Stemphylium blight (SB) caused by Ascomycete, Stemphylium botryosum Wallr. has been a serious threat to lentil cultivation, mainly in Bangladesh, Nepal, India, and Canada since its first outbreak in Bangladesh in 1986. The genus Stemphylium Wallr., a dematiaceous hyphomycete, comprises up to 150 species, and is pathogenic on a wide range of plants infecting leguminous as well as nonleguminous crops. In recent years, studies indicated overlapping in morphological characters among the different species under the genus Stemphylium, making the identification and description of species difficult. This necessitates different molecular phylogenetic analysis in species delimitation. Therefore, a detailed understanding of spatial diversity and population structure of the pathogen is pertinent for producing source material for resistance breeding. The role of different weather variables as predisposing factors for the rapid spread of the pathogen necessitates devising a disease predictive model for the judicial application of fungicides. A dearth of information regarding spore biology, epidemiology, race diversity, host-pathogen interaction, and holistic disease management approach necessitates immediate attention towards more intensive research efforts. This is the first comprehensive review on the current state of knowledge and research efforts being made for a better understanding of the SB resistance through cognizing biology, ecology, and epidemiology of S. botryosum and effective disease management strategies to prevent widespread outbreaks of SB. The information regarding the biology and epidemiology of S. botryosum is also crucial for strengthening the “Integrated Disease Management” (IDM) programme. The need for a regional research network is advocated where the disease is becoming endemic.

Molecular evolution analysis of 16S rRNA sequences of native Pseudomonas strains and different fluorescent pseudomonads were conducted on the basis of Molecular Evolutionary Genetics Analysis version 5.2 (MEGA5.2). Topological evaluations show common origin for native strains with other known strains with available sequences at GenBank database. Phylogenetic affiliation of different Pseudomonas sp based on 16S rRNA gene shows that molecular divergence contributes to the genetic diversity of Pseudomonas sp. Result indicate direct dynamic interactions with the rhizospheric pathogenic microbial community. The selection pressure acting on 16S rRNA gene was related to the nucleotide diversity of Pseudomonas sp in soil rhizosphere community among different agricultural crops. Besides, nucleotide diversity among the whole population was very low and tajima test statistic value (D) was also slightly positive (Tajima׳s test statistics D value 0.351). This data indicated increasing trends of infection of soil-borne pathogens under gangetic-alluvial regions of West Bengal due to high degree of nucleotide diversity with decreased population of plant growth promoting rhizobacteria like fluorescent Pseudomonads in soil.

Among seventy isolates, antagonistic twenty one representing biovars of Pseudomonas fluorescens (biovars I, II, III, and V) were collected from the rhizosphere of okra, chilli, ground nut, brinjal, cabbage and tomato from different agro-ecological regions of West Bengal and were subjected to evaluate for their antifungal activity under in vitro condition against Rhizoctonia solani, the most important soil-borne plant pathogen two isolates, PF-8 and PF-7 effectively inhibited the mycelial growth of Rhizoctonia solani (72.05 and 68.25%, respectively) in dual culture method. The vigour index of okra was also recorded maximum for the isolate PF-8 (2415.7) followed by PF-7 (2063.25). Mechanisms of fungal inhibition were elucidated by tracing secondary-metabolite production of the rhizobacterial isolates. Most of the isolates expressed a specific mechanism of antagonism, as represented by production of pigments, Siderophores, cyanide (HCN), Indole Acetic acid (IAA) and Salicylic Acid (SA) production, and Phosphate solubilization. Rhizobacterial isolate PF-8 was found to be effective as seed and soil treatment for management of root rot disease of okra. The antagonistic nature of fluorescent pseudomonads against fungal pathogens can be assigned to design a potential candidate for development of agriculture sector to be used in biological control of soil borne plant pathogens. Key words: Fluroscent pseudomonads, secondary metabolites, Rhizoctonia solani, okra root rot.

Physalis minima is an herbaceous plant and inhabitant of the porous and organic matter containing soil of bunds in crop fields, wastelands, around the houses, and on the roadsides. S. rolfsii is soil borne and it can infect over 500 plant species of different families. It is of interest to study the pathogenesis of S. rolfsii on P. minima. The S. rolfsii isolated from P. minima (physr1) was characterized by morphology and sequence of Internal Transcribed Spacer (ITS) region. The population structure determination and phylogenetic analysis showed the isolate physr1 significantly differs from other isolates. The null hypothesis of equal evolutionary rate was rejected throughout the Maximum likelihood (ML) tree topology of different S. rolfsii ITS sequences. The site-specific mean (relative) evolutionary rate analysis showed that most of the sites (80.59 % sites) evolved at a slower rate than average. Finally, the result of Tajima's neutrality test indicated that the population of S. rolfsii has recently begun to expand and that's why the pathogen was infecting the new host P. minima and pose a serious threat of infecting several other cropped and non-cropped hosts.