01890nas a2200145 4500008004100000245009400041210006900135300001200204490000700216520138800223100001901611700003301630700002101663856006001684 1992 eng d00aFactors influencing the enlargement of trunk cankers of Phytophthora cinnamomi in red oak0 aFactors influencing the enlargement of trunk cankers of Phytopht a367-3740 v223 a

Development of cankers on red oak (Quercus rubra L.) caused by Phytophthora cinnamomi Rands was studied with dendrochronological techniques. Factors of variation among lesions were investigated. Lesion parameters proved to vary with the particular tree to which the lesion belonged. A discriminant factorial analysis and principal component analysis showed that this tree susceptibility was made up of two components. The first accounted for root infection and wound healing. The second concerned susceptibility to vertical spread of the pathogen in bark tissues. Relationships between (i) tree susceptibility and (ii) tree age and vigor were studied. From the occurrence of the first lesion at the collar, number and severity of lesions increased with time, following an exponential and logistic curve, respectively. A comparison of ring widths in infected and healthy trees showed that the disease had no detrimental effect on tree growth. However, annual necrosis length was positively correlated with the annual radial tree growth. The observed differences among trees could not be explained by the effects of time and vigor only. Temperature and drought were analyzed to determine their effect on lesion development. No direct effect of drought on this disease could be shown. The low cold hardiness of P. cinnamomi in the trunk was determined.

1 aRobin, Cécile1 aDesprez-Loustau, Marie-Laure1 aDelatour, Claude uhttp://www.nrcresearchpress.com/doi/abs/10.1139/x92-04801872nas a2200145 4500008004100000245009100041210006900132300001200201490000700213520137300220100001901593700003301612700002101645856006001666 1992 eng d00aSpatial and temporal enlargement of trunk cankers of Phytophthora cinnamomi in red oak0 aSpatial and temporal enlargement of trunk cankers of Phytophthor a362-3660 v223 a

Phytophthora cinnamomi Rands is the agent of ink disease on northern red oak (Quercus rubra L.). Cortical cankers on the trunk are the visible symptoms. The fungus causes necrosis of the cambium and phloem, and the tree reacts by forming xylem callus curls. These features can be dated aposteriori on cross sections. The aim of this study was to describe the spatial and temporal development of cankers on cross-sectioned infected oaks. For each lesion, dates of cambium necrosis and formation of callus were recorded at different heights. The following parameters were measured for each lesion: age, height, rate of development, and length and duration of necrosis and canker. Two hundred sixty-three lesions, on 14 trees, were studied. Trees did not exhibit cankers before 9 years of age. All visible trunk cankers could be related to a collar lesion. Phytophthora cinnamomi spreads upwards and can persist for several years, being active seasonally. In this study cambium necrosis occurred preferentially during the first flush. Twenty-nine percent of the lesions were healed over at the collar after 1 year. The collar was less susceptible than the trunk. The other lesions spread rapidly in the cambium of the trunk, which was very vulnerable. They then progressively healed. Therefore, the canker progress curve was bell shaped.

1 aRobin, Cécile1 aDesprez-Loustau, Marie-Laure1 aDelatour, Claude uhttp://www.nrcresearchpress.com/doi/abs/10.1139/x92-04701836nas a2200193 4500008004100000022001400041245012100055210006900176260001600245520117000261100001901431700001901450700002001469700001801489700002001507700002601527700002001553856006901573 2014 eng d a0191-291700aPathogenicity of Phytophthora lateralis lineages on resistant and susceptible selections of Chamaecyparis lawsoniana0 aPathogenicity of Phytophthora lateralis lineages on resistant an cOct-10-20153 a

Phytophthora lateralis, the cause of Chamaecyparis lawsoniana root disease, was introduced in North America about 1950, and has since killed trees along roads and streams throughout the tree’s range. Recent results suggest an Asian origin for this Oomycete and four genetic lineages were identified. This raised questions for the genetic exapted resistance demonstrated in 1989 within the wild population of C. lawsoniana but with only one P. lateralis lineage. The main goal of the present research was to test the durability of the demonstrated resistance and to compare the pathogenicity of isolates representing the four lineages. No breakdown of resistance was observed in five separate tests using different inoculation techniques, resistant and susceptible C. lawsoniana trees, and seedling families. Differences in mortality and lesion length were observed between the lineages. The higher aggressiveness of isolates of the TWJ and PNW lineages and the lower aggressiveness of the TWK lineage are discussed in view of the hypotheses on the history of spread and evolutionary history of the P. lateralis lineages.

1 aRobin, Cécile1 aBrasier, Clive1 aReeser, Paul, W1 aSutton, Wendy1 aVannini, Andrea1 aVettraino, Anna Maria1 aHansen, Everett uhttp://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-07-14-0720-RE