In this article we will discuss about the occurrence of algae and fungi in aero-microbiology.
Work of K.C. Mehta lent support for Joshi (1972) and Nagarajan and Singh (1973) who found that brown and black rust of wheat are disseminated from the hills of South India to Central India by “hop jump” in which a storm depression formed in Bay of Bengal/Arabian Sea reaches Central India.
Nagarajan and Singh (1973) found the satellite television cloud photography as a possible tool for forecasting the spread of several plant pathogens such as Alternaria, Cercospora, Helminthosporium, Puccinia, etc.
Aeromicrobiological investigations on several crops such as rice, wheat, jwar, bajra, cotton, banana, citrus, sugarcane, and vegetables have been carried out by many Indian scientists.
Studies on microbial components of air over crop fields are useful in understanding the plant pathogens and in establishing the forecasting system for disease control. A lot of work has been done on aeromycology on several crop fields.
Navneet (1995-96) studied aeromycoflora over potato fields at Kurukshetra for two years and recorded 25 fungal species. The dominant fungi were Alternaria alternata, Aspergillus flavus, A. niger, Cladosporium herbarum, Epicoccum nigrum, Penicillium citrinum, P. cyclopium and Trichothecium roseum.
Rain has the propound effect on aerofungi. Verma (1998) recorded 62 aerospora over rice field by using Tilak sampler. The most dominant fungal taxa was Aspergillus (75%) followed by Penicillium (10%), Alternaria (3%) and Cladosporium (2%).
In general, aspergilli form a major component of aerospora including pathogenic species also (e.g. A. niger). A niger causes disease on jack fruit, onion, etc. Alternaria spp. (e.g. A. brassicae, A. dauci, A.porri, A. solani) cause disease on several crop plants.
Anatoxins by Aerofungi:
Aflatoxins are the secondary metabolites of some saprophytic fungi injurious for human health. Work on aflatoxin production from agricultural field to storage conditions in different parts of the country as well as in different crop fields has been done well by late Prof. K.S. Bilgrami and his associates (1975-1996) at Bhagalpur University, Bihar.
The species of fungi secreting aflatoxins are Aspergillus flavus, A. parasiticus and others. Aflatoxin of A. flavus is known to cause cancer. Rati and Ramalingam (1979) surveyed A. flavus in air samples in outdoor air and air of poultry shed.
They found that 72% of these were toxigenic, and the incidence of toxigenic strain was found to be greater in winter months. The concentration of aerospores inside poultry shed was about 10-100 times greater than that of adjacent outdoor environment. In 1960, outbreak of a lethal disease in turkey poults was resulted due to consumption of aflatoxin contaminated meals.
The disease symptoms included (a) rapid deterioration in the conditions of birds, and (b) subcutaneous hemorrhages leading to death. The livers of dead birds were pale, fatty and showing extensive necrosis and biliary proliferations.
Similar symptoms were also observed in duckling fed on “toxic groundnut meal”, and several other animals. Organs other than liver are also affected by aflatoxins such as kidney, adrenal glands, and lungs, skin, etc.
Moreover, aflatoxin B1 is known to cause mutagenicity through chromosomal aberrations and DNA breakage in plant and animal cells. Sinha (1987) observed the gross and individual types of chromosomal abnormalities and breakage in the chromosomes of bone marrow cells of mice. The breaks were more frequent in the distal regions of the longer chromosomes.
Seasonal Occurrence of Aflatoxin Producing Aerofungi:
Environmental factors are responsible for occurrence of aerofungi in different regions. Choudhary (1991) surveyed the climatic conditions on incidence and severity of aflatoxin contamination of field maize crop during 1986- 1990 which were cultivated as Kharif crop in Bihar.
He noticed that temperature (during July- August) and prevalence of relative humidity (90% RH) for prolonged time are the major determinants of aflatoxin contamination. Increased level of aflatoxins in non-irrigated maize crops has been linked to higher levels of air-borne inoculum of A. flavus.
A little work has been done on occurrence of algae in air. Generally, algae dominate upto a height of 2 meters. The most common algae found in air are the species of Chlorella, Chlorococcum, Chlamydomonas, Aulosira, Nostoc and Phormidium.
Ramalingam (1971) reported some of the algal types (e.g. diatoms, Protococcus, Spirogyra, Oscillatoria, etc.) from Mysore. Agnihotri (1977) have reported the lichen component of aerospora with special reference to allergenic ones, from hill districts of Uttar Pradesh.
The most common lichens were the species of Cladonia, Heteroderma, Parmelia, Usnea, etc. In rainy season beauty of the world fame Taj Mahal fades due to the growth of algae on it. However, it is properly cleaned regularly. A National Laboratory for Conservation of Cultural Properties has been established at Lucknow that takes care of developing methods for conservation of monuments, archives, etc.