Dosage Effect of the Spelta Gene Q of Hexaploid Wheat.
نویسنده
چکیده
A dosage effect of chromosome 5A (formerly IX) of common wheat, Triticum aestivum L. emend Thell. ssp. vulgare, has been well established. With increasing dosage from monosomic to tetrasomic, the phenotype changes from speltoid to normal vulgare type (squarehead) to subcompactoid to compactoid (HUSKINS 1946; SEARS 1952, 1954) (Figure 1 and Table 3) . This is due to the pleiotropic gene Q located near the distal end of the long arm of the chromosome (UNRAU, SMITH and MCGINNIS 1950; MACKEY 1954). The two major effects of Q, speltoid suppression and squareheadedness, were thought to be controlled by two different genes, k and q, until MACKEY (1954) found that the two genes were actually identical and incorporated them into a single dominant gene Q. It is the gene Q which makes ssp. vulgare different from ssp. spelta, and spontaneous or induced speltoid mutation (similar to ssp. spelta) in ssp. uulgare is considered to be a deficiency for a segment including Q (SMITH, HUSKINS and SANDER 1949; MACKEY 1954). MACKEY also suggested that the difference between the spelta and speltoid effects is simply due to the modifying effect of genes at other loci. In ssp. vulgare there are many varieties which are squarehead. The difference between squareheadedness and non-squareheadedness is also attributed to genes that modify Q rather than to any difference in Q itself (SEARS 1956). SEARS (unpublished) demonstrated this by substituting chromosome 5A from the non-squarehead strain “Hope” into the squarehead variety Chinese Spring. using a monosomic method (SEARS 1953). The resulting plant was as squarehead as Chinese Spring. Thus Chinese Spring provides a background that leads to squareheadedness in the presence of two Q genes. This dependence of squareheadedness on modifiers fits well with the fact mentioned by HUSKINS and SANDER (1949) that there is little difference in glume characters among speltoid mutants, although the parent strains show wide variation. The dosage series of the spelta gene q (an allele of Q) was also obtained up to four doses (SEARS unpublished). The gene behaved as a null allele. This result tends to favor MACKEY’S (1954) suggestion that ssp. spelta originated as a speltoid mutation-i.e., as a deficiency for Q locus. As SEARS (1954, 1956)
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عنوان ژورنال:
- Genetics
دوره 48 4 شماره
صفحات -
تاریخ انتشار 1963