The determination of Exserohilum turcicum virulence factors in Serbia

Abstract

The determination of Exserohilum turcicum virulence factors and resistance responses of three sets of maize inbred lines (four differential, eight isogenic and 22 commercial inbreeds) to three isolates of this pathogen under greenhouse conditions were studied. The maize inbreeds were selected according to previous testing of resistance based on lesion types in 194 inbreeds under field conditions of plant inoculation with the E. turcicum race 0 (designated as the isolate MRI-Et). The standard procedure was applied to obtained isolates MRIZP-1747 and MRIZP-1416 from resistant and susceptible lesion types, respectively. These lesions were developed on the same leaf of a plant of the experimental hybrid no. 163/99 grown in a nursery at Zemun Polje during 1999. The third isolate (MRIZP-1435) was isolated from a leaf sample originating from the location of Srbobran in which the occurrence of northern corn leaf blight (NCLB), caused by Exserohilum turcicum, was intensive. Based upon virulence/avirulence of three isolates of E. turcicum on differential maize inbred lines, it was found out that the isolate MRIZP-1747 could be classified as race 0, whereas isolates MRIZP-1416 and MRIZP-1435 could be classified as race 1. These are the first results that confirm the presence of race 1 of E. turcicum in Serbia. Not including differential lines, 22 and six lines were resistant to race 0 and race 1, respectively, while eight and five lines were resistant and susceptible to both races, respectively. All isogenic lines not containing the Ht gene were susceptible to both races 0 and 1.

U ovom radu proučavani su faktori virulentnosti Exserohilum turcicum i tipovi otpornosti tri seta samooplodnih linija kukuruza (četiri diferencijalne, osam izogene i 22 komercijalne linije) prema tri izolata ovog patogena u uslovima staklare. Linije su izabrane na osnovu prethodnog testiranja tipa otpornosti pega kod 194 samooplodnih linija u poljskim uslovima inokulacije biljaka rasom 0 vrste E. turcicum (označena kao izolat MRI-Et). Standardnim postupkom je iz otpornog tipa pege izolovana kultura izolata MRIZP-1747, a iz osetljivog tipa pege izolat MRIZP-1416. Ove pege su bile obrazovane na istom listu jedne biljke eksperimentalnog hibrida br. 163/99 u rasadniku kukuruza u Zemun Polju u 1999. godini. Izolat MRIZP-1435 je iste godine izolovan iz uzorka lista kukuruza poreklom iz lokaliteta Srbobran u kojem je bila neoubičajeno intenzivna pojava sive pegavosti lista koju prouzrokuje E. turcicum. Na osnovu virulentnosti i avirulentnosti tri izolata E. turcicum na diferencijalnim linijama kukuruza utvrđeno je da se izolat MRIZP-1747 može klasifikovati kao rasa 0, dok se izolati MRIZP- 1416 i MRIZP-1435 mogu klasifikovati kao rasa 1. Ovo su prvi rezultati koji potvrđuju da u Srbiji osim rase 0 postoji i rasa 1 E. turcicum. Ne uključujući diferencijalne linije, otpornost prema rasi 0 ispoljile su 22 linije i šest linija prema rasi 1. Istovremeno, osam linija je bilo otporno prema rasi 0 i pet linija prema rasi 1. Sve izogene linije koje nisu sadržavale Ht gen bile su osetljive prema ovim rasama.