Self incompatibility was investigated in the hexaploid garden chrysanthemum, a member of Compositae. Nine sibling clones selected from a highly compatible cross were all self incompatible. 14.8% of the crosses between these sibs in diallel were compatible, but one sib, 67-111-42, accounted for 10 of the 12 compatible crosses. 67-111-42 was also more compatible than the remaining 8 sibs in crosses to other closely related plants. Crosses of the 9 sibs to 12 unrelated tester clones indicated that none were male or female sterile. Inbreeding via pseudocompatibility was successful in increasing homozygosity at the S loci. The percentage of compatible crosses obtained in 3 sib diallels of I 2 clones from crosses of 67-111-42I 1 plants approached that of the original 9 × 9 diallel, but no one individual accounted for most of the compatible crosses. It was possible to separate the 9 sibs into 9 incompatibility patterns from the pollinations made in this study. The evidence suggests that the self-incompatibility reaction in the garden chrysanthemum is sporophytic and involves more than 1 locus.

A classification system for predicting high, medium and low seed set from Chrysanthemum morifolium crosses was developed. Stigmas collected and preserved 8 days after pollination were examined with a binocular microscope for adhering pollen grains. Florets from compatible crosses had brown stigmas with pollen grains attached and embryo development while florets from incompatible crosses had white stigmas with no or rarely 1 or 2 pollen grains attached and no embryo development. Using this method the occurrence of seed set was predicted with 78.5% accuracy in one year and 89% in the following. This provides a method of determining the compatibility of a chrysanthemum cross without waiting the 1 to 2 months required for seed ripening.

No abstract

Cycloheximide, a potent inhibitor of protein synthesis, placed in styles of Lilium longiflorum at 10(-4) M in stigmatic exudate before, 6, or 12 hr after compatible or incompatible pollination retarded all pollen tube growth. An inhibitor of RNA synthesis, 6-methylpurine, placed in the style at 10(-4) M in stigmatic exudate before, 6, or 12 hr after pollination restricted compatible pollen tube growth to lengths not significantly different thanincompatiblepollen tubes in treated or nontreated styles. While pollen tube growth in the style of L. longiflorum appears to require protein synthesis, only compatible pollen tube growth requires RNA synthesis. Stigmatic exudate proved to be an excellent carrier of exogenous substances into the style of L. longiflorum.

The exudate produced on the stigma of mature flowers of L. longiflorum Thunb. did not adversely affect pollen tube growth or the self-compatibility reaction when injected into lily styles before, 6, or 12 hr after pollination. Stigmatic exudate diluted with an equal volume of distilled water before addition to the style had no effect on pollen tube growth when injection occurred before or 6 hr after pollination. Although injection of exudate alone 24 hr after pollination or injection of diluted exudate 12 or 24 hr after pollination retarded pollen tube growth, the addition of exudate or diluted exudate did not obscure the self-incompatibility reaction. Stigmatic exudate appears to be an excellent milieu in which to carry exogenous materials into the environment of pollen tubes of L. longiflorum growing in vivo.