Abstract
The nuclear division in developing asci formed by hetrothallic mating within ragistrain of Pyricularia (5 combinations) is compared with that in the asci formed by inter-pathotype mating between either rice-strain (8 combinations) or weeping lovegrass-strain (3 combinations) and ragi-strain. Of the five nuclear divisions, the first two are meiotic, the third is a mitosis in which the four haploid nuclei give rise to eight, and the fourth and the fifth, also mitotic, occur after ascospore delimitation so that the mature spore comprises four uninucleate cells in all cases of mating combinations examined. Lagging chromosomes are observed in meiosis as well as in subsequent mitosis in developing ascus. The number of laggard is one or two per nucleus division. Pooled frequency of laggard-including division in inter-pathotype mating between rice-strain and ragi-strain is 76.7%. That is 13.8% in intra-pathotype mating within ragi-strain and 14.7% in inter-pathotype mating between weeping lovegrass-strain and ragi-strain. In some combinations between rice-strain and ragi-strain, reduced number of ascospores in an ascus, reduced number of cells in an ascospore, and anucleate cells are seen. The haploid number of chromosomes observed through the meiosis and mitoses is six in these strains of Pyricularia.
