Cytogenetics of coconut (Cocos nucifera Linn.) varieties catigan green dwarf (CAT) and Laguna tall (Lag) and their F1 hybrid
1996
Tudor, Ma. F.V.A. | Laude, R.P. (Philippines Univ. Los Banos, College, Laguna (Philippines). Inst. of Biological Sciences)
Cytogenetic investigation of the root tips and staminate inflorescences (fixed 1 1:2:1 v/v chloroform - ethanol - acetic acid solution and stained in acetocarmine) at CAT, LAG and their F1 hybrid revealed a diploid (2n) chromosome number of 32 (16 11). Root tip mitosis in CAT, LAG and their F1 hybrid were normal. Mitotic indices were relatively low: 2.36 percent, 2.50 percent, and 2.32 percent, respectively. Small chromosomes were either nearly median (NM) or nearly submedian minus (NSM(-)). Chromosomes with secondary constrictions were hardly identified due to variation in contraction. Relative lengths of the chromosomes ranged from 0.39 to 1.0 in CAT, 0.43 to 1.0 in LAG and 0.37 to 1.0 in the F1 hybrid. Karyotypic formulas of the coconut plantations were: 14 NM + 2 NSM(-) for CAT: 14 NM + 2 NSM(-) for LAG; and 16 NM for the F1 hybrid. Normal diakinetic chromosomes assumed bivalent as well as univalent configurations. Other unusual configuration such as early disjunction and laggards were noted in meiosis 1 while asynchronous behavior of daughter nuclei were noted in Meiosis 2. The three populations proceeded to similar normal stages of meiotic divisions which favored the formation of normal gametes and the production of fertile pollen grains. Pollen fertility were recorded at 94.96 percent in CAT, 94.66 percent in LAG and 94.84 percent in the F1 hybrid. Similarity in gross karyomorphology of CAT and LAG confirmed high homology in their genome. This could also explain the occurrence of regular bivalents (16 11), normal chromosome behavior in meiosis 1 and 2 and high pollen fertility in their F1 hybrid
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