Nuclear division and chromosome behavior during meiosis and ascosporogenesis in Pyricularia oryzae

Publisher Website
Google Scholar
Abstract
Meiosis and mitoses during ascosporogenesis in fertile mating strains of Pyricularia oryzae Cavara (teleomorph: Magnaporthe grisea) were studied using a propionic–iron–hematoxylin procedure which stained chromosomes, nucleolus, and spindle pole bodies. Meioses and mitoses in P. oryzae resembled those in other ascomycetes. Zygotene chromosomes were highly contracted followed by elongation at pachytene when close pairings of homologous chromosomes were observed. Nucleoli attained a maximum diameter of 3.8 μm during pachytene. Nucleolar growth was accompanied by a rapid growth of the ascus. Chromosome lengths varied among pachytene cells, with the longest chromosome averaging 8.5 and the smallest 2.9 μm. Telomeric knobs and chromomeres were discernible on fully extended pachytene chromosomes. Six chromosomes were observed at pachytene and diakinesis, and during metaphase of ascospore mitosis. Chromosome movement at meiotic and mitotic anaphase was asynchronous, resulting in lagging chromosomes. Electron microscopic observations revealed spindle pole bodies associated with profusion and early meiotic prophase nuclei. In pachytene nuclei, 50 nm wide structures resembling synaptonemal complexes were observed.