Élaboration d'un coefficient de résistance au gui chez le chêne

Abstract

The reactions of oak to mistletoe (Viscum album L.) were studied using about 100 sensitive and susceptible oak twigs belonging to three species of oak: Quercus robur, Quercus rubra, and Quercus petraea. The main parameters likely to be involved in the resistance mechanism to mistletoe were measured on longitudinal radial sections. After conducting several principal component analyses and discriminant analyses, four variables were shown to have high discriminant values: thickness of the cortex, density of polyphenol-containing cells, thickness of the first layers of fibers, and thickness of collenchyma. Statistical analyses were performed using a large number of samples to define a discriminating function linking the four variables and to propose a resistance coefficient. The significance of such a coefficient for forest managers and pharmacologists is discussed in relation to their own needs. Key words: Viscum album, Quercus, resistance coefficient, mistletoe.

Impact of Common Mistletoe (Viscum album L.) on Scots Pine Forests—A Call for Action

“…The most resistant cultivar possessed the greatest number of polyphenolic cells per unit surface area. Later research with three Quercus species confirmed the same pre-existing anatomical and chemical features of resistance as those of Populus: thicker cortex, collenchyma, and fiber layer and greater density of polyphenol-containing cells [125].…”

Bases structurales et biochimiques de la résistance au gui dans le genrePopulus

“…Mais dans le cas du gui, une correlation a ete demontree entre Ia resistance de certains cvs et Ia richesse en cellules a polyphenols des tissus sains (Armillotta, 1984 ;Salle et al, 1984 ;Hariri, 1989 ;Hariri et al, 1991) (Hariri et al, 1992).…”

Susceptibility of rubber trees toLoranthaceaein Gabon

“…In our study, another clone, PB 260, turned out to be slightly susceptible to P. capitata. It is noteworthy that rubber trees never displayed a complete resistance to mistletoe in contrast with some cultivars of poplars, such as Blanc de Garonne and Vereecken, totally resistant to Viscum album (Frochot et al 1978;Armillotta 1984;Hariri 1989;Hariri et al 1992), which never hosted mistletoe in natural conditions or after artificial infestations.…”

“…album, several parameters involved in resistance were well established (Hariri 1989;Hariri et al 1991): Anatomical features (phellem thickness, cortical parenchyma thickness), or biochemical characteristics (tannin-rich cell density). Moreover, it was shown on poplars that a positive correlation existed between these parameters and the behavior of mistletoe (Hariri 1989;Hariri et al 1991Hariri et al , 1992: the higher the values of these three variables, the more resistant the cultivar was. As far as rubber tree is concerned, no relation between these parameters and the susceptibility to Loranthaceae could be observed.…”

“…Parameters involved in this resistance are now well documented, i.e. anatomical structures and phenolic compounds (Armillotta 1984;Salle´et al 1984;Hariri 1989;Hariri et al 1991Hariri et al , 1992Salle´et al 1993). Nevertheless, these studies did not take into account the effect of the morphology of the host's tree crown.…”