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Cucurbit Genetics Cooperative Report 15:72-73 (article 28) 1992

Segregation Data Suggest Male Sterility Gene ms and the Spotted Gene Sp in Watermelon Are Not the Same Linkage Group

B.A. Murdock and N.H. Ferguson

Departments of Horticulture (1st author) and Agronomy (2nd author), Clemson University, Clemson, SC 29634 USA

Conflicting genetic explanations have been reported for the trait in watermelon characterized by varying sized yellow spots located on both leaves and fruit. A report in 194 involving the variety 'Sun, Moon and Stars' concluded that the spotted condition was due to a chloroplast deficiency situated in the cell cytoplasm and was not due to any nuclear gene (1). A report in 1986 involving a spotted variant labeled 'Moon and Stars' stated that the spotted condition was controlled by a dominant gene which was therein designated Sp (2). The pubescent male sterile trait in watermelon has previously been reported as the expression of the single recessive gene ms (3).

Male sterile segregates were crossed with two different spotted cultivars, 'Moon and Stars Yellow Flesh' and 'Moon and Stars Red Flesh'. All F1 plants were spotted. Self pollinations were performed on one spotted plant from both F1 populations. F2 segregation ratios are presented in Tables 1 and 2.

Table 1. F2 segregation ratios of the cross of a male sterile segregate of red flesh breeding line 'CRM.28' (ms ms sp sp) x 'Moon and Stars' Yellow Flesh (Ms Ms Sp SP).

Phenotypic class
Putative genotype
Number of plants
Expected if 9:3:3:1 segregation
Fertile spotted
(Ms_Sp)
22
27.56
Fertile non-spotted
(Ms_sp sp)
12
9.19
Sterile spotted
(ms ms Sp_)
8
9.19
Sterile non-spotted
(ms ms sp sp)
7
3.06
    Chi-Square - 7.815; 3 d.f. P>0.05  

Table 2. F2 segregation ratios of the cross of a male sterile segregate of red flesh breeding line 'DJB.29' (ms ms sp sp) with 'Moon and Stars' Red Flesh (Ms Ms Sp Sp)

Phenotypic class
Putative genotype
Number of plants
Expected if 9:3:3:1: segregation
Fertile spotted
(Ms_ Sp_)
97
89.44
Fertile non-spotted
(Ms_ sp sp)
31
29.81
Sterile spotted
(ms ms Sp_)
29
29.81
Sterile non-spotted
(ms ms sp sp)
2
9.94
 

Chi-Square = 7.04;3 d.f. P>0,05

These results verify dominant nuclear inheritance of the Sp gene from 'Moon and Stars' and independent segregation of Sp and ms.

Literature Cited

  1. Poole, C.F. 1944. Genetics of cultivated cucurbits. Journal of Heredity 35: 122-128
  2. Rhodes, B.B. 1986. Genes affecting foliage color in watermelon. Journal of Heredity 77:134-135.
  3. Zhang, Xing-ping and Ming Wang. 1990. A genetic male-sterile (ms) watermelon from China. Cucurbit Genetic Cooperative Report 13:45-46.
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Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
Created by T.C. Wehner and T. Ng, 1 June 2005; design by C.T. Glenn;
send questions to T.C. Wehner; last revised on 15 December, 2009