Phalaris canariensis is a domesticated form of P. brachystachys

Abstract

Three hybrid plants were obtained by hot-water emasculation of Phalaris canariensis L. panicles immediately before anthesis, followed by the daily application of pollen from P. brachystachys Link. The hybrids were fully fertile, and the seed retention characteristic of P. canariensis was inherited in the F1, F2 and F3 generations as a single recessive trait, showing that P. canariensis is a cultigen derived from P. brachystachys. The dominant allele for seed shedding is designated Ssh. All 1008 plants examined in segregating F3 families had either short sterile florets and shed their seeds, or long sterile florets and retained their seeds, i.e. there were no recombinants. No seed retaining BC1F2 plants could be found in the progeny of (P. truncata Guss.×P. canariensis)×P. truncata, suggesting that the ssh'allele' may be a number of mutant alleles in a segment of chromosome in which recombination is suppressed in hybrids of P. canariensis with P. brachystachys, but in not those with P. truncata. Compared with P. brachystachys, P. canariensis has heavier seeds, stronger panicle branches and thicker peduncles. These traits were polygenically inherited in F2 and thus appear to have been developed by the accumulation of alleles during cultivation of P. canariensis as a grain crop. Modified seeds with much reduced sterile florets were found in the terminal spikelets of most panicle branches of P. brachystachys. Unlike the typical seeds, the modified seeds were often retained in the outer glumes when the panicle fragmented. It seems that this system allows these seeds to be dispersed much further by animals, wind or water than typical seeds. This mechanism has been lost in P. canariensis.