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CHAPTER 11 Seed treatment J.K. Misra. T.W. Mew, and C.C. Huelma Seed treatment is physical or chemical seed therapy. Seed treatment dates back at least to the Roman empire, when wine and crushed cypress leaves were used to treat seeds for better harvest. Today, seed treatment is important in pest management. In western countries and Japan, where mechanized farming is practiced, seed treatment has become part of normal farm procedures. Seed treatment revolutionized production (Nakamura 1986, Bowling 1986) by controlling many pests and pathogens and by repelling birds. As new technologies and chemicals become available, the dimensions of seed treatment change significantly. Seeds are treated in the early stages of their germination and establishment to protect them from pests and pathogens, to promote better seedling stands, to minimize yield loss, to maintain and improve seed quality, and to avoid introduction and spread of harmful organisms. Advantages of seed treatment Among the many advantages of seed treatment are that it protects seeds and seedlings from pests and pathogens in the early stages of germination and establishment, is easier than plant treatment and can be done indoors with or without machinery, is unaffected by weather conditions, requires less chemicals than does plant treatment, pollutes the environment less than does plant treatment, does not result in much development of resistance in insect pests (although fungi are developing resistance to fungicides), and uses biocides that affect only targeted organisms and not the other beneficial entities in the soil. Limitations of seed treatment Advantages of seed treatment outweigh the limitations which include lack of effective broad-spectrum systemic fungicides for internally seedborne fungi and for fungal resting structures; no protection beyond the early growth or seedling stages; no potent biocides that protect the seeds from rodents, nematodes, insects, slugs, and birds; and chemicals do not continue to adhere to the seed surface, do not maintain the desired level during germination, and do not protect germinating seeds and seedlings from seedborne and soilborne pests and pathogens. Methods Seeds are treated by chemical, physical, or both methods. Aspects of general seed treatment are presented by Jeffs (1986), Neergaard (1979), and Anselme (1988). Information about rice seed treatment for quarantine purposes is presented here. Physical seed treatment is any method that does not employ chemicals. Normally, heat treatment is accomplished using hot water, dry heat, or steam. Heat treatment kills seedborne pests and pathogens without injury to most germplasm. Heat therapy may be injurious to and should be used cautiously with old or damaged seeds and varieties which have low heat tolerance. Japonica varieties are generally more heat-sensitive than indica varieties. Hot water treatment at 52-57 °C for 15 min eradicates seedborne Aphelenchoides besseyi. Heat therapy is often given in conjunction with chemical treatment. Biocidal chemicals (fungicides, bactericides, insecticides, nematicides) are applied as liquids or powders. Depending on the type of seed and the nature of the chemical, biocides may be applied as dust treatments, fumigants, wet treatments (steep, sprinkle, quick wet, and slurry), oil fungicide treatments, and by pelleting. Since no broadspectrum fungicide exists, mixtures of fungicides are commonly used. In Japan, the following chemicals are used to control blast, bakanae, and brown spot rice diseases (Nakamura 1986): thiram 20% and benomyl 20% (benlate T); thiram 30% and thiophanatemethyl 50% (Homai); thiram 10% and thiophanatemethyl 10% (Homai coat); captan 30% and kasugamycin 3% (kasumin C); and copper sulfate, basic 29%, and oxine-copper 20% (oxybordeau). Chemicals used for seed treatment in the USA are captan, thiram, maneb, chloroneb, difolatan ( cis --N-((l,l,2,2- tetrachloroethyl) thio)4- cyclohexene-1,2, dicarboximide), Vitavax (2,3-dihydro-6-methyl-5- phenyl carbamoyl-1,4-oxathiin),
terracoat (5-ethoxy-3- trichloromethy1-1,2,4-thiadiazole), and pentachloronitrobenzene. The most widely used fungicides for rice seed treatment are Bedate T and Homai. These also partly control A. besseyi. In Guyana, seeds are commonly treated with fungicides to control seedling diseases (Kennard 1965). The rice water weevil ( Lissorhoptrus oryzophylus) is an important insect pest that is not seedborne. It is controlled in the USA by treating seeds with organophosphate or carbamate insecticide. In Japan, seedlings are treated with cartap or propoxur granules (100 g/box) during transplanting. This effectively controls the larvae. Cartap (Padan), MEP (Sumithion), and MPP (Baycid) are common nematicides used to treat seeds for A. besseyi. To treat bacterial grain rot (caused by Pseudomonas glumae ), seeds in Japan are disinfected with kasumin, kasumin C, hot water, and dry heat. Seed treatment for quarantine No single treatment can eliminate all the important seedborne or seedtransmitted pests and pathogens. Therefore, a combination of therapies (thermo- and chemotherapy) is needed to ensure that seeds do not harbor pests or pathogens. (See Table 11.1 for recommended treatments.) Almost all importing and exporting countries meet international quarantine obligations. Some nations require exporting countries to apply prescribed treatments to seed lots before shipment. Treatments required by importing nations arc listed in Table 11.2. 11.1 Hot water treatment of rice seeds at 52-57 °C for 15 min. 11.2a. Slurry treatment. Small plastic bottle for 50-g seeds and bigger plastic bottle for 100-g seeds. b. Slurry treatment. Big plastic bottle for 1-kilo seeds placed on a roll mill and rotated for 510 min. 60 Rice seed health testing manual
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A Manual of Rice Seed Health Testin
Page 4 and 5:
Contents Foreword v Preface vi Part
Page 6 and 7:
Foreword Intensive collaboration ch
Page 8:
Part 1 Introduction CHAPTER 1 Rice
Page 11 and 12:
tional levels (Kahn 1988). Quaranti
Page 13 and 14:
Morphology of the mature plant Matu
Page 15 and 16: two-celled, besifixed, deeply sagit
Page 18 and 19: Part 2 Procedures for seed health e
Page 20 and 21: CHAPTER 3 Equipment J.K. Misra, T.W
Page 22: 3.2 Dry seed inspection using a mag
Page 25 and 26: Example. In a two-stage random samp
Page 27 and 28: solid pointed end. The tube and sle
Page 30: CHAPTER 5 Dry seed inspection J.K.
Page 33 and 34: Detection Blotter and agar plate me
Page 35 and 36: Results: Examine plates for charac-
Page 37 and 38: Extraction and isolation It is esse
Page 39 and 40: GRINDING METHOD (FOR SMALL-SCALE SE
Page 41 and 42: flagellum. Cells occur singly, in p
Page 43 and 44: 7.6 Oxidase test reaction. L = colo
Page 45 and 46: 7.9 Production of 2-ketogluconate.
Page 47 and 48: 1. Grow pathogen-free plants under
Page 49 and 50: 7.12 a. P. glumae type A colony on
Page 51 and 52: A1. Macerate 100 seeds in 10 ml of
Page 53 and 54: Results: 7.Streak the bacteria onto
Page 55 and 56: Sieve method (Fig. 8.1) Procedure:
Page 58 and 59: CHAPTER 10 Field inspection J.K. Mi
Page 60 and 61: Table 10.2. continued Disease Fungi
Page 62 and 63: Table 10.2. continued Disease Growt
Page 64: additional precaution, the multipli
Page 70: Part 3 Pests and pathogens CHAPTER
Page 73 and 74: elevant tests for determining the i
Page 75 and 76: Table 12.1 continued Family and spe
Page 77 and 78: Cryptolestes pusillus Schonherr The
Page 79 and 80: Rice weeviI Scientific name: Sitoph
Page 82 and 83: CHAPTER 14 Fungal pathogens J.K. Mi
Page 84 and 85: THE DISEASE—BROWN SPOT Sir John W
Page 86 and 87: Symptoms Glumes are discolored, and
Page 88 and 89: y low relative humidity. Released a
Page 90 and 91: THE DISEASE—STEM ROT Stem rot was
Page 92 and 93: THE DISEASE—SHEATH BLIGHT Sheath
Page 94 and 95: Sarocladium oryzae is seedborne. Th
Page 96: Although not currently considered a
Page 99 and 100: Pseudomonas fuscovaginae Pathogen:
Page 101 and 102: See Chapter 7 and Figure 15.4a for
Page 103 and 104: Infected seeds and contaminated wat
Page 105 and 106: For further details, see the Common
Page 107 and 108: nonfluorescent) and Erwinia herbico
Page 109 and 110: Franklin M T, Siddiqi M R (1972) Ap
Page 111 and 112: Tai F L, Siang W N (1948) 'I-chu-hs
Page 113 and 114: 106 Rice seed health testing manual
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108 Rice seed health testing manual
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After autoclaving the medium, add t
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smoniloid = having swellings at reg
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