Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2006
Publication Date: 9/15/2006
Citation: Zalapa, J.E., Staub, J.E., McCreight, J.D. 2006. Generation means analysis of plant architectural traits and fruit yield in melon (Cucumis melo l.). Plant Breeding. 125:482-487. Interpretive Summary: Melon is an economically important, cross-pollinated, vegetable species. In the United States, Western Shipping and Eastern Market types are most important for commercial production. Arizona, California, Texas, Georgia, and Indiana are the primary producers of cantaloupes for fresh market consumption. In 2003, U.S. farmers grew almost 37,000 hectares (90,000 acres) of cantaloupes for a total production in excess of one million tons having a market value of almost 400 million U.S. dollars. Yield in Western Shipping melon has increased gradually in the last 50 years mainly due to the incorporation of disease resistance genes and improved cultural practices. Standard melon cultivars possess a large plant mass (highly spreading), produce most of their fruit at the end of their lateral branches (relatively late in the season), are not typically highly branched. Melon yield can be improved through the incorporation of genes for plant habit such as branching, fruit set, and stature (size). It may be possible to increase yield potential of Western Shipping type melons by genetically developing a small statured, highly branched plant type that produces fruit early at the base of the plant. The USDA has developed such prototype plants, but has not identified the genetic mechanisms (the genetic reasons behind the appearance of such plant types) controlling these unique plant types. It is critical to understand the genetic control of branching, plant stature and fruiting habit in order to more effectively breed such characteristics into commercial melon cultivars. Therefore, a study was designed to determine the genetics of such plant characteristics. The data from this experiment indicates that relatively few genes control the development of lateral branches and plant stature (size; dwarf vs. large). However, the control of plant such traits as sex expression (male or femele flowers), fruit number and weight, and fruit development (early or late) is controlled by a complex interaction of many genes. Thus, the addition of increased number of lateral branches (i.e., increased possibilities for fruit development) into commercial melon will be relatively easy to accomplish. However, the development of plants with increased female sex expression (the possibility to produce more fruit), as well as the increase in the number of early maturing fruit will be more difficult and will require more time to accomplish. This information is important to plant breeders interested in increasing yield in commercial melon through changes in plant architecture. This information will allow for the development of more efficient and effective plant breeding strategies which led to the development of plant types with unique architecture. The commercial release of such high yielding plant types will allow the U.S. grower to be more competitive in the global market place.
Technical Abstract: Unique, highly branched phenotypes have the potential for increasing yield in commercial melon (Cucumis melo L.). Optimum horticultural performance of such phenotypes depends upon gaining an understanding of yield-related source-sink relationships and the inheritance of plant architecture and yield characteristics (hereafter designated yield components). Therefore, a generation means analysis (GMA) study was conducted to investigate the inheritance of days to anthesis, primary branch number, fruit number and weight, and average weight per fruit. Progeny (F1, F2, BC1P1, and BC1P2) from a cross between U. S. Department of Agriculture (USDA) line, USDA 846-1 (P1; 7-11 lateral branches) and “Top-Mark” (P2; 2-4 lateral branches) were evaluated at Arlington (AR) and Hancock (HCK), Wisconsin in 2001. Due to significant (p ' 0.05) environment effects and genotype x environment interactions (G x E), analyses were performed by location. Significant differences (p ' 0.05) among parents and generations were observed for all traits, and the two parental lines differed for primary branch number, fruit number, and average weight per fruit. Additive gene effects were most important in governing primary branch number, and fruit number per plant, while dominance and epistatic genetic effects mainly controlled days to anthesis, fruit weight per plant, and average weight per fruit. Narrow-sense heritabilities were 0.62 (AR) for days to anthesis, 0.71 (AR) and 0.76 (HCK) for primary branch number, 0.68 (AR) and 0.70 (HCK) for fruit weight per plant, 0.33 (AR) and 0.45 (HCK) for fruit weight per plant, and 0.06 (AR) and 0.79 (HCK) for average weight per fruit. Estimations of the least number of effective factors for primary branch number were relatively consistent at both AR (~ 4) and HCK (~ 2). These results suggest that selection for higher yield will likely require extensive replicated progeny testing over multiple environments using advanced generations (e.g., F3 families). The introgression of yield-related genes from highly branched melon types (e.g., USDA 846-1) into U.S. Western Shipping germplasm may aid in the development of high yielding cultivars with concentrated fruit set suitable for machine and/or hand harvesting operations.