Seed Health Management for Better Productivity - Govind Ballabh ...

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(Seed Health Management for Better Productivity)Management of Seed Borne Bacterial Diseases in Seed ProductionPlotsY. SinghDepartment of Plant Pathology, G.B.P.U.A.&T., Pantnagar-263145 (Uttarakhand)Use of clean seed and clean transplants is recommended as the starting point formanaging plant diseases. Starting crop production wilt clean seed and or transplants seemssimple, logical and obvious, yet it is very difficult to achieve. Seed borne bacterial diseasescontinue to be problematic and cause significant economic losses worldwide. Infested seeds areresponsible for the reemergence of the diseases of the past, movement of pathogens acrossinternational borders, or the introduction of diseases into new areas. In today’s era of globalizationand free trade, seed accounts more than ever for the movement of plant pathogens across vastdistances, natural barriers, and political borders. Seed borne bacterial pathogens are of particularconcern, because, unlike seed born fungi, strategies for the management of bacterial diseases areinadequate. Therefore, in this write up, attempt has been made to address various strategies forthe management of seed borne bacterial diseases.(I) Quarantine: The first step in disease control is to prevent movement of the pathogenicbacterium from infested to non infested areas by restricting the transfer of seeds, vegetativepropagules, plants and plant products etc. Both international and domestic transfer may bepotentially controlled by plant quarantine regulations. Many plant pathogens introduced fromabroad have caused serious epidemics in new areas where they were previously unknown. InIndia 550 plant pathogens have been notified in the Plant Quarantine (Regulation of Import intoIndia) Order, 2003. Out of this, 65 are plant pathogenic bacteria. The hazardous means ofintroduction of phytopathogenic bacteria are on the infested or infected seeds, and budwoods andyoung plants. It is imperative to detect, isolate and identify these bacteria by following specificdetection techniques to avoid inadvertent introduction of the exotic quarantine bacteria.(II). Disease management by cultural /farming practicesA. Production and use of pathogen free planting materialMany bacterial plant pathogens are transmitted by establishing themselves on or in theseed or other vegetative propagating material or as contaminants . For successful disease controlthis source of inoculums must be destroyed.i. Seed production areas:- Seed should be produced in areas where the pathogens of majorconcern are unable to establish or maintain themselves at critical level during periods of seeddevelopment. Areas with low rainfall and low relative humidity are favourable for production of highquality seeds e.g., bacterial blight of legumes. Certain guidelines have been suggested forwatermelon seed production free from bacterial fruit blotch of cucurbitsAcidovorax avenae sup sp. citrulli . These(BFB) caused byguidelines include producing seed in dry and cool- 150 -
(Seed Health Management for Better Productivity)climate and in countries or areas of Countries, known to be free of the pathogen (Gitaitis andwalcott, 2007).ii. Inspection of seed production plots:- Periodical inspection of crops raised for seedproduction is an important procedure in the production of clean and healthy seeds. Destruction ofdiseased plants/ organs at the time of inspection helps in reducing inoculum in the field and thus,the percentage of healthy seeds in the produce is increased. If the disease incidence is very high,the entire crop may be rejected for seed. However, Walcott et al., (2003) demonstrated thatsymptomless watermelon fruits derived from symptomless plants could still harbour infested seed.A. avenae sub sp. citrulli was detected in seed from 44% of the watermelon fruits that developedfrom inoculated blossoms, despite the absence of fruit symptoms.B. EradicationEradication methods are applied directly against the pathogen, to the host plants oralternate hosts. Practical eradication procedures include fumigation of storage houses andmachinery, heat treatment, solarization , or flooding of soil, and burning or removal of plantresidues.C. Field hygieneRemoval of diseased plant or plant parts from field is important to reduce the density ofinoculum. Defoliated leaves of pruned twigs of fruit trees and straw of cereals are preferably burnt.Infected woody stems such as tomato, eggplant and tobacco should be ploughed into soil becausethey may remain partly undecomposed in the soil. Disinfection of tools and equipment is importantto control the spread of bacterial pathogens through pruning or harvesting practices.D. Control of weeds and insectsAnother aspect of field sanitation is keeping the field free from weeds and insects. Weedsreduce the amount of nutrients available for the plants and by lowering their vitality increase theirdisease proneness’. Excess of weeds in the field also helps in increased humidity. In additionmany weeds harbour the pathogens which subsequently on release attack the crops in the field.Bacterial leaf blight of rice Pathogen survives on weed (Leersia spp.) which grows along canalsand ditches. The bacterium is dispersed through irrigation water and infects rice seedlings inlowland nurseries or those transplanted in paddy. Cruciferous weeds play role in diseasedevelopment of black rot of crucifers. Therefore, as sanitary precaution destruction of these weedsis necessary. Diseases like black rot of crucifers are facilitated by injuries caused by insects suchas stripped cabbage flea beetle, cabbage worm and cabbage armyworm.E. Disinfection of Seed and planting materials:-In perennial crops such as fruit trees, new diseases are often introduced by infectednursery stokes. Crown gall, citrus canker, and fire blight pathogens have been spread in thismanner. Because bacterial wilt of carnation is mostly spread by cuttings , hygienic treatment isrequired throughout the entire process of propagation. In seed borne diseases, the frequency ofprimary infection through infected seeds is generally low. However, pathogens can readily- 151 -
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potential. An improvement in qualit
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9. Session Arrangement CommitteeDr.
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9. Dr. Pradip Kumar BorahSr. Scient
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TRAININGONANNEXURE-IIISEED HEALTH M
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ANNEXURE-IVCENTRE OF ADVANCED STUDI
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SundayApril 6MondayApril 7TuesdayAp
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