Breeding of apple is a long-term and costly process due to the time and space requirements for screening selection candidates. Genomics-assisted breeding utilizes genomic and phenotypic information to increase the selection efficiency in breeding programs, and measurements of phenotypes in different environments can facilitate the application of the approach under various climatic conditions. Here we present an apple reference population: the apple REFPOP, a large collection formed of 534 genotypes planted in six European countries, as a unique tool to accelerate apple breeding. The population consisted of 269 accessions and 265 progeny from 27 parental combinations, representing the diversity in cultivated apple and current European breeding material, respectively. A high-density genome-wide dataset of 303,239 SNPs was produced as a combined output of two SNP arrays of different densities using marker imputation with an imputation accuracy of 0.95. Based on the genotypic data, linkage disequilibrium was low and population structure was weak. Two well-studied phenological traits of horticultural importance were measured. We found marker–trait associations in several previously identified genomic regions and maximum predictive abilities of 0.57 and 0.75 for floral emergence and harvest date, respectively. With decreasing SNP density, the detection of significant marker–trait associations varied depending on trait architecture. Regardless of the trait, 10,000 SNPs sufficed to maximize genomic prediction ability. We confirm the suitability of the apple REFPOP design for genomics-assisted breeding, especially for breeding programs using related germplasm, and emphasize the advantages of a coordinated and multinational effort for customizing apple breeding methods in the genomics era.

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Vegetatively propagated plants of three strawberry cultivars-'Senga Sengana', 'Elsanta' and 'Kent'-were grown for 20 weeks in rhizoboxes filled with 1.85 kg of sterilized mineral soil. Ten plants were treated with an N-P-K foliar fertilizer (F, control), or inoculated with a substrate containing arbuscular mycorrhizal fungi, Trichoderma viride and rhizosphere bacteria (PGPR-Plant Growth Promoting Rhizobacteria) without any fertilization (M), or inoculated with the mixture of microorganisms and treated with the foliar fertilizer (MF). Total plant biomass was increased by the M treatment in all cultivars. M treatment resulted in Eligio Malusa is Researcher, CRA-higher total root length and number of root tips in 'Senga Sengana', whereas the other two cultivars showed different responses of root morphology. Shoot/root ratio was decreased by the M and MF treatments in comparison with control plants. Foliar fertilization of inoculated plants caused different growth responses in the three cultivars and a general decrease of root growth. After the MF treatment, the biomass of 'Senga Sengana' increased and the biomass of 'Elsanta' and 'Kent' decreased. Inoculation with the mycorrhiza-PGPR substrate increased rhizosphere pH irrespective of foliar fertilization. Plant mineral content was highly modified by the treatments in all the cultivars examined. In particular, changes were noted in N, P, K, Fe, B and Mn uptake. The results show an interaction between foliar fertilization and root inoculation with microorganisms, as well as genotype-dependent influences, on growth responses and rhizosphere pH of strawberry plants.

Two PCR-based techniques, RAPD and ISSR, were utilized for determination of genetic relationship of 24 strawberry cultivars used in breeding program at the Research Institute of Pomology and Floriculture in Poland. Polymorphism of investigated genotypes was observed in reactions with 23 out of 48 tested RAPD primes and 41 from 90 tested ISSR primers. Relationship, determined on the base of polymorphic products analysis and showed in the form of dendrograms (UPGMA percent method), was generally similar for both techniques, although similarity values based on ISSR data were higher than those based on RAPD. The parallel use of two data sets seems to allow for precise estimation of cultivars relationship and diminishing mistakes connected with methods' technical limitations.Abbreviations: ISSR -inter simple sequence repeat; RAPD -randomly amplified polymorphic DNA; UPGMA -unweighted pair group method using arithmetic average

Szymajda M., Pruski, K., Żurawicz, E. and Sitarek, M. 2013. Freezing injuries to flower buds and their influence on yield of apricot ( Prunus armeniaca L.) and peach ( Prunus persica L.). Can. J. Plant Sci. 93: 191–198. Each spring, for 3 consecutive years, 2009–2011, the degree of freezing injury to overwintering flower buds of selected cultivars and clones of apricot and peach was evaluated at the Dąbrowice Research Institute of the Horticulture E$xperimental Orchard (District of Skierniewice, Poland). Apricot flower buds were damaged less severely than those of peach during the winter of 2009/2010 when the lowest temperatures (maximum drop in temperature) coincided with the full dormancy stage of the trees. Conversely, peach flower buds were less damaged than buds of apricot when the maximum drop in temperature occurred after the late winter thaw in both 2008/2009 and 2010/2011. Under Polish climatic conditions, peach proved to be more reliable than apricot in consistency to produce fruit. Results have shown that the most hardy apricot and peach cultivars can develop very strong winter hardiness allowing the trees to survive temperatures as low as −28°C, as long as there are no severe temperature fluctuations during late winter.

A half-diallel mating design (

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