ACTA BOTANICA GALLICA derm was rapidly torn out, allowing a rapid growth of the haustorium through the host tissues. In non paras~ized poplar branches, the nature and the amount of preexisting phenols turned out to be two basic parameters highly involved in the phenomenon of resistance.
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.
From 2016 to 2017, a survey was carried out during four vegetative cycles of date palm tree (Phoenix dactylifera L.) in Figuig oasis of Morocco. Two types of date palm culture were surveyed, that is traditional and modern plantations. The aim of the survey was mainly to explore date palm diseases, their incidence and geographic distribution in Figuig oasis. Results revealed the presence of two major diseases: the harmful Bayoud disease and Belaat disease. The rate of contamination of each disease reached respectively 3.38% and 3.31%. Spatial distribution of each disease varies for each one both in traditional and modern plantations, as shown in kernel density maps of diseases infestation. Bayoud disease spread more in traditional oasis. In fact, 60.96% of infested date palm trees by Bayoud disease were recorded in traditional plantations. On the contrary, in modern ones, Belaat disease was the main disease and the rate of infestation reached 67.13%. The survey also focuses on the influence of occurred farming practices in infested plantations which are often characterized by a lack of phytosanitary treatment, fertilization and weeding. Furthermore, pruning, gravity irrigation and the presence of underlying culture were also identified as increasing factors for pathogens dissemination.
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