In this article we will discuss about the major pathogens of post-harvested fruits and vegetables.
The important fungal and bacterial pathogens of harvested fruits and vegetables that cause infection during or after the harvest with disease and the primary hosts are listed in the Table 19.1.
Post-harvest Diseases Commencement:
The Pathogens:
Matured fruits and vegetables often become more susceptible to injury, therefore, more vulnerable to the attack of those microorganisms which require an injury or damaged tissue for penetration. Natural disease resistance, which acts in developmental stages of the plants, weakens as a result of separation of fruits and vegetables from parent plant.
In addition picked fruits and vegetables are rich in moisture and nutrients; consequently, their prolonged storage leads to the senescence of tissues that suits the development of pathogens.
Fungi and bacteria responsible for storage decay often originate in field or orchard. Many fungi viz. Alternaria, Fusarium, Penicillium, Aspergillus, Rhizopus, Mucor, Botrytis are among the most important cause of decaying which affect harvested fruits and vegetables. Post-harvest pathogens perpetuate on crop debris in the field and under suitable conditions produce abundant spores.
These fungal spores are easily carried by winds, rain, or dispersed by insects to flowers and young fruits at various stages of development and form a potential source of infection. Soil, irrigation water and infected plant debris forms an important source of infection.
Soil-residing fungi and bacteria can attack the bulb, tuber, root and other vegetal parts through contact with the soil, lifting of soil particles by winds, rains or by arriving in storage with attached soil residues.
Some soil microorganisms such as species of the fungi Botrytis, Sclerotinia and Fusarium or the bacterium Erwinia carotovora, are among the main decay agents in stored vegetables and fruits. Host infection can occur on pre harvest, harvest or any of the Post-harvest handling stages.
Harvesting instruments, containers, hands of the labours, packing and storage rooms are all prolific sources of fungal and bacterial spores. Fruits and vegetables carry the microorganisms into storage, only a few species can attack naturally while other species inhabits on the surface in large quantities will not penetrate or cause any decay.
The development of disease during storage depends primarily on the existence of the appropriate microorganisms along with particular host. However, fungal spores or bacterial cells that have reached the suitable host should be capable of penetration or infection into the host tissues.
The right environmental temperature, available moisture and presence of nutrients transferred from the host into water are the most important congenial factors for spore germination which is a preliminary stage for fungal penetration into the host.