Variation in virulence and aggressiveness among pathotypes of Sclerospora graminicola on pearl millet uri icon

abstract

  • Five pathotypes of S. graminicola, specific to Pennisetum glaucum genotypes, were evaluated for virulence (a qualitative measure of the relative capacity of an isolate to infect a host genotype), aggressiveness (a quantitative measure of the infection causing potential of an isolate, calculated as disease incidence), and virulence index (a quantitative measure of virulence, measured as disease incidence√ólatent period-1) on a set of P. glaucum genotypes in a greenhouse. The pathotypes were selected from a field population of the pathogen through a number of successive asexual generations on specific host genotypes. These were named as pathotype, Path 1 (host NHB 3), Path 2 (BJ 104), Path 3 (MBH 110), Path 4 (852B) and Path 5 (a field population from a mixture of NHB 3 and 7042S). The pathotypes differed significantly in virulence, aggressiveness and virulence index on the host genotypes. Highly significant (P<0.001) pathotype√óhost genotype interaction effects for virulence, aggressiveness and virulence index suggested the existence of host-pathogen specificity in the P. glaucum-S. graminicola system. Differential interactions for virulence were evident on 8 of the 14 host genotypes. All 5 pathotypes were moderately virulent (3.75-7.03 virulence index) and less aggressive (28-46% incidence) on ICMP 85410 suggesting the presence of non-pathotype-specific resistance which could be more stable. It is concluded that the other P. glaucum genotypes (IP 18292, IP 18293, 7042R, P 7-4 and P 310-17), to which the pathotypes were either avirulent or less virulent, can serve as sources of stable resistance

publication date

  • 1997
  • 1997