Elimination of a Reproductive Barrier Facilitates Intergeneric Hybridization of Sorghum bicolor and Saccharum

Sorghum [Sorghum bicolor (L.) Moench] and sugarcane (Saccharum spp.) are now being bred to enhance the quantity and quality of biomass while maintaining or improving biotic and abiotic stress tolerances. Introgression of complementary traits between sorghum and sugarcane may be an important tool for breeders as they work toward these objectives. We show that by using a sorghum line with the lap mutant, intergeneric Sorghum bicolor x Saccharum spp. hybrids can be readily produced. Using Tx3361 as sorghum seed parent, 14,141 seed were produced from 252 sorghum x Saccharum spp. crosses. Seed set frequency in the intergeneric crosses was affected by sugarcane pollinators. The best pollinators had an above average pollen rating and favorable genetic and/or genomic compatibility, implying that breeding and selection of sugarcane pollen parents could further enhance successful hybridization. Avoiding vivipary through premature seed harvest and eliminating a physical barrier by removing the seed coat increased seedling recovery rates from 1.5 to 33%. Using these methods, our programs have grown 1371 sorghum saccharum intergeneric hybrid plants. Sufficient quantities of seedlings were produced to impose selection criteria with the goal of developing a new intergeneric cultivar with potential to be used for sugar or as a biomass feedstock.