Low temperature seed germination of cucumber: genetic basis of the tolerance trait

Cucumber (Cucumis sativus L.) germinates in an optimal temperature ranging from 24 to 28 °C. In order to develop cultivars with low temperature germination ability, knowledge regarding its genetic basis is needed. In our earlier study, we identified the accession PI 390953 as chilling tolerant and a good cold germinator. The objective of our present study was to compare cold germinability of cold tolerant breeding line B 5669 with PI 390953, and to measure the inheritance of this trait. At 13 °C, both tested cultigens (B 5669, PI 390953) showed the highest germinability and we found no significant differences between them regarding the rate of germination, days to germination (DTG), or germination index (GI). We also observed differences in the germination ability at 13 °C among seven hybrid populations of cucumber, derived from the cross between good cold germinator B 5669 (P1) and B 6115 (P2) lacking cold-germination ability. The fastest low temperature germination and the highest low temperature germination percentages were observed in B 5669 (P1) with germination of 78 and 100% on the 6^th and 10^th day of the test, respectively. In addition, the cultigen B 5669 exhibited the fastest germination, reaching on average of DTG = 5.7. B 6115 (P2) and BC1P2 proved unable to germinate at 13 °C even within 21 days. The seed germinability of F2 population fits a three-recessive gene model. Cucumber cultigens B 5669, PI 390953, and PI 246903 showed low temperature tolerance, but of them B 5669 may become the most desirable to breeders since it exhibits cold germinability combined with good fruit quality traits.