Pine Wilt Disease Progression Differs Among Pinus elliottii and P. elliottii × P. caribaea Taxa and Suggests

ABSTRACT

Pine wilt disease (PWD) caused by the pinewood nematode Bursaphelenchus xylophilus threatens subtropical pine plantations, yet family‐level phenotyping remains scarce for Pinus elliottii and its hybrids with P. caribaea . We inoculated 176 two‐year‐old seedlings representing 22 breeding families (11 P. elliottii ; 3 P. elliottii × P. caribaea var. caribaea ; 8 P. elliottii × P. caribaea var. hondurensis ) with a virulent nematode isolate and scored ordinal disease severity at 17 time points over 132 days, with mortality tracked to 9 months. Mixed models tested taxon effects and family effects nested within taxa. Taxa differed mainly in symptom onset, disease severity trajectories and mortality timing: P. elliottii developed symptoms later and showed lower mid‐stage severity, but mortality accumulated earlier than in the hybrids, and differences diminished by 9 months. Across families, time to first symptom, integrated disease burden, and fixed‐time mortality showed limited differentiation, whereas mid‐stage severity (41–55 days post inoculation) provided more consistent within‐taxon differentiation. These results highlight distinct response dynamics among taxa and identify a candidate mid‐stage phenotyping window for breeding‐oriented screening under the present assay conditions.