Mutants Induced by Pollen Irradiation in Cucumber

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Cucurbit Genetics Cooperative Report 14:32-33 (article 12) 1991

Shuichi Iida and Etuo Amano
Institute of Radiation Breeding, National Institute of Agrobiological Resources, MAFF, P. O. Box 3, Ohmiya-machi, Naka-gun, Ibaraki-ken 319-22, Japan

Due to differentiation of male and female flowers and chimerism of mutated sectoring, seed irradiation is not an effective means to obtain induced mutants in cucumber. In order to solve that problem, we irradiated pollen to get uniform genotype within each seed embryo and were successful in obtaining 10 mutant lines (1, 2).

A cultivar “Nishiki-suyo” was self pollinated twice to confirm genetic stability and homozygosity before using in the experiment. Pollen (from staminate flowers) was irradiated by 137Cs gamma-ray with 1, 2, 4, 6, 8 and 10 kR. Seeds from crossing using treated pollen were sown and each plant was self pollinated. In the progeny, we found interesting morphological mutants which are described below, along with a proposed gene symbol.

  • Wavy rimmed cotyledons (wy). Center of cotyledons occasionally white and rims green, later becoming wavy.
  • Albino cotyledons (al). Cotyledons white, hypocotyl light green.
  • Horn-like cotyledons (hn). Cotyledons warped like the thorns of a bull, but transverse section of stem was circular.
  • Dwarf cotyledons-1 (dwc-1). Cotyledons small and hypocotyl short; leaves not expanding.
  • Dwarf cotyledons-2 (dwc-2). Same as dwc-1.
  • Light green cotyledons-1 (lg-1). Initially, cotyledons and young leaves light green, becoming normal green later.
  • Light green cotyledons-2 (lg-2). Initially, cotyledons and young leaves light green, becoming normal green earlier than lg-1.
  • Shrunken leaves (shl). First leaf shrunken, but later leaves progressively more normal.
  • Wilty leaves (wi). Rim of leaves wilted.
  • Heart shaped leaves (hsl). Leaves round-heart shaped; tendrils often branched.

Some mutants (wy, lg-1, lg-2 and hsl) could be reproduced by self pollination, but others could be maintained only as heterozygotes because of lethality of poor viability of homozygote.

Segregation of self pollinated heterozygotes suggested that wy, al, hn, dwc-1, lg-1, lg-2, shl and hsl indicated inheritance by a single recessive gene (Table 1). Therefore, we have proposed gene symbols for these mutants until genetic analyses to compare with comparable genes already reported. Two of the mutants, dwc-2 and wi, deviated from the expected ratio of 3:1, but were recessive. Further genetic analysis is needed to clarify the reason for the deviation.

Table 1. Segregation of cucumber mutants obtained by pollen irradiation.

Number of plants

X²

Mutant line

Irradiation dose (kr)
Normal
Mutant
(3:1)

Prob.

Tentative gene symbol
wavy rimmed cot. 2 49 17 0.20 P>0.70 wy
albino cot. 2 46 10 1.52 P>0.20 al
horn-like cot. 2 40 17 0.71 P>0.70 hn
dwarf cot. -1 2 36 15 0.53 P>0.70 dwc-1
dwarf cot. -2 2 45 4 7.41 P>0.01 dwc-2
light green cot. -1 4 46 11 0.99 P>0.80 lg-1
light green cot. -1 8 33 11 0.00 P>0.99 lg-2
shrunken leaves 4 40 10 0.67 P>0.80 shl
wilty leaves 2 67 12 4.05 P>0.05 wi
heart shaped leaves 6 33 15 1.00 P.0.80 hsl

Literature Cited

  1. Iida, S. and E. Amano. 1987. A method to obtain mutants in outcrossing crops. Induction of seedling mutants in cucumber using pollen irradiation. Technical News No. 32 (Institute of Radiation Breeding).
  2. Iida, S. and E. Amano. 1988. Pollen irradiation method to obtain mutants in cucumber. Mutation Breeding Newsletter No. 32:2-3.