Disease scoring by taking inoculum densities into consideration in leaf disc inoculations with poplar and willow rusts.

MingHao, Pei; Hunter, T.; Pei, M. H.; McCracken, A. R.

doi:10.1079/9780851999999.0131

Cited by 3 publications

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“…Recent study suggested that the number of spores applied can greatly influence the number of pustules produced in M. larici‐epitea (Pei et al ., 2002). In this study, disease was scored based on pustule area and inoculum density data according to the method described by Pei & Hunter (in press) using the following steps: (i) for each clone/isolate combination, a slope factor was calculated by dividing average square root pustule area per leaf disc by the square root of the inoculum density per leaf disc for the isolate; (ii) for each isolate, the clone which produced the largest pustule area (the most susceptible reaction) was chosen and the maximum slope factor was calculated by dividing its average square root of the pustule area by the square root of inoculum density (an average maximum slope factor, AMSF) was calculated by averaging the maximum slope factors for all the isolates); (iii) disease was scored for each clone/isolate combination using 0–4 scales. An assumption was made that the average maximum slope factor represents the midpoint for the scale 4, the most susceptible reaction.…”

Section: Methodsmentioning

confidence: 99%

Rust resistance in Salix to Melampsora larici‐epitea

et al. 2004

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A total of 174 Salix (willow) clones belonging to 57 species and 14 interspecific hybrids were inoculated with seven pathotypes of Melampsora larici-epitea using the leaf disc method. Infection types were scored based on the uredinial pustule area data and the inoculum density. A close correlation ( R 2 = 0·82) was found between the average pustule area and the average number of spores produced. Most of the willows were also assessed in the field for rust in 1999. Most willow clones belonging to the species native to western Europe were infected by the rust. In inoculation experiments, uredinia developed on 46 S. viminalis clones, out of a total of 47. In the field, all the S. viminalis clones were infected by rust. Within the subgenus Vetrix , eight out of the 17 willow species that originated from North and South America produced rust pustules in inoculation experiments. Of these, S. pellita was most susceptible. Salix irrorata and S. lasiolepsis var. bracelinae produced well developed pustules after inoculation but no rust infections were detected in the field. In both leaf disc tests and field assessments, no rust infections were found on S. candida , S. cordata , S. drummondiana , S. eriocephala , S. hookeriana , S. houghtonii , S. humilis , S. rigida var. mackenziana and S. syrticola . Of 12 species of subgenus Vetrix native to northeast Asia and Japan, only S. kochiana was susceptible both in inoculation tests and in the field. Salix rossica produced no symptoms in leaf disc tests but showed low levels of infection in the field. The maximum infection type scores in leaf disc tests were highly significantly correlated with field disease severity scores (Spearman rank correlation coefficient was 0·76, P < 1 × 10 − 10 ).

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Section: Methodsmentioning

confidence: 99%

Rust resistance in Salix to Melampsora larici‐epitea

et al. 2004

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“…Also, in Melampsora rusts on willow and poplar, inoculum densities can greatly influence the number of pustules produced (Pei et al. , 2002, 2004b; Pei & Hunter, 2005). In the present study, direct measurement of uredinia provided objective and precise data and the weighting of the differences in inoculum density made it easier to compare the disease data between inoculations.…”

Section: Discussionmentioning

confidence: 99%

“…Disease severity was scored for each willow genotype by dividing the average square root of pustule area per leaf disc by the square root of inoculum density in each combination of willow family and rust isolate. This method of disease scoring was proposed previously (Pei & Hunter, 2005) based on the linear relationships between uredinial pustule area and inoculum density in the willow rust M. larici‐epitea and the poplar rust M. larici‐populina . A relative disease score (RDS) was calculated for each genotype by dividing its disease score by the highest disease score for that willow family/rust isolate combination.…”

Section: Methodsmentioning

confidence: 99%

Mendelian inheritance of rust resistance to Melampsora larici‐epitea in crosses between Salix sachalinensis and S. viminalis

et al. 2010

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Two F 1 , two F 2 and two backcross (BC) full-sib families of Salix sachalinensis · S. viminalis were tested for resistance to two pathotypes of Melampsora larici-epitea in leaf-disc inoculation experiments. Two single-pustule isolates, VM and ST, belonging to pathotypes LET1 and LET5, respectively, were used in the tests. Disease was scored based on the number of uredinia, uredinial diameter and inoculum densities. Both F 1 families were completely resistant to both VM and ST. Resistance to VM segregated at a 9:6:1 ratio in the F 2 families and at a 1:2:1 ratio in the BC families, suggesting that two independently segregating genes controlled rust resistance, with resistance dominant over susceptibility. This also indicates incomplete dominance of the resistance alleles over the susceptibility to VM. For ST, the equivalent ratios were 3:1 and 1:1, showing that a single dominant gene was responsible for rust resistance. The broad sense heritabilities were >0AE91 for uredinial diameter and 0AE1-0AE33 for the number of uredinia. There were significant overall correlations between data from inoculations with VM and those from inoculations with ST in the number of uredinia, uredinial diameter and disease scores (Spearman's rank correlation coefficients = 0AE31-0AE75).

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Pathogenic variation in poplar rust Melampsora larici-populina from England

et al. 2005

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Using a leaf disc method, 19 isolates of the poplar rust, Melampsora larici-populina, and one isolate of M. populnea from England were inoculated on to 25 poplar clones belonging to Populus nigra and P. trichocarpa, and hybrids between P. deltoides and P. nigra, P. deltoides and P. trichocarpa, P. tacamahaca and P. trichocarpa, and P. alba and P. tremula. Disease was scored based on the pustule area and inoculum density. In terms of whether sporulating uredinia formed, the 19 isolates showed seven different patterns to the tested poplar clones. The majority of the rust isolates infected P. nigra 'P3090' and 'Vereecken', P. nigra · P. deltoides 'Casale' and 'Tasman', P. tacamahaca · trichocarpa '36' and 'Balsam Spire', and P. trichocarpa 'Blom'. Populus trichocarpa · P. deltoides '69039/4' was infected by only three isolates collected from southern England. No visible symptoms appeared on P. alba · P. tremula 'Tower' and P. trichcarpa · P. deltoides · P. deltoides '76028/5' in inoculations with M. larici-populina isolates. Populus alba · P. tremula 'Tower' was infected only by M. populnea. When M. larici-populina isolates were tested using AFLP, no differences were found either between isolates from different geographical regions or between those having 'narrow' spectrum of virulence and those showing 'wide' spectrum of virulence on the tested clones. The results suggest that the UK rust populations possess virulences which were found in races E1, E2, E3 and E4 in continental Europe and that rust having virulence patterns similar to race E4 has occurred in UK poplar plantations since 1996.

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Disease scoring by taking inoculum densities into consideration in leaf disc inoculations with poplar and willow rusts.

Cited by 3 publications

References 0 publications

Rust resistance in Salix to Melampsora larici‐epitea

Rust resistance in Salix to Melampsora larici‐epitea

Mendelian inheritance of rust resistance to Melampsora larici‐epitea in crosses between Salix sachalinensis and S. viminalis

Pathogenic variation in poplar rust Melampsora larici-populina from England

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