A. Kandan

Diagnostics of Seed-Borne Plant Pathogens for Safe Introduction and Healthy Conservation of Plant Genetic Resources

Most of the crop diseases are either seed or soil-borne or both. Hence, seeds alone or along with soil clods, plant debris and fruiting structures of the pathogens are primary source of inoculum for long distance dispersal. Some of the examples of dangerous pathogens/diseases disseminated during transboundary movement of seeds and other planting materials in international trade and exchange caused havoc and leading to profound political, economic and social consequences such as late blight of potato (Phytophthora infestans) from Central America (Peru) to Ireland in 1845, powdery and downy mildews of grapes (Uncinula necator and Plasmopara viticola) from Central America to France in 1847, flag smut of wheat (Urocystis agropyri) from Australia to Mexico, chestnut blight (Cryphonectria parasitica) from orient countries including Japan and Korea to USA, coffee rust (Hemileia vastatrix) from Sri Lanka to India in 1875, Karnal bunt of wheat (Neovossia indica) from India to USA in 1996 and bunt of wheat (Tilletia caries) from India to Mexico in 1970 and pine wood nematode (Bursaphelenchus xylophilus) introduced from North America to Japan in the early 1900s and then to have distributed in China, Korea, and Taiwan, etc. Therefore, seed health testing (SHT) involving conventional and molecular techniques has major applications in quarantine processing of plant genetic resources (PGR) under exchange as well as conservation of PGR for long-term storage in Gene Bank after making them free from associated pathogens, seed certification and decision making for seed-treatment. Thus, critical laboratory examinations with specialized tests, involving conventional and molecular approaches, are conducted in seed health testing for quarantine as well as conservation of PGR to ensure the interception/detection and identification of associated pathogens with seeds and other planting materials.

Advance Detection Techniques of Phytopathogenic Fungi: Current Trends and Future Perspectives

Plants including economically important crops are infected by a large number of fungal pathogens causing the most detrimental diseases which are responsible for considerable yield loss worldwide. Detection and diagnosis of phytopathogenic fungi are the most important steps towards developing strategies for their management. Developing direct detection assays is challenging because of existence of formae specialis, races, biotypes and strains within the species of fungal pathogens which are also changing depending upon the changing environmental conditions and crop cultivation in a particular area. Fungal plant disease diagnostics rely on a diverse technologies ranging from traditional taxonomy to advanced molecular tools. Major limitations of traditional methods include- ability of the organism to be cultured, time consuming and the requirement for extensive taxonomical knowledge. Early and accurate diagnoses of pathogens are necessary to predict the outbreaks and to have the required time for development of mitigation strategies. Now a days, molecular methods like conventional PCR, real-time PCR, nested PCR, co-operational PCR, reverse transcriptase PCR, magnetic capture-hybridisation (MCH)-PCR, loop-mediated isothermal amplification (LAMP) etc. are commonly used for phytopathogenic fungal detection. They are highly sensitive, repetitive, fast, and also allow the quantification of the target pathogen. In addition, DNA based microarray technology has also been developed in order to analyse hundreds of targets simultaneously. Some of the advanced biochemical diagnostic techniques, including, spectroscopy, imaging and biosensor have revolutionized research on detection and identification of fungal species. The advances in biosensor technologies have potential to deliver point-of-care diagnostics that match or surpass conventional standards in regards to time, accuracy and cost. However, their real application lies in achieving sensitivities comparable to the established methods and at a low cost. Recently, a novel technology, the PLEX-ID system has been developed which uses broad-range PCR amplification coupled with electrospray ionization-mass spectrometry (ESI-MS) for the direct detection of pathogens without the need to wait for growth in culture. Development of new and exciting methods for the detection and identification of phytopathogenic fungi is a continual process, as emerging and re-emerging plant pathogens continue to challenge our ability to safeguard plant health worldwide.

Survival of Alternaria brassicicola in Cryo-Preserved Brassica spp. Seeds for Longer Duration

Seed health testing of seven accessions of Brassica spp. conserved in the year 2001 at -180°C in liquid nitrogen at National GeneBank, ICAR-NBPGR, New Delhi resulted in detection of Alternaria brassicicola in three accessions of B. juncea, IC-113148, Pusa Bold and Prakash in the year 2015. Detection of A. brassicicola in cryopreserved Brassica seeds shows that the fungus can survive even at ultra-low temperature for a long duration.

Acalypha indica (Indian-nettle) harbours and spreads root-knot nematode in agricultural fields

Acalypha indica L. is a commonly growing weed in India, which is also known as Indian nettle. These plants were growing as a weed in pots wherein okra was planted for experimental purpose. Infestation of the root-knot nematode, Meloidogyne incognita was observed on it. Soil and root samples were taken for analyses of nematode infestation. Roots of the infested plants were severely galled and second stage juvenile recovered from soil samples. The root galling and presence of high population of nematode eggs and J2 revealed that A. indica can be a reservoir for M. incognita during non-host cropping and serve as a source of infestation to other hosts in the next cropping season.