Characterization of cytoplasmic male sterility in Petunia hybrida. I. Localization, composition and activity of esterases

Abstract

INDEX WORDSPetunia hybrida, petunia, cytoplasmic male sterility, esterase activity, esterase isoenzymes, histochemical analysis. SUMMARYAnthers of male fertile, cytosterile and restored male fertile clones of Petunia hybrida were compared for esterase activity and composition in subsequent stages of microsporogenesis. Three methods were applied (i) ultra-thin layer isoelectric focussing on polyacryl amide gels, (ii) quantitative spectrophotometricat assay, (iii) histochemical determination of total esterase activity associated to the azo-coupling method (PEARSE, 1972).In male fertile and restorer idiotypes the isozyme patterns were quite similar. Both the number and intensity of bands increased gradually till the tetrad stage. In contrast, esterase activity in cytosterile anthers remained at a low level and hardy any new bands showed up in later stages. This unvariable, low activity level in cytosterile anthers was also found in the spectrophotometric assay. Histochemical determinations revealed that in male fertile anthers esterase activity is concentrated in the outer tapetal layer at late prophase and that it accumulates there till the early microspore stage. In male sterile anthers esterase accumulation in the tapetal cells stops at the moment that tapetal breakdown becomes visible. This suggests that differences in esterase activity and composition are an effect rather than a cause of the failing pollen formation. GENERAL INTRODUCTIONAs yet cytoplasmic male sterility (CMS) is the most widely adopted tool for hybrid seed production. Male sterility is necessary to prevent the maternal line (seed line) from selfing or sibbing where hand emasculation is not feasible. Nevertheless, its application is limited by a number of severe drawbacks: (i)the non-availability of the cms characteristic in many crops and their wild relatives; (ii) the necessity of a time-consuming series ofbackcrossings to introduce cms in breeding stocks; (iii) the need for fertility restorer genes in seed or fruit producing hybrids; (iv) the complexity of seed production and maintenance of parental lines. Breeders are therefore looking for systems of artificial prevention of selfing which can be applied on call. In connection with this the 77 G. A. M. VAN MARREW1JK~ R. J. B1NO AND L. C. J. M. SUURS main attention has been directed at developing gamete killing chemicals (gametocides) such as maleic hydrazide, gibberellins, Ethrel (2-chloroethane phosphonic acid) and (sodium 2,3-dichloroisobutyrate). Wide scale use of gametocides has hitherto been impeded by serious shortcomings, of which female sterility and unreliable activity are the most notorious. Only in one single case (wheat) have hybrids, that were produced on the basis of gametocides, been released or have been put on trial (JENSEN, 1985).

Activity and isoenzyme composition of peroxidase and esterase in fertile and male-sterile lines of tomatoes (Lycopersicon esculentum Mill.)

“…In MS stamens it almost does not change its intensity and this might be an indication of the absence of pollen grains (Karim et al 1984). Absence of specific esterase isoenzymes, less isoenzymes or lower activity have been also found in CMS lines as compared to their fertile counterparts (Markova and Daskaloff 1976;Van Marrewijk et al 1986). The latter authors are of the opinion that changes in esterase activity and its molecular composition are the result of degeneration processes in tapetum.…”