-NonCommercial-ShareAlike Unported License (http://creativecommons.org/licenses/by-nc-sa/3.0/). Location and histopathology of seed-borne bacterial pathogen Pseudomonas syringae pv. pisi carried by pea seeds Ashwani Kumar Verma 1 *, Kailash Agrawal 2 1 Department of Botany, R.R. Govt. (Autonomous) P.G. College, Alwar, Rajasthan, India. 2 Department of Botany, University of Rajasthan, Jaipur, Rajasthan, India. ARTICLE INFO Article history: Received on: June 30, 2017 Accepted on: September 05, 2017 Available online: January 17, 2018 Key words: Categorization, Incidence, Pea seeds, Pseudomonas syringae pv. pisi, Symptoms ABSTRACT The present study aims to determine the location and histopathology of seed-borne bacterial pathogen Pseudomonas syringae pv. pisi associated with pea seeds. The pea seeds categorized (asymptomatic, moderately discolored, and shrivelled discolored seeds) and seeds of each category were assayed for the presence of bacterial pathogen P. syringae pv. pisi. Seed samples carrying high incidence (89.5% and 91.34%) of the bacterial pathogen were used for the microtome sectioning individually. It was observed that the cells of P. syringae pv. pisi were found in large numbers in radicle and hilum region and space between seed coat and spermoderm in shrivelled discolored seed category while in moderately discolored seed category bacterial cells were less in numbers and found into the inner side of seed coat and endosperm. Bacterial colonization within seed tissue caused necrosis, formation of lytic cavities, and reduction in cell contents. 1. INTRODUCTION Pea (Pisum sativum L.) seeds are used for human consumption and to feed livestock as it is good source of protein, fiber, and vitamins. India is a major dry pea seed producing country with the production of approximately 6 lac tonnes per year [1]. Seed-borne pathogens carried by seeds can cause severe seed deterioration and reduction in yield. Pseudomonas syringae pv. pisi (Sackett) Young et al. is a Gram-negative rod causes bacterial blight disease of pea attacks all parts of the plant and transmitted internally by means of seeds. The bacterial pathogen reduces seed quality and alters the biochemical constitutes of the seeds [2]. The location of a bacterial pathogen in infected seeds depends on the host cultivar, mode of infection, prevailing environmental conditions, and other factors. The colonization of P. syringae pv. pisi has been observed in embryos of sorghum seeds [3]. Seed contaminated with seed-borne pathogens can cause dissemination of pathogen and disease development. Seed-borne pathogens can be managed effectively if the location of the pathogen can be determined. Hence, the objective of this work was to investigate the location of inoculum within pea seed tissues. 2. MATERIALS AND METHODS Two infected seed samples (acc. no. Pa-2529 and Pa-2552) carrying high incidence (89.5% and 91.34% on KmB agar media) for bacterial *Corresponding Author Ashwani Kumar Verma, Department of Botany, R.R. Govt. (Autonomous) P.G. College, Alwar, Rajasthan, India. Email: ashwani14286@gmail.com pathogen P. syringae pv. pisi were selected to study the histopathology and location of the pathogen. 2.1. Dry Seed Examination Pea seed samples collected from different regions of Rajasthan state were subjected to dry seed examination. Four hundred seeds per samples were taken randomly and examined under naked eyes as well as under stereoscopic binocular microscope (×10-40). On the basis of presence and absence of water-soaked patches, bacterial oozing, brown or black spots, discoloration, shrivelling, etc. seeds were categorized into asymptomatic, moderately discolored, and shrivelled discolored seeds [4,5]. 2.2. Microtome Studies The categorized seeds from the selected naturally infected seed samples were soaked in sterilized distilled water kept in hot air oven at 80°C for 40 min. The selected softened seeds were fixed in 70% alcohol for 48 h in glass vials, dehydrated through tertiary-butyl alcohol series, infiltered, and embedded in paraffin wax. The embedded material was cut into blocks, sectioned at 8-10 µ thickness, deparaffinized, stained within safranin and light green combination, and mounted in DPX [6]. Microtome section were studied under a compound microscope (X-20-100). 3. RESULTS AND DISCUSSIONS 3.1. Dry Seed Examination In each sample, the seeds were categorized into asymptomatic, moderately discolored, and shrivelled discolored seeds (Fig. 1a - I-III). Journal of Applied Biology & Biotechnology Vol. 6(1), pp. 20-22, Jan-Feb, 2018 Available online at http://www.jabonline.in DOI: 10.7324/JABB.2018.60104 © 2018 Ashwani Kumar Verma and Kailash Agrawal. This is an open access article distributed under the terms of the Creative Commons Attribution License