THE INCORPORATION OF THE FRACTAL GROWTH HABIT INTO WESTERN SHIPPING MELON

Abstract

Plant improvement incorporating quantitatively inherited yield component traits is technically difficult, time consuming, and resource demanding. In melon (Cucumis melo L.), the inheritance of yield components is poorly understood. A unique highly branched fractal melon plant type has been developed by the U.S. Department of Agriculture (USDA) from exotic germplasm to improve yield of U.S. Western Shipping type melons (Group Cantalupensis). In order to more effectively develop useful germplasm for commercial use the genetic of components of yield must be clearly understood. Thus, the genetics of branching, an important yield component, was investigated. Melon progeny derived (F1, F2, F3, BC1P1, and BC1P2) derived from a cross between USDA line 846-1 (P1) and Top-Mark (P2) were used to evaluated in two locations (Wisconsin and California) to estimate of components of variance, and narrow-sense (h2N) and broad-sense (h2B) sense heritabilities. Lateral branch numbers among 71 to 119 F3 families were significantly different (P ¾ 0.01) regardless of test environment. Covariance analyses indicates that branching is moderately heritable (h2B = 0.62 to 0.76, h2N = 0.43 to 0.48), and conditioned by several additive factors (perhaps 2 to 4) that are highly additive. Although environment plays an important role in lateral branch development, family rankings over environments were relatively consistent, indicating that effective selection for this trait should be useful for incorporating the fractal plant habit into Western Shipping melon. The significant additive component underlying lateral branch number indicates that quantitative trait loci (QTL) conditioning this yield component might be identified for use in marker-assisted selection.