Relative Competitiveness and Virulence of Four Clonal Lineages of Cephalosporium maydis from Egypt Toward Greenhouse-Grown Maize

Abstract

Four clonal lineages of Cephalosporium maydis, a soilborne vascular wilt pathogen that causes late wilt of maize, were differentiated previously with molecular markers. In Egypt, this fungus can cause significant losses in infected susceptible plants. In greenhouse tests of individual isolates we found that these lineages differ in their virulence toward a series of maize accessions commonly used in Egyptian maize breeding programs. We also determined the relative competitiveness of representatives of the four lineages when incorporated into the soil as a mixed inoculum. The lineage (IV) with greatest mean disease incidence (virulence), when tested alone, was the least competitive on susceptible maize accessions when coinoculated as a component of mixed inocula of all four lineages. In these coinoculation experiments, one of the less-virulent lineages (II) dominated (70% of infections) and appeared to be the most competitive. These results suggest that virulence and competitive ability are not the same in this host-pathogen system. These results also suggest that standard protocols that rely on mixed inocula for resistance screening need to be altered, and that the relative proportion of the different lineages of the pathogen recovered in a field may be influenced by the maize variety/hybrid planted.

Diagnosis and Control of <i>Harpophora maydis</i>, the Cause of Late Wilt in Maize

“…Since H. maydis is capable of undergoing pathogenic variations [18,43], new virulent strains could develop and breeding for resistance will remain a continuous process. To exemplify this importance, a virulent lineage exists in Egypt that is a threat to some resistant maize cultivars [18], while in Israel the relatively resistant maize cultivar, Royalty, which has become the leading maize cultivar since the late disease outburst, started to show wilting symptoms in the summer of 2010 and caused significant economic damage when a disease outburst caused its collapse in Beit She'an (Jezreel Valley, Lower Galilee region in Israel) maize fields in the summer of 2013 (Israel Northern R & D, Migal-Galilee Research Institute, Kiryat Shmona, Israel, unpublished data). According to the same logic, the need to identify new effective compounds against the late wilt causing agent is urgent and requires uninterrupted efforts.…”

“…Three of the lineages are widely distributed throughout the country. The fourth lineage was the most virulent but least competitive on susceptible maize accessions when inoculated as a mixed inoculum of all four isolates [18].…”

“…The Egyptian, Indian and Hungarian isolates of H. maydis differ in morphology, pathogenicity and route of infection [15]. The four clonal lineages of Egyptian isolates of H. maydis show diversity in amplification fragment length polymorphism (AFLP), and differ in colonization ability and virulence on maize [16][17][18][19]. Three of the lineages are widely distributed throughout the country.…”

Lineage, Temperature, and Host Species have Interacting Effects on Lesion Development in Phytophthora ramorum

“…Zoospore and mycelial inoculations were performed without wounding in order to allow an assessment of the ability of the pathogen to survive on and infect the host, which may have more relevance when trying to model the factors affecting the risk of infection spread in natural ecosystems and nurseries. have shown differences in phenotype between clonal lineages in terms of growth rate, spore size, latent period, and aggressiveness (6,17,78). After initial infection, P. ramorum progresses to a necrotrophic phase, inducing the necrotic lesions necessary for sporulation and, thus, transmission.…”

Plant growth hormones suppress the development of Harpophora maydis, the cause of late wilt in maize

“…The Egyptian, Indian and Hungarian isolates of H. maydis differ in morphology, pathogenicity and route of infection (Warren 1983). In Egypt, there are four clonal lineages of H. maydis that differ in colonization ability and virulence on maize (El-Assiuty et al 1999;Saleh et al 2003;Zeller et al 2000Zeller et al , 2002.…”