IV. 6. Coordinator's report: Chromosome 6.
K. J. Kasha, Crop Science, University of Guelph, Ont., Canada N1G 2W1, "R".
Rather than adding genes this year, we will remove a couple from association with chromosome 6. The first is f6 chlorina, which Tsuchiya (BGN3:101) suggested as associated with chromosome 6. However, from correspondence with N. A. Tuleen, it should have been placed near the centromere of chromosome 7. I have run linkage of f6 with o and gs4 (markers on 6) and found independence of f6 with these markers based on F2 populations of 113 and 140 plants respectively.
Tsuchiya (BGN 3:101) also suggested clh, curly leafed dwarf, was associated with chromosome 6. Therefore, it was mentioned (Kasha, BGN 5:75 and BGN6:100) as associated with chromosome 6. However, Tsuchiya (BGN6:112) pointed out that clh was associated with chromosome 5 by Ramage (1962, BN6:67). Walker et al. (1963) found a weak linkage of cu with o (31.5 + 6.6%) on chromosome 6. It is probably confusion of symbols of cu (curly lemma & awns) and clh that has led to these erroneous listings of clh on chromosome 6 rather than on chromosome 5 where it apparently belongs. I am presently running linkage studies between cu and other markers on chromosome 6. This plant is also dwarfed. There is another curly dwarf (cud) listed as associated with chromosome 7 (Takahashi et al. BGN5:56-60 and Fedak BGN6:101:) and probably cu, cud and clh should be tested for allelism. At this time I would remove clh from chromosome 6 but tentatively add cu as being associated.
Please also note a gene symbol change has been made. The gene se6 on chromosome 6 (BGN 6:100) now has the symbol sex1 (see BGN6:114 and BGN6:21) and will therefore be so designated in the future as stock BGS382 (BGN6:140). Further linkage data of sex1 with o and ms,,bk has been provided by Eslick and Ries (BGN6:21).
A new albino seedling mutant has been reported associated with chromosome 6 by Clark and Ramage (BGN6:8-9) but it has not been allele tested with alb,,f or assigned a symbol.
There are no changes in the chromosome map drawn up last year, except for the symbol change to sex1. During the summer of 1976, F2 populations were grown to check linkage values between: uc2 and ms,,bk; uc2 and gs4; gs4 and ms,,bk; uc2 and ea7; uc2 and o; o and ms,,bk; o and sex1; o and gs4; alb,,f and o; alb,,f and ms,,bk, and alb,,f with ms6. After the F3 progeny are classified in 1977, the combined values from F2 and F3 data will be reported, with many of the data being 3-point linkage data to assist in clarifying gene orders.
The light green seedling mutant has been confirmed as located on chromosome 6 (see Kasha and Ho-Tsai, BGN 7), probably in the long arm. A gene symbol is not available at this time.