Embryo Rescue Protocol for Interspecific Hybridization in Squash

Interspecific hybridization in Cucurbita crops (squash) is desirable for widening genetic variation and for the introgression of useful alleles. Immature embryos generated from these wide crosses must be regenerated using appropriate embryo rescue techniques. Although this technique is well established for many crops, a detailed description of the appropriate methodology for squash that would allow its routine application is lacking. Here, we describe an embryo rescue protocol useful for interspecific hybridization of C. pepo and C. moschata. To identify viable combinations for embryo rescue, 24 interspecific crosses were performed. Fruit set was obtained from twenty-two crosses, indicating a 92% success rate. However, most of the fruits obtained were parthenocarpic, with seeds devoid of embryos (empty seeds). Only one cross combination contained immature embryos that could be regenerated using basal plant growth media. A total of 10 embryos were rescued from the interspecific F1 fruit, and the success rate of embryo rescue was 80%. The embryo rescue protocol developed here will be useful for interspecific hybridization in squash breeding programs.