Linkage of Red Stem and Male Sterile-1 in Muskmelon

Cucurbit Genetics Cooperative Report 6:48 (article 24) 1983

J. D. McCreight
U. S. Department of Agriculture, Agricultural Research Service, P. O. Box 5098, Salinas, CA 93915

The seedling marker gene red stem (3) was crossed with male sterile-1 (1) to determine the linkage relationship between these two loci. Three F₂ families segregated 559 green, fertile:195 green, male sterile:221 red stem, fertile:2 red stem, male sterile, X2=66.6316, which strongly suggested linkage between these loci. Eleven repulsion phase backcross (BC) progenies segregated in a poor fit to the expected 1:1 single factor and 1:1:1:1 dihybrid ratios (Table 1).

Table 1. Repulsion phase backcross segregation data for red stem and male sterile-1.
	Phenotype
	Normal		red stem		Single Factor X2		Linkage X2
	fertile	male sterile	fertile	male sterile	r	ms-1
Deviation	484	990	1127	243	3.8030	50.2405	711.5384
Heterogeneity					14.6701	42.1054

Two of the 11 BC progenies had a poor (P<0.05) fit to the expected 1:1 ratio for red stem. Seven progenies had a poor fit to the expected 1:1 ratio for male sterile-1. The BC, contingency table (2), linkage X²=711.5384 which strongly supported the F₂ data. The recombination fraction, p (2) between these loci was 0.2556±0.0081.

Literature Cited

1. Bohn, G. W. and T. W. Whitaker. 1949. A gene for male sterility in the muskmelon (Cucumis melo L.). Proc. Amer. Soc. Hort. Sci. 53:309–314.
2. Mather, K. 1963. The measurement of linkage in heredity. John Wiley and Sons, New York. 149 pp.
3. Mc Creight, J. D. and G. W. Bohn. 1979. Descriptions, genetics, and independent assortment of red stem and pale in muskmelon (Cucumis melo L.). J. Amer. Soc. Hort. Sci. 104:721–723.