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A biofertilizer with diazotrophic bacteria and a filamentous fungus increases Pinus pinaster tolerance to the pinewood nematode (Bursaphelenchus xylophilus)

Publication . Silva, M. Nunes da; Pintado, M. E.; Sarmento, B.; Stamford, N. P.; Vasconcelos, M. W.

The pine wilt disease (PWD), caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus, is a devastating illness that mainly affects P. pinaster trees, and that poses great environmental and economic challenges. Current disease management involves the cut down of infected trees, tree fumigation, use of nematicides, or the control of the insect vector; however, these methodologies are expensive, labour-intensive and have limited success. The aim of this work was to evaluate the effect of a biofertilizer enriched with diazotrophic bacteria and a chitosan-producing fungus, Cunninghamella elegans, in inducing P. pinaster and P. pinea resistance against the PWN. In non-inoculated (control) P. pinaster plants, PWN population significantly increased (ca. 2.3-fold) throughout the experimental period, whereas in plants treated with 7.5 and 15% of biofertilizer nematode numbers were up to 36.3-fold lower than in control plants. In P. pinea, nematode numbers decreased with time for all biofertilizer concentrations tested, and P. pinea had up to 27.3-fold lower nematode counts than P. pinaster. In addition, the biofertilizer prevented the decrease of photosynthetic pigments and the reduction of water content in infected P. pinaster plants. In P. pinea the biosynthesis of phenolics increased in PWN-inoculated plants, especially in the presence of the biofertilizer. The addition of this biofertilizer to soils forested by P. pinaster may improve plant defence and could be a potentially simple and inexpensive strategy for the control of the PWD.

2019Journal article

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Susceptibility to the pinewood nematode (PWN) of four pine species involved in potential range expansion across Europe

Publication . Silva, Marta Nunes da; Solla, Alejandro; Sampedro, Luis; Zas, Rafael; Vasconcelos, Marta W.

The pine wilt disease (PWD), caused by the pinewood nematode (PWN) Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, is one of the most serious threats to pine forests worldwide. Here we studied several components of susceptibility to PWN infection in a model group of pine species widely distributed in Europe (Pinus pinaster Ait., P. pinea L., P. sylvestris L. and P. radiata D. Don), specifically concerning anatomical and chemical traits putatively related to nematode resistance, whole-plant nematode population after experimental inoculation, and several biochemical and physiological traits indicative of plant performance, damage and defensive responses 60 days post inoculation (dpi) in 3-year-old plants. Pinus pinaster was the most susceptible species to PWN colonization, with a 13-fold increase in nematode population size following inoculation, showing up to 35-fold more nematodes than the other species. Pinus pinea was the most resistant species, with an extremely reduced nematode population 60 dpi. Axial resin canals were significantly wider in P. pinaster than in the other species, which may have facilitated nematode dispersal through the stem and contributed to its high susceptibility; nevertheless, this trait does not seem to fully determinate the susceptible character of a species, as P. sylvestris showed similar nematode migration rates to P. pinaster but narrower axial resin canals. Nematode inoculation significantly affected stem water content and polyphenolic concentration, and leaf chlorophyll and lipid peroxidation in all species. In general, P. pinaster and P. sylvestris showed similar chemical responses after infection, whereas P. radiata, which co-exists with the PWN in its native range, showed some degree of tolerance to the nematode. This work provides evidence that the complex interactions between B. xylophilus and its hosts are species-specific, with P. pinaster showing a strong susceptibility to the pathogen, P. pinea being the most tolerant species, and P. sylvestris and P. radiata having a moderate susceptibility, apparently through distinct coping mechanisms.

2018Journal article

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Chitosan as a biocontrol agent against the pinewood nematode (Bursaphelenchus xylophilus)

Publication . Silva, M. Nunes da; Cardoso, A. R.; Ferreira, D.; Brito, M.; Pintado, M. E.; Vasconcelos, Marta

The pine wilt disease (PWD) is caused by Bursaphelenchus xylophilus and poses great environmental and economic challenges. Thus, the development of sustainable techniques for the control of this epidemic disease is of major importance. This work aimed at evaluating if the application of different molecular weight (MW) chitosans as a soil amendment could be used to control the PWD in maritime pine (Pinus pinaster, very susceptible to the disease) and stone pine (Pinus pinea, less susceptible). At the end of the experimental period (24 days after inoculation), P. pinaster and P. pinea untreated plants presented ca. 3825 100 and 70, 47 nematodes, respectively. In P. pinaster, the high-MW chitosan prompted the most drastic results, inducing a 21.9-fold reduction in nematodes numbers, whereas in P. pinea, the most effective was the low MW chitosan, which reduced nematodes numbers up to 7-fold, compared with untreated plants. P. pinea seems to be highly resistant to the disease, presenting nematode numbers up to 54.6-fold lower than P. pinaster and less severe chlorophyll loss (ca. 2-fold).

2014Journal article

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