An apomictic polyhaploid obtained from a pearl millet x Pennisetum squamulatum apomictic interspecific hybrid

In a research program to transfer apomixis from Pennisetum squamulatum Fresen to pearl millet, P. americanum L. Leeke, a polyhaploid plant (2n=21) was discovered in the uniform open-pollinated progeny of an apomictic interspecific hybrid (2n = 41) between pearl millet and P. squamulatum. The polyhaploid was shorter, less vigorous and was smaller morphologically than its maternal parent. It probably originated by parthenogenetic development of a reduced gametophyte in the apomictic interspecific hybrid. The most common metaphase I chromosome association in the polyhaploid was 4 bivalents plus 13 univalents. Irregular chromosome distribution, tripolar spindles, bridges and fragments were observed at anaphase I and telophase I. The polyhaploid was male-sterile and partially female- fertile having multiple aposporous embryo sacs in 95% of the ovules. Seed set was 3% when open-pollinated and 33% when pollinated with pearl millet pollen. Low seed set was due to competition among multiple embryos developing in the same ovule. Seventeen progeny from seed produced under open-pollination on the polyhaploid each had 2n=21 chromosomes and were morphologically uniform and identical to the female parent. The expression of obligate apomixis in the polyhaploid conditioned by the P. squamulatum genome between the simplex and duplex condition indicates that apomictic reproduction is possible in nonpolyploid plants.