Dempsey, Wesley H.
Pollen aged for four and 13 months (stored and applied as described in TGC 10:14) was used to produce 69 plants which vere carefully screened for possible mutations. Only four plants were obviously mutants as judged by leaf and flower characteristics. Pollen staining tests of these four gave the following percentages of good pollen: 100, 50, 10, and 0. Further tests will be carried out with these plants to determine their genetic and cytological nature.
When pollen staining tests were made on the remaining plants, 16 showed between 0 and 50% good pollen while 49 were normal (90 to 100% good pollen). Staining was repeated at weekly to monthly intervals for six months to make certain these readings were accurate, but few changes were noted. Also, 50 control plants produced by the same female parents (but with fresh pollen) were screened for pollen sterility; however, all of these were normal.
In a smaller test the previous year using pollen stored five months, only one plant out of 23 showed reduced pollen production (50%). No morphological differences were detected among the group. Selfed progeny from the semisterile plant unaccountably segregated 2:1 (37:22) for normal vs. semisterile. Progeny tests of the new semisteriles will perhaps give a clearer picture of the mode of inheritance than this group did.
These results suggest that care should be taken in using stored pollen. Semisterility could reduce the value of F1 commercial hybrids or upset a genetic investigation. Perhaps storage over CaCl\2 at 0 deg. F or even colder temperatures would be more satisfactory for keeping pollen free from mutations. As for the induction of genetically useful mutations, aging does not appear at this time to be as valuable a technique as radiation.