Premium
I. Pathogenic variation in fungi and bacteria and mycorrhizal compatibility: The genetic architecture of aggressiveness in Ustilago maydis
Author(s) -
BASSI F. G. A.,
BURNETT J. H.
Publication year - 1980
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1980.tb03924.x
Subject(s) - biology , ustilago , pathogen , host (biology) , genetic architecture , allele , heritability , genetics , gene , genetic variation , phenotype , botany
Isolates of Ustilago maydis (D.C.) Cda are known to differ in the degree to which they can parasitise maize and, as no differential reaction occurs between pathogen and host, these differences must be differences in aggressiveness. Inoculation of juvenile maize plants induced morphological changes which provided a means of assessing and distinguishing U. maydis isolates in respect of their aggressiveness. Thus it was possible to carry out a survey of the genetic architecture of aggressiveness in natural populations of the pathogen. The distribution of aggressiveness within a single gall suggested that selection had taken place over a number of generations in favour of genes or gene systems tending to increase aggressiveness. Diallele analyses of isolates from two natural populations revealed that aggressiveness had a low heritability and was determined by genes exhibiting mainly non‐allelic interaction. It has been proposed that horizontal resistance in host cultivars would have a more long lasting protective effect against disease. However, the genetic architecture of aggressiveness in U. maydis should enable the pathogen to respond rapidly to changes in host resistance and the skewed distribution found within a single gall tends to support this. Therefore, the use of higher levels of host resistance should rapidly select for higher aggressiveness in the pathogen.