NEMATODE (HETERODERA SCHACHTII) RESISTANCE AND MEIOSIS IN DIPLOID PLANTS FROM INTERSPECIFIC BETA VULGARIS × B. PROCUMBENS HYBRIDS

Abstract

Three diploid nematode-resistant plants derived from hybrids between Beta vulgaris L. and B. procumbens Chr. Sm. were crossed with diploid nematode-susceptible plants. The rates of resistance transmission from the F₁ hybrids to the F₂ varied from 7 to 27%. The transmission rate of F₂ plants derived from F₁ plants with transmission rates over 20% averaged 20.9%. The rate for F₂ plants derived from F₁ plants with transmission rates of 10% or lower averaged 11.3%. In diploid plants nematode resistance was transmitted through the pollen at lower frequencies than through egg cells. Transmission through female gametes varied from 11.0 to 31.4% and through male gametes of the same plants from 0 to 19.7%. In some pollen mother cells (PMCs) of diploid nematode-resistant plants meiosis was normal and gametes derived from these cells transmitted resistance to the next generation. Abnormalities were observed in other PMCs, including the detachment of the B. procumbens segment from the translocated chromosome, the formation of bridges, and the lagging of broken translocated chromosomes. The inadequate transmission of resistance was caused by a loss of the B. procumbens segment in some B. vulgaris bivalents.