Axnic cultures of rust fungi from the haploid state

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1. Axnic cultures of Puccinia coronata var. coronata and P.recondita f.sp.tritici were established by placing aseptic leaf segments with spermogonia originated from a single basidiospore infection on the artificial medium containing a 25 % concentration of Murashige & Skoog's minerals and vitamins, sucrose, Peptic peptone, Lab-lemco broth, and agar.2. Microscopic observation and measurement of DNA content of the nucleus in hyphal cells of the cultures showed that they were haploid and uninucleate.3. Pairs of 15 single-basidiospore cultures of P.coronata var. coronata were placed approximately 1 mm apart on the medium in all possible combinations. When the nuclear number of hyphal cells in a contact zone was investigated one month after confrontation, monokaryotic hyphae were observed in selfing combination. On the other hand, dikaryotic hyphae were observed in 90.5% of crossing combinations between different cultures. Two isolates are considered compatible if dikaryotic hyphae are present in the contact zone but are incompatible if dikaryotic hyphae are absent. The mating type of the fungus could be estimated by multiple-allelomorphic tetrapolar incompatibility controlled by the "A" and "B" incompatible factors.4. Spermogonia originated from a single basidiospore infection on a leaf of Berchemia racemosa were placed on 15 single-basidiospore cultures of P.coronata var. coronata. Aecia were produced on the leaf in 7 mating tests out of 45. Aeciospores produced in the aecia were capable of infectiong Calamagrostis arundinacea.