Virulence and aggressiveness of Phytophthora infestans isolates collected in Poland from potato and tomato plants identified no strong specificity

Abstract

Late blight is a devastating and worldwide potato and tomato disease caused by Phytophthora infestans (Mont.) de Bary. The aim of the study was to compare P. infestans isolates collected from potato and tomato plants by determining their virulence, aggressiveness, and sporulation intensity on both hosts in reciprocal testing with the goal of elucidating possible host specialization of the pathogen. Isolates were multiplied on leaflets of their primary hosts. In total, 76 potato-derived P. infestans (P) isolates and 100 tomato-derived P. infestans (T) isolates collected from 2005 to 2007 were studied in detached-leaflet assay experiments. Virulence was assessed on Black's potato differentials R1-R11 and cv. Bzura, as well as on the set of six tomato genotypes, namely cv. New Yorker (Ph-1 gene), Solanum pimpinellifolium L 3708 (Ph-3), West Virginia'63 (Ph-2), West Virginia 700 (Ph-1, Ph-2), Ottawa 30 (Ph-1, Ph-2), and BALU-30 (Ph-1, Ph-2, fruit resistance). Aggressiveness scored as disease severity and sporulation intensity assessed on a 0-3 grade scale were evaluated on leaflets of susceptible cultivars of both hosts. All 176 of the tested isolates were pathogenic to both hosts, indicating that extreme host specialization has not occurred. However, we did observe differences between P and T virulence spectra and their race structures supporting the notion of host adaptation of P. infestans. P and T isolates were more frequently virulent to differentials of their own hosts. P isolates had higher sporulation intensity on their own hosts than on tomato hosts, while for T isolates a similar sporulation intensity was observed on both hosts. Significantly stronger severity of the disease development on T testers was evoked by T isolates. All isolates showed stronger aggressiveness on susceptible potato than on susceptible tomato hosts, and the latter finding indicates a relatively greater suitability of potato host tissue for P. infestans pathogenicity. The host adaptation observed in this study was not conditioned by an ability to evoke disease, but rather by quantitative differences in pathogenic fitness. Genetic characterization of P and T populations is needed to place the present findings in a fuller context.

Virulence Phenotypes on Chili Pepper for Phytophthora capsici Isolates from Michoacán, Mexico

“…Nonvirulent P. capsici isolates have been reported previously when using the NMRILs as differential hosts (da Costa Ribeiro and Bosland, 2012). The isolate CPV-273 was isolated from Solanum lycopersicum, and it is possible that they were not pathogenic to C. annuum due to host specificity (Cohen 2002;Michalska et al, 2016). The remaining isolates were virulent to CW and at least to one NMRIL.…”

Culture storage age and fungal re‐isolation from host‐tissue influence Colletotrichum spp. virulence to pepper fruits

“…However, longer storage deprived fungi of nutrients. Thus, the length of storage or the culture's age could affect the fungus aggressiveness, virulence and pathogenicity when introduced back to its host (Dahmen et al, 1983;Michalska et al, 2015). This study found that culture age can Aggressiveness can be determined by measuring the time between the introduction of the disease up to the onset of symptoms (Allingham & Jackson, 1981) and hence can be assessed through the earliness of symptom expression.…”

“…However, longer storage deprived fungi of nutrients. Thus, the length of storage or the culture's age could affect the fungus aggressiveness, virulence and pathogenicity when introduced back to its host (Dahmen et al, ; Michalska et al, ). This study found that culture age can affect aggressiveness and virulence of the pepper anthracnose fungus Colletotrichum truncatum and C. scovillei .…”

“…However, when cultures are required for new selection trials, particularly new germplasm collected and new breeding populations, the stored fungi are revived and are used for the subsequent experiments. As fungi are deprived of their nutrients during storage, they may exhibit loss of virulence and pathogenicity (Dahmen, Staub, & Schwinn, ; Michalska, Sobkowiak, Flis, & Zimnoch‐Guzowska, ), which can affect comparison between the previous and current experiments.…”

“…For example, a C. scovillei isolate infects ripe fruits of C. baccatum PBC81 but not ripe fruits of C. baccatum PBC80 (Mongkolporn et al, 2010). (Dahmen, Staub, & Schwinn, 1983;Michalska, Sobkowiak, Flis, & Zimnoch-Guzowska, 2015), which can affect comparison between the previous and current experiments.…”