LINKAGE: RELATIONS OF A MUTANT CONFERRING MECHANICAL STERILITY

48 RESEARCH REPORTS

PNL Volume 12

1980

Marx, G. A. New York State Agricultural Experiment Station, Geneva, NY USA

After treating one of his lines with EMS, L. G. Cruger recovered a

mutant which affects floral morphology and reproductive behavior. Subse-

quently he made seeds of the mutant available to me.

Mutant behavior is, in a number of respects, similar to that of crpt

(crumpled petal), a mutant isolated and described by Sharma and Aravindan

(PNL 3:50-51, 1971). Flowers are characterized by exserted pistils and

crumpled petals and stamens. This abnormal floral morphology leads to

mechanical sterility because the anthers are denied close proximity with

the stigma. Still, based on the description of crpt, the two mutants appear

to have some important dissimilarities. Unlike crpt, the plants are not

waxless, fertility of selfed plants apparently is normal, and flowers are

not typically "ball-shaped".

Plants homozygous for this recessive gene may show a range of mutant

expression. Sterility appears to be enhanced under field conditions, whereas

greenhouse conditions seem to promote more normal floral morphology and

greater fertility (occasionally completely normal). Typically in the green-

house the flowers are near normal in size, the corolla is more or less

tubular when fully open, and the banner is not reflexed backward. The keel

may be rather sharply curled and the filaments of the stamens compressed

and twisted at the apex of the keel. Depending on the specific conditions,

the pistil may or may not extrude from the keel.

PNL Volume 12 1980

RESEARCH REPORTS 49

Even in the field, where conditions are generally favorable for mutant

expression, and where sterile plants can easily be distinguished from normal

sibs in segregating populations, sterile plants occasionally produce a few

seeds. Progeny tests revealed that such seed was a product of selfing.

In general, the flowers borne at the higher reproductive nodes have a greater

tendency to produce selfed seed. In this and some other respects, mutant

behavior resembles the mutant re (infecunda) reported by Nilsson (Hereditas

17:71-99, 1932; see also Lamprecht, Agr Hort. Genet. 18:181-204, 1960).

Thus, given the uncertainty of identity among crpt, re, and the Cruger mutant,

a name and symbol for the latter will not be suggested pending the outcome

of allelism tests. The designation "mes" is only a working symbol for

convenience.

In crosses between the Cruger mutant and normal fertile lines, the

F1's were fertile and the F2 ratios were in accord with monogenic control.

There was no indication of the deficiency of recessives as was noted by

Nilsson and by Lamprecht for re. Moreover, there is rather clear evidence

of linkage with af on chromosome 1 (Table 1). Lamprecht (1960) found re

to be loosely linked (ca. 35-40% CrO) with A on chromosome 1, but the

contingency chi-square for linkage between A and the Cruger mutant did not

reach statistical significance in one small population of 212 plants (Table 1