| Research Abstract |
To give a stable fruit set and reduce labor for fruit thinning in European pear (Pyrus communis L.), we developed a CAPS marker system for S-genotyping cultivars and evaluated early fruit drop after cross-pollination.
Seventeen full-length cDNAs (Sa-, Sb-, Sc-, Sd-, Se-, Sg-, Sh-, Si-, Sk-, Si-, Sm-, Sn-, Sp-, Sq-, Sr-, Ss-, St-RNase) were cloned from stylar RNA of European pear cultivars using RACE cloning, and predicted to be typical Rosaceae S ribonucleases (S-RNases). Genomic PCR with a set of primer designed from these DNA sequences was successful to amplify 17 S-RNase alleles ; 1906 by (Sg), 1642 by (St), 1414 by (Sl), ca. 1.3 kb (Sk and Sq), 998 by (Se), 440 by (Sb) and ca. 350 by (Sa, Sc, Sd, Sh, Si, Sm, Sn, Sp, Sr and Ss). Among them, S-RNase alleles of similar size were discriminated by digestion with 11 restriction endonucleases. The PCR amplification of 17 S-RNase alleles following digestion with the restriction endonucleases provided a CAPS marker system for rapid S-genotyping of European pear cultivars. Using the CAPS system, 109 cultivars were assigned. The cultivars sharing the same S-genotype were cross-incompatible, revealing that there were many cross-incompatible combinations among European pear cultivars.
Pollination management based on S-genotypes provides a stable fruit set, but increased labor and time in fruit thinning. Fruit drop was initiated from 2 weeks after cross-pollinations in 'Le lectier', 'Aurora' and 'Starkrimson', which cultivars reduced the number of young fruits per flower cluster to about one fruit. Fruit quality of these cultivars is good without fruit thinning, indicating a possibility that early fruit drop is used to produce fruits.
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