Dr. Wolfgang Langner produced S|'s of Japanese larch {Larix leptolepis (Sieb. 5 



Zucc. ) Gord.) in Germany from self-pollinations made in 1936. Later, Langner (1961) 



reported upon second-year height of S2's coming from these Si's, and on related prog- 

 enies, as shown below. 



Outcrosses Half-sibs Full-sibs ^2 's 



Inbreeding coefficient (F) 0.000 0.125 0.250 ^Q.yso 



Average height (cm) 37.3 32.7 29.7 24.7 



Just a few years later in 1938 and 1941, Dr. C. Syrach Larsen also selfed Japanese 

 larch, as well as European larch {Larix deoidua Mill.). Later, Keiding (1962) crossed 

 the Japanese and European larch S^'s, noting that the single cross interspecies hybrids 

 produced outgrew the parents. Effects of inbreeding within species could not be sepa- 

 rated, however, from effects of interspecies hybridization: Keiding stated, "It was 

 not possible to prove any additional effects of inbreeding and outcrossing." 



The next oldest material is that of Orr-Ewing (1954, 1965, 1969). Self-pollinations 

 of Douglas-fir {Pseudotsuga menziesii (Mirb.) Franco) parental trees were begun in 1952, 

 and continued through 1968. Within 8 to 10 years about one-third of the S^ trees in 

 seven out of eight Si families (1 to 98 trees per line) were producing an average of 

 10 to 14 female strobili per tree (Orr-Ewing 1965). In the same time. Si's in only three 

 of the eight families produced male strobili. Amounts of pollen ranged from inadequate 

 for a single pollination to enough for four or more pollinations. Outcrossed sibs of 

 the same parent trees had almost twice as many sporophylls per male strobilus, but 

 pollens of Si's or outcrossed sibs were indistinguishable. Orr-Ewing (1965) went on to 

 show that on the average about half of the filled S2 seed germinated (here in eight 

 S2 lines), and finally, that the average first-year height of S2 seedlings in six lines 

 varied between 27 and 59 mm. Many Si backcrosses. Si sib crosses, and two single crosses 

 were also reported upon. Cone and seed yields of the S2 and these crosses also are 

 given in "Discussion," starting on page 12, Orr-Ewing (1969) reinforced his earlier 

 finding of variability in average height of 1-year-old S2 seedling families (range 79 

 to 158 mm). His general conclusions (Orr-Ewing 1954, 1965, 1969) were that in Douglas- 

 fir, inbreeding would be sufficiently rapid and easy to be entirely feasible, and that 

 variation in inbreds was great enough so that an inbreeding program probably would be 

 rewarding. Some of the single-cross progenies looked quite promising, and selection 

 among Si's would have had pronounced effects on single cross seedlings. Unfortunately, 

 no control (outcrossed) seedlings were compared with the single cross seedlings. 



The youngest material reported upon is that of Katsuta (1966), who began selfing 

 Japanese black pine (Pinus thunbergiana Franco) and the Japanese red pine {Pinus 

 densi flora Sieb. and Zucc.) in 1956. Within 7 to 8 years. Si trees of Japanese black 

 pine were fruiting so that S2's and Si sib crosses. Si backcrosses, and single crosses 

 could be attempted. Cone and seed yield from these second-generation inbred crossings 

 also are given in "Discussion," starting on page 12. Apparently second-generation in- 

 bred seeds were not sown. Katsuta remarked that S2 seed yields were "considerably high." 



Useful comparisons have been made of the association of certain characteristics 

 with increasing inbreeding coefficient F. Langner (1961) showed a decrease of about 

 5 percent in height of 2-year-old Japanese larches, and Squillace and Kraus (1962) 

 showed decreases of five seed per cone and 8 percent in germination in 1-year-old 

 slash pine (Pinus elliottii var. elliottii Engelm.), for each 0.1 increase in F. 



Given by Langner as 0.625. 



4 



