Specific adaptation of colletotrichum falcatum pathotypes to sugarcane cultivars

Abstract

Colletotrichum falcatum pathotypes exhibit distinct differential host interaction where certain pathotypes specifically infect their adapted host cultivars. This adaptation phenomenon was tested with two distinct pathotypes,viz. Cf1148 and Cf7717 isolated from cultivars Co 1148 and Co 7717, respectively. The results revealed that pathogenicity of both the pathotypes was influenced by their respective/host specific parental cultivars and not vice versa. Cane juice from the host cultivars influenced cultural characters of the pathogen including mycelial growth and conidial germination and they were also varied depending on juice from position of cane stalk. Adaptability of Cf1148 and Cf7717 was tested by cross inoculation on their incompatible hosts viz. Co 7717 and Co 1148, respectively. On cross inoculation, restricted symptoms were produced. Reisolation from such canes yielded fungal activity with changes in growth pattern as compared to original cultures was noticed. After repeated inoculations the dark isolates at initial phases become light with increased sporulation on their adapted hosts. Development of light isolates and reduced latent period for symptom expression by repeated inoculations on incompatible hosts indicated the increased virulence or pathogenicity of that pathotype for adaptation on a particular cultivar.