Effect on nursery and field performance ofPinus patulaseedlings after inoculation withFusarium circinatum

Abstract

Fusarium circinatum is an important fungal pathogen of Pinus species. In South Africa, it is the most significant pathogen of Pinus patula seedlings in forestry nurseries where it presents a substantial constraint to productivity and can continue to cause mortality in-field for up to two years after establishment. This study describes the results from two trials where P. patula seedlings were inoculated with F. circinatum to determine the impact of the pathogen on nursery and field performance. Seedlings were also subjected to water stress treatments to ascertain whether this would trigger the onset of disease symptoms. Inoculum load and timing of inoculation had significant effects on seedling survival in both the nursery and field. High inoculum concentrations caused greater levels of mortality and, where seedlings were inoculated at a young age, they showed higher levels of susceptibility to F. circinatum. Temporary water-stress in the nursery produced smaller plants and improved in-field survival, but this treatment did not trigger higher mortality in inoculated treatments. On the other hand, transplant stress was a major contributor to the higher levels of mortality observed in inoculated treatments. Overall, these studies confirmed that infection in the nursery leads to the disease problems observed during early plant establishment in the field.

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

“…An impact of symptomless infections on plantation forestry is already apparent, because seedlings with infected roots are more prone to failure following transplanting (Jones et al., ). On the other hand, the ecological significance of symptomless infection in the forest is not yet clear.…”

New insights into radiata pine seedling root infection by Fusarium circinatum

“…F. circinatum had traditionally been considered to be an airborne pathogen, but the capacity of this fungus to infect pine roots was reported by Viljoen et al . () after having re‐isolated F. circinatum from roots of Pinus patula seedlings that had been soilborne inoculated by means of spore suspensions. The 2‐month‐old diseased seedlings used in this study presented needle discolouration, wilting of the shoot and underdeveloped roots, with discoloured lesions and necrosis of the cortex.…”

“…The 2-month-old diseased seedlings used in this study presented needle discolouration, wilting of the shoot and underdeveloped roots, with discoloured lesions and necrosis of the cortex. The large impact of this pathogen in nurseries of South Africa has extended over time to new plantations, contributing significantly to post-planting mortality (Mitchell et al, 2004;Jones et al, 2014). It is not clear whether the pathogen actually gains access to the host via wounds made during planting, or whether the host is already infected upon planting (Mitchell et al, 2011).…”

The Causal Agent of Damping-off in Pinus patula (Schiede) and Pinus tecunumanii (Schwerdtf.)

“…Additionally, F. oxysporum produces a large amount of chlamydospores that allow it to survive in the soil for long periods of time, as well as in dead tissue of the host plant, and in plant remnants in the soil in the absence of a host plant, making it difficult to control (Gordon et al, 2015). In addition, Jones et al (2014), found that high concentrations of inoculum caused higher mortality levels in P. patula seedlings. For these reasons, the handling of damping-off should be focused on avoiding the arrival of infectious propagules of the pathogen to the growth substrates used in the nursery, as well as in an early detection.…”

“…Several investigations found that conifer trees obtained from seedlings that presented damping-off caused by Fusarium spp. can suffer significant damage from resinous canker in the field (Stewart et al, 2012;Steenkamp et al, 2012;Jones et al, 2014). This could be attributed to the fact that the pathogen can be latent in the transplanted seedling; therefore, an early detection of these pathogens would be crucial to avoid sending them to the field (Jones et al, 2014).…”