The Transmission of the Monosomic Condition in a Wheat Variety, Chinese Spring, II. A Critical Analysis of Nine Year Records

Abstract

Frequencies of monosomics in progenies from self- or cross-pollinated monsomics of a common wheat variety, Triticum aestivum ssp. vulgare var. Chinese Spring (2n=42), were estimated from the data accumulated during 9 years in the U.S.A., Canada and Japan. Analysis was made of several factors which might be concerned with the frequency of monosomics. The overall frequency of monosomics in self-pollinated progenies was lower than in cross-pollinated ones, showing a tendency to be most pronounced in monosomics of homologous group 1. In general, frequencies of monosomics observed in America and Japan were the same. But mono-5A showed an extremely high transmission rate of monosomic condition in Japan. The monosomic frequency differed significantly among 21 monosomic lines. Mono-6 B showed the lowest frequency (57.3%) and mono-5 A the highest (81.9%). Frequencies of the other monosomics were intermediate. Monosomics belonging to the same homologous group showed in general similar frequencites: homologous group 1=79.5% except mono- 1 B; group 6=77.8% except mono-6 B; group 3=76.3%; and group 2=67.1%. High correlation was found between the frequency of monosomics and both seed-setting percentage and germination rate. No correlation was detected between the former and either chromosome length, frequency of pollen tetrads with micronuclei or frequency of chromosome-deficient male gametes. It was suggested that the transmission rate of monosomic condition was mainly determined by the viability of monosomic embryos.