Action of Manganous Chloride on Induced Somatic Segregation in Penicillium Chrysogenum Diploids.

ITROGEN mustard (HN-2), at doses which bring about almost total inactiNvation of the treated conidia, has a powerful stimulating effect on somatic segregation in some heterozygous Penicillium chrysogenum diploids (MORPURGO and SERMONTI 1959). On plating the surviving conidia, color marker segregants appear as yellow or white entire colonies, or yellow or white sectors emerging from the green phenotype of the heterozygous diploid colonies. The color of the colonies and sectors is due to the color of the conidia which they produce. Some colonies with colored sectors obtained after HN-2 treatment give rise to clones whose conidia produce colonies almost all of which show sectors segregant for color. Each one of these “unstable” clones displays its own individual segregation pattern ( MORPURGO and SERMONTI 1959). Similar unstable clones have been obtained from X-ray irradiated conidia. The inactivation produced by HN-2 is strongly reversed by the action of manganous chloride (MnC1,) added to the plating medium; however, this salt has no reactivating effect on conidia inactivated by X-ray irradiation ( SERMONTI and MORPURGO 1958). The object of the present research was to establish the effect of MnC1, on the somatic segregation processes induced directly or indirectly by HN-2. Some further experiments concern the same problem in connection with X-ray-induced segregation.