Rick, C. M.
We have continued the search for male-sterile mutants in new varieties of tomatoes as they are first grown in large acreages in the vicinity, of Davis. Since the last report vas made on this subject (TGC 6:26) a number of sterile plants have been found in commercial fields, and from these 8 mutants in 7 varieties were selected on the basis of normal genetic behavior, clearly defined male sterility, well-exposed stigmas, and other characteristics of merit for breeding and genetic purposes. It is safe to assume that each represents an independent mutation because all of these lines (except ms\32) were recently derived from a single plant selection known to be free of any sterility mutations. Whether any of this group represent repeat mutations of previously known genes or mutations to new alleles at known loci is not known. Since allele tests have not yet been made, it is logical to assume that each represents a new locus until future tests should prove otherwise.
The morphological and cytological observations are summarized in the following table.
(See image "10p36f.gif") In addition to the foregoing summary a few notes should be recorded about special features of certain mutants. In many respects ms\26 is an unusual mutant. Its anthers are extremely reduced and deformed, being variously shrivelled and twisted, seldom connate, then only at tips, widely separated below. They seldom ascend more than 2/3 the length of the style, leaving stigmas well exposed in all flowers. Occasional anthers are adnate to the ovary, leading to protrusions and other defects of the mature fruit. In about 5% of the flowers a tinge of normal color appears on an anther, and in these regions a trace of pollen can be forced from the anthers. This condition might be comparable to the variable sterility of ms\5. Pollen of fertile appearance is produced by ms\30, and artificial selling resulted in the production of a low percentage fruits with seed. Sterility in this mutant likely results from the failure of normal pollen release from the anthers.
Seed yields following controlled pollination of these mutants appeared normal except for ms\29, which produced roughly 25% of normal.
For each mutant, all seeds that were naturally set on the original plants yielded fertile plants. Each mutant was recovered in later generations. Most of the progenies were small, but the nature of segregation, as summarized in the table below, is compatible with the assumption that a single recessive gene was responsible in each case.
Summary of segregations
_______________________________
F2 Backcross
___________ __________
Mutant Fert. ms Fert. ms
__________________________________________________
ms\25 8 3 19 25
m\s26 46 12
ms\27 18 16
30 26
ms\28 21 8
ms\29 17 10
ms\3O 25 5 17 10
ms\31 45 11
ms\32 43 14