Symptomatology and morphological, cultural characterization of Entomosporium leaf and fruit spot disease of pear (Pyrus communis L.)

Abstract

The disease on leaves was characterized by the appearance of small, reddish to dark brown pin-pointed spots measuring approximately 3 mm in size, with angular to irregular margins, and as the spots grew, they become more or less circular in outline, with reddish brown to black centers and were surrounded by a yellowish halo which on coalescing formed irregular necrotic patches. Severe infection resulted in pre-mature defoliation. Small, sunken, circular, black spots, averaging 6 mm in size surrounded by reddish brown margins, embedded with dark brown to black acervuli releasing creamy white spore droplets under moist conditions. Severely infected fruits were roughened and developed cracks were the characteristic disease symptoms observed on fruit. The pathogen constantly associated with the disease was isolated. The pathogen on potato dextrose casein hydrolysate thiamine agar medium produced compact, glistering, dull white to reddish brown cottony mycelial mat after 45 days of incubation at 22±1°C. The morphological characters of the pathogen associated with the disease were studied both on host (in vivo) as well as on after culturing on potato dextrose agar medium incorporated with casein hydrolysate thiamine (in vitro). On the host the hyphae were branched, smooth, thick walled, septate, hyaline and measured 8.25-8.75 µm in width averaging 8.48 µm, the size of the conidia ranged from 14.46-20.68 ´ 9.42-12.46 µm. with an average size of 17.57 ´ 10.94. From culture on potato dextrose casein hydrolysate thiamine agar medium the fungus exhibited compact, dull, white, glabrous, glistering cottony growth. The white colour of the fungal colony finally changed to reddish brown after 30 days of incubation at 22±1°C. The hyphae were hyaline, smooth, thick walled, branched, septate, and measured 8.54 to 8.98 µm in width averaging 8.76µm, the conidial size ranged from 16.36-22.70 µm in length and 10.37-14.65 µm in width averaging (19.56´12.51 µm).