Spatial and temporal dynamics of the colonization of<i>Pinus radiata</i>by<i>Fusarium circinatum</i>, of conidiophora development in the pith and of traumatic resin duct formation

Summary Fusarium circinatum is widely regarded as a necrotrophic pathogen of pines that infects shoot tissue through mechanical or insect‐mediated wounds, causing girdling lesions that result in death of infected branches. However, in the study reported here, F. circinatum colonized 100% of seedling stems and 70% of mature tree branches that were not wounded. Hyphae were observed beneath the epidermis of non‐wounded shoot tissue within 14 days following inoculation. In both seedlings and branches, most infections of non‐wounded tissue did not induce symptoms for the duration of the trial (seven to eight weeks). In surveys of native Pinus radiata stands in California, F. circinatum was recovered from 7.5% to 100% of healthy‐looking seedlings (2–3 years old) across three of the four stands surveyed. These results suggest that wounding is not a requirement for shoot infection under all circumstances and that F. circinatum can grow within shoot tissue without causing symptoms.

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“…Martín‐Rodrigues et al. () reported extensive growth of the pathogen in stem tissue prior to the development of symptoms. Likewise, Swett et al.…”

Section: Discussionmentioning

confidence: 99%

Infection without wounding and symptomless shoot colonization of Pinus radiata by Fusarium circinatum, the cause of pitch canker

2018

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“…This is in accordance with Martín‐Rodrigues et al . () who described conidiophores inside the stem of infected seedlings after the rapid colonization of the pith via medullary rays from the inoculation point at early stages of infection. Here the pathogen appeared to colonize the parenchymatous pith in the root collar region from the primary xylem and the resin ducts associated with the primary xylem poles of the tap root (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…This transformed strain has previously been described in detail in Martín‐Rodrigues et al . (). Fungal cultures were established from colonies resulting from the subculture of a monoconidial stock (stored in 25% glycerol v/v at −80°C) and were routinely grown at 22–28°C on potato dextrose agar (PDA; Difco Laboratories) for up to 2 weeks.…”

Section: Methodsmentioning

confidence: 97%

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New insights into radiata pine seedling root infection by Fusarium circinatum

et al. 2015

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Pine root infection by Fusarium circinatum has been reported in the literature, but the underlying pathogenic interaction is poorly understood. A green fluorescent protein (GFP)‐tagged F. circinatum isolate, together with confocal microscopy, was used in order to monitor the events associated with root infection of Pinus radiata seedlings. It was found that in order to reach and successfully infect pine roots, F. circinatum employed features that are similar to those previously described for other root‐infecting pathogens, such as mycelial strands, single runner hyphae and simple hyphopodia as well as other features that are reminiscent of those that are known to be involved in biotrophic invasion, such as bulbous invasive hyphae and filamentous invasive hyphae. Abundant sporulation was observed at the root surface as well as inside tracheids both in roots and in the root collar region. The fungus can spread from the roots to the aerial parts of the plant, and once there, colonization appears to be similar to the process that occurs when the pathogen is inoculated in the stem. Wilting symptoms and plant demise may be the result of a reduction in water uptake by roots and of the blockage of the vascular system by fungal hyphae and resin.

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“…It causes Pine Pitch Canker (PPC) disease, which leads to reduced growth of adult trees in forest plantations, resinous bleeding cankers on trunks and large branches, and death of trees due to girdling [1]. It also has detrimental effects in nurseries [2].…”

Section: Introductionmentioning

confidence: 99%

Vertical Transmission of Fusarium circinatum Mitoviruses FcMV1 and FcMV2-2 via Microconidia

Romeralo

Bezos

Martínez‐Álvarez

2018

Forests

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Pine Pitch Canker disease, caused by the pathogenic fungus Fusarium circinatum, affects conifer species worldwide. However, the virulence of the pathogen may be affected by the presence of mycoviruses. The aim of this laboratory-based study was to investigate the probability and rate of transmission of F. circinatum mitoviruses FcMV1 and FcMV2-2 via microconidia. Ten isolates of mitovirus-infected F. circinatum were subcultured to produce a total of 100 single-spore colonies (ten replicates per isolate). The total RNA and cDNA obtained from each spore isolate (monosporic culture) were amplified by PCR with specific primers for detection of F. circinatum mitoviruses FcMV1 and FcMV2-2. The mitoviruses were detected in a high percentage of the individual spore isolates (between 60% and 100% depending on the fungal isolate). However, the probability of transmission was not statistically significantly associated with either the F. circinatum isolate or the viral strain. A high proportion of transmission via microconidia is critical for development of a biological control program against Pine Pitch Canker (PPC) disease in forests. However, further studies are needed to establish the effect of these mitoviruses on the virulence of F. circinatum.

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Spatial and temporal dynamics of the colonization ofPinus radiatabyFusarium circinatum, of conidiophora development in the pith and of traumatic resin duct formation

Cited by 46 publications

References 59 publications

Infection without wounding and symptomless shoot colonization of Pinus radiata by Fusarium circinatum, the cause of pitch canker

Infection without wounding and symptomless shoot colonization of Pinus radiata by Fusarium circinatum, the cause of pitch canker

New insights into radiata pine seedling root infection by Fusarium circinatum

Vertical Transmission of Fusarium circinatum Mitoviruses FcMV1 and FcMV2-2 via Microconidia

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