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Recent new outbreaks of Bursaphelenchus xylophilus in Spain and adverse pine wilt disease expansion forecasts must be met with rapid advances in genetic breeding against this pathogen. The optimal approach for breeding trees that are more resistant to pine wilt disease is to use the most virulent isolates in inoculation assays. A series of controlled inoculation experiments on Botrytis cinerea cultures, along with Pinus pinaster and P. radiata branch sections and seedlings, was conducted to investigate differences among seven virulent B. xylophilus isolates of diverse geographic origin (USA745 from USA, KA4 and S10 from Japan, Pt52T and Pt72CH from Portugal, SpPO1 and SpSA1 from Spain). Results from the experiments showed significant differences among B. xylophilus isolates. The virulence classification of the isolates studied differed for P. pinaster and P. radiata, indicating that PWN isolates vary according to host specificity. Isolates Pt52T and SpP01 proved the most virulent to P. pinaster, so either of them could be used as 'test isolates' in future assays to identify resistant or tolerant genotypes. For P. radiata, any isolate except SpSA1 could be used, as all the others were more virulent and all presented the same significant level of virulence. The results indicate that use of P. pinaster branch sections, rather than P. radiata branch sections or multiplication assays on B. cinerea, could be an accurate, time‐saving method for evaluating virulence levels of new B. xylophilus isolates. [ABSTRACT FROM AUTHOR]

Context: Pinus pinaster Ait. is found in the Iberian Peninsula under Mediterranean and Atlantic conditions. Both climates encounter each other in Galicia (NW Spain), where two bioclimatic regions can be differentiated: coastal and inland. A breeding program was launched in the coastal area, with two breeding and deployment areas delimited. Aims: We analyse plasticity patterns across regions in a coastal breeding population to assess the suitability of current breeding areas and how genetic material will likely respond to future climate. Methods: Total height at ages 3 and 8 years was assessed in 16 trials established along the coast and in inner Galicia. Clustering of environments with similar genotypic performance, family sensitivities to climatic factors and stability analyses were performed. Results: Sizeable genetic variation in plasticity was found among families, and crossover genotype-by-environment interactions were detected within and between regions. It was unfeasible to regionalize Galicia into alternative areas of stable genotypic performance. Only the cold regime was found to noticeably underlie the array of phenotypic responses to changing environmental conditions. Conclusions: Results suggest that previous delimitation in two breeding areas is pointless and indicate reduced effects of a changing climate towards Mediterranean conditions on decreasing population fitness. [ABSTRACT FROM AUTHOR]

With 3 figures and 4 tables Hazelnut ( Corylus avellana L.) has been a traditional crop in northern Spain. As a result of germplasm exploration over 3 years (2003–05), 90 trees were selected in this region. This study describes phenotypic variation in nut and husk traits and investigates genetic relationships among selections and cultivars using inter simple sequences repeat (ISSR) markers. The local selections were phenotypically diverse and many had characteristics appreciated by the market. Eleven ISSR primers, which generated 66 polymorphic bands, were used in the analysis. The graph from principal coordinates analysis of the molecular marker data showed two main groups, one for the local selections and the other for the standard cultivars. The dendrogram generated from UPGMA cluster analysis showed the same two main groups. The results suggest that the local accessions are closely related to each other, but are relatively distant from the standard cultivars of eastern Spain, Italy and the USA. Selections from northern Spain may be directly useful as new cultivars or alternatively as parents in breeding programmes. The collection and preservation of this genetic diversity is important. [ABSTRACT FROM AUTHOR]

Full understanding and control of pine wilt disease (PWD) is a work in progress and breeding for disease resistance constitutes an essential management strategy for reducing its impact, as evidenced by advanced breeding programs in countries such as Japan. Since Pinus radiata is one of the most commercially relevant species in northern Spain, we designed a study to assess genetic variation in susceptibility to this pathogen using 44 P. radiata half-sib families from the Galician breeding program. Three Bursaphelenchus xylophilus (pinewood nematode, PWN) inoculation experiments were performed to evaluate disease-related variables, estimate genetic parameters, and study sources of genotype by environment interaction (G × E). We also looked at differences in the constitutive chemical compounds of susceptible and non-susceptible individuals. The results showed great variation in PWN susceptibility, with survival rates for P. radiata families ranging from 0% to 90%. In addition, heritability estimates (hi2 = 0.43, hf2 = 0.72) and genetic gain (>26% selecting 50% of the families) were both moderately high for survival. Significant differences in several constitutive chemical compounds were found between susceptible and non-susceptible seedlings in the two susceptibility groups considered. These results confirm the potential of breeding to obtain P. radiata genotypes that are resistant to pine wilt disease and open possibilities for mitigating its future impact on P. radiata stands. [ABSTRACT FROM AUTHOR]

• Resin yield was highly variable among provenance regions. • Narrow-sense heritability of resin yield was high. • Genetic correlation between pine growth and resin yield was not significant. • Across phenotypes and provenance regions, resin yield and growth were correlated. • Selection and breeding programs will help to increase resin yield. The potential of pine resin as a renewable non-timber product is furthering the socioeconomic relevance of the resin industry in Europe, where maritime pine (Pinus pinaster Ait.) is the main tapped species. Characterizing maritime pine genetic resources in terms of resin yield potential and its covariation with tree growth is crucial to implement efficient tree breeding programs aiming to maximize resin yield without negatively impact tree growth. We explored genetic variation in resin yield and tree growth among provenance regions, populations within regions, and families of maritime pine. We used a progeny trial located at Central Spain to estimate additive genetic variation and heritability of resin yield, and a common garden located at Northwest Spain to explore variation among provenance regions and populations within regions. Resin yield was assessed in both trials with and without sulphuric-based stimulant paste. Association between growth and resin yield at different levels (phenotypes, families, populations and provenance regions) was also explored. Growth and resin yield were highly variable within populations, with narrow-sense heritability estimates being particularly high for resin yield (h i 2 = 0.49). Growth varied significantly across provenance regions and populations within regions, while resin yield was only variable among provenance regions. Genetic variation in resin yield was similar in trees with and without stimulant paste. We did not find evidence of genetic correlations between growth and resin yield. However, at the phenotype level resin yield and growth were significantly correlated, although the sign of such association switched between trials. Across provenance regions, growth and resin yield where negatively correlated. Altogether, the high narrow-sense heritability estimate, the highly consistent genetic variation and the lack of negative genetic correlation with growth evidence the opportunity for implementing breeding programs to increase resin yield in maritime pine forests. [ABSTRACT FROM AUTHOR]