Arup Kumar Mukherjee

A stochastic cellular automata model of innovation diffusion

Abstract A stochastic cellular automata model of new product diffusion is proposed. It is found that the growth for a given market potential can be determined by a parameter that quantifies chance preferences of individuals for the product and can be estimated from field surveys. It is also found that the “takeover time” in a given seed region is almost independent of the number of innovators. The results suggest possible strategies for the successful introduction of a new product.

PROSPECTING CYANOBACTERIA-FORTIFIED COMPOSTS AS PLANT GROWTH PROMOTING AND BIOCONTROL AGENTS IN COTTON

The potential of cyanobacteria-based compost formulations was evaluated in cotton crop at two agro-ecological locations (Nagpur and Sirsa) as plant growth promoting (PGP) and biocontrol agents. Compost-based formulations fortified with Calothrix sp. or Anabaena sp. enhanced germination and fresh weight of plants, and microbiological activity by 10–15%, besides increased available nitrogen (by 20–50%) in soil at Nagpur. In the fungi-infected fields at Sirsa, Anabaena – T. viride biofilmed formulation performed the best, recording 11.1% lower plant mortality than commercial Trichoderma formulation. Scanning electron microscopy confirmed the colonisation of inoculated cyanobacteria/biofilms on roots. Significant correlation between mortality, increased activity of hydrolytic enzymes and fresh weight of plant roots were recorded. Calothrix sp. and Anabaena sp. proved promising as both PGP and biocontrol agents, while biofilmed formulations substantially reduced mortality of cotton plants in sick plots. This study illustrates the promise of cyanobacteria as viable inoculation option for integrated nutrient and pest management strategies of cotton.

Estimation of area under the disease progress curves in a rice-blast pathosystem from two data points

Attempts were made to estimate the area under the disease progress curve (AUDPC) of rice blast disease caused by Pyricularia grisea from two data points on the disease progress curve. Forty-two rice genotypes were exposed to high disease pressure in a nursery over nine seasons. A conducive condition was created for maximum disease development through high nitrogen application, close spacing and maintenance of high relative humidity. Disease severity was recorded on alternate days beginning from disease initiation until the end of the epidemic. The estimation of AUDPC, and logistic and Gompertz apparent infection rates using either all-points (AP) or two-point (TP) methods revealed significant correlations among them. This was also confirmed through regression analysis and factor analysis. Hence, the estimation of AUDPC from two data points i.e. initial and final disease scores of the disease progress curves is recommended as providing information similar to that from all the data points; this should save valuable time, labour and economic resources.

Reclassification of Trichoderma Viride (TNAU), the Most Widely Used Commercial Biofungicide in India, as Trichoderma Asperelloides

Trichoderma viride TNAU is the most widely used biofungicide in India with more than 250 registered commercial formulations being available. We have studied the phylogenetic position of this strain using a molecular marker and determined that this commercial strain is, in fact, a strain of Trichoderma asperelloides, and not T. viride. The implications of these findings on the registration and commercial distribution of biofungicides based on this strain has been discussed.

Biocontrol potential of three novel Trichoderma strains: isolation, evaluation and formulation

We have isolated three novel strains of Trichoderma (two T. harzianum and one T. atroviride) from wild mushroom and tree bark, and evaluated their biocontrol potential against Sclerotium delphinii infecting cultivated cotton seedlings. T. harzianum strain CICR-G, isolated as a natural mycoparasite on a tree-pathogenic Ganoderma sp. exhibited the highest disease suppression ability. This isolate was formulated into a talcum-based product and evaluated against the pathogen in non-sterile soil. This isolate conidiated profusely under conditions that are non-conducive for conidiation by three other Trichoderma species tested, thus having an added advantage from commercial perspective.

Detection of seedborne Aspergillus flavus from rice cultivars using molecular markers

Aflatoxins are carcinogenic metabolites produced by Aspergillus flavus. Rice seeds may be contaminated by it at the time of harvesting or during storage. Detection of aflatoxigenic strains by TLC and analysis of genetic variability among 50 A. flavus cultures from seeds of various rice genotypes by PCR using 18 RAPD primers is reported here. About 58% isolates were aflatoxigenic whereas 42% were non-toxic. There were 246 bands and 48 haplotypes. Approximately 99% bands were polymorphic, and thus high degree of genetic variability was observed. All the primers were informative with PIC values of range 0.75–0.95. Seventeen RAPD markers were not found to be useful for the detection of aflatoxigenic A. flavus. However, one RAPD primer 3B could differentiate aflatoxigenic and non-toxigenic isolates to some extent. One allele of Primer 3B at approximately 480u2009bp was present in 85% aflatoxin non-producers and in 6% aflatoxigenic isolates. This information may be utilised for designing markers for differentiating toxic/non-toxic isolates of A. flavus.

Mating Types Analysis of Magnaporthe oryzae Populations by Molecular Methods

Rice blast is a devastating disease which is caused by the heterothallic fungus Magnaporthe oryzae. Compatible sexual recombination which occurs between two M. oryzae strains of different mating types, can enhance genetic variability. Assessment of mating type alleles is used as a marker to measure population diversity. Forty six isolates of M. oryzae were collected from infected rice leaves from various ecosystems of coastal Odisha, India, and the mating type analysis using molecular markers was carried out. MAT1-1 mating type was dominating in all the ecosystems and MAT1-2 was found to be present in uplands as well as in irrigated fields. Both mating types could be found in the same field in irrigated ecosystem. The disease spread was very fast vertically as well as horizontally in those fields resulting in blast lesions looking as green islands (gi) produced in senescence leaves, and MAT1-2 was found to be associated with all gi lesions. Consequently, the management of the disease in those plots was very difficult. Interestingly, ribosomal RNA IGS region could not be amplified in MAT1-2 isolates but consistent amplification was obtained in MAT1-1 mating type isolates.

Molecular phylogeny of endophytic Dendryphiella: In quest of finding out ancestor of important rice seed Micro-Flora

Thirteen endophytic non sporulating fungi present in healthy seeds of rice cultivars, popular in coastal India, were isolated by ‘host tissue transplant ’method. Those were identified by the molecular technique and phylogenetic analysis by Phylogeny fr software was done. The phylogeny tree of 32 taxa including 27 Dendryphiella species and five Cochliobolus miyabeanus spp. was rendered. There were two major groups. Five Cochliobolus miyabeanus spp. (out group) were together the smaller cluster whereas all the Dendryphiella species with same internal node. The Dendryphiella group was further subdivided in two sub groups where 10 marine Dendryphiella and 17 terrestrial endophytic Dendryphiella grouped in two different sister groups. The high bootstrap values for each subcluster justified their grouping in the proper bunch. This analysis indicated that marine and ‘terrestrial endophytic Dendryphiella ’had common ancestors.

Genetic Similarity between Cotton Leafroll Dwarf Virus and Chickpea Stunt Disease Associated Virus in India

The cotton leafroll dwarf virus (CLRDV) is one of the most devastating pathogens of cotton. This malady, known as cotton blue disease, is widespread in South America where it causes huge crop losses. Recently the disease has been reported from India. We noticed occurrence of cotton blue disease and chickpea stunt disease in adjoining cotton and chickpea fields and got interested in knowing if these two viral diseases have some association. By genetic studies, we have shown here that CLRDV is very close to chickpea stunt disease associated virus (CpSDaV). We were successful in transmitting the CLRDV from cotton to chickpea. Our studies indicate that CpSDaV and CLRDV in India are possibly two different strains of the same virus. These findings would be helpful in managing these serious diseases by altering the cropping patterns.