Six decades of Aerobiology research in NE India
- Part 1 -

Dr N Irabanta Singh *

Center of Advanced Study in Life Science at Manipur University :: Pix - Bunti Phurailatpam

Preamble

The pioneer Aerobiologist from North East India was H.K. Baruah, Ph.D. (Cantab., 1942) and is now regarded as the Father of Aerobiology in the region. He started his aerobiological research works in the region after visiting Imperial College of Science and Technology, London where he worked with P.H. Gregory, F.R.S. under Colombo plan fellowship (1955-56).

Remarkable progress in aerobiology research in N .E. India had been made during his tenure as Professor and Head, Botany Department, Gauhati University (1948-1974) and later on as Vice -Chancellor of the same University (1974-1979). The present speaker had an opportunity to study his M.Sc.(Botany) and Aerobiology research for Ph.D. degree under the guidance this great personality. Whatever he learnt ABC of Aerobiology till today is because of this grea1 soul. So, please accept my humble salute.

Definition and Scope of Aerobiology

The term Aerobiology was first coined by F.C. Meier of USA in 1930's. Aerobiology can be defined as the study of bioaerosols of airborne particles of biological origin, their sources, liberation, dispersal, deposition and impact on other living organisms and the effects of environmental conditions on each of these processes described as the aerobiological pathway (Edmond, 1979).

Aerobiology deals not only with many different types of organisms but also with their products including: viruses; cells and spores of bacteria; actinomycetes and fungi and associated metabolites; spores of bryophytes and pteridophytes; pollen grains of higher plants; mites and insects, their fragments and faecal pellets; protein released from the plant and animals cells during industrial processing; and products of biotechnological process (enzymes). The impact on other organisms includes infection, allergy and toxicosis in men, animals and infection of plants. Aerobiology is thus a discipline in itself but one that draws on and is utilized by workers in many different fields (Lacey, 1995a).

In India, the systematic aerobiological work was first performed by David. C. Cunningham, a British army medical officer at the Presidency jail, Calcutta. His aerobiological finding was published as a book entitled “Microscopic Examination of Air" in 1873. Aerobiology research in North East India can be considered decadewise as it is nearing six decades.

Aerobiology research during 1958 to 1967 (First decade)

The relationships between airspora presence in storage chamber or a plantation field with incidence of potato diseases in Shillong (Meghalaya) were studied by Konger and Baruah (1958) by employing vaseline coated micro slides and nutrient petriplate exposure.

A study of airspora over arecanut plantations in Assam by employing microslide fixed on kite revealed that there was a strong relationship between the airspora and spoilage of ftuit and their sterility. The microbial metabolites isolated from the stigmas of areca nut flowers, inhibited in vitro germination of pollen grains and growth of pollen tubes (Baruah and Raghavan, 1959).

Aspergillus fumigatus, Geotrichum candidum and Mucor sp. were isolated from aborted cattle in Assam. Aspergillus, Penicillium, Nigrospora, Cladosporium, Mucor and Geotrichum were isolated from hay and straw samples used as cattle feed. It was suggested that the variation in the density of airborne spores in atmosphere causes mycotic abortion in cattle and also human allergic respiratory diseases such as asthma (Baruah and Ahmed, 1963).

It was also illustrated that there was a strong connection between air spora and angiospermic reproduction and to human allergic diseases. Cladosporium, Aspergillus, Penicillium, Curvularia, Alternaria, Helminthosporium, Nigrospora, Fusarium, etc. were present in the air of paddy field in Guwahati. The highest 2occurrence of spores was found in the month of November, October and December while the lowest in the rainy season, July (Chetia, 1964).

The aerospora present in the outdoor air and in rooms occupied by asthmatic patients in Guwahati (Assam) by employing nutrient petriplate revealed predominance of fungal spores of Cladosporium, Aspergillus, Penicillium, Curvalaria, and Alternaria which causes allergenic manifestations (Baruah & Chetia, 1966).

The air samplers used were mainly nutrient pertiplate exposure method, vaseline coated micro slide exposure method and kite fitted with vaseline coated microslides.

Aerobiology research during 1968 to 1977 (Second decade)

Airborne spores of Alternaria, Aspergillus, Clasdosporium, Curvalaria and Penicillium were found dominant in Guwahati. Airborne pollen grains such as Polygonum, Amaranthus-Chenopad, Gramineae (Poaceae), Cyperaceae, Hibiscus rosa sinansis, Ricinus communis, Psidium guava, Caesalpinia pulchaerem, etc. were observed to be present in Guwahati. These were main airspora for allergenic manifestations. Further, the antigenic reactions of various experimental animals treated with extracts of these pollen grains and fungal spores were found significant in treating allergic human diseases (Baruah and Bora, 1971).

Aerobiological studies using smeared slides and nutrient plates revealed the presence of Colletotrichum falcatum conidia in the sugarcane plantation in Sibsagar district, Assam. The presence of C. falcatum in relation to other fungi present in the air was not so marked as to suggest that C. falcatum conidia were predominantly present. It was, however, possible that dispersal of C. falcatum took place at different times of the day or in different seasons (Ahmed and Baruah, 1975). .

Thrust areas of aerobiology research during second decade (1968-1977) were use of experimental animals for treating allergic human diseases and forecasting plant diseases. The samplers used were exposure by smeared slides and nutrient petriplates.

Aerobiology research during 1978 to 1987 (Third decade)

The germination potential study of the airborne spores of Shillong and its suburbs revealed presence of thirty nine fungal types. Aspergillus, Aureobasidium, Blastomycetes, Botryotes, Cladosporiium, Gliocladium, Monillia, Mucor, Penicillium, Scopulariopsis, Drechslera, Fusarium, Thielaviopsis, etc., were important fungal types. The results showed that there was no significant different in the maximium temperature but there was highly significant difference in the rainfall (Nameirakpam and Baruah, 1979).

The Presence of airborne pollen grains and fungal spores inside hospital ward and an operating cinema hall in Shillong (Meghalaya) revealed pollen grains of Graminae, Pinus, Cyperaceae, Polygonaceae and colonies of Aspergillus, Mucor, etc. as principal airspora. In all 35 and 37 pollen types were reported from the air of hospital ward and cinema hall respectively in Shillong (Meghalaya), Pinus contributed 34.24%, while Graminae 33.19% of the total yearly count. The pollen mould ratio was 4.39/64.93 while mould spore/colonies were 22.84/72.70 respectively (Nameirakpam, 1980).

Mycoflora of air, leaf surface and soil fungi of potato and paddy fields in Shillong (Meghalaya) was also reported (Satpute et. al., 1987). The study revealed maximum microbial population at higher altitudes.

The airspora of Imphal, its seasonal fluctions and relationship to the occurrence and intensity of major crop diseases especially rice, pea, mustard reported for the first time (Singh, 1987). These investigations suggested timing for fungicidal spray and thereby prevent future outbreaks of epiphytoties.

Aerobiology and epidemiology of certain fungal diseases of rice in Imphal by employing vertical glass cylinder method revealed rice -blast (Pyricularia oryzae cavara), brown spot (Helminthosporium oryae Bride de Han.) and false smut (Claviceps oryzae sativae Hasioka) as most important airborne fungal diseases of rice (Singh and Singh, 1989).

Air monitoring over common bean field in Imphal by employing Tilak Volumetric air sampler revealed Uromyces phaseoli Arth (Syn. U. appendiculatus Pers.) as most important air borne fungal disease of common bean in Manipur.

Air monitoring over Pea fields in Imphal by employing Vertical Glass Cylinder method revealed six fungal pathogens viz., Peronospora pisi (downy mildew), Uromyces fabae (Pers.) de Barry (rust), Colletotrichum pisi (Anthacnose), Erysiphe polygoni DC. (Powery mildew), Alternaria sp. Leaf blight and Cladosporium sp. Leaf spot) as important airborne fungal disease of pea (Singh, 1987).

Leaf spot disease caused by Cercospora sp. was most severe disease of tomato in Imphal. Aebiological approach to leaf spot disease of tomato (Lycerposicon esculentum Mill) in Imphal and its suburbs by employing gravity slide method revealed the highest concentration of Cercospora spores in the night spora. The period coincides with pre-flowering to flowering phases of the crop (Singh and Singh, 1986).

Aerobiology and epidemiology of certain fungal diseases of mustard in Imphal by employing vertical cylinder revealed mustard blight (Alternaria bassicae ((Berk.) Sac.); While rust (Albugo candida (Pers.) Kunts.); Powdery mildew (Peronospora brassicae Gaun) as most important airborne fungal diseases of mustard Imphal (Singh, 1987).

The air samplers used during this decade were Durham type aeroscope (modified), microthread exposure method; nutrient petriplates, microslides exposure method in Durham type aeroscope and Tilak air sampler.

To be continued...