Estimation of the Degree of the Natural Self-Fertilization by the Frequencies of Chlorophyllous Variants in Japanese Red Pines, <i>Pinus densiflora</i> SIEB. et ZUCC., and the Inheritance of the Variants

The degree of natural self-fertilization was estimated by the frequencies of chlorophyllous variants derived from open pollinated seeds in Japanese red pines, Pinus densiflora Sieb. et Zucc. The variants from each individuals in five variant groups are thought to be inherited with each single recessive gene after crossing experiment respectively. The variants are as follows:<br> (1) Albino: White seedlings. Some of them have pinky hypocotyl. They are lethal (Photo. 1).<br> (2) Yellow seedlings: Yellow to yellowish green seedlings. Under natural field conditions, most of them die within one year after germination. Survived seedlings. (from a tree, OK-16) have light green needles in summer, and they change color to golden yellow in winter. The seedlings show marked retardation in height growth.<br> (3) Light green seedlings (LG): Cotyledons and hypocotyl are light green. The seedlings seem to be lethal in the field (Photo. 3).<br> (4) Seedlings with white primary leaves (WPL): Cotyledons and hypocotyl are normal green, but primary leaves are white to yellowish white. Two to three months after germination, the white primary leaves develop into normal green. Height growth of the variants is inferior to the control (Photo. 2, 3).<br> (5) Transient albino: Just after germination, the seedlings have purely pinky hypocotyl and yellowish white cotyledons. Soon, they recover to yellowish green, then to normal green.<br> Out of 320 individuals investigated from 3 pine stands (cf. Table 1), 22 individuals (6.87%) are expected to be heterozygous for the recessive genes mentioned above, and the ratios of the heterozygous individuals for respective genes are as follows: albino-2.50%, LG-2.50%, WPL-1.25%, yellow seedlings-0.31 and transient albino-0.31%/.<br> As these ratios were estimated from pooled population of 3 stands with individually open pollinated seeds by, mostly, one trial in 1963, they might be lower estimated.<br> Fifty six observed percentages of the chlorophyllous variants in each open pollinated progeny during 1961 and 1966 ranged to 0 to 6.0%. They showed a distribution with a mean of 0.97% and a standard deviation of 1.39%. As the most of the variants being homozygous for the recessive gene are lethal, the gene frequency (P), rate of self-fertilization (S) and frequency of the variants (F) under random mating in a population satisfy the following equation: F=¹/₄S+¹/₂P(1-S). Thus, S=^2F-P/_0.5-P. If P is sufficiently small to zero as in the cases of the yellow seedlings and the transient albino in this report, S may be estimated by S=4F.<br> The degrees of natural self-fertilization for yellow seedlings and for the transient albino were estimated to be about 11% and 2% respectively. The maximum range of the degreeof natural self-fertilization of these pines were 0 to 24%. Meanwhile, average degrees of the selfing are as follows: WPL-2.0%, albino-1.4% and LG-0.0%.<br> Although the degrees of natural self-fertilization of pines in stands are variable by individuals and years owing to the gene frequency concerned, amount of flowers of both sexes, degree of self-compatibility etc., the average degree of the selfing seems to be less than 5%.