A comparative study of Colletotrichum species causing anthracnose in Hevea

Colletotrichum acutatum and C. gloeosporioides are destructive fungi causing diseases in a wide range of plants. In many instances they are responsible for mixed infections. The present study revealed that the spore productivity is higher in slow growing species C. acutatum at all temperatures investigated. Spores of C. gloeosporioides germinated earlier but both reached a maximum after 7-8 hrs and in C. gloeosporioides the elongation of germ tubes was much faster. The temperature influenced greatly the germination of spores in the two species and self-inhibition of C. acutatum occurred at much higher spore concentrations than in C. gleosporioides. The germination response of dry smears to temperature change was poor in both the species and drying reduced germination. Free water was not essential but when present promoted germination in both the species. None of the spores germinated below 85% RH at RT. The slower growth rate of C. acutatum was also evident in the liquid medium. PG activity of C. acutatum was higher than that of C. gloeosporioides and molecular weights of the enzyme were significantly different in the two species. The activity of PL was more or less similar in the two species. In laboratory studies C. acutatum appeared to be less virulent than C. gloeosporioides.