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Title: Bottle gourd genotypes vary in clomazone tolerance

item CUTULLE, MATTHEW - Clemson University
item Harrison Jr, Howard
item Kousik, Chandrasekar - Shaker
item Wadl, Phillip
item Levi, Amnon

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2017
Publication Date: 10/6/2017
Citation: Cutulle, M.A., Harrison Jr, H.F., Kousik, C.S., Wadl, P.A., Levi, A. 2017. Bottle gourd genotypes vary in clomazone tolerance. HortScience. 52:1687-1691.

Interpretive Summary: Command 3ME herbicide (clomazone) controls a number of annual grass and broadleaf weeds that are important pests in watermelon fields, and it is used extensively by watermelon growers. Grafted watermelon production is popular in many countries and the practice is being evaluated for use by U.S. growers. Bottle gourd is an important root stock species for watermelons, because its roots are more resistant to diseases, flooding, drought and salt than watermelon roots. Research is needed to identify the best bottle gourd varieties for U.S. production. The objective of this study was to assess the tolerance of bottle gourd varieties to clomazone, an important watermelon herbicide. A genetically diverse collection of bottle gourd lines was evaluated in the greenhouse to determine if differences in tolerance could be identified. Considerable variation in tolerance was observed in the preliminary studies. Replicated experiments were used to confirm these differences. Three highly tolerant lines were identified. These lines may be preferable to susceptible lines for use as rootstocks. Highly tolerant lines can be used to reduce the risk of losses due to clomazone injury in grafted watermelon.

Technical Abstract: A greenhouse trial was used to evaluate 159 accessions of bottle gourd (Lagenaria siceraria (Mol.) Standl.) obtained from the U.S. National Plant Germplasm for tolerance to clomazone herbicide. Most accessions tested were moderately or severely injured by clomazone at 3.0 mg/kg incorporated into greenhouse potting medium; however several exhibited lower injury. Seeds were produced from tolerant and susceptible plants for use in a greenhouse concentration-response experiment. Approximately three to four times higher clomazone concentrations were required to cause moderate injury to tolerant bottle genotypes in comparison to susceptible genotypes. The differences in tolerance among genotypes were observed with injury ratings, chlorophyll measurements, and shoot weights. Clomazone may be used safely on tolerant bottle gourd genotypes, but the herbicide may not be safe for susceptible genotypes. Also, tolerant genotypes such as Grif 11942 may be desirable for use as root stocks in grafted watermelon production.