Components of quantitative resistance to powdery mildew (Erysiphe pisi) in pea (Pisum sativum)

Abstract

Components of quantitative resistance in pea (Pisum sativum) to Erysiphe pisi, the pathogen causing powdery mildew, were investigated. Conidium germination, infection efficiency, latent period and conidium production dynamics on cv. Quantum (quantitatively resistant) were compared with those on Pania and Bolero (susceptible). There was an additional comparison in conidium germination experiments with the resistant cv. Resal. Quantitative resistance in Quantum did not affect conidium germination, but infection efficiency of conidia on this cultivar was 34% less than on the susceptible Pania. More conidia germinated on 5-day-old leaflets than on 15-day-old leaflets but the age of the plant did not affect percentage germination or infection efficiency. The length of the latent period did not differ between cultivars. Total conidium production (AUC) per unit leaflet area on Quantum was 25% less than on Pania. The maximum conidium production per day (CMAX) per unit leaflet area on Quantum was 33% less than on Pania. The time to maximum conidium production per day (TMAX) was 10% longer on Quantum than on Pania. The cv. Bolero, reported to be susceptible, also showed some degree of quantitative resistance, but this differed from that of Quantum. Total conidium production was less on Bolero than on Quantum, but the conidia on Bolero were produced sooner, and for a shorter period, than on Quantum. The stability of these responses was tested by analysing components in three different temperature regimes and testing for interactions with temperature, and with leaflet age. Temperature affected all conidium production variables. AUC per leaflet area was nearly seven times as great and CMAX nearly 15 times greater at 23ЊC than at 13ЊC. TMAX increased by 1·5 times when temperature increased from 13ЊC to 18ЊC or 23ЊC. Several interactions occurred and these are described.

Effect of temperature, relative humidity, leaf wetness and leaf age on Spilocaea oleagina conidium germination on olive leaves

“…In a similar study, Viljanen-Rollinson et al (1998) showed that more Erysiphe pisi conidia germinated on 5-day-old leaflets (79.8%) than on 15-day-old leaflets (69.7%) of pea plants. It was also demonstrated that on apple leaves, the germination and infection by Venturia inaequalis conidia (Spilocaea pomi) was higher on younger leaves than older ones (Schwabe 1979;MacHardy 1996).…”

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

“…Reports show that often experimental conditions are the same to display different components of resistance. Vijanen- Rollinson et al (1998) for instance, used the same conditions to study diverse components of quantitative resistance to powdery mildew in pea (conidial germination, infection efficiency, latent period and conidial production). Bouhassan et al (2003) also analysed various components of partial resistance to chocolate spot in faba bean (incubation period, number of spots, lesion diameter, latency period and sporulation) under environmental conditions common to all components.…”

Screening techniques and sources of resistance to rusts and mildews in grain legumes

“…Differences in sporulation, represented by number of conidiophores bearing conidia per colony, were also detected in a set of pea lines with variable reactions to powdery mildew (Banyal & Tyagi, 1997a). Similarly, the incomplete resistance shown by the pea cultivar Quantum was found to be based on a lower infection efficiency and conidial production accompanied by a longer time to reach maximum conidial production per day (Viljanen-Rollinson et al, 1998). In P. fulvum accessions, a posthaustorial hypersensitive response conferred effective resistance in field and growth cabinet conditions.…”

“…The use of a settling tower allows greater control of inoculum density and uniformity which is important in assessment of partial resistance (Smith et al, 1996). Cut leaves placed on the bottom of the settling tower are inoculated by shaking conidia from infected leaves into the top of the tower (Smith et al, 1996) or collecting conidia in glass vials with a vacuum pump-operated cyclone spore collector and dispensing them by compressed air (Viljanen-Rollinson et al, 1998). Numbers of conidia deposited per cm 2 are estimated by placing microscope slides at the bottom of the settling tower and counting them after allowing them to settle for 5 min.…”