This article briefly reviews the history of white pine blister rust, attributed to Cronartium ribicola, and addresses current research and management issues in South Korea, Japan and other regions of eastern Asia (China, Russia and Himalaya). For each region, the distribution, damage, aecial hosts, telial hosts and management of C. ribicola and other blister rust fungi on native and introduced white pines are summarized. In addition, blister rust behaviours in eastern Asia and North America are compared; and the potential evolutionary and management implications are discussed.

Pine wilt disease caused by the pinewood nematode (PWN), Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, has destroyed huge areas of pine forest in East Asia, including Japan, China and Korea. No protection against PWN has been developed, and the responses of pine trees at the molecular level are unrecorded. We isolated and analyzed upregulated or newly induced genes from PWN-inoculated Japanese red pine (Pinus densiflora Sieb. et Zucc.) by using an annealing control primer system and suppression subtractive hybridization. Significant changes occurred in the transcript abundance of genes with functions related to defense, secondary metabolism and transcription, as the disease progressed. Other gene transcripts encoding pathogenesis-related proteins, pinosylvin synthases and metallothioneins were also more abundant in PWN-inoculated trees than in non-inoculated trees. Our report provides fundamental information on the molecular mechanisms controlling the biochemical and physiological responses of Japanese red pine trees to PWN invasion.

Six pine species or hybrids were tested for susceptibility to pitch canker caused by Fusarium circinatum. Pinus densiflora, Pinus thunbergii, Pinus x rigitaeda (Pinus rigida · Pinus taeda), P. rigida · P. x rigitaeda, Pinus echinata and Pinus virginiana were inoculated with three spore loads (50, 500 and 5000 per tree) of F. circinatum. External symptoms, lesion length, and the frequency of reisolation of the fungus were investigated. External symptoms were greatest in P. echinata, followed by P. virginiana, however, P. densiflora was not susceptible to F. circinatum. Based on mean lesion lengths, the six pine species or hybrids differed significantly (p < 0.01) in susceptibility to pitch canker. Pinus echinata sustained the longest lesions, whereas P. densiflora sustained the shortest lesions. The effect of inoculum density was not significant among three spore treatments within species (p = 0.17), although lesion length was slightly greater at higher spore loads over all pine species. The fungus was reisolated from inoculated stems of all pine species tested, even on trees showing little or no damage from the disease. Additional studies are needed to further explore the basis for resistance to pitch canker.

No abstract

Needle traits were evaluated on three groups of western white pine (Pinus monticola Dougl.) seedlings: four open-pollinated families that ranked high for the "reduced needle lesion frequency" type of resistance to blister rust; four blister rust susceptible families; and two bulk lots from a seed orchard selected for blister rust resistance. No statistically significant differences were found for most traits in pairwise comparisons among the three groups. However, needles of susceptible families had significantly wider and larger stomata (greater area) than did those of resistant families and seed orchard lots; their stomata were also rounder (smaller ratio of stomatal length to width) than those of the seed orchard lots. Needles of the resistant stocks were significantly shorter than those from seed orchard bulks. Contact angles of water droplets on adaxial needle surfaces were also significantly larger on resistant families compared with the other genetic stocks. Results suggest the possibility of some threshold stomatal size and (or) critical stomatal shape related to infection by the blister rust fungus, Cronartium ribicola J.C. Fisch. ex Rabenh., and possible differences among the groups in wax chemistry and (or) surface textures, both of which may alter behavior of blister rust germ tubes and (or) be altered by blister rust infection.