SARATOV, RUSSIA
University of Saratov

Expression of nuclear genes in different cytoplasmic sources
--Alexandra Zavalishina and Valery Tyrnov

By means of androgenesis in vivo, brown marker isogenic lines (a B Pl C R Pr) were produced in different cytoplasmic sources: Wisconsin 23 (W23), Kinelsky 103 (K103), cms-T, and cms-S.

It was ascertained: 1) in progeny of isogenic lines carrying cytoplasms W23, cms-T, cms-S, every year 3 to 60% atypical plants (light brown, green with tracks of brown color on stem or tassel) appeared for 8 tested generations, whereas in progeny of isogenic lines, carrying the cytoplasm K103, all plants were typical brown (for 12 generations); 2) if atypical plants were crossed by normal ones, only atypical plants appeared in progeny (for 6 generations). When these atypical plants were crossed by a line with gene A, the whole spectrum of color (sun red, pale purple, sun purple, pale purple with some dark spots) appeared in progeny. This shows that dominant genes B Pl in atypical plants manifest themselves as recessive ones; 3) in reciprocal crosses between typical and atypical plants, irrespective of cytoplasm source in the maternal plant, only atypical descendents arose in F1. F2 also consists of atypical plants. It is difficult to give an explanation to this fact. The phenomenon of occurrence of atypical plants we observed also in brown marker isogenic lines in cytoplasms cms-S,-T,-C, produced by means of backcrosses. After 10 backcrosses only atypical plants arose. At the same time the same method led to production of atypical isogenic line in teosinte cytoplasm. Thus, cytoplasmic-nuclear interactions continue to act in many generations. We don't exclude the possibility that it affects a wider spectrum of characters and has, probably, breeding and evolutionary effects. 


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