Cucurbit Genetics Cooperative Report 1:35 (article 32) 1978
W. N. Whitwood and J. L. Weigle
Robson Seed Farms, Hall, NY 14463
Mutations were induced in a cultivar of C. pepo, ‘Early Prolific Straight Neck’, by ethyl-methanesulfonate (EMS). A 0.035 m concentration of EMS was used to treat 2,000 seeds for 24 hours. The seeds were rinsed in distilled water, treated with a fungicide and planted in the field. An untreated population was soaked in water and treated with a fungicide to serve as a check. Germination of the treated population was 60% vs. 93% in the check population. The number of off-type plants, and fruit characters in the M1 generation was not statistically different between the treated and untreated population. From the M1 selfed plants, 946 M2 entries were grown in the greenhouse and remnant seed was planted in the field. The seedling mutations observed in the greenhouse included 31 lines with chlorophyll deficiencies, five lines with abnormal foliage, and two lines with compact plants. In the field one line segregated for male sterility, one line segregated for fasciated plant habit and five lines with temperature induced chlorosis were found. Adverse field environmental conditions probably contributed to the low number of mature plant mutations observed. The M2 entries which segregated for seedling mutation were selfed to produce the M3 generation.
In the M3 generation, 17 of the M2 entries segregated for a similar phenotypic mutation. The M3 populations for the remaining M2 entries were not sufficiently large to ascertain if the M2 mutation was genetically controlled. Two new seedling mutations were observed in the M3 generation. These mutations were different from the ones observed in the M2 generation.
The mutation frequency in the M2 generation was 4.62% for the EMS population compared to a mutation frequency of 1.01% observed in the untreated population. The mutation frequency in the M3 generation was 6.89%.
One hundred fifty-five bush and semi-bush plant introductions of C. pepo were observed for seedling mutations. Two accessions PI 288241 and PI 172866 segregated for a yellow lethal character. A third accession, PI 169435 segregated for a light green chlorotic plant character. The inheritance of these mutations were not studied due to the difficulty in obtaining selfed fruit under greenhouse conditions.