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With 3 figures and 3 tables Previous studies have demonstrated that genotypes of PpACS1 and PpACS2 genes are associated with certain levels of ethylene production in Japanese pears ( Pyrus pyrifolia Nakai). This study was undertaken to examine further the relationships of PpACS1 and PpACS2 genotypes and internal ethylene concentration (IEC) with fruit firmness/softening in both European ( P. communis L.) and Japanese pears ( P. pyrifolia Nakai). Our data showed that P.  communis L. lacked genotypes ‘AB’/‘Ab’ and ‘aB’, for high and medium IEC respectively, irrespective of high levels of IEC found in the European pear cultivars/selections. PpACS1 and PpACS2 genotypes were related to IEC at 20 days after harvest (DAH) in P. pyrifolia Nakai but IEC did not have any significant relationship with fruit firmness at 50DAH in either P. communis L. or P. pyrifolia Nakai . Harvest firmness was a better predictor of postharvest firmness than IEC across both species and genotypes, explaining 46% of the variation in fruit firmness at 50DAH. We recommend breeding for higher harvest firmness within low ethylene cultivars in order to extend the shelf life/storage potential of Japanese pears. [ABSTRACT FROM AUTHOR]

Identification of apple clonal rootstocks based on visual morphological characteristics is often difficult because of the genetic similarity of many rootstocks and the restriction of observable characteristics at the nursery stage. In this study, a total of 66 rootstock clones representing a sub-sample of a collection of apple rootstocks from different countries maintained at NIFTS, Morioka, Japan, was screened with seven simple sequence repeat (SSR) markers to establish genetic identities, estimate genetic diversity, verify parentage and examine genetic relationships. All seven SSR loci produced one or two amplified fragments and made it possible to differentiate among the rootstocks, except between virus-free subclones and their original parents as well as between‘Aotea 40’ and‘Aotea 106’. The parentage of all but one rootstock clone was confirmed. The placement of individual rootstock clones into subgroups in a phenogram generated from un-weighted pair group average cluster analysis was generally based on parentage or genetic origin. Based upon the ability of the SSR data to differentiate these apple rootstocks and the high level of gene diversity, it is proposed that all commercial apple rootstocks be fingerprinted to provide a mechanism to verify the identity of individual clones. [ABSTRACT FROM AUTHOR]