Value of Locations for Representing Mega-Environments and for Discriminating Yield of Watermelon in the U.S

In a crop breeding program, multiple-location trials can be used to define target regions and mega-environments that, in turn, will help the breeder develop stable cultivars. In addition, locations can be chosen that are efficient for distinguishing among cultivars (genotypes) and that are good representatives of the target regions. The objectives of this study were to study mega-environments and identify test locations that were both discriminating and representative of target regions. Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] fruit yield and yield components were evaluated in 3 yr and eight locations using replicated, multipleharvest trials. Data were analyzed using genotype main effect and genotype ́ environment interaction (GGE) biplot model as well as other methods for stability analysis. Marketable yield and percentage early fruit had a nonrepeatable crossover pattern and thus, formed a single and complex mega-environment. Two key locations, (Kinston, NC, and Charleston, SC) were efficient representatives of two mega-environments for fruit count. Locations at Woodland, CA, and College Station, TX, can be used interchangeably for identifying genotypes with high percentage cull fruit. There was only one mega-environment for fruit size. Identification of mega-environments for watermelon in the southern United States has implications for future breeding and genotype evaluation in the United States including the use of specialized genotypes for high performance in specific locations. M. Dia and T.C. Wehner, Dep. of Horticultural Science, North Carolina State Univ., Raleigh, NC 27695-7609; R. Hassell, Clemson Univ., Coastal Research and Education Center, 2700 Savannah Hwy, Charleston, SC 29414; D.S. Price, Georgia County Extension, SW District, 110 West 13th Ave, Suite C, Cordele, GA 31015; G.E. Boyhan, Univ. of Georgia, Dep. of Hort., 1111 Miller Plant Science Bldg., Athens, GA 30602; S. Olson, North Florida REC, Univ. of Florida, 155 Research Road, Quincy, FL 32351-5677; S. King, Texas A&M Univ., Dep. of Hort. Sci., 1500 Research Pkwy, Ste A120, College Station, TX 77845, A.R. Davis, USDA–ARS, 911 East Highway 3, Lane, OK 74555; G.E. Tolla and J. Bernier, Monsanto/Seminis Veg Seeds, 37437 State Hwy 16, Woodland, CA 95695, B. Juarez, 2387 McNary Way, Woodland, CA 95776. Received 16 Nov. 2015. Accepted 26 Mar. 2016. *Corresponding author ([email protected]). Abbreviations: AEC, average environment coordinate; CA, Woodland, CA; CI, Clinton, NC; FL, Quincy, FL; G ́ E, genotype ́ environment interaction; G ́ L, genotype ́ location interaction; GA, Cordele, GA; GGE, genotype main effect and genotype ́ environment interaction; GGL, genotype main effects plus genotypic ́ location interaction effect; KN, Kinston, NC; L ́ Y, location ́ year interaction; OK, Lane, OK ; SC, Charleston, SC; TSS, total sum of squares; TX, College Station, TX. Published in Crop Sci. 56:1726–1735 (2016). doi: 10.2135/cropsci2015.11.0698 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. Published June 15, 2016