Primary trisomic analysis of the yellow stripe 3 (yst3) gene in barley

S. Wang
Department of Agronomy, Colorado State University
Fort Collins, CO 80523, U.S.A.

A spontaneous mutant gene (yst3) for yellow stripe (streak) 3 was found in the barley variety 'Lion' (BGS 462; BGN 14:99). This yellow streak gene is monofactorial recessive and not allelic to yst and yst2. Primary trisomic analyses have been conducted with all seven trisomics (Wang and Tsuchiya, 1990). The results indicated that yst3 is not located on chromosome 1, 3, 4, 5, or 6, only chromosomes 2 and 7 showed possible association with this gene. Primary trisomic analyses of Triplo 2 and 7 were conducted in 1991. The combined F₂ data of analyses for mutant gene yst3 were listed in Table 1. From the analysis of Triplo 7 × yst3, there were two homozygous recessive plants out of 104 plants in trisomic portion. The ratio of wild type vs yst3 type in disomic portion and total population were close to 3:1. However, in the cross Triplo 2 x yst3, no homozygous recessive plants were observed in 47 trisomic plants, and the ratio of wild type vs yst3 type deviated from 3:1 in both disomic portion and the total F2 population. Thus, it can be concluded that yst3 gene is located on chromosome 2 of barley.

Telotrisomics 2L and 2S were used for further analyses of chromosome arm association with yst3 gene. Table 2 listed the results of telotrisomic analyses. Surprisingly, this gene could not be associated with either arm of chromosome 2 because all F₂ populations showed 3:1 segregation of wild type vs yst3 type. Several trisomic plants with homozygous recessive yst3 type were observed in the F₂ population of all cross combinations.

Telocentric chromosome 2L and 2S, especially telosome 2S, have been suspicious for their abnormality in chromosome structure for many years (Tsuchiya, unpublished). This might explain why the yst3 gene could not be associated with an arm of the chromosome. Further studies are needed to confirm the location of yst3 on chromosome 2.

Table 1. F₂ data from primary trisomic analysis of crosses to BGS 462, which contained the mutant gene yst3.

Table 2. F₂ data of telotrisomic analysis for mutant gene yst3.

Acknowledgements:

I wish to thank Dr. T. Tsuchiya for his support and assistance with this study and for the genetic materials provided.

References:

Tsuchiya, T., and A. Hang. 1979. BGN 9:106-108.

Wang. S.. and T. Tsuchiya. 1990. BGN 19:62-63.

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