Efficacy of hot water treatment to reduce the incidence of Fusarium circinatum on Pinus radiata seeds

Hot water treatments (HWTs) were evaluated for their ability to reduce the incidence of Fusarium circinatum on Pinus radiata seeds. The effect of HWTs on conidial germination and mycelial growth of F. circinatum isolates representative of both mating types (MAT-1 and MAT-2) was determined by incubating conidial suspensions and agar plugs with mycelium in a hot water bath. The percentages of conidial germination and mycelial growth relative to the non-treated control decreased with increasing temperature and time of HWTs. MAT-2 isolates were more sensitive to HWTs than those of MAT-1, and no germination or mycelial growth of MAT-2 isolates was observed for temperatures above 50°C. The effect of HWT on P. radiata seed germination was also evaluated. The decrease in the percentage of seed germination compared with the non-treated seeds was always below 30 per cent for treatment temperatures <53°C. In addition, two naturally infected seed lots of P. radiata were used to assess the effect of HWTs on naturally infected seeds and on 3-month-old seedlings obtained from treated seeds. There was no infection detected in most of the treatments evaluated for either seed lot. Only 1 per cent of infection was detected on seeds treated with 50°C for 30 min in seed lot 1 and on seeds treated with 50°C and 52°C for 45 min in seed lot 2. The results obtained in this study show that HWTs at 51-52°C for 30 min can be used to reduce F. circinatum contamination on P. radiata seed. © 2012 Institute of Chartered Foresters. All rights reserved.