Abstract:

To investigate the role of nitric oxide (NO) and nuclease in pine wilt disease, we examined NO content and nuclease activity in pine needles of Pinus taeda,P. massoniana,P. thunbergii inoculated with nematodes (Bursaphelenchus xylophilus) for 4, 12, 24, 48, 72, 96 and 120 h. The results showed that NO content in pine needles after the inoculation was P. taeda < P. massoniana < P. thunbergii, and this phenomenon was particularly evident at 12-48 h after the inoculation; the increase range of NO content in pines compared to their treatment which inoculated with distilled water was ranked as P. taeda > P. massoniana > P. thunbergii at 48 h after the inoculation. Meanwhile, the nuclease activity was significantly different in pine species after inoculation of the nematodes. The activity of single-stranded nucleic acid enzyme was in a rank of P. taeda > P. massoniana > P. thunbergii at 4-48 h after inoculation, however the activity of double-stranded nucleic acid enzyme in P. taeda was lower than P. thunbergii and P. massoniana during 4-96 h after inoculation. These results suggested that changes in activity of double-stranded nucleic acid or single-stranded nucleic acid enzyme in different pines were related to their resistance. The observation of symptoms showed that P. thunbergii first appeared wilt symptoms, followed by P. massoniana, and then P. taeda. The changes of NO content and nucleic acid enzyme activity were closely related to the development of pine wilt disease symptoms.

Key words: Pinus taeda, P. massoniana, P. thunbergii, Bursaphelenchus xylophilus, NO, nuclease