Genetic parameters for<i>Fusarium circinatum</i>tolerance within openpollinated families of<i>Pinus patula</i>tested at screening facilities in South Africa and the USA

The pine pitch canker fungus, Fusarium circinatum, has caused large-scale mortality of Pinus patula Schiede & Deppe ex Schltdl. & Cham. crops in South African nurseries. This disease is now managed with strict hygiene practices and mortality in commercial nurseries has been drastically reduced. During the last 10 years, however, the disease started to manifest in the field, impacting on post-planting survival. Tree breeders have identified selection and breeding of tolerant material as the likely long-term solution to this disease. This study demonstrates that, under greenhouse conditions with artificial inoculation of young seedlings, there is significant genetic variation in tolerance to F. circinatum among open-pollinated P. patula families. Tolerant families can be identified and can be utilised in breeding programmes and for seed production. The study provided strong evidence that these artificial inoculation experiments are highly repeatable within specific laboratories, with lower but still meaningful repeatability between different laboratories.