Systemic Infection of Avocado, Persea americana, by Raffaelea lauricola, Does Not Progress Into Fruit Pulp or Seed

Avocado, Persea americana, is an important fruit crop in the tropics and warm subtropics. Laurel wilt, caused by Raffaelea lauricola, is a systemic vascular wilt of avocado that spread recently to Florida, an important producing state in the USA. As fruit and seed of avocado produced in Florida are sold in other states and countries where this crop is produced, there is concern that commerce in these commodities might spread this disease. Potted, fruit-bearing trees were artificially inoculated with R. lauricola, and plants were systemically colonized by the fungus. In no instance did infection progress further than the hilum (87 total fruit), as determined by re-isolation of R. lauricola on a semi-selective medium or its detection, with qPCR and high fidelity PCR, of diagnostic small subunit (SSU) 18s rDNA. Thus, it would apparently be safe to propagate avocado with seed from trees affected by this disease. Pedicels/peduncles and hila associated with these fruit were colonized by the pathogen. The latter tissues would be associated with/attached to marketed fruit, but they do not harbour the pathogens ambrosia beetle vector, Xyleborus glabratus. Thus, commerce in avocado fruit appears to be a negligible risk for expanding the geographic range of laurel wilt.