S2 Progeny of Japanese Pear (Pyrus pyrifolia Nakai) 'Osa Nijisseiki' Having Self-compatibility and Their Homozygosity Estimated By SSR Analysis

In pear, any self-pollinated progeny are difficult to produce because they have self-incompatibility.  Using a self-compatible cultivar ‘Osa Nijisseiki’ with a mutation about the style phenotype, we produced self-pollinated progeny of Japanese pear (Pyrus pyrifolia Nakai) in this experiment.  Twenty-eight seeds were obtained by self-pollination of S₁ cultivar ‘Nou 1 gou’.  Twenty-two seedlings were germinated and established in the field.  All seedlings were inspected such as true S₂ progenies about 42 SSR loci on a reference map of ‘Housui’ (Terakami et al, 2009).  Their homozygosity (No. of locus as homozygote / No. of locus scored) estimated by the 42 loci were varied among 0.69 to 0.82 higher than 0.64 in ‘Nou 1 gou’ and 0.24 of ‘Osa Nijisseiki’.  The negative correlation observed between the homozygosity and plant height in S₂ individuals in first year reflected a negative effect of the homogeneity on their growth.  We concluded that the S₂ progeny was valuable for the genomic research such as the recessive gene effects in pear.