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Rice is one of the major staple food crops in the world and an excellent model system for studying monocotyledonous plants. Diseases caused by nematodes in rice are well documented and among them, root-knot nematode (RKN), Meloidogyne graminicola, causes extensive yield decline. It is therefore necessary to identify novel sources of natural resistance to RKN in rice and to investigate the rice-RKN interaction in detail to understand the basal plant defence mechanisms and nematode manipulation of the host physiology. To this end, six different cultivars of rice were initially screened for RKN infection and development; Pusa 1121 and Vandana were found to be most susceptible and resistant to RKN infection, respectively. In order to investigate the role of major hormoneregulated plant defence pathways in compatible/incompatible rice-RKN interaction, some wellidentified marker genes involved in salicylate/jasmonate/ethylene pathway were evaluated for their differential expression through qRT-PCR. In general, our study shows a remarkable discrepancy in the expression pattern of those genes between compatible and incompatible rice-RKN interaction. As most information on the molecular interplay between plants and nematodes were generated on dicotyledonous plants, the current study will strengthen our basic understanding of plant-nematode interaction in the monocot crops, which will aid in defining future strategies for best plant health measures.Plant-parasitic nematodes (PPNs) have proved to be one of the most difficult to manage and stubborn pest of agricultural crops. PPNs display a wide variety of interactions with their hosts. Most advanced of them are sedentary endoparasites, which induce a specialized feeding cell in the host tissue. These feeding structures are believed to serve as the singular nutrient source for the nematode development and reproduction. A plethora of nematode effector proteins have been identified which interact with the several plant proteins to initiate and maintain the feeding cell and usurps innate host defence 1,2 .Being one of the major staple food crop, and a promising model monocotyledonous plant, rice (Oryza sativa L.) has garnered considerable attention from the nematologists studying the physiological and molecular interaction between rice and PPNs. Root-knot nematode (RKN), Meloidogyne graminicola is emerging as a serious bottleneck in rice-wheat cropping system of Indo-Gangetic plains and is causing substantial yield losses in all the rice growing belts of South-east Asia. The infective second-stage juvenile (J2) penetrates the rice root behind the root tip zone, traverses the vascular tissue and induces a typical feeding cell, known as the giant cell (GC). Cells surrounding the GC are hypertrophied to render the formation of macroscopic hook-like galls on the root system 3-5 .To date, almost all grown O. sativa cultivars tested are known to be susceptible to RKN infection, while the non-cultivated African relatives, O. glaberrima and O. longistaminata are reported to be resista...

It has long been recognized that chemotaxis is the primary means by which nematodes locate host plants. Nonetheless, chemotaxis has received scant attention. We show that chemotaxis is predicted to take nematodes to a source of a chemo-attractant via the shortest possible routes through the labyrinth of air-filled or water-filled channels within a soil through which the attractant diffuses. There are just two provisos: (i) all of the channels through which the attractant diffuses are accessible to the nematodes and (ii) nematodes can resolve all chemical gradients no matter how small. Previously, this remarkable consequence of chemotaxis had gone unnoticed. The predictions are supported by experimental studies of the movement patterns of the root-knot nematodes Meloidogyne incognita and Meloidogyne graminicola in modified Y-chamber olfactometers filled with Pluronic gel. By providing two routes to a source of the attractant, one long and one short, our experiments, the first to demonstrate the routes taken by nematodes to plant roots, serve to test our predictions. Our data show that nematodes take the most direct route to their preferred hosts (as predicted) but often take the longest route towards poor hosts. We hypothesize that a complex of repellent and attractant chemicals influences the interaction between nematodes and their hosts.

BackgroundAnalysis of gene expression patterns leads to functional understanding of biological processes. Quantitative real-time PCR has become the most commonly used technique for in-depth studies of gene expression. To quantify variation in specific gene expression, accurate and reliable normalization across different samples and tissues is necessary. This can be achieved by selecting one or more suitable reference genes to compare the target mRNA transcript levels. In the present work, we illustrate the first evaluation of potential internal control or reference genes across different developmental stages of eggplant for reliable quantification of transcripts by real-time PCR.ResultsWe have evaluated the stability in expression of six candidate reference genes (18s rRNA, APRT, GAPDH, Cyclophilin, Actin, and RuBP) in a set of tissues representing six developmental stages of eggplant. The candidate genes were cloned from cDNA and analysed by real-time PCR. The expression data analyzed by three statistical methods (geNorm, NormFinder and BestKeeper) identified 18s rRNA, Cyclophilin and APRT as the most stable and suitable reference genes in eggplant. This was further confirmed in four different varieties, two representative lines of transgenic eggplant as well as in nematode infected eggplant.Conclusion18s rRNA, Cyclophilin and APRT have been found to be appropriate for the normalization of real-time PCR data for gene expression studies in eggplant.