Inhibitors of cyanide-insensitive respiratory pathway induce male sterility in broccoli (Brassica oleracea)

We have found that inhibitors of the cyanide-insensitive respiratory pathway induce male sterility in Broccoli (Brassica oleracea L. cv. De Cicco). All three major specific inhibitors; salicylhydroxamic acid (SHAM), propyl gallate and disulfiram (tetraethylthiuram disulfide), were effective in inducing male sterility whenever they were applied to the flower buds with anthers less than about 2mm in length, which those pollen developing stages corresponded to be earlier than early microspore stage. These chemlcally induced male sterile flowers which were characterized by shorter filaments and a reduction in the number of total and fertile pollen grains per flower, were similar to the cytoplasmic male sterile flowers. However, when pollinated with normal pollen, the percentage of seed-setting in the chemically induced male sterile flowers decreased considerably in comparison with that in the cytoplasmic male sterile flowers. All the progeny plants derived from the male sterillty (female) × normal pollen grains showed male fertility. Morphological characters of the progeny plants were very similar to those of normal Broccoli. Although the physiological sign{ficance of the cyanide-insensitive respiratory pathway remains unknown, some physiological pathways, such as the alternative pathway may be associated with male sterility in Brassica species.