The genotyping of European fruit tree collections has helped to identify synonyms, determine parentage, reveal key specimens in the collections and provide information on the development of modern cultivars from one or several progenitors. However, studies on European plum Prunus domestica have been lagging behind, mainly because of the hexaploid chromosome number. In this co-operative study, 104 accessions conserved by 14 partners across Europe were phenotyped for 20 descriptors, and genotyped for 8 SSR loci together with 8 reference cultivars. Based on the descriptors as well as additional information supplied by the partners, as well as the scientific and horticultural literature, each accession was assigned to one of six pomological groups; (1) egg plums sensu lato (E), (2) prunes of the French d'Agen type (P/A), (3) prunes of the Central-Southeast European Zwetschen type (P/Z), ( 4) greengages (G), ( 5) mirabelles (M) and ( 6) bullaces, damsons and var. pomariorum (D/B). A MANOVA conducted on descriptor data revealed significant differentiation among the pomological groups as well as a ManuscriptClick here to access/download;Manuscript;Revised Manuscript 2020.docx Click here to view linked References 2 geographic impact on the differentiation of local plum accessions in Europe. SSR data showed that two trios and seven pairs of genotypes had very similar allele profiles and possibly are genetically identical in spite of different accession names. An AMOVA indicated sparse genetic differentiation when accessions were grouped according to geographic origin whereas significant differences were obtained among pomological groups. A Bayesian analysis of genetic structure, as well as a discriminant analysis of principal components (DAPC), further revealed levels of similarity among and within the different pomological groups, suggesting that egg plums sensu lato (E) and greengages (G) can be referred to subsp. domestica while damsons and bullaces (D/B) but also Central-Southeast European prunes (P/Z) show more affinity to subsp. insititia. The small and possibly heterogeneous groups with mirabelles (M) and prunes of the d'Agen type (P/A) take an intermediate position suggesting a hybridogenic origin.

Based on a protocol for microspore culture in apple ( Malus domestica Borkh.), the embryo induction phase has been improved with regard to pretreatment of microspores for initiation of microspore embryogenesis, the concentration of carbon source in the induction medium and the microspore density in the suspension. Furthermore, the effect of the genotype was studied. To determine the efficiency of in vitro androgenesis, both methods, via anther and microspore culture, were investigated using the same bud material. A comparison of the efficiency of embryo induction in anther and microspore cultures showed that microspore culture resulted in an increase up to 10 times, depending on the genotype. The regeneration route in microspore culture is similar to that of androgenic embryos via anther culture and showed adventitious shoot formation in most cases after a long period of secondary embryogenesis.

No abstract

To break the juvenile stage of apple (Malus x domestica Borkh.) we transferred the LFY gene of Arabidopsis into the genome of the apple cv. 'Pinova'. A total of five transgenic clones constitutively overexpressing the LFY gene were obtained. Approximately, 20 shoots of each clone were rooted and transferred to the glasshouse. No flowers were obtained on transgenic plants during the first 2 years of cultivation. Evaluation of the expression of possible LFY targets revealed that no transcripts could be detected for MdAP1-1 and MdAP1-2. MdTFL1 was unaffected. Based on the absence of the LFY core-binding sequence within promoter sequences of MdAP1-1 and MdAP1-2, it was concluded that LFY was not able to induce these genes. The LFY genes of apple were unaffected in transgenic plants and sequence alignments of the C-terminal amino acid sequence showed a high conservation of these proteins. A change in binding ability to DNA can therefore be excluded. Instead of early flowering, the transgenic plants showed an altered phenotype, which is similar to the columnar phenotype of the 'McIntosh Wijcik' mutant of apple. The transgenic plants showed shortened internodes and a significantly reduced length of the regrowing shoot. A negative correlation was observed between the length of the regrowing shoot and the LFY mRNA transcript level. Furthermore, the LFY transgenic apple plants showed an increased shoot diameter at node 20, which was positively correlated with the LFY mRNA transcript level. Based on our results, we assume an alternative role of LFY in apple.

The grey mould disease caused by Botrytis cinerea leads to substantial economic losses in strawberry production all over the world. Control of the disease requires an extensive amount of fungicide that is applied in varying complexes because the pathogen easily develops resistance against the active compounds. Planting of resistant cultivars seems to be a promising alternative for fruit growers, but there are currently no cultivars available combining resistance to B. cinerea with attractive horticultural traits. Breeding of new cultivars requires the effective identification of resistant strawberry genotypes; therefore the current study was aimed at the evaluation of strawberry genetic resources under controlled conditions by establishing an artificial inoculation assay. The method presented in this study is an artificial inoculation of ripe fruits with a defined spore suspension under laboratory conditions. The results show that this assay is fast and simple and leads to reproducible results that correlate with field observations. Over 3 years a total of 107 strawberry genotypes of the German National Fruit Genebank at the JKI in Dresden‐Pillnitz were evaluated. Five partly resistant genotypes, cultivars Diana, Joerica and Kimberly, and Fragaria virginiana ‘Wildmare Creek’ and F. vesca subsp. bracteata, were identified with mean disease levels of <20% at 6 days post‐inoculation. The obtained results are discussed with regard to future breeding activities.