Inheritance of seed dormancy in Cummis sativus var. hardwickii (Royle) Alef.

Abstract

Reciprocal matings were made between two Cucumis sativus var. sativus L. inbred lines (WI 1606 and WI 2808) and two var. hardwickii (Royle) Alef. accessions (PI 215589 and PI 183967). Each case produced a series of reciprocal F1, F2, and BC1 and BC2 progenies which were used to evaluate seed dormancy in var. hardwickii. Under controlled conditions (25°±1°C and 85%±5% RH; 12 h fluorescent light, 30 μmol s(-1) m(-2)), no seed dormancy was observed in the var. sativus inbred lines 36 days following seed extraction from fruit. With rare exception, var. hardwickii accessions were dormant for at least 60 days. Seed dormancy in the F1 was absent 36 days post extraction, indicating that dormancy in var. hardwickii is conditioned by recessive genes present. Seed of some F1 progeny germinated between 36 and 50 days post-extraction, indicating the presence of transient dormancy or the more variable expression of the dormancy of var. hardwickii. No significant reciprocal differences in either germination rate or percentage were detected in either of the F1 and F2 progeny sets, suggesting lack of cytoplasmic or maternal control over these traits. It was estimated that three to seven factors or loci are involved with the expression of this trait depending on the method of calculation, and that a complex interaction between embryonic and non-embryonic tissue exists. Least square estimates indicate that both additive and dominance effects were important in the expression of dormancy. Comparison of theoretical geometric and arithmetic F2 means to observed F2 means also suggests that non-additive gene action contributes substantially to the observed variation. Broad-sense heritability ranged between 78 and 95%.