Designation of four dominant mutants

--M. G. Neuffer

Fbr1 (Few-branched-1602) is an EMS-induced dominant mutant whose phenotype is expressed in the tassel only as a reduced number of tassel branches (0 to 3). The second tassel branch from the base is often replaced by a small leaf bract. In some plants irregularly formed awns appear on the tips of the glumes. The plant is otherwise quite normal. Homozygotes are slightly more extreme. Location is still unknown but since the phenotype is unique we are designating it Fbr1.

Blh1 (Bleached-1593) is an EMS-induced dominant mutant whose phenotype is expressed just before tassel emergence as bleaching of the lower 1/3 of those leaves from the 1st ear node to the top. The bleaching appears as a diminishing of chlorophyll to give a pale green appearance in the midvein regions of the leaf blade and progresses until some areas are almost white. Plant vigor is not affected until onset of mutant phenotype at which time growth is clearly reduced as compared to normal sibs. Homozygotes are viable but more extreme than heterozygotes. T wx linkage data listed below (for chromosome 1 only) show 22cM from wx T1-9c(1S.48); 42cM from wx T1-9(4995) (1L.19) and no linkage to wx T1-9(8389) (1L.74) or to any of the other 14 wx translocations tested. These data indicate that this mutant, which we have designated Blh1, is located on the short arm of chromosome 1, 22cM distal to the T1-9c breakpoint.
 
  M Wx N Wx M wx N wx c2 p
T1-9c 40 11 9 31 28.59 22
T1-9(4995) 67 39 50 57 7.85 42
T1-9(8389) 20 25 24 22 0.64 54

Ws4 (Pale green-1589) is an EMS-induced dominant mutant whose phenotype is first expressed in the late seedling stage as a lighter green whitish-appearing leaf sheath, which becomes more pronounced towards flowering. Leaves are near normal green and plants are vigorous. Homozygous mutant plants are indistinguishable from heterozygotes. T wx linkage data listed below (for chromosome 1 only) show closest linkage (14cM) to wx T1-9(4995) (1L.19); clear but less close (30cM) to wx T1-9c (1S.48) and suggestive linkage (45cM) to wx T1-9(8389) (1L.74). There was no significant linkage with any of 15 other wx translocations. This indicates location between T1-9c and T1-9(4995), which would place it near the centromere.
 
  M Wx N Wx M wx N wx c2 p
T1-9c 41 19 15 40 19.43 30
T1-9(4995) 51 9 8 51 60.74 14
T1-9(8389) 30 27 24 32 1.30 45

Wi2 (Wilted-1540) is an EMS-induced dominant mutant whose phenotype is expressed beginning at the 5-leaf stage as wilting of the top leaves whenever subjected to drought conditions (i.e., reduced moisture and high temperatures). Under low stress conditions the mutant grows well and is not distinguishable from normal sibs. Homozygotes are viable but more extreme than heterozygotes. Linkage data for wx T3-9c only show 11cM from the T3-9c breakpoint (3L.09) and no linkage for the other 16 translocations. This would place the mutant on chromosome 3.
 
  M Wx N Wx M wx N wx p
T3-9c 29 2 4 19 11


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