Abstract
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.
Highlights
Our results revealed significant genetic variation with a broad range of susceptibility to pinewood nematode among P. radiata half-sib families from the Galician breeding program
The moderately high heritability estimates and genetic gain obtained from these experiments confirm the potential of this species for breeding pine wilt disease (PWD)-resistant trees to mitigate future damage to P. radiata plantations
Resistance breeding has proven successful in controlling diverse pests and pathogens that affect forest tree species [41,42,43]
Summary
As one of the most widely planted tree species in the world, it is cultivated in Australia, New. Zealand, Chile, South Africa, and southwest Europe. In the latter region, plantations are mainly located in northern Spain, in the Basque Country and Galicia, which contain 47.6% and 33.3% of the total area covered by P. radiata in Spain, respectively. In 2019, 2.2 million m3 of this species were harvested in the Basque Country and 1.8 million m3 in Galicia, representing 95.2% and 46.2% of the total conifer harvest volume in each region, respectively [2]. Tree species are under increasing threat worldwide from diseases and insect pests, many of which are non-native. One health menace to P. radiata is Bursaphelenchus xylophilus (pinewood nematode, PWN), the organism that causes pine wilt disease (PWD).
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