Cytology of Puccinia sorghi

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Abstract
Nuclear fusion in the cells of the teliospore of Puccinia sorghi Schw. terminates the dicaryotic phase of its life cycle. The diploid nucleus and associated cytoplasm move from the germinating spore into an elongating basidium. The nucleus enlarges and undergoes meiosis. Five pairs of chromosomes are present at diplotene and later stages of meiosis I. The chromosomes vary in length from 6-7[mu]. to 2.5[mu]. Chromosome 1, the longest, has a submedian centromere and bears a satellite on the short arm. The nucleolus is associated with the short arm. Chromosome 2 with two unequal arms is 6[mu]. in length. The 3 remaining chromosomes have median centromeres and vary in length from 5[mu] to 2.5[mu]. The chromosome pairs become regularly oriented on the metaphase-I plate and 5 more to each pole. Following the second meiotic division a linear row of 4 haploid nuclei is produced. Septation of the basidium occurs after each of the meiotic divisions, producing 4 cells. Development, maturation and ejection of the basidio-spores proceed in basipetal succession. The mature basidiospores, 9 to 14 x 7 to 11[mu] in size, are hyaline and thin-walled. The haploid nucleus divide mitotically prior to or at the time of basidiospore germination and both nuclei migrate into the germ tube. Five chromosomes are present at this mitosis. The meiotic divisions and subsequent mitoses are regular under optimal temperatures and moisture conditions.