Genelics of internode length in melons

Sequential intemodes on the main stem and first three branches were measured in representatives of three melon (Cucumis meio L.) plant types. Internodes were longest in vine-type cultivars Noy Yizre'el and Top Mark, shorter in birdsnest-type accession Persia 202, and shortest in short-internode (bush) type accession U. C. Top Mark Bush. The three plant types also were differentiated by their distinct patterns of sequential internode length along the main stem and branches. Results of crossing Persia 202 (birdsnest) with Noy Yizre'el (vine) indicated that the relatively short internodes of the former are conditioned mainly by a single recessive gene, but that one or more modifier genes as well as environmental factors also were involved in determining internode length. Reciprocal crosses of Persia 202 (birdsnest) and U. C. Top Mark Bush (short-internode) resulted in plants having long internodes, indicating that the major recessive gene for short internodes possessed by each accession is not identical. Given the similar primary effect of each gene on the phenotype, it is suggested that the symbol for the gene possessed by U. C. Top Mark Bush be changed to si-1 (short-internode-1) and that the gene possessed by Persia 202 be designated si-2 (short-internode-2).