The Use of Dinitrocresol-Mineral Oil Sprays for the Control of Prolonged Rest in Apple Orchards

Summary

Pluots are putative hybrids between plums (Prunus salicina Lindl.) and apricots (P. armeniaca L.). The capability to distinguish among plum and pluot cultivars is important in breeding and cultivation. We investigated the genetic diversity among 14 plums, 6 pluots and one plumcot representing commercial cultivars in California, with 28 microsatellite markers. We also tested seven apricot cultivars as a reference to ®nd evidence of apricot in the ancestry of pluots and plumcot. The parental material used in the original cross that produced the pluot and plumcot was not available. Of the 28 SSR markers, 25 were from sweet cherry (Prunus avium L.) and three from peach (Prunus persica L.). Approximately 80% of the cherry primers generated ampli®cation products in plum and pluots, showing transportability between these Prunus species. One to eight putative alleles per locus were displayed by the tested SSRs in plums and pluots. In plum and pluot samples a total of 100 alleles were identi®ed with an average of 4.3 alleles per primer combination. The SSR markers were successfully used for the discrimination of all tested cultivars. In pluots, 76 alleles were found in which 63 (83%) were speci®cally coming from plum, 9 (12%) were common in plum, pluots and apricot while no allele in the pluots was observed that was contributed from apricot. In plumcot, 49 alleles were observed in which 25 (51%) were from plum, 18 (36%) were speci®cally from apricot and 6 (12%) were common in plum, plumcot and apricot. Relationships among the 28 plum, pluot and apricot cultivars were represented by a dendrogram, constructed on the basis of 168 SSR markers. The dendrogram showed the plums and pluots form a cluster distinct from the apricots, with pluot cultivars interspersed among plum cultivars and more closely related to plum than to apricot. Plumcot made a separate branch and was placed between the plum and apricot cluster. These results suggest that the SSR markers are valuable tools for identi®cation of cultivars and diversity analyses in plum.