ROOT ROTS OP SOME GARDEN CROPS Thesis presented in partial fulfillment for the degree of Master of Arts at The University of Western Ontario I9kl fcy Margaret A. M. Pettipher R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: EC54095 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. ® UMI UMI Microform EC54095 Copyright 2009 by ProQuest LLC. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 E. Eisenhower Parkway PO Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The writer wishes to express her sincere appreciation to Professor A. R. Walker for kind and helpful criticism. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table of Contents Introduction ........ Historical Review '1 ...... 2 Aim ....... 9 Materials 9 ..... Methods A. Isolation methods ...................... 10 B* Inoculation Methods 1h Experimental Results Tables I - III Summary Literature Cited ..... . ..... l6 Discussion of each ...... 27 ...... 29 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. HOOT ROTS Of SOME GARDEN CROPS Introduction The study of root rots of cereals has been recognized as a national problem for over twenty five years, ever since Bolley first advanced his theory that root rots were chiefly responsible for much of the increasing unproductiveness of our wheat lands. But the problem of vegetable root rots has continued to remain local in character, since it is largely concerned with special garden crops that are being grown, in limited areas, for export or canning purposes. That all micro-organisms, capable of producing root rots in our garden vegetables, are fungi seems highly improbable. However, the present paper is entirely concerned with fungi con nected with root rots, and with the role played by them in attack ing young seedlings especially. The investigation was carried on over a period of eight months, beginning in September 19^0, and experiments were per formed in the greenhouse at the University of Western Ontario. The initial collection of material was made from a wide range of vegetables grown in various localities around London. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - 2 - Historical Review Apparently one of the first reports of a vegetable root rot caused by a fungus, was made in 1850, when a root rot of peas due to Thlelavla basicola Zopf., was reported from England. This same fungus, which produces root rots of lupines, turnips, beans and violets, was first reported in America in 1891* However, during the 1890's and early 1900's the role played by fungi in the root rot problem was pushed into the back ground by 1. 7. Smith's (16) and others outstanding investiga tions of bacterial diseases of plants. Many investigators con sidered the bacteria they isolated from plants suffering with root rot as the causes of the disease, yet they frequently failed to reproduce the disease in subsequent inoculation experiments with these bacteria. The presence of bacteria as secondary in vaders of diseased roots is now well known. Doubtless many of the bacteria isolated then were, in reality, only saprophytes, and hence were incapable of invading healthy tissue. By 1896, the continued severity of a root disease of tomatoes — commonly known as tomato blight or yellow blight — compelled the Washington State Experiment Station to undertake an investigation of the cause of the disease, which was very prevalent in the Snake, Columbia, and Yakima river valleys. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Early investigations were carried out by C. V. Piper from 1696 - 1902* He made several pure culture isolations of bacteria from the diseased plants* but was able to reproduce the disease in only one series of inoculation experiments made with one of his cultures* His successors* believing that bacteria were the causal organisms* made numerous unsuccessful attempts to recover the parasite from the aerial parts of the plant* In 1909* the project was assigned to H* B* Humphrey (10)» who successfully isolated the causal organisms from the roots* These pathogens were fungi I Fusarium orthoceras App* & Wollw** and rosarium oxysporum (Schlecht)* Both produced *prompt and severe root infection** Drechsler (5) reports, in 1927* that two members of the Saprolegniaceae are capable of producing rootlet injury in tomatoes* The organisms responsible are Aphanomyces eutelehes, which is also associated with pea root rot, and Plectospira ayrjandra* A previous report of fungi in connection with a root rot was made in 1903* V Van Hall* who reported that Fusarium vug* infectufl Atk* was the cause of St*Joha*s disease of peas in Holland* However* his pathogenicity tests were indefinite* and subsequent experiments by Jones (11) have indicated that this Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. fungus is not Tory pathogenic, Wollenweber (22) Mad Appel, who classified Van Hall's pathogen as Fusarium falcatum, claim that "more than one species of fusariumM nay cause St.John's disease, from 1911 - 1919 further reports , by European and American investigators, of root rots of garden peas included identifications of other species of Vasarium by Gueguen, Mortensen, Turessan, Gif* ford and Levis, .Fusarium orthoceras was isolated by Levis in 1913, and fusarium redolens and fusarium oxysporum by Wollenweher in 1913 And 191^, Later work by Jones (11) in 1923 indicates that P. redolens is only weakly parasitic, and that the only fusarium par asitic on peas in the United States is f^ marti war, pisi, which was isolated by Westerdijk in 1915 as a possible cause of St. John's disease of peas. Jones however claims that these are less importand than Aphanomyees injury. The mose recent report on the pea root rot problem by Harter (9) in 1938. indicates that the greatest root rot losses are due to Phycomycetes. particularly Pythium and Aphanomyces. Nevertheless he has frequently isolated a very vigorous fusarlum parasite which kills pea seedlings almost as soon as they emerge. This fungus agrees best with Fusarium coeruleum and pro duces symptoms identical with those produced by Jones' F. mart! pisi. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - 5- Investigations into the corn root rot problem appear to have begun to bear fruit about 1889* when Burrill (3) described a bacterial disease of corn roots but since his original work has not been confirmed Branstetter (l) feels that something else besides bacteria was responsible for the disease. Years later losen (1*0 re-examined Burrill*s original specimens and claimed that these exhibited symptoms similar to those produced by Diplodia zeae. The first report of a fungus parasite of corn roots was made in 1910 by Selby (15), who observed a corn root rot caused by a species of fusarium. Pammel (13) described corn root rot in 191*+• In that year losses due to corn root rot in Iowa amount ed to $15*000,000. By 1918 the corn root rot problem had become of such national importance that the United States Department of Agri culture organized a project to investigate the problem: "Corn root, stalk and ear rots.* The project listed the following fungi as harmful: G-ibberella, fusarium, Verticillium, Rhizopus, and the bacterium, Pseudomonas. G-ibberella sauhinetil (Mont.) Sacc. was held to be responsible for the greatest amount of root rot, but Valleau (21), in a 1920 report, claims that fusarium monillforme is a more active parasite. Manns and Phillips (12) list four principal organisms Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. m 6 m associated with, root rot of corn seedlings. These are: Fusarium moniliforme Sheldon, G-ibberella saablnetll (Mont) Sacc., Diplodla zeae (Schw) lev., and Cephalosporium saechari Butter. Branstetter (1) worked on the problem in Missouri in 1927 and came to the conclusion that Biplodia zeae, Fusarium monili forme, Cephalosporium acremonium, and Gibberella saubinetil were capable of producing root rot in seedlings only, and that true corn root rot which develops as the plant reaches maturity is caused in Missouri by a soil-borne Pythium-like fungus. Valter H. Burkholder (2) claims to be the first to report a dry root rot of the bean including lima beans which are sus ceptible. He warns against confusing dry root rot with two other root diseases of beans: Khizoctonia blotch and black root rot due to Thielavla basicola, previously reported as causing pea root rot in 1850, (See page 2). The Burkholder report of dry root rot was made in 1916. The causal organism was Fusarium martii phaseoH. lima beans have also been reported as sus ceptible to Phymatotrlchum root rot of onions. This was re ported by Taubenhaus (19) in 1929* When Selby (15) reported a fungus in connection with corn root rots in 19*0, mention was also made of a Fusarium bulb rot of onions. Many species have been Isolated from this Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. rot but Fusarium cepae and Fusarium zonatum were consistently pathogenic. Davis and Reddy (h) in 1932 indicate that there is a seedling hlight stage of onion bulb rot. The pink root of onions was first reported from Texas hy J. J. Tanhenhaus and Mally (20) about 1917* The organism isolated was Fusarium aalli, but its ability to reproduce the disease was so poor that Taubenhaus and Mally concluded that other species Shsarium may be necessary to increase this. H. N. Hansen (8) was only able to produce pink root rot when Phoma terrestris was combined with F. malll, so concluded that the latter was a sec ondary parasite. Phymatotrichum root rot reported in 1929 by Taubenhaus and Ezekiel (19) is also pathogenic on tomato, onion, and lima bean roots. In 1921 spinach in Texas suffered from a very serious attack of wilt. Taubenhaus (18) succeeded in Isolating the causal organism Fusarium solaril which normally parasitizes Irish potatoes. A similar wilt due to Fusarium spinaciaS was reported from Idaho in 1923* Taubenhaus claims that Ihizoctoaia frequently opens the way for infection of spinach with Fusarium species. The 1935 - 1937 Progress Report of the Dominion Botanist (7) indicates the presence of a corn root rot at St. Catharines, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ontario. She parasitic organisms isolated were Fythium, Helminthosporium, and Fusarium. which were parasitic to varying degrees on corn, sugar beet and tomatoes. The same report contains mention of an onion root rot near St. Catharines and also a Fasarium wilt of spinach at Summerland, B. C. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9 Aim She aim of the present investigation was to identify those fungi associated with root rots of our commonest garden vegetables, and to determine their relative pathogenicity on seedlings. Materials The organisms isolated in connection with root rot were obtained from two main sources. (a) from mature roots collected during September and October from various localities in the vicinity of Lon don, and (b) from roots of vegetables growing in the green house on soils previously collected from four widely separated areas. The areas chosen were as follows: A. North Thames district. Soil from a cabbage field. B. Cowln farm. Same district as A, but two miles south at the Soil from wheat field. G. Brescia Hall corn field. D. Oxford Street, west. Mature roots collected during the fall included the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - 10 - following: corn,'beans, cabbages, onions, Swiss chard, parsnips, tomatoes, beets, and radishes. Vegetables grown in the greenhouse on the four soils were: beans (Golden Wax), lima beans, peas, onions, corn (Golden Bantam), lettuce, beets, parsnips, carrots, celery, Swiss chard, radishes, tomatoes and broccoli. These were examined at the end of six weeks for evidence of root rots. Methods Methods employed daring the investigation have been divided into two categories, viz.: (A) isolation methods and (B) inoculation methods. A. Isolation Methods These are concerned entirely with the isolation of fungi from roots, showing evidence of root rot. All roots to be examined were first washed very care fully in running water, and any showing root rot symptoms, such as browning or definite lesions, were sterilized in 1/1000 mercuric chloride. The amount of sterilization nec essary depended somewhat upon the size of the roots being treated, but the usual period ranged from fifteen to forty- five seconds. The most satisfactory results were obtained Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - 11 when roots were sterilized between thirty and forty-five seconds, since at shorter periods than this, bacteria over ran the cultures; while, at longer periods, penetration by the mercuric chloride was sufficient to kill all organisms present in the roots. The sterilized roots were immediately washed in two changes of sterile distilled water. Frequently a sterilized scalpel was used to cut open the roots in order to facilitate the emergence of the fungi. fhe infected roots were then planted on agar and in cubated at 24° C for twenty-four to seventy-two hours. The formula for the agar used was as followsi •3$ beef extract, •5$ peptone, 1.5$ agar, 39$ potatoes Distilled water * 1000 cc. A potato decoction was made by boiling the potatoes in 800 cc. of distilled water for about half an hour. The liquid was then filtered and enough distilled water added to make up for evap oration losses. The beef extract - peptone - agar mixture was dissolved in the remaining 200 cc. of water, by heating Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - 12 - it in the autoclave under 15 lbs. pressure for 15 minutes. Any losses due to evaporation were restored, and the two liquids were mixed, tubed and sterilized. Hyphae emerging from the sterilized roots were identified at once and transferred to agar slants. Pure cultures were prepared by the agar "streak plate" method, and from these were prepared monospore cultures for sub sequent pathogenicity tests. The "loop dilution" method proved to be the most satisfactory means of obtaining man©spore cultures. The inoculating needle was Just touched to the hyphae and then transferred to a tube of cooled melted agar. The organisms were mixed thoroughly and then the agar was poured into sterile petri dishes. Very clear agar was essential. All cultures were re-examined within twelve hours and an isolated germin ating spore was then transferred to an agar slant. In some cases a special malt agar, recommended by Clara Fritz (6), was used for certain Fusarium cultures, which would produce only chlamydospores and microconidia after the third or fourth transfer had been made. It was found that these cultures would again produce macroconidia, which were however usually reduced in size. The formula used Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 25 gins* extract of malt, 25 gins, agar 1 L. distilled water. The agar was soaked overnight and the unassorted water replaced "by an equal amount containing the malt extract. This was than steamed for 20 minutes at 15 Its. pressure, strained, tuhed and sterilised. Fusarium strains isolated during the investigation were very difficult to identify fry their macroconidia alone. Therer fore, they were grouped according to growth and color features* The medium used was that recommended fry Sherfrakoff (17) to show up color differences. Potato The formula was the following: 200 gms, Agar 20 gms, Olucose 50 gms, Distilled water 1000 cc. To 1000 cufric centimeters of a potato decoction were added the agar and glucose, and the whole was cooked for 20 min utes at 15 lfrs. pressure. After carefully filtering to obtain a very transparent medium, the tubes of agar were sterilized. The above medium was extremely helpful in the pre paration of single spore cultures. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - £. i4 - Inoculation Methods These were necessary in order to determine the pathogenicity of organisms obtained hy means of the is olation methods previously described. In order to limit the problem of secondary organ isms as far as possible, the tests were performed under more or less aseptic conditions. Therefore all seeds used were sterilized. The period of sterilization had to be varied some what to suit the seed, but broadly speaking the seeds used were sterilized from two to eight seconds. Radish and let tuce seeds were only able to withstand two seconds without having their germination power seriously affected; but beans, Swiss chard, corn, and peas were sterilized for eight seconds* Seed were then transferred to (l) sterile filter paper in sterile petrl dishes, and incubated at 2*f° C., (2) to soil which had first been sterilized at 15 lbs. pressure for tyj minutes. The inoculum for the petri dish experiments was agar on which a monospore culture of the fungus was growing. This was placed beneath the roots of healthy seedlings and in con tact with them. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Inoculum for the soil experiments was prepared by growing the fungus on sterile oatmeal, which was eventually mixed, by means of a sterile scalpel, into the soil* fhe sterile seeds were then transferred to this and the flat was placed tinder a humidor which had been washed with l/lOOO mercuric chloride, fhe purpose of the humidor was to cut down external contamination to a minimum. Seedlings in the petri dish experiments were examined regularly; but at the end of a week any showing symptoms of root rot were removed, re-sterilized and plated out on agar, fhe number of re-isolations of the fungus under consideration at the time was recorded. In the case of seedlings growing on inoculated soil, examination of their roots was made three weeks after planting. Ee-isolations were also made from .any showing evidence of attack. fhe pathogenicity of the fungi isolated by method A was determined by these inoculation experiments and the results were tabulated. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - 16 - Experimental Results Results of Isolation Experiments Discussion Results of the experiments performed in order to isolate fungi from root rots are summarized by Table I. In most cases, external evidence of root rot, as Indicated by the above ground portions of the plant, was meagre* An exception was provided by corn and peas, the leaves of which were occasionally yellowed* In severe cases of root rot infection in corn and peas, the radicle was destroyed by the time the plumule was an inch above ground. Stands were consistently poor with peas grown on soil A* In one experiment six out of eight peas failed to appear above ground. Examination revealed that the radicles, in all cases, were badly rotted and completely permeated by Fusarium 17. Evan the two which emerged above ground, had lesions caused by this fungus. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE I - Fungi isolated from root rots of garden crops. Host Location of Host Age of Plant Beans (G.W.) *London Garden Soil B Mature Seedlings Evidence of Soot Rot General jAppearance of Roots Appearance Appearance of Leaves and Stem of Stand Good tt Organisms Isolated Slight wilting Generalized Browning Fusarium IV Hormal Blackened areas, Slight restrictions Fusarium IV Soil A| C tt it n lorraal 0 Soil A « Poor »t Reddish streaks 0 Soil B tt it it Brown roots, black lesions Fusarium III Soil C t» it Elongated rotted areas. Tips black Fusarium III Rhizopus Soil D tt tt Brown roots, black lesions Fusarium III Beets Soil B n Excellent Slight wilting on one or two lower leaves Roots buff coloured. Crowns dark Fusarium VII Fusarium IV Rhizopus Broccoli Soil A it Fair Uormal Roots badly rotted Fusarium V Soil B it Good Crown regions dark Fusarium V Fusarium II Lima Beans Very poor it tt » Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABUS I - Ftmgi isolated from root rots of garden crops. Host Corn Location of Host *Hyde Park Age of Plant Evidence of Root Rot General Appearance Appearance of Appearance of Roots of Stand Leaves and Stem Mature Crop harvested Alternaria inoculated Seedlings Normal soil*(See Table III discussion) Soil A* B n H Celery Soils A, B, C n tt Lettuce *London garden Soils A, B, C Peas Organisms Isolated Badly rotted Alternaria sp, Fusarium VI n Generalized rotting Fusarium III n Roots completely destroyed in two cases out of 10 plants on A, Others have lesions Fusarium V Normal Slight yellowing Normal Mature It tt n Seedlings tt tt tt Browned n 0 Alternaria sp* Alternaria sp. Soil A tt Very poor n it 6 out of 8 have completely rotted radicles and failed to reach soil surface Fusarium IV Soil C n Fair tt it Lesions Fusarium. IV Soil I) m Poor Generalized browning Fusarium IV Margins of leaves yellow Plants wilting Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE I - Fungi isolated from root rots of garden crops. Host Location of Host Age of Plant Radish Soil A, B Swiss Chard *London Carden N.B. Evidence of Root Rot General Appearance of Roots Appearance Appearance of of Stand Leaves and Stem Seedlings Normal Mature tt Normal « Organisms Isolated Slight darkening Fusarium I Generalized browning with one or two lesions Fusarium V Those marked with an asterisk * indicate that the roots were collected from fields in London and ■vicinity* All others were obtained from seedlings grown on soils A, B, C, or D in the greenhouse* Terminology of Fusarium strains used On the basis of oolour differences as revealed by culturing on Sherbakoff*s medium. (see page13). Fusarium I 1 week old - Pure white, matted hyphae agar clear 21 days old - as above Fusarium II 1 week old - Hyphae pale pink* Growth flocculent. Substratum immediately beneath streak, deep rose. By transmitted light, agar clear, 21 days old - as above Fusarium III 1 week old - Hyphae white, fluffy, abundant. Substratum murky yellow by transmitted light. 21 days old - Substratum pale orange yellow by transmitted light. Fusarium IV 1 week old — Hyphae pinkish white. Growth very fluffy. Substratum clear, except for white area below mycelium. 21 days old - Substratum deep rose. R eproduced with permission of the copyright owner. Further reproduction prohibited without permission. - 21 - Fusarium V 1 week old Hyphae pure white* Magenta streaks on mycelium. Substratum by trans mitted light, rosy pink 21 days old Substratum becoming a dull blood red. Fusarium VI 1 week old Mycelium depressed. Substratum rosy pink but clear. Color intensity of substratum darker than in Fusarium YII 21 days old Substratum deep orange. Fusarium VII 1 week old Mycelium fluffy, salmon pink. Substratum clear, salmon pink. 21 days old Growth fluffier than in VI. Substratum identical with YI Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - 22 Results of Pathogenicity fests on sterile seedlings grown in sterile petri dishes. Discussion Table II indicates the result of Inoculation of healthy sterile roots, under aseptic conditions, with single spore cultures of the fungi isolated from affected roots. The pathogenicity ranges from extreme parasitism in which 100$ of the plants inooulated became affected, to mild parasitism in which only 10$ were attacked. Subsequent experiments with corn inoculated with Alternaria suggest that Alternarla is probably only a sec ondary invader. (See Discussion of Table III) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE II - Relative Pathogenicity of Monospore Cultures of Isolants on roots of seedlings grown from sterile seeds in sterile petri dishes. — ....------------ Host Inoculum Beans fG.W.) Fusarium 17 Humber of Roots Humber of Roots Effect on Roots Inoculated Attacked 10 7 lumber of Re isolations Pathogenicity Deep lesions. Mycelium abundant penetrating through to -vascular cylinder 6 Deep lesions. Tflxole root light brown 9 + 16 + + + lima Beans Fusarium III 9 9 Broccoli Fusarium II 20 16 Fusarium 7 12 2 Slight browning 2 Altemaria gp. 9 1 Root has badly rotted tip 1 Fusarium III 5 5 Rotting severe 3 ■f Fusarium 7 3 3 Slight browning 3 ♦ Fusarium 71 16 16 Tips attacked* Lesions wherever agar is touched, 7ery severe rotting 9* ♦ 3 3 Generalized rot. lot severe •z Corn Lettuce Alternaria sp. Slight browning. Tips dark. One root has severe lesion * The meagre number of isolations may be explained by the almost instantaneous penetration of E g rotted roots. C Doubtful lg into severely Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE II - Relative Pathogenicity of Monospore Cultures of Isolants on roots of seedlings grown from sterile seeds in sterile petri dishes. (Continued) * Pathogenicity Host Inoculum Psas Fusarium IF 8 5 Slight rotting , 3 ♦ Radish Fusarium I 8 h Generalized rotting 2 + Swiss Chard Fusarium V 5 5 Roots badly rotted 5 + N.B. Number of Roots Inoculated Number of Roots Attacked Effect on Roots Number of Re isolations Those forms not producing more than 50% infection under the ideal conditions of the experiment were designated as slightly pathogenic. * Pathogenicity is designated + pathogenic 2 slightly pathogenic: up to 50?° infection * non-pathogenic - 25 - Results of Pathogenicity tests on sterile seedlings grown in inoculated soil Discussion Table III summarizes the results obtained from seed lings grown in artificially inoculated soil. The fungi used for inoculum were those previously isolated from broccoli and corn roots, as indicated in Table I. The pathogenicity of Alternaria sp. on corn roots is doubtful. In both experiments IV and V, fusarium III, as well as Alternaria. was obtained six times from the most badly rotted roots, for example, Alternaria was re-isolated from the severely attacked tips, while fusarium III was obtained from the more normal appearing tissue about half an inch back from the rotted tips. This suggests the possibility that invasion of fusarium III may be primary, via the tips; while the Alternaria attack is secondary* Evidently the fusarium strain isolated had been in the roots for a longer period, or else was a more vigorous parasite since it had progressed further up the root. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABliE III - Relative Pathogenicity of Fungi on Seedlings growing in Sterilized Soil as determined at the end of three weeks* Host Inoculum Source of Appearance of Inoculation above-ground parts Appearance of Roots l*Broceoli Fusarium 7 Broccoli grown on Soil A Generalized browning 100 100 100 Hone on 3-weeks old plants In all cases + 2 ,Brooooli Fusarium V Broccoli grown on Soil A Roots light brown, Crown regions dark. Ho lesions below crown. 100 , 100 100 Hone on 3-weeks In all cases old plants ♦ 26$ of plants In' all oases + + 3.Com Fusarium 7 Corn grown on Soil D l+.Com Alternaria sp. Corn from Hyde Park 5.Com Altemia sp. 6.Swiss chard Fusarium 7 * Pathogenicity - Corn from Hyde Park Swiss chard from London garden Healthy !f Humber; Humber planted of Roots Examined Humber Effect on Host of Roots Attacked +’ Re isolations Leaves on 9 plants yellow; in 2 cases plants wilting Roots of I4. of these 9 plants have lesions 25 Healthy Roots badly rotted in plants up to 1" high. Those above 1" have constricted roots in 7 oases 21 21 11 not serious 3 Roots with lesions in 11 Sases Crown susceptible. Rotting severe in smallest plants 1+9 1+9 11 not serious 3 Crown and tip region badly affected. Roots of large seedlings constricted. Some roots badly rotted. 50 : 50 50 Ho serious effeci In all n 11 + parasitic £ weakly parasitic up to 25% infection - non-parasitic 25 7 affectedj 16% showing above-ground symptoms on above-ground parts oases Patho- * genicity - 27 Summary 1* Of thirteen common garden vegetables examined for evidence of root rot, four showed no evidence of attack. These were carrots, celery, parsnips and tomatoes. 2. The organisms most frequently found were various strains of Fusarium, one species of Alternaria, and Rhizopua which was apparently a saprophyte. 3* Seven strains of Fusarium were isolated altogether, and these were present on all vegetables showing evidence of root rot, except lettuce which was attacked by Alternaria. The effect of these on their hosts was as follows; Fusarium I was slightly pathogenic on radish, but could not be considered as a serious parasite since the seedlings were apparently quite vigorous. Fusarium II caused 80$ infection on broccoli seedling’s roots without causing any reduction in stand. Fusarium III was extremely pathogenic causing 100$ infection on lima beans and corn roots. It was apparently responsible for the reduction in stand of both vegetables. Fusarium I? was pathogenic on Golden Wax beans to the extent of 70$, and on peas to the extent of 62$. It was responsible for severe reduction in stand of pea seedlings, by attacking the radicles almost as soon as they emerged, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. wm 28 Siunmary (oont»d) and thus reducing the number of seedlings to reach the soil surface. Fusarium V was lOOfo pathogenic on corn and Swiss chard, but only 16$ so on broccoli roots. Fusarium VI produced 100ft, infection on corn roots but did not seriously affect the stand in young seedlings. Alternaria sp* is a very doubtful pathogen on corn roots, probably being a secondary invader. However, it is considerably more pathogenic on lettuce oh'which it produced 100^ infection* Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - 29 - Literature Cited 1* Branstetter, B.B. - Corn Boot Hot studies, Univ. of Missouri Agr. Expt. Sta. Res. Bui 113. 19272, Burkholder, Walter H. - The Dry Boot - Hot of the Bean. Cornell Univ. Agr. Exp, Sta. Memoir 26. 19193, Burrill, T. J, - A bacterial disease of Indian corn. Soc. Prom Agr. Sai, 10th Ann. Proc. pp. 9-27 1889* Davie, Glen H. and Chas. S. Reddy - A seedling blight stage of onion bulb rot (Fusarium sp.) Abstr. in Phytopath. V 22. 1932. 5. Drechsler, Charles - Two water molds causing tomato rootlet injury. Jour. Agr. Res. 3^(3)• 1927* 6. Fritz, Clara W. - Cultural Criteria for the Distinction of Wood-destroying fungi, p. 201. 1923* 7. Gussow, H. T. Progress report of the Dominion Botanist. Gan, Dept. Agr. 1935 - 37• 8. Hansen, H. W. Etiology of the Pink Root disease of onions. 9. Harter, L. L. 10. Humphrey, H. B. Phytopath. V. 19• 1929 Root rot of peas. Phytopath. V.28. 193® Studies on the relation of certain species ffuBerlum to Tomato Blight of the Pacific Worth West. State College of Wash. Exp. Sta. Bui. 115- 191^. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. • - 30 - IX. Jones, F. R. - Stem and root rot of peas in U.S.A. caused "by species of Fusarium. Jour. Agr. Res. 7. 26, 1923* 12. Manns, f. F. and C. 1. Phillips - Corn root rot studies. Jour. Agr. Res. 7. 27. 192*+. 13* Pammel, L. A. - Serious root and stalk disease of com. Iowa Agr. Exp. Sta. Bui. 13. 191^> 14. Rosen, H. R. - Bacterial stalk rot of corn. Ark. Agr. Exp. Sta. Bui. 209. 1926. 13. Selby, A. D. - A brief handbook of diseases of cul tivated plants in Ohio. Ohio Agr. Exp. Sta. Bui. 21^:390, 1910. 16. Smith. E. F. - An Introduction to Bacterial Diseases of Plants. Published by W. B. Saunders Co., Philadelphia, 1920. 17* Sherbakoff, C. D. - Fusaria of Potatoes. Cornell Univ. Agr. Expt. Sta. Memoir 6, 1915* 15. Taubenhaus. J. J. Studies on a new Fusarium wilt of spinach in Texas. Tex. Agr. Exp. Sta'. Bui. 3I+3, 1926. 19. " and Ezekiel U. S. Dept. Agr. Bur. Plant Indus., Plant Disease Reporter 15(6), 1931* 20 » and F. W. Mally - Pink root disease of onions and its - control. Ex. Ag. Exp. Sta. Bui. 273* 1921. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 31 21. Valleau, W. D. - Seed corn infection with PuBarium moniliforme and its relation to the root and stalk rots. Ky. Agr. Exp. Sta. Bui. 226, 1920. 22. Wollemweber, H. ¥. Studies on the Fusarium problem. Phytopath 3» 1913* ) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.