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Varietal reaction of wheat to leaf infection by Leptosphaeria nodorum and Septoria tritici
500
Transactions British Mycological Society
whereas T. thermophile does not grow below 22 °. Thus the latter has a somewhat narrower temperature range for growth. From these differences and the fact that S. thermophile does not produce cleistothecia, we conclude that these two fungi are distinct. Cultures of T. thermophile (I MI 145136) and S. thermophile (IMI 145135) have been deposited in the Commonwealth Mycological Institute, Kew, and in the Centraalbureau voor Schimmelcultures, Baarn. REFERENCES
CHANG, Y. & HUDSON, H.J. (1967). The fungi of wheat straw compost. J. Ecological studies. Trans. Br. mycol. Soc. 50, 649-666. COONEY, D. G. & EMERSON, R. (1964). Thermophilic fung i, Eumycota. San Francisco: W. H. Freeman Publ. Co. FERGUS, C. L. & SINDEN, J. W. (1969). A new thermophilic fungus from mushroom compost: Thielaoia thermophile spec. nov. Can. ]. Bot. 47, 1635-1637. SEMENUlK, G. & CARMICHAEL,]. W. (1966). Sporotrichum thermophile in North America. Can.]. Bot. 44, 105-J08.
VARIETAL REACTION OF WHEAT TO LEAF INFECTION BY LEPTOSPHAERIA NODORUM AND SEPTORIA TRITICI
J. BAKER * Department of Botany, Uniuersity of Exeter CELIA
Leptosphaeria nodorum Muller and Septaria tritici Rob. can both cause considerable damage to wheat leaves. S. tritici appears to be most damaging early in the growing season, when it may kill many of the lower leaves, whereas L. nodorum is more severe from May onwards, particularly on the flag leaves. It is known that some varieties of wheat appear more susceptible to attack by these fungi than others. S. tritici is commonly found only on the leaves while L. nodorum can infect all aerial parts of the plant. The present communication records the results of tests carried out to ascertain the susceptibility of leaves of the same age, but of several different varieties, to both pathogens. Excised leaf portions (the top 4 em) from 14-day-old wheat plants grown in the glasshouse were first stroked lightly between finger and thumb to remove the bloom then painted on their dorsal surfaces with spore suspension using a squirrel-hair brush. The leaf portions were placed dorsal side uppermost in Petri dishes containing 5 ml of 75 p.p.m. benzimidazole, two leaves from each plant in the same dish. Six replicates of each variety were set up and a seventh set of dishes containing leaves treated with water only served as controls for each variety. Similar experiments were carried out with both fungi. The L. nodorum pycnidiospore suspension, at a concentration of approximately 70000
* Present address: Coffee R esearch Foundation, P.O. Box 4, Ruiru, Kenya. Trans. Br. mycol. Soc. 54 (3), (1970). Printed in Great Britain
Notes and Brief Articles
501
spores/ml, was prepared from a IO-day-old slope culture on oat agar grown under 'black light'. Artificially infected leaf material was soaked in sterile water to give the same concentration of spores of S. tritici. Infection was assessedon the basis of the percentage of the photosynthetic area of the leaf affected, after 6 days in the case of L. nodorum, and after 8 days in the case of S. tritici, at room temperature.
I
• 0%
1% Text-fig.
I.
o
5%
10%
25%
50%
75%
100%
Percentage of wheat lamina area affected by Leptosphaeria nodorum.
For assessment of L. nodorum infection the key used by Bronnimann (1968) was employed (Text-fig. I), while the Ministry of Agriculture Plant Pathology Laboratory's Selenophoma donacis assessment key (Text-fig. 2) was found to be more suitable for S. tritici. Leptosphaeria nodorum. Table 1 shows all varieties given a disease rating compared with that of Cappelle-Desprez (= I), which is the most widely grown variety and is known to be highly susceptible. Septoria tritici. The results of this experiment are expressed in a similar way in Table 2. Cappelle-Desprez is known to be tolerant to the pathogen (Arsenijevic, 1965). The level of tolerance of L. nodorum may be judged by lesion character Trans. Br. mycol. Soc. 54 (3), (1970). Printed in Great Britain
502
Transactions British Mycological Society
and size. A tolerant variety such as Engelen 565 develops leaf lesions which are discrete in character and very much resemble the typical symptoms produced by S. tritici in these in vitro tests. These have dark brown centres around the area of penetration but the chlorotic region does not extend further than the immediate border of the brown area.
• •
••
•
r
00
,.
"• •• . ,. 0
•
•
•
"
•
•
•
10
•
•
•
•
It
., • 25%
50% Text-fig.
2.
.J
5%
1%
1%
Percentage of wheat lamina area affected by Septaria tritici.
In contrast, widespread chlorosis occurs on leaves of the varieties susceptible to L. nodorum, and lesions spread to give an eventual overall necrotic effect in the most severe cases. Thus a higher susceptibility is associated with more diffuse lesions and a larger chlorotic area, while tolerance is associated with the limiting of lesion size rather than with actual prevention of infection. Trans. Br. mycal. Soc. 54 (3), (1970). Printed in Great Britain
Notes and Brief Articles Increased susceptibility to S. tritici is characterized by an increase in the number of lesions and their eventual coalescence. A tolerant variety retains the green colour of the leaves and lesions are limited in either number or size or both. Table
I.
Varietal tolerance of wheat leaves to L. nodorum compared with Cappelle-Despre; Disease rating
Variety Engelen 565 Maris Totem Hybrid 46 Maris Widgeon Champlein Viking Mildress Petkus 71/64 Belloy C98/58 West Desprez Blondeau 31 Benoist 1499 Svenno Cappelle-Desprez
0'1 0'1 0'2 0'3 0'3 a'S a'S 0,6 0'7 0,8 0,8 0,8 1'0 1'0
Variety Maris Teal Kolibri Margin Elite Lepeuple Kloka Maris Ensign Joss Cambier Rothwell Sprite Clarion Koga II Janus Maris Ranger Maris Beacon Professeur Marchal Troll
Disease rating 1'1 1'3 1'3 1'4 1'4 1'5 1'5 1'5 1'5 1'5 1'5 1,6 1,8 2'4 2'4
Key: a-a'S, Tolerant; 0'5-1'5, susceptible; 1'5-3'0, highly susceptible,
Table
2.
Varietal tolerance of wheat leaves to S. tritici compared with Cappelle-Desprez
Variety Engelen 565 Maris Totem Cappelle-Desprez Petkus 71/64 Maris Widgeon West Desprez Blondeau 31 Belloy C98/S8 Benoist 1499 Svenno Kolibri Viking Janus Joss Cambier
Disease rating 0'5 0'9 1'0 1'0 I'D
1'0 1'0 2,8 3'0 3'1 3'3 4"3 5"0 5"0
Variety Mildress Cama Troll Champlein Hybrid 46 Maris Teal Margin Professeur Marchal Clarion Rothwell Sprite Maris Beacon Kloka Maris Ranger Maris Ensign Koga II
Disease rating 5'5 6'5 7'5 7,8 8,8 10'3 10'3 11'3 13,8 16'3 25'0 25'0 3 1'S 35'0 36"9
Key: 0-5, Tolerant; 5-15, susceptible; above 15, highly susceptible,
Certain differences in the reaction of varieties to leaf infection and to ear infection by L. nodorum are apparent. The spring varieties Svenno, Troll, Kloka, Koga II and Kolibri, and the winter varieties Elite Lepeuple, Maris Beacon and Professeur Marchal seem far more susceptible to leaf infection than to ear infection. However, certain varieties which showed tolerance in this experiment also show tolerance to glume infection, Trans, Br. mycol. Sac'54 (3), (1970), Printed in Great Britain
504
Transactions British Mycological Society
namely: Engelen 565, Hybrid 46, Maris Widgeon, and Maris Totem. Maris Ensign, Maris Ranger, Blondeau 31, Benoist 1499 and CappelleDesprez are highly susceptible at all growth stages. A comparison of the results obtained for L. nodorum with those obtained for S. tritici reveals that Engelen 565, Maris Totem and Maris Widgeon show considerable tolerance to both pathogens and that Maris Ranger, Maris Ensign, Maris Beacon and Koga II are susceptible to both. Noteworthy differences in reaction are the greater susceptibility of Hybrid 46 to S. tritici and the higher degree of tolerance which Cappelle-Desprez exhibits to this fungus. These results serve as a guide to the type of reaction which may be expected when leaves of different varieties are infected in the field. Under natural conditions the fungi often co-exist so that any accurate assessment of varietal reaction is difficult. However, field observations do indicate that Cappelle-Desprez shows considerable resistance to S. tritici, but is highly susceptible to L. nodorum, and also that Engelen 565 and Hybrid 46 have a high degree of tolerance to L. nodorum. REFERENCES ARSENIJEVIC,
M. (1965). Septaria tritici-a parasite of wheat in Serbia. ZaIt. Bilja 16,
5-7°·
(1968). Zur Kenntnis von Septaria nodorum Berk. den Erreger der Spelzenbraune und einer Blattdurre des Weizens. Phytopath, Z. 61, 101-147.
BRONNIMANN, A.
SURVIVAL OF CERCOSPORA BETICOLA, THE CAUSAL AGENT OF SUGAR BEET LEAF SPOT, IN ISRAEL Z. SOLEL
Volcani Institute of Agricultural Research, Bet Dagan, Israel The survival of Cetcospora beticola Sacc., the causal organism of sugar beet leaf spot, has been studied in temperate countries, where sugar beet is a summer crop. Overwintering of the pathogen occurs on debris of infected leaves (Pool & McKay, 1916; Canova, 1959) and on seed (Canova, 1959). Cultivated and wild plants are listed as hosts of the fungus (Vestal, 1933; Chupp, 1953; Canova, 1959), but their role in the perpetuation of the disease has not been elucidated. In Israel, with a subtropical climate, sugar beet is a winter crop, harvested in May-July. Infection of C. beticola usually starts in December, 2-3 months after planting, when the vegetative growth is already well developed, suggesting that seed-borne inoculum is not responsible for the introduction of the pathogen into the field. Further, commercial sugar-beet seed is not produced in Israel, but imported from Europe and tested specimens from various lots of this disinfected commercial seed proved to be free of infection (SoleI, 1967). The objective of the present investigation Trans. Br. mycol. Soc. 54 (3), (1970). Printed in Great Britain
Transactions British Mycological Society
whereas T. thermophile does not grow below 22 °. Thus the latter has a somewhat narrower temperature range for growth. From these differences and the fact that S. thermophile does not produce cleistothecia, we conclude that these two fungi are distinct. Cultures of T. thermophile (I MI 145136) and S. thermophile (IMI 145135) have been deposited in the Commonwealth Mycological Institute, Kew, and in the Centraalbureau voor Schimmelcultures, Baarn. REFERENCES
CHANG, Y. & HUDSON, H.J. (1967). The fungi of wheat straw compost. J. Ecological studies. Trans. Br. mycol. Soc. 50, 649-666. COONEY, D. G. & EMERSON, R. (1964). Thermophilic fung i, Eumycota. San Francisco: W. H. Freeman Publ. Co. FERGUS, C. L. & SINDEN, J. W. (1969). A new thermophilic fungus from mushroom compost: Thielaoia thermophile spec. nov. Can. ]. Bot. 47, 1635-1637. SEMENUlK, G. & CARMICHAEL,]. W. (1966). Sporotrichum thermophile in North America. Can.]. Bot. 44, 105-J08.
VARIETAL REACTION OF WHEAT TO LEAF INFECTION BY LEPTOSPHAERIA NODORUM AND SEPTORIA TRITICI
J. BAKER * Department of Botany, Uniuersity of Exeter CELIA
Leptosphaeria nodorum Muller and Septaria tritici Rob. can both cause considerable damage to wheat leaves. S. tritici appears to be most damaging early in the growing season, when it may kill many of the lower leaves, whereas L. nodorum is more severe from May onwards, particularly on the flag leaves. It is known that some varieties of wheat appear more susceptible to attack by these fungi than others. S. tritici is commonly found only on the leaves while L. nodorum can infect all aerial parts of the plant. The present communication records the results of tests carried out to ascertain the susceptibility of leaves of the same age, but of several different varieties, to both pathogens. Excised leaf portions (the top 4 em) from 14-day-old wheat plants grown in the glasshouse were first stroked lightly between finger and thumb to remove the bloom then painted on their dorsal surfaces with spore suspension using a squirrel-hair brush. The leaf portions were placed dorsal side uppermost in Petri dishes containing 5 ml of 75 p.p.m. benzimidazole, two leaves from each plant in the same dish. Six replicates of each variety were set up and a seventh set of dishes containing leaves treated with water only served as controls for each variety. Similar experiments were carried out with both fungi. The L. nodorum pycnidiospore suspension, at a concentration of approximately 70000
* Present address: Coffee R esearch Foundation, P.O. Box 4, Ruiru, Kenya. Trans. Br. mycol. Soc. 54 (3), (1970). Printed in Great Britain
Notes and Brief Articles
501
spores/ml, was prepared from a IO-day-old slope culture on oat agar grown under 'black light'. Artificially infected leaf material was soaked in sterile water to give the same concentration of spores of S. tritici. Infection was assessedon the basis of the percentage of the photosynthetic area of the leaf affected, after 6 days in the case of L. nodorum, and after 8 days in the case of S. tritici, at room temperature.
I
• 0%
1% Text-fig.
I.
o
5%
10%
25%
50%
75%
100%
Percentage of wheat lamina area affected by Leptosphaeria nodorum.
For assessment of L. nodorum infection the key used by Bronnimann (1968) was employed (Text-fig. I), while the Ministry of Agriculture Plant Pathology Laboratory's Selenophoma donacis assessment key (Text-fig. 2) was found to be more suitable for S. tritici. Leptosphaeria nodorum. Table 1 shows all varieties given a disease rating compared with that of Cappelle-Desprez (= I), which is the most widely grown variety and is known to be highly susceptible. Septoria tritici. The results of this experiment are expressed in a similar way in Table 2. Cappelle-Desprez is known to be tolerant to the pathogen (Arsenijevic, 1965). The level of tolerance of L. nodorum may be judged by lesion character Trans. Br. mycol. Soc. 54 (3), (1970). Printed in Great Britain
502
Transactions British Mycological Society
and size. A tolerant variety such as Engelen 565 develops leaf lesions which are discrete in character and very much resemble the typical symptoms produced by S. tritici in these in vitro tests. These have dark brown centres around the area of penetration but the chlorotic region does not extend further than the immediate border of the brown area.
• •
••
•
r
00
,.
"• •• . ,. 0
•
•
•
"
•
•
•
10
•
•
•
•
It
., • 25%
50% Text-fig.
2.
.J
5%
1%
1%
Percentage of wheat lamina area affected by Septaria tritici.
In contrast, widespread chlorosis occurs on leaves of the varieties susceptible to L. nodorum, and lesions spread to give an eventual overall necrotic effect in the most severe cases. Thus a higher susceptibility is associated with more diffuse lesions and a larger chlorotic area, while tolerance is associated with the limiting of lesion size rather than with actual prevention of infection. Trans. Br. mycal. Soc. 54 (3), (1970). Printed in Great Britain
Notes and Brief Articles Increased susceptibility to S. tritici is characterized by an increase in the number of lesions and their eventual coalescence. A tolerant variety retains the green colour of the leaves and lesions are limited in either number or size or both. Table
I.
Varietal tolerance of wheat leaves to L. nodorum compared with Cappelle-Despre; Disease rating
Variety Engelen 565 Maris Totem Hybrid 46 Maris Widgeon Champlein Viking Mildress Petkus 71/64 Belloy C98/58 West Desprez Blondeau 31 Benoist 1499 Svenno Cappelle-Desprez
0'1 0'1 0'2 0'3 0'3 a'S a'S 0,6 0'7 0,8 0,8 0,8 1'0 1'0
Variety Maris Teal Kolibri Margin Elite Lepeuple Kloka Maris Ensign Joss Cambier Rothwell Sprite Clarion Koga II Janus Maris Ranger Maris Beacon Professeur Marchal Troll
Disease rating 1'1 1'3 1'3 1'4 1'4 1'5 1'5 1'5 1'5 1'5 1'5 1,6 1,8 2'4 2'4
Key: a-a'S, Tolerant; 0'5-1'5, susceptible; 1'5-3'0, highly susceptible,
Table
2.
Varietal tolerance of wheat leaves to S. tritici compared with Cappelle-Desprez
Variety Engelen 565 Maris Totem Cappelle-Desprez Petkus 71/64 Maris Widgeon West Desprez Blondeau 31 Belloy C98/S8 Benoist 1499 Svenno Kolibri Viking Janus Joss Cambier
Disease rating 0'5 0'9 1'0 1'0 I'D
1'0 1'0 2,8 3'0 3'1 3'3 4"3 5"0 5"0
Variety Mildress Cama Troll Champlein Hybrid 46 Maris Teal Margin Professeur Marchal Clarion Rothwell Sprite Maris Beacon Kloka Maris Ranger Maris Ensign Koga II
Disease rating 5'5 6'5 7'5 7,8 8,8 10'3 10'3 11'3 13,8 16'3 25'0 25'0 3 1'S 35'0 36"9
Key: 0-5, Tolerant; 5-15, susceptible; above 15, highly susceptible,
Certain differences in the reaction of varieties to leaf infection and to ear infection by L. nodorum are apparent. The spring varieties Svenno, Troll, Kloka, Koga II and Kolibri, and the winter varieties Elite Lepeuple, Maris Beacon and Professeur Marchal seem far more susceptible to leaf infection than to ear infection. However, certain varieties which showed tolerance in this experiment also show tolerance to glume infection, Trans, Br. mycol. Sac'54 (3), (1970), Printed in Great Britain
504
Transactions British Mycological Society
namely: Engelen 565, Hybrid 46, Maris Widgeon, and Maris Totem. Maris Ensign, Maris Ranger, Blondeau 31, Benoist 1499 and CappelleDesprez are highly susceptible at all growth stages. A comparison of the results obtained for L. nodorum with those obtained for S. tritici reveals that Engelen 565, Maris Totem and Maris Widgeon show considerable tolerance to both pathogens and that Maris Ranger, Maris Ensign, Maris Beacon and Koga II are susceptible to both. Noteworthy differences in reaction are the greater susceptibility of Hybrid 46 to S. tritici and the higher degree of tolerance which Cappelle-Desprez exhibits to this fungus. These results serve as a guide to the type of reaction which may be expected when leaves of different varieties are infected in the field. Under natural conditions the fungi often co-exist so that any accurate assessment of varietal reaction is difficult. However, field observations do indicate that Cappelle-Desprez shows considerable resistance to S. tritici, but is highly susceptible to L. nodorum, and also that Engelen 565 and Hybrid 46 have a high degree of tolerance to L. nodorum. REFERENCES ARSENIJEVIC,
M. (1965). Septaria tritici-a parasite of wheat in Serbia. ZaIt. Bilja 16,
5-7°·
(1968). Zur Kenntnis von Septaria nodorum Berk. den Erreger der Spelzenbraune und einer Blattdurre des Weizens. Phytopath, Z. 61, 101-147.
BRONNIMANN, A.
SURVIVAL OF CERCOSPORA BETICOLA, THE CAUSAL AGENT OF SUGAR BEET LEAF SPOT, IN ISRAEL Z. SOLEL
Volcani Institute of Agricultural Research, Bet Dagan, Israel The survival of Cetcospora beticola Sacc., the causal organism of sugar beet leaf spot, has been studied in temperate countries, where sugar beet is a summer crop. Overwintering of the pathogen occurs on debris of infected leaves (Pool & McKay, 1916; Canova, 1959) and on seed (Canova, 1959). Cultivated and wild plants are listed as hosts of the fungus (Vestal, 1933; Chupp, 1953; Canova, 1959), but their role in the perpetuation of the disease has not been elucidated. In Israel, with a subtropical climate, sugar beet is a winter crop, harvested in May-July. Infection of C. beticola usually starts in December, 2-3 months after planting, when the vegetative growth is already well developed, suggesting that seed-borne inoculum is not responsible for the introduction of the pathogen into the field. Further, commercial sugar-beet seed is not produced in Israel, but imported from Europe and tested specimens from various lots of this disinfected commercial seed proved to be free of infection (SoleI, 1967). The objective of the present investigation Trans. Br. mycol. Soc. 54 (3), (1970). Printed in Great Britain