IV. Studies in the genera cytosporina , Phomopsis , and Diaporthe. VI. - On the conversion of one strain of Diaporthe perniciosa into another

Abstract

An account of saltation in the older parts of cultures of Diaporthe perniciosa strain DH C was given in an earlier paper (Horne and Das Gupta , 1929). The main features of this saltation were its occurrence in every cultural generation at a definite age ; the gradual transformation of the whole parent mycelium into the saltant DH F ; the absence of visible indications of saltation in the body of the parent culture ; and the inability of the saltant, which spreads relatively fast in fresh medium, to outgrow the slow-growing parent. While attempting to discover if there were any change with age in the nature of the branching of DH C hyphae concomitant with the appearance of saltation, it was found that viable hyphal tips from the advancing mycelium of DH C usually develop into DH F . Very minute fragments of older mycelium were also found to give rise to DH F when grown in fresh medium. Hence there was the possibility that DH C might be an intimate association of hyphae of two different characters DH C and DH F , with the DH C dominating the form of growth of the latter. It was therefore thought advisable to make a careful study of the behaviour of DH C and DH F in both separate and associated culture. Preliminary experiments with individual cultures of DH F showed that inocula taken from all parts usually bred true. On occasions, however, some inocula developed as mixed growth of the DH C and DH F , but no relation could be observed between the nature and position of inoculum and the occurrence of mixed growth. Attention was therefore devoted to the DH C culture. The results presented in this paper relate chiefly to the behaviour of DH C and the effect of inoculating DH F with DH C mycelium.