384 Produce Degradation: Reaction Pathways and their Prevention
Downy mildew disease of plants, especially in cool, humid regions, is caused
by several fungi, including species of Basidiophora, Bremia, Peronospora, Phytoph-
thora, Plasmopara, Pseudoperonospora, and Sclerospora. White, gray, bluish, or
violet downy patches of mildew form mostly on the undersides of leaves in damp
weather. Pale-green to yellow or brown areas usually develop on the upper leaf
surface opposite the downy growth. Affected leaves often wilt, wither, and die early.
Stems, flowers, and fruits are sometimes infected. Garden plants, bush fruits, vege-
tables, and certain trees, shrubs, field crops, and weeds are susceptible. The black
spots seen on tomatoes are usually caused by Alternaria, which appears when the
weather is warm and is often found on window frames where condensation has
occurred [58].
TABLE 12.2
Microbial Spoilage of Different Unripe and Ripe Fruits
Spoilage Type Microorganisms Involved Fruits Affected
Anthracnose Colletotrichum lindemuthianum Watermelon, tomato, cucumber, beans
Alternaria rot Alternaria tenuis Pumpkin, winter squashes, persians,
cantaloupe, honeydew, crenshaw, casabas, bell
pepper, eggplant, etc.
Bacterial soft rot Erwinia carotovora and others Tomato, cantaloupe, honeydew, persians,
crenshaw, asparagus, casabas, bell pepper,
eggplant, etc.
Bacterial spot Pseudomonas spp. and
Xanthomonas spp.
Tomato, cucumbers, bell pepperBlack rot Mycosphaerella citrullina Watermelon, cucumber
Blue mold rot Penicillium spp. Cantaloupes and Honeydews mainly
Buckeye rot Various Phytophthora spp. Tomato
Cottony leak Pythium butleri Cucumbers, beans
Cladosporium rot Cladosporuim spp. Tomato, cucumber, cantaloupe, honeydew, bell
pepper, etc.
Fusarium rot Various Fisarium spp. Cantaloupe, honeydews, persians, crenshaw,
casabas, asparagus, etc.
Gray mold rot Botrytis cinerea Tomato, bell pepper, peas
Late blight rot Phytophthora infestans Watermelon, tomato
Phompsis rot Phompsis vexans Eggplant
Phytophthora rot Various Phytophthora spp. Asparagus
Pleospora rot Pleospora lycopersici Tomato
Rhizopus rot Rhizopus stolonifer Cantaloupe, honeydews, persians, crenshaw,
tomato, bell pepper, cucumber, casabas, etc.
Soil rot Rhizoctonia solani Tomato, beans
Stem-end rot Diplodia natalensis Watermelon
Watery soft Rot Various Sclerotinia spp. Beans, peas
Source:From Rubatzky, V.E. and Yamaguchi, M., World Vegetables: Principles, Production and Nutritive
Values, 2nd ed., Aspen Publishing, Gaithersburg, MD, 1999.