Genetic Linkages in Muskmelon

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Cucurbit Genetics Cooperative Report 8:50-54 (Article 19) 1985

Pitrat, M.
Institut National de la Recherche Agronomique, 84140 Montfavet, France

We have continued the work presented in the 1984 CGC report (5) on the research of genetic linkages in muskmelon.

1. Necrotic spot virus resistance (nsv)

This gene was already found independent from genes belonging to linkage groups 2 to 6 (5). Its linkage with bush (b) (group 1) was investigated. In a F2 progeny between VA 435 (nsv b+) and Topmark bush (nsv+ b) we have observed: 226 virus susceptible and long internode plants, 81 susceptible and bush, 59 resistant and long internode and 32 resistant and bush. With a chi- square value equal to 5.877 (Prob. = 12%) we conclude to the independence between nsv and b. The gene for nsv being independent from the 6 linkage groups already described is alone in linkage “group” 7.

2. Localization of Pale mutant (Pa)

Pale (Pa) is a semi dominant marker (3). Homozygous Pa/Pa (white pheno-type) ia lethal. Only Pa/Pa+ (yellow phenotype) and Pa+/Pa+ (normal green) have been observed for linkage with other characters.

The following genes have been used:

a. Pale (Pa) is 30567 (supplied by J. D. McCreight)
b. bush (b) in Topmark bush (F. W. Zink)
c. glabrous (gl) in Arizona glA (R. E. Foster)
d. Zucchini yellow mosaic resistance (Zym) in PI 414723 (G. W. Bohn)
e. Flaccida necrosis (Fn) and Fusarium oxysporum f. melonis resistance
(Fom-1) in Doublon.

Pa was found linked with gl (linkage group 3) and independent from b (group 1), Fn (group 2), Zym (group 4), and Fom-1 (group 5) (Table 1).

Four genes belong to linkage group 3: red stem (r), male sterile-1 (ms-1), gl, and Pa. Pa and r have been found independent (2). Distance between r and ms-1 was estimated to 25.6 ± 0.8 (2) and between r and gl to 30.9 ± 3.6 (5). Distance between Pa and gl was estimated on the test cross F1 (Pa/Pa+ gl/gl+) x (Pa+/Pa+ gl/gl). We have observed 167 [Pa gl+], 174 [Pa+ gl], 22 [Pa gl], and 19 [Pa+ gl+]. The distance can be estimated to 10.7 ± 1.6.

In linkage group 3 gl is very probably between r and Pa. The position of ms-1 is under study.

3. Localization of halo marker (h)

Halo cotyledons (h) gene has been still found independent from glabrous (gl) and yellow green (yg) (4).

We found halo independent from b (linkage group 1), Fn (group 2), r (group 3), and nsv (group 7) but linked with Zym (group 4) (Table 2). The distance may be estimated using the maximum likelihood method to 15.0 ± 7.5. Zym was already found linked with andromonoecious (a) and one gene for powdery mildew resistance (Pm-x). The order between Zym, a, h, and Pm-x in group 4 is unknown.

4. Localization of male sterile-2 (ms-2)

Male aterile-2 (ms-2) has been described as independent from male sterile-1 (ms-l) (1). Male sterile-2 (ms-2) was found independent from b (group 1), gl (group 3), h (group 4), and nsv (group 7) but linked with yg (group 6) (Table 3). The linkage between ms-2 and yg is very loose as the distance may be estimated to 37.1 ± 5.4. The order in linkage group 6 (Fom-2 – yg – ms-2) is unknown.

5. Research for other linkages

Linkages between virescent (v) (supplied by P. E. Nugent) and other genes were investigated. Virescent plants (v/v) may sometimes die before turning green. So there may be a deviation from the 3:1 expected ratio from normal: virescent in F2 progenies. We only present in Table 4 the segregation for the second character among the normal green plants.

The results indicate the v segregates independently from Virus aphid transmission resistance (Vat) (group 2), r (group 3), ms-2 (group 6), and nectarless (n).

We also found no linkage between nectarless (n) (in 40099 supplied by J. D. McCreight) and Vat (group 2), a (group 4), yg (group 6), and nsv (group 7) (Table 5).

6. Conclusion

The linkages described in muskmelon may be summarized as follows:

group 1 : b – yv
2 : Vat – Fn
3 : r – g1 – Pa – ms-1 (place of ms-1 unknown)
4 : Zym – a – h – Pm-x (order unknown)
5 : Wmv – Fom-1
6 : yg – Fom-2 – ms-2 (order unknown)
7 : nsv

v is independent from group 2, 3, 6, and n
n is independent from group 2, 4, 6, 7, and v

Table 1. Segragation data for Pale (Pa) marker and b, Fn, g1, Zym, and Fom-1 in F2 progenies.
Genotypes [yellow] [normal green] chi square (6:3:2:1)
Pa/Pa+ Pa+/Pa+ Value Probability
b+/- 143 65
b/b 35 26 3.342 34 %
Fn/- 94 41
Fn+/Fn+ 33 21 2.651 45 %
gl+/- 104 10
gl/gl 13 53 135.300 <.01 %
Zym/- 113 43
Zym+/Zym+ 40 27 6.964 7 %
Fom-1/- 83 24
Fom-1+/Fom-1+ 29 16 7.211 7 %

Table 2. Segregation data for halo (h) marker and b, Fn, r, Zym, or nsv in F2 progenies.
Genotypes [normal green] [halo cotyledons] chi square (9:3:3:1)
h+/- h/h Value Probability
b+/- 160 54 0.446 93 %
b/b 54 15
Fn/- 168 65 2.177 54 %
Fn+/Fn+ 54 15
r+/- 148 53 1.505 68 %
r/r 48 12
Zym/- 106 14 91.344 <.01 %
Zym+/Zym+ 11 37
nsv+/- 185 47 2.860 41 %
nsv/nsv 56 19

Table 3. Segregation data for male sterile-2 (ms-2) and b, g1, h, yg, and nsv in F2 progenies.
Genotypes [male fertile] [male sterile] chi square (9:3:3:1)
ms-2+/- ms-2/ms-2 Value Probability
b+/- 118 41 3.568 31 %
b/b 33 7
gl+/- 141 53 4.306 23 %
gl/gl 34 16
h+/- 108 34 1.279 73 %
h/h 32 15
yg+/- 117 58 10.732 1 %
yg/yg 58 11
nsv+/- 104 39 1.742 63 %
nsv/nsv 42 15

Table 4. Segregation data observed among the normal green plants in F2 progenies segregating for virescent (v) and Vat, r, ms-2, or n.
Genotypes Segregation among the
normal green plants		 chi square (3:1)
Value Probability
Vat/- : Vat+/Vat+ 141 : 46 0.016 90 %
r+/- : r/r 167 : 52 0.184 67 %
ms-2+/- : ms-2:ms-2 134 : 44 0.007 93 %
n+/- : n/n 175 : 49 1.167 28 %

Table 5. Segregation data observed in F2 progenies between nectarless (n) and Vat, a, yg, or nsv.

 
Genotypes [with nectar]
n+/-		 [without nectar]
n/n		 chi square (9:3:3:1)
Value Probability
Vat/- 53 20 4.444 22 %
Vat+/Vat+ 9 6
a+/- 50 18 3.420 49 %
a/a 9 5
yg+/- 94 39
yg/yg 33 13 1.628 65 %
nsv+/- 94 34
nsv/nsv 31 10 0.226 97 %

Literature Cited

  1. Bohn, G. W. and J. A. Principe. 1964. A second male sterility gene in the
    muskmelon. J. Heredity 55:211-215.
  2. McCreight, J. D. 1983. Linkage of red stem and male sterile-1 in
    muskmelon. Cucurbit Gen. Coop. Report 6:48.
  3. NcCreight, 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.
  4. Nugent, P. E. 1978. Independence of halo, glabrous and yellow green
    mutants in muskmelon. HortScience 13:287-288.
  5. Pitrat, M. 1984. Linkage studies in muskmelon. Cucurbit Genet. Coop.
    Report 7:51-63.