Cytogenetic study of synthetic wheats from National Small Grain Collection of USDA-ARS in the conditions of Nechernozemnaya zone of Russia

CIMMYT collection of synthetic wheats is widely used in breeding programs in many countries due to easy hybridization with domestic varieties, which enhances positive effects in the hybrids. In Russia this collection has never been checked for plant resistance to diseases or used for breeding. We investigated 400 samples of synthetic wheats, obtained in 2009 from National Small Grains Collection (NSGC USDA-ARS, Idaho, USA) to be tested in Nechernozemnaya zone of Russia under brown rust and mildew infection. During 2 years the high-yielding samples were found which were resistant to brown rust, to mildew, and to both pathogens. Nevertheless, the plant response to brown rust attack differed, and the segregation was observed on morphological parameters of ears, leaves and stems. To elucidate why the instability appears, the chromosome conjugation in meiosis was examined and a meiotic index was calculated in 71 synthetic wheats. It was shown that only 63 % of the samples were cytogenetically stable. In the remaining samples the chromosome number varied from 2 n = 40 to 2 n = 43, and different abnormalities (univalents and multivalents) were observed in meiotic metaphase I. Usually in these plants the meiotic index was lower. It is concluded that in the collection a genetic stabilization is still continuing by the appearance of aneuploids. For further genetic and breeding investigations, there are selected the forms with stable cytogenetic parameters, disease resistance and good yielding components (weight per 1000 kernels up to 56 g, and grain yield per ear up to 2.5 g).