RACE DIFFERENTIATION IN FUSARIUM OXYSPORUM F. SP
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RACE DIFFERENTIATION IN FUSARIUM OXYSPORUM F. SP
RACE DIFFERENTIATION IN FUSARIUM OXYSPORUM F. SP. DIANTHI AND VARIETAL SUSCEPTIBILITY ( ° ) A. Garibaldi I s t i t u t o di Patologia vegetale Torino Italy Abstract Two races o f F u s a r i u m o x y s p o r u m f . sp. d i a n t h i are present i n almost equal r a t i o i n I t a l y : among the v a r i e t i e s tested to race 1 are susceptible 7 "mediterranean" and 13 " m i n i a t u r e s " , to race 2 are susceptible a l l the 52 v a r i e t i e s belonging to "american", "mediterranean" and " m i n i a t u r e " groups. F u s a r i u m w i l t , known to occur i n I t a l y from the beginning of t h i s century (Cuboni, 1908),became recently one of the most dangerous and severe diseases of carnation not only i n Northern I t a l y , but also i n new areas of production i n the South (Zanardi et a l . , 1971; F r i s u l l o and P i g l i o n i c a , 1976). The control by steam s t e r i l i z a t i o n and chemical fumigation i s not always completely successful! on commercial holdings and, besides, i s very expensive. The use of systemic f u n g i cides i s less e f f e c t i v e than i n the case of P h i a l o p h o r a ci n e r e s c e n s ( G a r i b a l d i , 1970) and a complete f a i l u r e of s o i l treatments w i t h benzimidazole d e r i v a t i v e s has been r e c e n t l y report ed due to the presence of a s t r a i n of F. d i a n t h i resistant to these fungicides (Tramier and B e t t a c c h i n i , 1974). Only a l i t t l e m i n o r i t y of carnation v a r i e t i e s shows resistance to the pathogen (Garibaldi and Pergola, 1975). The successfull t r a n s f e r by breeding of resistance from these v a r i e t i e s to more desirable agronomic l i n e s of carnation l a r g e l y depends con race composition of F u s a r i u m o x y s p o r u m f . sp. d i a n t h i . In t h i s paper we describe some of the r e s u l t s of the t r i a l s c a r r i e d out from 1971 to 1975 at the I s t i t u t o di Patologia vegetale of Turin with the aim o f : 1) studying physiologic s p e c i a l i z a t i o n w i t h i n s p o r u m f . sp. d i a n t h i ; F u s a r i u m oxy 2) t e s t i n g a large number of carnation v a r i e t i e s belonging to the "american" and "mediterranean" ecotypes and to the "miniature" group f o r resistance to the two races of F . d i a n t h i , which have been reported i n I t a l y ( G a r i b a l d i , 1975. ( ° ) Work supported by a grant of the National Research Council, Acta Horticulturae 71, 1977 Carnations Italy. 97 Materials and methods The strains of F u s a r i u m o x y s p o r u m f . sp. d i a n t h i used in t h i s work were i s o l a t e d from carnation plants grown in I t a l y , France, and Spain (table 1). A l l cultures were singlespored, preserved on PDA at 3°C and subcultured at six months i n t e r v a l s . New cultures were i n i t i a t e d from infected carnation stems at least once during the work. A l l the experiments were carried out in a greenhouse during the summer, under natural l i g h t , at 20-35°C, o r , during the. other seasons, in a controlled temperature room under fluorescent l i g h t /12 hr of l i g h t (1 000 foot candles) at 26°C, 12 hr of darkness at 23°C/. Carnation plants of each v a r i e t y were a r t i f i c i a l l y inoculated by dipping t h e i r roots in a suspension of conidia ( l - 5 x l 0 ^ / m l ) and myceli a l fragments of each isolate of F . d i a n t h i obtained by grinding a 4 days old culture of the pathogen on casein hydrolisate medium. To d i f f e r e n t i a t e the races, the f o l l o w i n g v a r i e t i e s were used: "Arthur" and "Scania" (resistant to race 1 ) ; "Astor" and "Torino" (susceptible to race 1). 10-25 plants of each v a r i e t y were inoculated with every isolate and transplanted i n steam-sterilized s o i l . The severity of the disease symptoms was rated on each plant at d i f f e r e n t intervals of time a f t e r the appearance of the f i r s t symptoms using a disease index from 0 (healthy plant) to 100 (dead p l a n t ) . Results and discussion Physiologic specialization The race 1 of F . d i a n t h i has been obtained not only by "mediterranean" but also by "miniature" carnation v a r i e t i e s on Riviera Ligure and in Spain (table 1). 13 (42%) of the strains isolated in 1974, 1975, and 1976 can be referred to t h i s pathotype. On the contrary, 18 (58%) of the isolates can be put in race 2: these have been obtained from every group of v a r i e t i e s . Very recently, a t h i r d pathogenic race has been isolated by a "Sim" v a r i e t y on Riviera Ligure; t h i s race is v i r u l e n t on the "american" and not on some of the "meditej^ ranean" v a r i e t i e s . On t h i s race the investigations are s t i l l in progress in order to investigate the d i f f u s i o n e and the s u s c e p t i b i l i t y of a large number of v a r i e t i e s . Varietal susceptibility Race 2 has been confirmed ( G a r i b a l d i , 1975) to be v i r u l e n t on a l l the carnation varieties tested belonging to every group of carnation (table 2). Race 1, on the contrary, was f u l l y v i r u l e n t only on some of the v a r i e t i e s belonging to the "mediterranean" ecotype and to the "minia ture" group. More exactly, 7 of the 25 "mediterranean" and 13 of the 19 "miniature" varieties tested were susceptible to race 1. 98 References Cuboni, G., 1908. Malattie di garofani prodotte da F u s a r i um d i a n t h i . Relazione sulle malattie delle piante studiate durali te i l biennio 1906-07, Roma. F r i s u l l o , s . , and P i g l i o n i c a , V., 1976. Malattie fungine presenti nelle colture di garofano del Salento e indicazioni sui mezzi di l o t t a . 1° Conv.Floricoltura Salento: 69-77. Garibaldi, A., 1970. Impiego di sostanze ad azione endoterapica nella l o t t a contro la f i a l o f o r o s i del garofano. A g r i c o l t . i t a l . 70: 226-235. Garibaldi, A., 1975. Race d i f f e r e n t i a t i o n in F u s a r i u m oxys p o r u m f . sp. d i a n t h i . F i r s t contribution. Med.Fac. Landbouwwv.Rijksuniv.Gent 40: 531-537. Garibaldi, A., and Pergola, G., 1975. F u s a r i u m w i l t resistance in carnation varieties and Di a n t h u s species. Med. Fac.Landbouwwv.Rijksuniv.Gent 40: 545-554. Tramier, R., and Bettacchini, A., 1974. Mise en évidence d'une souche de F u s a r i u m o x y s p o r u m f . sp. d i a n t h i résistant aux fongicides systémiques. Ann.Phytopathol. 6: 231-236. Zanardi, D., Loi, T . , and Deligia, S., 1971. Un biennio di l o t t a contro la fusariosi del garofano in serra. Giornate f i t o p a t o l . : 303-309. 99 Table 1 - C l a s s i f i c a t i o n of the isolates of Fusarium oxysporum f . sp. dianthi tested during t h i s study. Isolate 1 75 106 102 112 111 103 114 115 116 117 119 120 121 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 l o c a l i t y of i s o l a t i o n 1968 1972 1974 S. Remo Albenga S. Remo II II II II ii •I ii 1975 1976 II II II II II II II II II II II II II II II II II II II II II II Italy II II II II II II II Riva Ligure Imperia il Ventimiglia I I Cipressa II Albenga II Dolceacqua II Coldirodi II S. Remo Cabrils Spain Antibes France Italy Bussana H S. Remo H Ventimiglia ii M H Latina n H Host v a r i e t y "Astor" "William Sirrt' "Sam's Pride?' "Sara" "Sam's Pride?' "Torino" "Torino" "Hobby" "Fulvio" "Oscar" "Red Dimond" "Scania" "Sam's Pride" "Astor" ? ? "Red Sim" "Oreste" "Arthur" "Nora" "Lorena" "C.C.Red" •I H H S. Remo H "Tony" "Nora" M H Imperia » Riva Ligure Ventimiglia ii ii Imperia H H H H u ? 7 "Scania" "Arthur" "Le rêve" "Ingrid" Race 1 2 1 2 1 1 1 1 2 2 2 2 1 1 1 1 2 2 2 2 2 2 1 1 2 2 1 2 2 2 2 Table 2 - Reaction of d i f f e r e n t carnation varieties to the two races of Fusarium oxysporum f . sp. d i a n t h i . Variety Reaction to race 1 2 "American" Scania 3 C Red Diamond White Sim Arthur Le rêve Nora C.C.Red C.C.White R R R R R R R R S S S S S S S s "Mediterranean" Orizzonte Chanel Mose Parsifal Oscar Davide Simona Liguria Marte Fulvio Ciuffetto G i a l l o Nova Grazia Manon Susanna Manuela Nicola R R R R R R R R R R R R R R R R R s s s s s s s s s s s s s s s s s Variety Helen Matuzia Katia Giallo Gambino Cristina Hobby Torino As tor Reaction to race 1 2 R S S S S S s s S S S s s s s s "Miniatures" Sunshine Lisa Peachy Red Baron Orange " I f Ginger Snap White Royal ette Purple " Cerise Gus Vuppi Du Country Sam's Pride Barbi Pink Barbi Ingrid Pauline Bonanza Tony R R R R R R S S s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 101