Cytology of Carica papaya x C. cauliflora interspecific hybrids
1997
Geronimo, S.B. | Sierra, Z.N. | Villegas, V.N. (Philippines Univ. Los Banos, College, Laguna (Philippines). Dept. of Horticulture)
The chromosome behavior during microsporogenesis in Carica papaya and C. cauliflora and their specific hybrids was studied to elucidate the observed sterility in the interspecific hybrids. Meiosis in the parents was normal. The chromosomes showed regular pairing into nine bivalents at diakinesis and separated synchronously to each pole. At telophase 2, tetrads of uniform size were generally produced. The chromosome number in both parents was consistent at 2n=18. Pollen fertility score was high, ranging from 81-98 percent and 91-97 percent in C. papaya and C. cauliflora, respectively. The interspecific hybrids exhibited meiotic irregularities during microsporogenesis. Univalents, chromosome elimination, and clumping of chromosomes were observed at diakinesis. In subsequent stages, chromosomal aberrations such as laggards, bridges and fragment formation, late and non-congression or early disjunction of bivalents, asynchrony, divergent spindle, and polyspory were found. Unequal distribution of chromosomes were evident even at anaphase 1. The frequent occurrence of these abnormalities suggests their positive correlation to the fertility status of pollen grains. Pollen fertility count was very low in all interspecific hybrids, at 0.0-1.3 percent
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