Techniques of Screening Peas for Resistance to Phoma medicaginis var. pinodella¹

Abstract

Footrot and foliar phases of the disease caused by Phoma medicaginis var. pinodella in peas (Pisum sativum L.) were studied. Major objectives were to develop repeatable inoculation procedures and to identify pea lines resistant to footrot and foliar infection. All tests were conducted under controlled environmental conditions. Fungal spore concentrations and plant age at inoculation were important for identifying differences in disease reactions among lines. Significant differences in reactions to footrot were obtained among lines when pea seeds were immersed for 5 min. in inoculum adjusted to 1 ✕ 104 spores/ml, planted in a sterile soil mixture, and scored 10 days later. Significant differences in resistance among pea lines to the foliar phase of the disease were obtained when 15‐day‐old pea seedlings were sprayed with inoculum containing 1 ✕ 105 spores/ml and scored 10 days later. Footrot scores ranged from 1.2 to 4.8, and foliar disease scores ranged from 2.1 to 4.9 when 96 pea genotypes were rated on a 1 to 5 scale (1 = symptomless and 5 = very severe disease). There was no significant correlation between footrot and foliar disease scores, indicating that different genetic factors may control reactions to the two phases of the disease.

Biotic factors affecting the expression of partial resistance in pea to ascochyta blight in a detached stipule assay

“…We show that the best conditions to identify partial resistance are those with intermediate inoculum pressure, marginally favouring the pathogen. This idea was supported by Sakar et al (1982) who showed that intermediate concentrations of P. medicaginis var. pinodella inoculum gave a better separation of mean foot-rot disease scores for three cultivars, compared to low or high concentrations.…”

Genetical analysis of resistance to Mycosphaerella pinodes in pea seedlings

“…In one experiment, where a larger number of plants was inoculated, inoculum was applied to seeds instead of directly to stems. To do this, seeds were surface-sterilised in sodium hypochlorite solution, washed in sterile water, as above, then immersed in a suspension of 106 spores m1-1 for 10 minutes (Sakar et al, 1982). After 14 days growth in compost (Fisons Universal) in a seed tray in a glasshouse at 15 ° C, each plant was assessed on a six-category scale (Table 2).…”

Relative Host Resistance to Black Spot Disease in Field Pea (Pisum sativum) is Determined by Individual Pathogens

“…Screening for black spot resistance in field pea in Australia and elsewhere has largely focused on D. pinodes (6,18,23,35,50,52,53), much less so on P. pinodella (2,22,36), and not at all on P. koolunga. was the most virulent of the three pathogens in terms of stem disease, and its AUDPC MR was significantly higher than that of D. pinodes, previously considered the most important pathogen in the black spot complex (31,32).…”