Canker Length Research Articles

Response of Siberian Elm to Inoculations withSphaeropsis ulmicola

Eighty-one clones of Siberian elm (Ulmus pumila) were screened for resistance to Sphaeropsis ulmicola (=Borryodiplodia hypadermia) to determine if different levels of disease reaction or canker development could be detected. In 1989, inoculations with S. ulmicola resulted in significant differences among clones for branch dieback and canker length. In 1990, three clones with some resistance (small cankers) and three susceptible clones (large cankers) were inoculated with six isolates of S. ulmicola. On the basis of branch dieback and canker length, these clones were significantly different and responded similarly to inoculations performed in 1989. No significant differences in canker development among the six isolates were detected, and the isolate X clone interactions were not significant

Hydraulic Conductance in Susceptible versus Tolerant Peach Seedlings Infected with Leucostoma persoonii

Eight open-pollinated peach families [Prunus persica (L.) Batsch] were selected from a germplasm collection that was screened for tolerance to Leucostoma persoonii (Nits.) Höhn. [imperfect state, .Leucocytospora leucostoma (Pers.) Höhn] following field inoculation. The eight peach families were either susceptible or tolerant to L. persoonii infection based on canker length measurements. Three open-pollinated seedlings per family were chosen for evaluation. Following artificial inoculation, measurements of hydraulic conductance per pressure gradient (Kh) were made on 2-year-old branch segments from the 24 seedlings, and safranin dye was used to mark the conductive xylem pathways. For the peach families tolerant to L. persoonii, the specific Kh of the canker branch segments was greater than that for the most susceptible peach families. The inoculated branch segments from the tolerant peach families maintained ≈15% to 30% of the water transport of control segments. Safranin dye movement indicated that the sapwood in inoculated branch segments of seedlings from the susceptible peach families was almost completely blocked. Isolation experiments indicated deeper penetration of the fungus into the xylem of seedlings of susceptible than tolerant families. Xylem dysfunction appears to be correlated with a reduction in Kh, and the seedlings in the tolerant peach families are better able to maintain water transport through the stem segment invaded by the fungus.

Pathogenic variability of various isolates of Seiridium cardinale, S. cupressi and S. unicorne inoculated on selected Cupressus clones and seedlings

AbstractComparative studies of the pathogenicity of eight isolates of three Seiridium species were carried out by stem inoculations on Cupressus sempervirens and C. glabra seedlings and clones. Seiridium cardinale and S. cupressi caused bigger and more severe cankers than all strains of S. unicorne. During the first nine months after inoculation, the canker length of S. cardinale was larger than the cankers of S. cupressi. However, during the second year after inoculation, S. cupressi cankers were larger and more severe than those of 5. cardinale.

Infection of Pruning and Small Bark Wounds in Almond byCeratocystis fimbriata

Ceratocystis fimbriata caused cankers at pruning cuts on branches of Nonpareil almond trees inoculated in all months from September through February. Pruning cuts were susceptible when 0-14 days old, and canker length was greatest where fresh wounds were inoculated. Small dead or living twigs of Mission almond trees, broken without visible exposure of the subtending branch cambium, and wounds inflicted with a lancet became infected when inoculated in alternate months throughout the year. Superficial abrasions of the periderm were less susceptible than were full- and half-depth penetrations of the bark

Heritability of Leucostoma persoonii Canker Resistance among Diverse Peach Genotypes

Heritability and the genetic and environmental variance components of resistance to the canker-causing pathogen Leucostoma persoorrii were estimated in a population of diverse peach (Prunus persica L.)-genotypes. Disease resistance was measured as the length of necrotic tissue, i.e., canker length, following artificial inoculation in the field. Genetic and environmental variations were partitioned as variance components of the linear statistical model. Heritability was estimated by regressing average performance of seedlings on performance of their maternal parent. The genetic variance was highly significant, and the heritability for canker necrotic length was relatively high (0.72), suggesting that it should be possible to select L. persoonii -resistant individuals within the population.

LEUCOSTOMA TOLERANCE IN PEACH: FUNGAL ISOLATE × PEACH GENOTYPE

Seven peach clones which were previously identified as resistant, intermediate, or susceptible to Leucostom a persoonii were screened against 3 different L. persoonii and L. cinct a isolates to determine if the resistant reaction was fungal species and/or isolate specific. Canker necrotic length varied significantly with the most resistant genotypes; NJ672017002 (1-8) and Yennoh (1-39) having the shortest canker lengths. The virulence of the fungal species and isolates also varied significantly and there was a significant species/isolate × peach genotype interaction. However, this interaction tended to be among the intermediate and susceptible genotypes with the 2 resistant peach genotypes least affected by all isolates.

Differential reaction in Pinus spp. to inoculation by various isolates of Ascocalyx (Gremmeniella) abietina

AbstractStem inoculations of 3 species of pole‐size pines with 4 diverse isolates of Ascocalyx (Gremmeniella) abietina revealed Pinus pinea to be more susceptible than either P. pinaster or P. nigra in terms of canker length. Isolate type and geographical aspects considered more briefly, also have some effect.

White Pine Blister Rust in British Columbia II. Can Stands be Hazard Rated?

Twelve to 30-year-old western white pine (Pinus monticola Dougl.) in 23 stands in British Columbia were surveyed for blister rust (Cronartium ribicola J.C. Fisch. ex Rab.) cankers. Canker length, mid-point diameter, and height above ground were measured. The number of cankers per tree tended to increase with tree diameter, was variable within stands, and on 15 to 20 cm diameter trees ranged from a mean of one to 14 per stand and the overall mean was four cankers per tree. Large branches bore longer cankers and tended to be higher in the tree than small branches which bore short cankers. Incidence of cankers above 2.5 m tended to increase with increasing slope and they were on the side of the tree subject to evening breezes. Based on Idaho standards all sites in British Columbia were rated as low hazard, but trees growing on slopes had a higher risk than those on flat sites.Key words:Cronartium, Pinus monticola, hazard rating

The Effect of Iron on Growth and Bacterial Canker Susceptibility of Peach Seedlings1

Abstract Peach seedlings [Prunus persica (L) Batsch] were grown in liquid culture with 0,1,4, 7 and 10 Mg/ml Fe++. After 6 months, the plants were inoculated with Pseudomonas syringae van Hall, the causal agent for bacterial canker, or water, and cankers were measured over a 5 month period. Plants not receiving iron were chlorotic and smaller than those grown in 1,4, 7 μg/ml of iron. Ten μg/ml of Fe++ reduced plant weight when compared to the 1 μg/ml rate. Plants receiving no Fe++ developed the longest bacterial cankers. No significant differences in canker length occurred between treatments containing Fe. In the 0 and 1 μg/ml rate, P. syringae was recovered farther from the inoculation site and after a longer time following inoculation than in other rates of Fe++. P. syringae was not recovered from water inoculated seedlings. The possible relationship of these findings to peach tree short-life is discussed.

Variability of host and pathogen in Hypoxylon canker of aspen

Sapling-sized quaking aspen (Populits tremuloides) in five natural clones were inoculated with mass and single ascospore cultures of Hypoxylon mammatum. Fungus isolates varied in ability to produce cankers. 'Conidial-type' isolates generally produced few cankers, while 'mycelial-type' isolates produced cankers on 87.7% of inoculated branches. Isolates from a given ascus inoculated into a clone generally produced cankers of similar length after 2 months. However, some significant differences in canker length did occur. Clones varied in susceptibility to canker enlargement. No single isolate produced the largest cankers on all clones.