Studies of Ethephon as a Possible Selective Male Gametocide on Tef
1978
Berhe, Tareke | Miller, Dwane G.
The gametocidal effect of ethephon (2-chloroethyl phosphonic acid) was studied in two varieties of tef [Eragrostts tef (Zucc.) Trotter] ‘DZ-01-99’ and ‘DZ-01-186’. Foliar applications of 600, 900, and 1,200 ppm were applied three times during heading. The primary objective was to investigate if ethe~phon could be used as a substitute for hand emasculation in tef, therefore alleviating the floral sensitivity problem associated with hand manipulation of florets. All rates of ethephone reduced seed set. The lowest seed set reduction (33%) was obtained from one 600 ppm application and the highest (74%) from three 1,200 ppm applications. Reduction in seed set was not altered by artificial pollination of florets after chemical treatment. Phytotoxicity due to ethephon spray was minimal. The gametocidal effect of ethephon on male gametogenesis was first noted at the free microspore stage. Development of microspores was arrested. When pollen grains developed, they were malformed and stained poorly. In some cases, the pollen grains or anthers aborted completely. Histological studies of ethephon-treated florets revealed that embryo sac development was not affected up to the time of fertilization. However, soon after the megagametophyte matured into the eight-nucleate stage and at about the time of fertilization, ovary and ovular tissue in sterelized florets underwent premature desiccation and collapse. It is assumed that this response led to female sterility since ethephon-sterilized florets yielded no seed. Therefore, ethephon seems unsuitable for use in tel breeding. However, since conventional emasculation and pollination techniques also have not yielded hybrid seed, the induced sterility cannot be ascribed entirely to chemical application.
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