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  • Author or Editor: Roberto Botta x
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Six polymorphic sequence-tagged microsatellite sites (STMSs) were used to characterize 65 accessions of old garden roses [OGRs (Rosa L. spp.)] from seven botanical sections and 13 horticultural groups. Aims of the study were to define the genetic profiles of accessions and to provide information useful for the classification and pedigree reconstruction of OGRs. In roses, a precise botanical classification is difficult due to repeated hybridization carried out in breeding; OGRs are classified in horticultural groups on the basis of their original parentage or of their morphological traits. A total of 82 alleles were detected at six loci. The number of alleles per locus ranged from six to 21, with an average of 13.7 alleles per locus. A dendrogram was constructed by cluster analysis, displaying the relative genetic similarities between species' accessions, hybrids, and cultivars. Cluster analysis grouped the genotypes into seven major clusters that were substantially consistent with their classification into botanical sections and horticultural groups. Several hypotheses of apportionment of accessions to horticultural groups were evaluated on the basis of the relative position in the dendrogram of the analyzed individuals. Results demonstrated that DNA analyses can contribute to drawing the botanic classification of rose accessions, improving the genetic knowledge on the background of modern rose, and providing the basis for breeding programs.

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In Spain, hazelnut is mainly cultivated in Catalonia, a region in the northeast. The province of Tarragona accounts for 88% of the total Spanish area planted to hazelnut. Almost 80% of the production in Tarragona is of the local cultivar Negret, with others cultivated to a lesser extent. Minor cultivars are only sporadically present in older orchards, farm yards and gardens, and have been collected for preservation. In this work, 16 SSR markers were used to fingerprint 18 minor hazelnut cultivars from northeastern Spain. Their microsatellite profiles were combined with those of 15 Spanish cultivars characterized in a previous work, and used to study the genetic diversity in 33 genotypes including local Spanish germplasm. The SSR analysis allowed development of unique profiles of each of the 18 cultivars, and no new case of synonymy was detected. A high level of genetic diversity (mean H e = 0.7) was observed in 33 genotypes, although a high number of them showed a close genetic relationship. The dendrogram generated by UPGMA cluster analysis placed the 33 accessions into nine main groups, related to their putative pedigrees or geographical area of cultivation. All investigated Negret-type cultivars were found to be distinct from Negret, and only a few cultivars within this germplasm appeared to be seedlings of Negret. The results will be useful in the conservation of hazelnut germplasm and in the selection of parents for use in breeding.

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Floral biology of chestnut, from sporogenesis to mature embryo, is described. Microsporogenesis in flowers of unisexual catkins occurred in the first week of June 1991. Anthesis started in mid-June (≈70 days after budbreak) and lasted 2 weeks. In mid-June, in each pistillate flower, six to eight styles began to emerge, and 4 to 7 days later, they were extended fully (i.e., full bloom). In each flower, 10 to 16 anatropous ovules developed from the ovary axis. The megaspore mother cell had formed by the end of bloom. The mature ovule consisted of two integuments and a long, narrow nucellus with a small embryo sac of the Polygonum type. Zygotes were found 15 to 20 days after pistillate flower full bloom. Embryo development followed the Onagrad type, Trifolium variation. Seeds attained full size in mid-September, and fruit were mature in early November. The embryonal axis averaged 4.5 mm long × 2.1 mm wide. An apical meristem and the radicle were evident at opposite ends of the axis.

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‘Tonda gentile delle Langhe’ hazelnut bloomed from 22 Dec. to 19 Jan. Fertilization occurred about 5 months later, in the last 10 days of May. In the first days of June, the embryo was globular whereas the free nuclear endosperm had started to become cellular. Around the middle of June the embryo was heart-shaped and the endosperm was entirely cellular. In the following 2 weeks, the endosperm became vacuolated and then disintegrated. Cotyledons formed (torpedo stage) and grew quickly, filling the ovule by the end of June. The seed had its final shape and dimension by 20 July, but the embryonal axis continued elongating until nut maturity, 15 to 30 Aug. Mature embryos contained six to eight leaf primordia, the apical meristem, and the radicle.

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