use in our watermelon rootstock breeding program. Seedlings of the resistant germplasm lines along with a commercial rootstock ‘Emphasis’ and a susceptible check (PI 381848) were spray inoculated (105 conidia/ml) in a greenhouse and PM development was recorded after 14 days. The hypocotyls, cotyledon and first true leaf from all plants were collected in individual Ziploc bags and weighed. Conidia present on plant tissue were dislodged in sterile water (0.02% Tween 20) and quantified using a Cellometer Auto T4 cell counter (Nexcelom Biosciences, Cellometer size specification for the conidia was set at 42 x 15 µm. PM severity on hypocotyl (8%) cotyledon (8%) and true leaves (17%) on the two resistant germplasm lines was significantly less compared to the susceptible check (all >73%). The rootstock Emphasis was significantly less susceptible than PI 381848 but it was not resistant as the USVL lines. PM conidial counts on all plant parts were significantly lower on USVL resistant lines (range 102-104/g) compared to PI 381848 (106-107/g). The cellometer can be a useful device to quantify pathogen propagules such as PM conidia for confirming disease resistance.