Relationships between morphological traits and resistance to pine wood nematode in two Japanese pines

Abstract

It has been suggested that certain morphological traits of Japanese pines function as resistance factors against the pine wood nematode (PWN), Bursaphelenchus xylophilus. The aim of this study was to verify this concept, and to determine the relationships between traits and resistance at both the individual and family levels. Relationships between survival rate and morphological traits of Pinus densiflora and Pinus thunbergii were studied after inoculation with PWN. Morphometric parameters used were height, basal diameter of the axis, and the number of branches from the axis. Three indices of relationships were analysed: (1) among individuals within a family (survival difference between smaller and larger morphometric populations within each family); (2) among individuals (correlation between each morphometric average and survival rate in quintile populations of all subjects within each pine species based on the order of morphometric values); and (3) among families (correlation between each morphometric average and survival rate in the family). Both significant and non-significant differences were detected within a family, indicating a need for macro techniques. Among individuals, a thicker axis and more branches were correlated with increased survival, indicating that they are resistance factors. However, these correlations were not significant among different families. These results indicate that morphological traits cannot be used to evaluate resistance at a family level, even if they are significant at an individual level. Further studies on traits associated with resistance should be conducted at a family rather than an individual level, to breed for Japanese pines with resistance to PWN.

Assessing Genetic Variation in Resistance to Pinewood Nematode (Bursaphelenchus xylophilus) in Pinus radiata D. Don Half-Sib Families

“…This relationship was also reported for P. pinaster families from the Galician breeding population: trees from the most susceptible families also had greater height growth [20]. The same has been reported for other pests [50,51] and points to a growth-defence trade-off, though other studies found no relation or a negative correlation between growth and mortality [52,53].…”

Variation in pinewood nematode susceptibility among Pinus pinaster Ait. provenances from the Iberian Peninsula and France

“…Significant relationships for growth traits were found at both the phenotypic and genetic level in previous experiments on P. pinaster families, where the tallest families and those with fewer branches were the most susceptible (Menéndez-Gutiérrez et al 2017a). Yamanobe (2009) hypothesized that more branches and wider diameter would act as resistance factors, pointing out the greater potential of wider trees to maintain xylem and phloem transport. The author supported the idea of higher susceptibility in trees with fewer branches with other studies indicating that joints with abundant branches might physically or chemically affect PWN migration (Kawaguchi 2006;Kuroda 2008).…”

Resistencia de Pinus pinaster Ait. al marchitamiento del pino causado por Bursaphelenchus xylophilus (Steiner & Burher), Nickle

“…Tanto la mortalidad como los daños se correlacionaron significativamente con el número de ramas y el crecimiento en diámetro, de forma que los genotipos más tolerantes resultaron tener mayor crecimiento en diámetro y mayor ramosidad. Sin embargo, estas relaciones requieren mayor estudio, ya que no fueron encontradas en todos los ensayos en los que se estudiaron; además, si bien existen trabajos que apoyan nuestros resultados (Kuroda, 2004;Toda and Fujimoto, 1987), también hay otros que los contradicen (Hakamata et al, 2013;Yamanobe, 2009).…”