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

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of cells, becomes enclosed by periderm, then turns brown, shrinks, and collapses to produce a cavity: 2) necrotic starchfree cells differentiate, causing a brown spot approximately I mm in diameter, often in the center of very small tubers, and produce a cavity that enlarges with tuber growth and is surrounded by a partially suberized cambium layer: 3) internal tissue tensions cause splitting, which results in a lens-shaped cavity not preceded by cell necrosis. Translocation of substances from the central portion of the tuber and resorption in other parts of the plant may also be involved. Epidemiology Epideology hbefore Hollow heart is most severe during growing seasons or under cultural practices favoring rapid tuber enlargement. Rapidly growing tubers have a relatively higher incidence of hollow heart than do those that grow more slowly. Moisture stress (deficiency) followed by conditions favoring rapid growth predispose the uber to hollow heart, HJollo%%heart is lre(luc tis severe in fields with poor stands where plants are irregularly spaced. Practices that inhibit rapid tuber growth or that stimulate large numbers of small tubers, such as close spacing of plants, reduce incidence of hollow heart, Marginal potassium deficiency may be a factor in hollow heart predisposition, particularly in cultivars prone to the disorder, Increasing potassium fertility over that required for normal growth reduces hollow heart incidence. Identification for Marketing X-ray examination of whole tubers under water effectively identifies the condition without tuber destruction. Removal of large tubers and those with low specific gravity is only partially effective in eliminating hollow heart potatoes before marketing. Control I) Potato cultivars differ ii severity of incidence and in the type of internal cavity produced. 2) Close and regular spacing of plants increases competition and prevents excessively rapid tuber enlargement, which usually reduces incidence of hollow heart. 3) Avoid missing hills in planting, and use sound cultural practices to assure good stands. 4) Maintain uniform soil moisutre levels to stimulate uniform tuber growth rates. 5) Additional potassium fertiliation reduces incidence of hollow heart even though total yields may not be increased. Selected References CRUMBIL. I.I ). C. NELSON, and M. E. DUYSI-N. 1973. Relationships of hollow heart in Irish potatoes to carbohydrate reabsorption and growth rate of tubers. Am. Potato .1.50:266-274. FINNEY. E. R., Jr., and K. II. NORRIS. 1978. X-ray scans for detecting hollow heart in potatoes. Am. Potato . 55:95-105. NEI.SON, ). C. 1970. Effect of planting date. spacing, and potassium Fig. 15. Hollow heart, showing transverse and longitudinal splitting. 14 on hollow heart in Norgold Russet potatoes. Am. Potato J. 47:130-135. VON WENZI,, H. 1965. Die histologische tnterscheidungdreier'lypen von Ilohlheriigkehbe Kairtoffelk nollen. Z. Pflan7enk1r. Pflanienschut,72:411-417. (Prepared by W..i. Hooker) Surface Abrasions Immature tubers that are mechanically injured during harvest the periderm is mature exhibit feathering, i.e., shreds of loose skin exposing underlying flesh (Fig. 16). The wound may heal under optimum conditions but frequently dehydrates, becomes somewhat sunken, and turns dark brown with a sticky surface due to bacterial growth. Such tuers do not store well. Mature tubers mav be skinned by rough handling during harvesting and grading operations, thus providing infection courts for wound pathogens. Sunken scald spot develops when fresh wounds are dehydrated, especially after tubers are allowed to stand for some time in direct sunlight or desiccating ind before storage. Surface discoloration of wounds, with associated rot problems, also follows low emperature storage before wound healing is complete. Such tubers may become flaccid from dehydration. Control I) Avoid mechanical damage at every stage of the digging, harvesting, and grading operatiots. 2) Protect tubers from sunlight and heat;avoid excessive dehydration before storage. 31 Provide optimum storage conditions until wounds are completely healed. Selected References SMITH. W. ... Ir. 1952. Effect of storage temperatures, injury, and exposure on weight loss and surface discoloration of new potatoes. Am. Potato .1.29:55-61. WHITEMAN, T. M., and .1.1M.L.UTZ. 1954. Sunken scald spot field injury evident in stored potatoes. Am. Potato .1 31:43-49. (Prepared by W. .1.Hooker) Tuber Cracks Tuber cracking is of four types: I) growth cracks from internal pressure, 2) growth cracks from virus infection, 3) mechanically produced cracks, and 4) harvest cracks. Growth cracking (bursting) usually follows the long axis of the tuber and results from internal pressure exceeding the tensile strength of surface tissues during tuber enlargement. High internal turgor pressure develops from tissue expansion during rapid tuber growth. Fertilizer placed so that growth is excessively rapid increases growth cracking. Growth cracks in '' Fig. 16. Immature tuber surfaces, skinned and abraded.
identifying tissue bruised by black spot without rupture of the surface, nor is the reaction obtained after wounded tissue has hea led. Corntrol I) Little can be done to avoid cracking during the growing period except by judicious irrigation, fertilizer application, plant spacing, and cultivar selection. 2) Delay harvest until vines have been dead for some time and tuber periderm has matured. Avoid harvesting from cold soil. 3) Avoid sudden impact on tubers, and protect them from rapid drying after digging and during transit from field to storage. Fig. 17. Cracking: A,crack caused by impaction of turgid tuber during digging; B, growth crack that healed over before digging. - . •. Selected References IRIIANI. W. M. 1968. [he use of catechol for enhancing bruise detection. Am. Potato J. 45:312. PAINTER. C.G..and .. AUiUS I N. 1976. the effect of soil moisture and nitrogen on yield and quality of the Russet Burbank potato. . ' ,: L ', jP ., Am. Potato .1.53:275-284. SM IT I.E., 1). A., R. E. TIIORNION. C. IL.PETERSON, and B. B. IFAN. 1974. ltarscsting potatoes with minimum damage. Am. Potato .1.51:152-164 WER NER. II.0.. and .1.0. I)FT T. 1941. Reduction of cracking of late crop potatoes at harvest time b\- root cutting or vine killing. Am. ota t o .1. 18: 189- 208. (Prepared by W. .1. Hooker) Blackspot Fig. 18. Harvest or thumbnail cracks following mild bruising and surface drying. (Courtesy W. C. Sparks) Blackspot is alays caused by bruising injury. either from ctied bfotr hirvcst o requetit wound heal aid. as tubers impact during harvest, handling, and grading, or from pressure during storage. File and disorder northern Europe is well known and has in become North America atn increasingly serious consttl to groi. becotie relanets shallow a nd of little problem in most potato-growing areas that have adopttd contisequtenice (Fg. 17131. Wound-healed cracks seldom become mechanical harvesting and handling techniques. infected. Potato culti\ars differ in susceptibility to injury. (Itorwth cracks may also develop in tubers of plants with tile Symptoms yello\\ dwarf \irus. potato mop-top virus, or certain strains of Blue-gray to black discolored areas develop just beneath the the spindle tuber viroid. tuber skin (Fig. 19). Internal symptoms do not appear Mecha nical cracking during harvesting may follow sudden immediately after brusing but develop to full intensity impacts over (Fig. a 17A). Cracking is dependent upon varietal period of 1-3 days as flattened, spheroidal blue-gray patches response. tuber maturity, internal tuber turgor, and degree of centering in the vascular region. Margins are diffuse and grade mechanical cmnpressiin during Iaiest and iovetntient into into the unaffectcd tissue. Blackspot is usually storage. more Imutture noticuablc tubers and large tubers are most easily at the stolon end of the tuber than at the apical inilured. end. Tubers Severit\ with is greatest when tuber temperatures are low internal blackspot frequtentilv show no external sylmptols. and tissue is turgid. Iu bers s\ith high internal turgor are easily Melanin is present on intracellular cracked protoplast to a depth surfaces of 5 and min or on more. Extreme turgidity results inner wall surfaces of affected cells. The absence of wound \when soil moistuire le\cls are hlgh :atd tuts contitnue to function periderm in lesions is characteristic of blackspot after and helps \ines to hase been suddenly killed by frost, by herbicides, or differentiate this disorder from other internal defects such b\ harvesting as tubers when vines are green. Root pruning. internal brown spot, heat necrosis, and certain internal lesions undercutting, or prc-har\est vine killing reduces incidence of caused by pathogens. cracking. I)eiayingdigging fora few htlrsCarhlin thledaV until the soil is %\ar ied may also reduce cracking considerabyh. Histopathology Seserel\ cracked tubers are of little %,alue because wound Bruising injury initiates a series of biochemical oxidations healing in is incon,pletc, deh.ydration is rapid. and incidence of damaged cells. Phenyl substrates such as tyrosine are oxidized tuber rot may be high. Paradoxically. shatter bruising becomes to conjugated quinones by polyphenol oxidases. The no10 quinones se crc \kith high tuber turgor and black spilt intensifies polymerize to produce the black pigment. Oxidation reactions %%11 lth Io tuber turuor. are usually completed within 24 hr of bruising. and spots neither Ilaivest cracks are crescent shaped. resembling cracks made enlarge nor disappear during subsequent storage. with a 0humbriail. lhrev are usually shallow, 1-2 Inm deep. aInd result rom ough handling and drying of the tuber surface Epidemiology tissue after digging. particularly when tubers are turgid (Fig. Severity if' blackspot is determined by both the number of 18). Severity 10 injury depends on intensity of bruising and damaged rapidity cellsand ol deh.dration. the amount Direct of melanin harvesting produced by iachinery in each one. often An impact will damage more cells in susceptible tubers reduces than incidence it of harvest cracks as compared to harvesting will in resistant ones, and larger, deeper spots will form. Tuber by lifting tubers to the soil surface and gathering them later, susceptibility is influenced [Hie by a catechol number of test factors. (I- 1.5"1 practical grade) reveals areas of Tubers with low turgor pressure arc more likely injury to by have turii ig severe them dark red to purplish within 3-5 min of blackspot. Iherclore, blackspot is usually nmore serious treatment. after Catcchol, a a polyphenol, is oxidized by phenolase, dry growing season in nonirrigated growing areas. Conditions which isreleased from recently broken cells. It is net effective in such as low soil moisture, poor root development, or hot dry 15
Page 1 and 2: , ,. ,o . ; , . o , . r. , -' .L ,
Page 3 and 4: Compendium of Potato Diseases W. J.
Page 5 and 6: In memory ofimy respected colleague
Page 7 and 8: Acknowledgments Planning Committee
Page 9 and 10: Introduction 1 Potato Disease 1 The
Page 11 and 12: A potato disease is an interaction
Page 13 and 14: Fig. 1.A, Lower portion of young po
Page 15 and 16: +q I B Fig 4. Natural openings in a
Page 17 and 18: Part I. Disease in the Absence of I
Page 19 and 20: more heavily in the vascular region
Page 21 and 22: the air temperature when tubers are
Page 23: iiO A B 'D C Fiq. 14 Second growth:
Page 27 and 28: Internal Sprouting multiple sprouts
Page 29 and 30: conditions permits normal leaf deve
Page 31 and 32: Epidemiology Oxidant injury is pres
Page 33 and 34: sevritof stnting, chiorosis. loss o
Page 35 and 36: Selected Reference brown to bronze
Page 37 and 38: Part II. Disease in the Presence of
Page 39 and 40: should be planted on land with at l
Page 41 and 42: Control I) Use disease-free tubers
Page 43 and 44: FOI-SO M. D, and I. A. FRIEDMAN. )9
Page 45 and 46: Fungi Powdery Scab liberating powde
Page 47 and 48: Histopathology Sort of sporangia de
Page 49 and 50: any time but generally occurs late
Page 51 and 52: '40 ff .. . '1 f . ."L', . '1 .,. "
Page 53 and 54: A \, 2) Powdery mildew is rarely a
Page 55 and 56: R., Inst.. Kew. Surrey. ngland. 609
Page 57 and 58: TORRES, H.. E. R. FRENCH, and I.. W
Page 59 and 60: d AC D A 0 Fig 53 Gray mold. A, Bot
Page 61 and 62: strands of pigmented hyphae. Sclero
Page 63 and 64: tuber malformation. Roots are also
Page 65 and 66: 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 and 118:
The "yellows" types of disease, cha
Page 119 and 120:
modifying cultural practices and by
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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Compendium of Potato Diseases - (PDF, 101 mb) - USAID

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