Studies on the phytohormone in the malformed portion of the diseased plants. 9. Metabolic production of indole-acetic acid in the culture of Taphrina deformans and 3 species of fungi causing witches'-broom.

Abstract

In the previous reports the present writer stated that the free-auxin in the tissues of abnormal galls, tumors and blisters caused by Protomyces, Albugo, Exobasidium, rust and sumt fungi was contained in much quantity compared with that of the healthy tissues, and reported on the condition of free-auxin in the tissue and also on the auxin formation in the tissue of Brassica napus infested with Albugo candida. The present article deals with experimental studies on the auxin formation by using the cultures of 15 species of Exobasidium, 5 species of Taphrina and 8 species of Ustilago as indicated in Table 1. The results obtained are summarized as follows. The material fungi were all cultured for 15 -30 days at 23°C. The filtrates of liquid media in which the fungi were grown were concentrated to one tenths at 40°C., and 10 agar pieces of 1×2×2mm. in size were immersed into the filtrates. On the other hand an agar block of 10×6×8mm. in size was cut off from the bottom of the solid culture medium in the test tube, and the contained auxin was made to diffuse on an agar plate (1×6×8mm.) by putting the block upright on it. The quantity of the auxin contained in these materials was measured by applying the Went's Avena-coleoptile method. The experimental results on the auxin formation of the organisms on sucrose-potato medium are given in Table 2. When they were cultured for 15 days on liquid media, they produced larger quantity of auxin than those cultured for 30 days, and the latter frequently showed plus-curvature in the case of Avena-coleoptile test. When the culture was done for 15 days on Czapek's medium containing KNO3 as nitrogen source for the nutriment, several fungi slightly produced auxin as shown in Table 3, and the filtrates of these cultures sometimes slightly showed Gordon and Weber's IAA color reaction, but the growth rate and the auxin formation of the fungi were much less than those in the case of the potato media. The growth rate of the fungi on Czapek's media containing L-tryptophane in substitution for KNO3 was much better than those in the cases of the media described above, and showed deep brown color. In this case every fungi produced auxin in much quantity as shown in Table 3, and the concentrated filtrates positively showed Gordon and Weber's IAA reaction, especially in the cases of the media on which gall- or tumor-fungi were cultured. This fact seems to the writer that these fungi have the ability of producing indole acetic acid. Wolf already demonstrated that Exobasidium gracile and Ustilago zeae produced indol acetic acid on L-tryptophane media. The similar results were also obtained by the writer. On the Czapek's medium containing KNO3, however, several fungi produced auxin in some quantity, and this data was shown to be contrary to the result obtained by Wolf. In the present experiments of the writer it was shown that Ustilago nuda and U. tritici produced auxin in large quantity, and this fact may give some hint on the physiology of parasitism of these fungi.