Compendium of Potato Diseases - (PDF, 101 mb) - USAID

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may form. When the causal agents survive storage in seed tubers. plants in the second year develop symptoms. In the more usual situation, in which causal agents failto survive in seed tubers. plants in the second year may he normal, lack diagnostic symptoms, be smaller than normal, or failto emerge. Hair sprouts frequently develop on tubers from infected plants (Plate 79). Plants with stolbur may bear simplified "round" leaves, but this symptom disappears in subsequent years. Causal Organisms Mycoplasmalike organisms (MLO) occur in phloem sieve cells and occasionally in phloem parenchyma cells of infected plants (Fig. 97C). They ,are pleomorphic, lack a cell wall. and are bounded by aunit membrane. M I.O vary in diameter from 50 to 1,000 nm. The larger, more prevalent forms are roughly spherical and contain a central fibrillar network of strands, presumably DNA. and a peripheral area of ribosomelike granules. The presence of elongate forms and small, dense "elementary bodies" suggests propagation by binary fission. budding, or fragmentation. Epidemiology The principal leatfhopper vector ol aster yellows. .iacrosteh's fascifrons,overwinters on weeds, grasses, and small grains. The favorite host of tile main vector of stolbur, Iiraesthe.s obsohtus, is perennial hindweed, (on volvulu arven.sis, which simultaneously acts as the main inoculum reservoir plant. All pathogens are transmitted by and propagative in lea fh oppers. Potato is not a fhavored host and usualIv escapes extensive disease incidence. Stolbur is an exception that, in certain European regions, mav become ,cry destructive. Leafhopper vectors do not complete their life cycles on potato. Neither nymphs nor adults can acquire the pathogen from potato. Transmission to potato occurs only when the leafhopper has fed on some other infected host. two to three weeks before feeding on potato. Other Hosts Many vegetable. ornamental, field crop plants, and weeds tire among the 350 species froni at least 54 families susceptible to aster yellows. Witches' Broom Witches' broom. also called northern stolbur and dwarf shrub virosis, has been reported from North America, Europe, and Asia but is of minor economic importance. Several distinct pathogens or strains of a single pathogen may be involved in different geographical areas. Symptoms Symptoms are generally similar. Plants have many axillary and basal branches with simple "rotnd" leaves, which may he chlorotic (Fig. 98A). This disease is distinct from wilding, a somatic aberration. Current symptoms appear late. if at all. and consist of an upright habit of growth. rolling of leaflets, and some chlorotic or anthocyanin discoloration in apical leaves. Most strains cause no flower symptoms. but witches' broom strains of central and eastern Europe are characterized by virescence, phyllody, and associated flower symptoms (Fig. 98B). Mycoplasmas offwitches' broom are tuber-perpetuated, in contrast to those of aster yellows, which usually are not. Affected hills usually produce tubers that appear normal during the year of infection hut gIive rise to plants with advanced symptoms the subsequent 'ear. Tubers from infected plants frequently produce hair sprouts. Such plants have many small tubers and an abnormally high number of sprouts with simplified, small leaves. Occasionally these sympt(ms follow 92 early infections during the current season. Infected tubers usually lack dormancy. Causal Organism Pathogens are mycoplasmalike organisms, such as those that cause aster yellows. Epidemiology The pathogens are transmitted by leaf hopper vectors, Ophiola (Scleroracus)lavopitu.s, S. dasidus (Fig. 98C),and S. halli, in which they are propagative. In most areas, the vectors are not yet known, nor are the natural host ranges of the pathogens. lcafhuoppers are unable to acquire the pathogen from potato. Spread to potato occurs when a vector feeds on oth-r infected hosts several days before feeding on potato. Witches' broom in perennial legumes isusually more serious than in potato because the former are preferred hosts by the vector and inoculum is usuall, available within the crop. Other Hosts L.r,'oliervicon escuhe'ttm, C, 'vphomandra betacea, and Nicotiana tahactum have been used to distinguish between strains. ifedicago sativa, Jelilotus alba, or l.otus corniculatusserve as natural reservoirs and may be used as indicator plants. Trifolium r 'ens isalso susceptible. Control I) Generally these diseases are of minor importance and do not justify elaborate control measures. 2) Control leafhopper migrations into potato fields by ,, .. C Z Fig. 98. Witches' broom: A, in potato plant; B, current season, medium intensity flour phyllody of Czechoslovak type II; C, Scleroracus dasidus female, one of the leafhopper vectors. (A, Courtesy N. S. Wright; B, courtesy V. Valenta: C, courtesy J. Raine) :.
modifying cultural practices and by using insecticides. 3) Spread from potato to potato is believed not to occur. 4) Heat treatment may be useful on individual plants, 5) Remission of symptoms often follows treatmlent with tetracclines tetracy lines.6 Selected References BRCAK. ..O. KRAI.'IK. J.I. II fERK. and NI. LI.RYCIOV,. 1969. Mycoplasm-like bodies in plants infected %% ith pota:o witches' br ,o disease and the response of plants to tetracycline treatment. Biol. plant. 11:470-476. CIHAI'MAN. R. K., moderator. 1973. Smrnposiunm: Asteryvelloss. Proc. N. Cent. Branch. Fntomiol. Soc. Am. 28:38-99. l)Ol. Y.. M. ITRAMAKA, K. YORA. and if. ASLYAMA. 1967. MNcoplasma or PI. group-like microorganisms found in the phloem elements totplants infected % itt mulberr \dwarf, potato %% itchtes' broon. aster ,sellosiss, or Paulo%%nia \sitches' broom. Ann. h'livtopailhol. Soc. .apan 33:259-266. I:FtKt;SIl. I..I. SIIIKAIA. II. SHIO).A. F. SFK'YANI.A, I.. TANAKA, N. ()SIINIA. and Y. NISIIIA. 1955. Insect transmission of poltato silches' broomn in lapan. Proc .. Ipn. Acad. (Nihon (akusiNj.... .31234-236. N.A(iAICtI, I). B..I. K. PI'RI. R. C. SINIIA. N1 K. )l1INGRA, and V. It. LI.AR I)\VA,\.l. 1974. %tscoplasna-like organisms inplants affected %%itht purple top-roll, marginal flasecence and broott ,itcltes' diseases ofpotatoes. 'hs%tmpalthol. Z.81:273-279. Psyllid Yellows This disorder results from insect feeding, and no infectious microorganism is involved. ()trs ines. \Ong leis es. shIcll arC Ofteni rCL O purple. he1otte erect and hasc ctppedf basal portitm . Nodes of Nuitng stetts hecote cnlargcd: [lte a\illars angle bet %ccnstctIs ami pettiles is larger than lustual: and aerial tuhcrs ,,tistocks sltots. Irequct t11.. 1k tlci, i Ito Inat tle Iaf a \ils. Plants ha\c a p ramidal shape and are gcncrall% scllos tobitolttd. lit ad\a cctdstages, oldCr lCaCs rll Up\sard. become ello\ \ith necrotic areas.,t break dti \s rapidll. I lie tip lea\cs Iot-it a rosette (PlaC 80). Plants do[l tgenciralls*\\sill cn under escttcc dttght. Iorder parcicht \tia surrounding the phlcli is first allected. atd later tissue breakdti\s.t extends laterally. causing phllt necrosis. Abtirillh large dcptisits of starch dcvclop inthe Corte\ anid pith. I-\ if an\ tubers are set oinplants attacked in early de\clpmntnt. When older plants are affected, stolon tips may produce sprouts and secondary sho.ots that emerge front the soil as smiall plants. Masses tif small tubers mav orn oi secondary stolon bra nches. or successi\c tubers nas forn oila stolon in a chain or beadlikc arrangement. Abnormnalls small tubers sprout without a dormant period. Similarly. trnancv may be lacking iii tubers that appear normal. IBecause (t tie nman\ small tubers. tie number of inarketa ble tubers is greatly reduced. 1he disorder is not tuber-transinitted. Artificial methods of' transmission from plant to plant have not been successful. Insect Toxins Nematodes RAINE. .J.1967. Ieafhlopper transmission of vitchos'broomand clover phyllod %iruses frotm British Columbia to closer, alfalfa. and potato. (an..I. Bot. 45:441-445. SENIAN('K. .J. S.. and .1. PI [RSON. 1971. Association of a mycopsna ih havsire disorder of polatoes. Phytopathology 1':1316--1317. VA. EN IA. V. 1957. Potat o "itches' bro o i %j rus in Cech oslo va kia. Pages 246-250 in: I..Quak..I. l)ijkstra, A. II. R. licemster. and J. P. II. Van der Want. eds. Proc. Ihird (ont. Potato Virus Dis. 24-28 June, 1957. If.Veenman and Zonen. Lisse-Wageningen, The Netherlands. 282 pp. VA I.E NI A, V. 1969. Vergleich cines aus Niedersachsen stammenden Kartoffelhexenhesen-Virus mit anderen aus Europa bekannten Viren dieser (iruppe, Zentralbl. Ifakteriol. Parasiteuk. Infektionskr. 1lyg. Alt. 2. 123:352-357. VAI.ENIA. V., M. NI SII.. and S. MIS.IGA. 1961. Investigations on European veIlos, s-tpe\iruses. 1.lhestolhur virus. Phvtopathol. Z. 42:1-38. VA NIA. V..dand M. MI I.. 1963. Investigations otnEuropean yellowks-type iruses. II. 1he cloer dwarf atnd parastolbur viruses. Phytopathol. Z.47:38-65. \VR1(Ill. N.S. 1957. Potato witches'broom in North America. Pages 239-245 in:1-.Quak..I. l)ijkstra. A. If. R. FHeemster. and J. P. H. Van der \Vant. eds. Proc. third Cont. on Potato Virus Dis. 24-28 June, 1957.11. Veenmanand Zonen. lisse-Wageningen, The Netherlands. 282 pp. (Prepared by N. S. Wright, J.Raine, and V. Valenta) Tubers from affected plants produce plants that appear normal except for a slightly spindly or weakened appearance. Seed tubers from affected fields are not of satisfactory quality. [he disease results from toxic substances introduced during feeding of nymphs of Paratrio:a cockerelli, the tomato or potato psyllid. also known as the jumping plant louse. As few as three to five n\'nplts may cause car. symptoms, but higher populations (15-30 per plant) are required for full symptom expression. Adults tip to 1.00 per plant do not induce symptoms. Progress in symptom development is stopped abruptly svhen nymphs are removed, and affected plants frequently recover. During the 1 9 30s, the disease caused considerable damage in the United States vest of the Missouri Riverand extending from New Mexico into Canada. In certain areas it was the most destructive disease. Symptoms are most severe in high intensity sunlight, at high field temperatures, and during drought. Similarity between psyllid yellows, the mycoplasma disorder haywire, leafrolls of various types, and Rhizoctonia has caused some confusion in diagnosis. Selected References EYIRS,.1.R. 1937. Physiology ofpsyllid yello's of potatoes. J. Econ. RICIIAIS,.If.I.., IAntArIl. 30:891-898. and II.L. BLIOOD). 1933. Psyllid yellows of the potato... Agric. Res. 46:189-216. SCIIAA I.. L A. 1938. Some factors affecting the symptoms of the psyllid yellows disease tif potatoes. Am. Potato .1.15:193-206. (Prepared by W. .1.Hooker) Nematodes pathogenic to potatoes (Table II) occur in all appear on aboveground parts of the plant except for unthrifty climates and cause serious crop losses, but much of this damage top growth resulting from poor root systems. Low densities in is unrecognized or attributed to other causes. Because the soil cause no top symptoms but may reduce tuber yields. As nematodes attack roots and tubers, no diagnostic symptoms the world population increases, soil suitable for potato culture 93
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, ,. ,o . ; , . o , . r. , -' .L ,
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Compendium of Potato Diseases W. J.
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In memory ofimy respected colleague
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Acknowledgments Planning Committee
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Introduction 1 Potato Disease 1 The
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A potato disease is an interaction
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Fig. 1.A, Lower portion of young po
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+q I B Fig 4. Natural openings in a
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Part I. Disease in the Absence of I
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more heavily in the vascular region
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the air temperature when tubers are
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iiO A B 'D C Fiq. 14 Second growth:
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identifying tissue bruised by black
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Internal Sprouting multiple sprouts
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conditions permits normal leaf deve
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Epidemiology Oxidant injury is pres
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sevritof stnting, chiorosis. loss o
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Selected Reference brown to bronze
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Part II. Disease in the Presence of
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should be planted on land with at l
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Control I) Use disease-free tubers
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FOI-SO M. D, and I. A. FRIEDMAN. )9
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Fungi Powdery Scab liberating powde
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Histopathology Sort of sporangia de
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any time but generally occurs late
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'40 ff .. . '1 f . ."L', . '1 .,. "
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A \, 2) Powdery mildew is rarely a
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R., Inst.. Kew. Surrey. ngland. 609
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TORRES, H.. E. R. FRENCH, and I.. W
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d AC D A 0 Fig 53 Gray mold. A, Bot
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strands of pigmented hyphae. Sclero
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tuber malformation. Roots are also
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1. Giant-hill plants, taller than n
Page 67 and 68: 13. Bacterial soft rot. Erwinia car
Page 69 and 70: 24. Wart. Synchytrium endobioticum
Page 71 and 72: 34. Pleospora herbarum (Stemphylium
Page 73 and 74: 44. Charcoal rot. Macrophomina phas
Page 75 and 76: 55. Leafroll virus. Current season
Page 77 and 78: 67. Mop-top virus. Primary tuber 68
Page 79 and 80: 77. Aster yellows mycoplasma sympto
Page 81 and 82: Symptoms Small, localized, light br
Page 83 and 84: obovoid, and 14-30 X 5-10 pm. Pycni
Page 85 and 86: invaders through the IFusarium lesi
Page 87 and 88: necrosis extending into the tuber t
Page 89 and 90: do not survive drying. Both species
Page 91 and 92: cauisal. Tesis Magister Scientiae e
Page 93 and 94: penetration, and subsequent disease
Page 95 and 96: have been demonstrated, including t
Page 97 and 98: In P..floridana,strains of PVY" and
Page 99 and 100: infects certain comnie,-cial stocks
Page 101 and 102: cytoplasm of infected potato cells
Page 103 and 104: WETTER, C. 1971. Potato virus S. No
Page 105 and 106: 3) Resistance has not been identifi
Page 107 and 108: nm), which do code for coat protein
Page 109 and 110: Symptoms AMV may induce Other predo
Page 111 and 112: Disease Cycle I)escriptions of Plan
Page 113 and 114: Selected References KASSANIS, B. 19
Page 115 and 116: Control 1)Avoid locations in wkhich
Page 117: The "yellows" types of disease, cha
Page 121 and 122: immature females in the white or ye
Page 123 and 124: l.aboratory, Control. and Quarantin
Page 125 and 126: They attack many major crops in the
Page 127 and 128: infested areas of North America sev
Page 129 and 130: antennal tb l tuberce u antenna eye
Page 131 and 132: carbon tetrachloride, applied at th
Page 133 and 134: Diagnostic Microbial Structures Scl
Page 135 and 136: Surface and or interior Shades of g
Page 137 and 138: Equivalent Names of Potato Diseases
Page 139 and 140: Common Name Causal Factor Other Nam
Page 141 and 142: Common Name Causal Factor Other Nam
Page 143 and 144: coalesce-union of similar structure
Page 145 and 146: many days following removal of the
Page 147 and 148: Index Abrasions, tuber surfaces. 14
Page 149: Irost tolerance in. 9 aniligena. 68
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