Influence of gametocidal chromosome 4Sl on the segregation ratio in genetic analysis of the common wheat lines

Abstract

The character “hairy leaf sheath” was studied in two groups of introgressive common wheat lines and shown to be under control of dominant gene Hs being situated in chromosomes 4Sl and 4D of Aegilops sharonensis and Triticum miguschovae (AAGGDD), respectively. Using experimental data on genetic analysis of introgressive lines for character “hairy leaf sheath” controlled by the gene of “cuckoo” chromosome 4Sl, the algorithm for calculation the theoretical segregation ratio in F2 was developed. Segregation distortion is caused by non-viability of majority of gametes lacking 4Sl. Frequency of functioning gametes without 4Sl is determined by the probability p. Then, the ratio 7 nonviable : 9 viable zygotes is formed as 0.75-0.5p-0.25p^2 : 0.25+0.5p+0.25p^2. Since segregation involves two characters, gamete viability and hairiness, not monogenic ratio 3:1 but ratio 15 hairy : 1 hairless was used as a base for search of frequency p by maximum-likelihood method. Using 16 populations F2 from crossing lines differing in character studied, it was shown that theoretically expected ratio is equal to 0.9676:0.0325 and 0.9787:0.0213 in two different years. Judging by the chi^2 criterion, actual segregation ratios do not differ from theoretical ones calculated using p , the frequency of functioning gametes lacking the “cuckoo” chromosome.