Inheritance of Mottled Leaf in Cucurbita moschata

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Cucurbit Genetics Cooperative Report 12:70-71 (article 30) 1989

A. Ribeiro and C.P. da Costa
Department of Genetics, ESALQ/USP, CP 83, CEP13400, Piracicaba, SP, Brazil

The mottled leaf trait in the genus Cucurbita has been described as silver gray areas in axils of leaf veins controlled by a single dominant gene, M, in C. maxima, C. moschata and C. pepo (1, 2, 3). Modifier genes have been reported as extending and/or intensifying the character expression, and at least five phenotypes were described (2, 5). According to Shifriss (6) cell position and environment also contribute to variation in mottling.

Shifriss (4, 5, 6, 7) reported an association between mottled leaf trait and an escape mechanism against aphid-transmitted virus diseases. Mottled leaf plants either repelled aphids similarly to aluminum mulch or slowed speed of virus multiplication.

In the cv. Pira-Moita (C. moschata), we observed a great range of expression for the trait, from non-mottled to highly mottled plants. Contrasting lines were isolated after three selfing cycles, and six generations (P1, P2, F1, F2, BC1, and BC2) were compared from the cross, highly mottled leaf (P1) x non-mottled leaf (P2). Plants were evaluated for degree of mottling at first leaf stage, and data analyzed by chi-square (Table 1).

Table 1. Inheritance of mottled-leaf character in different generations from the cross between two lines, highly mottled leaf (P1) and non-mottled leaf (P2), derived from cv. Pira-Moita (Cucurbita moschata).

Number of plants

Generation
Mottled leaf
Non-mottled leaf
Tested ratio
X²
P
P1 all – 1:0 – –
P2 – all 0:1 – –
F1 all – 1:0 – –
F2 627 214 3:1 0.09 0.75-0.90
BC1 819 2 1:0 – –
BC2 549 581 1:1 0.91 0.25-0.50

All of the F1 plants showed intermediate phenotypes, moderately mottled leaves, indicating partial dominance. The chi-square test indicated good fit to a 3:1 ratio for F2 generation and to a 1:1 ratio for BC2 generation, corroborating earlier published studies. A single, partially dominant gene confers mottled leaf, but there are modifier genes affecting the character as indicated by the continuous variation in mottled expression in F2.

Besides, the possible partial protection of Cucurbita plants against aphid-transmitted virus diseases, the trait may be useful as a seedling genetic marker.

Literature Cited

  1. Coyne, D.P. 1970. Inheritance of mottled-leaf in Cucurbita moschata poir. Hortscience 5:226-227.
  2. Scarchuk, J. 1954. Fruit and leaf characters in summer squash. J. Heredity 45:295-297.
  3. Scott, D.H. and E. Riner. 1946. A mottled-leaf character in winter squash. J. Heredity 37:27-28.
  4. Shifriss, O. 1981. Do Cucurbita plants with silvery leaves escape virus infection? Origin and characteristics of NJ 260. Cucurbit Genetics Coop. Rpt. 4:42:43.
  5. Shifriss, O. 1982. On the silvery-leaf trait in Cucurbita pepo. Cucurbit Genetics Coop. Rpt. 5:48-50.
  6. Shifriss , O. 1982. Reflected light spectra from silvery and non-silvery leaves of Cucurbita pepo. Cucurbit Genetics Coop. Rpt. 6:89-90.
  7. Shifriss, O. 1984. Further notes on the silvery-leaf trait in Cucurbita. Cucurbit Genetics Coop. Rpt. 7:81-83.