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Post-penetration antagonism by Cladosporium tenuissimum to uredinial induction by Melampsora larici-populina
Notes and brief articles dung incubated under warm, humid conditions in the laboratory (Webster, 1970) with acess to free water is beyond question an artifact in the sense that it does not closely reflect the natural succes sion in the field. Single rabbit pellets lying on sand or short turf are probably in a saturated atmosphere for only a small proportion of their existence. Further studies or fruitbody and mycelial succession under conditions approaching those found in the field would be rewarding. REFERENCES
KHAN, R. S. & CAIN, R. F . (1977). The occurrence of amyloid plugs in the asci of A scotricha erinacea. Mycotaxon S, 409-4 14. MINTER, D. W., KIRK, P. M . & SUTTON, B. C. (1982). Holoblastic phialides. Transacrions of the British Mycological Society 79, 75--93. MINTER, D. W., KIRK, P. M. & SUTTON, B. C. (1983). Thal1ic phialides. Transactions of the British Mycological S ociety 80, 39-66.
373
MULLER, E . (1959) . Uber die Stel1ung der Ascornycetengattung Wa welia Namyslowsky. In Omagiu lui Traian Sd oulescu, pp. 515-518. Editura Acad . Rep . Pop. Romine. MOLLER, E. & ARX, J. A. VON ( 1973) . Pyrenomycetes : Meliolales, Coronophorales, Sphaeriales. In The Fungi, 4A (ed. G. C. Ainsworth, F. K. Sparrow and A. S. Su ssman ), pp . 87-132. New York , London, Academic Press. NAMYSLOWSKI, B. (1908). Sur la structure et Ie developpernent de Wawelia regia nov. subfan. gen.sp. Bull etin international de Academie des sciences et des lettres de Cracovie (Classe des sciences mathematiques et naturelles : S erie B ) Sciences naturelles, 597-603 . WALKER, J. C. & MINTER, D. W. (1981). Taxonomy of Nematogonum, Gonatobotrys , Gonatobotryum and Gonatorrhodiella. Transactions of the British Mycological S ociety 77, 299-3 1 9. WEBSTER, J. (1970). Coprophilous fungi. Transactions of the British Mycological Society 54, 161-180.
r
POST-PENETRATION ANTAGONISM BY CLADOSPORIUM TENUISSIMUM TO UREDINIAL INDUCTION BY MELAMPSORA LARICI-POPULINA BY 1. K. SHARMA AND W . A. HEATHER
Department of Forestry, Australian National University , P.O. Box 4, Canberra , A.C.T. Australia Cladosporium tenuissimum Cooke is antagonistic to the production of uredinia by races of Melampsora larici-populina Kleb. on leaf disks cut from Populu s x euramericana (D ode) Guinier cv. 1-488 (Sharma & Heather, 1981). It has been suggested that this antagonism results from two prepenetration phenomena; (a) the antibiosis by conidia of C. tenuissimum to urediniospores of M .larici-populina and (b) hyperparasitism of the germ tubes of the rust by the mycelium of C. tenuissimum (Sharma & Heather, 1981). This communication reports an experiment designed to test whether C. tenuissimum affects also the post-penetration phase of the parasitism of leaf disks of cv. 1-488 by three races of M. larici-populina. Procedures for raising plants in a rust-proof glasshouse, selection of leaves, preparation and inoculation of the leaf disks with urediniospores and conidia have been described (Sharma & Heather,
Fig .
1.
1981). Incubation of the inoculated disks used the procedure of Singh & Heather (1981). Following the deposition of urediniospores of the three races on groups of separate leaf disks, ten replicate disks inoculated with each race were incubated for 0, 12, 24 or 48 h (the pre-treatment period) at 20°C under cool, fluorescent lights, (int ensity 100 pEm- 2 s" , 16 h photoperiod). Following pre-treatment, groups of disks were returned to the spore settling tower and conidia of C. tenuissimum deposited on the abaxial surface (Sharma & Heather, 1981). Conidia were not deposited on 40 disks (four groups, each of 10 replicates, inoculated with the separate races) which served as controls. The disks were then reincubated, and the number ofuredinia per leaf disk (U L D ) was assessed at 15 days after inoculation with the urediniospores. The data were analysed using the ANOVA procedures detailed elsewhere (Sharma & Heather, 1981) and least significant differences (L SD) in mean ULD for
Rabbit pellets with str omata, some of which bear perithecia (actual size).
Fig . 2. Detail of single pel1et with stromata ( x 4). Fig. 3. Str oma and peritheciurn in vertical section . Fig . 4. Detail of anamorph. Fig . 5. Paraphyses, asci and ascospores. Tran s. Br . my col. Soc. 80 (2) , ( 1983).
Printed in Great Britain
Notes and brief articles
374
Table 1. Number of uredinia developed on leaf disks of P , x euramericana cv , 1-488 when inoculated separately with urediniospores of thr ee races of M, larici-populina and incubated fo r certain pretreatm ent periods prior to deposit ion of conidia of C. tenuissimum
P re-treatment per iod (h) 0
12 24 48 Control
N umber of uredinia produ ced per leaf disk (U L D) : race of M , larici-populina A
D
E
27'6 37'7 52 '9 5 8 'S 67'3
22' 2 29 '2 4 6 '2 5° '7 55'S
23'9 33 '9 42 9 53' 1 61 8
L.S.D. (P = 0 '01 ) for races period = 1,88.
= 2'43,
for pr e-t reatment
race s and for pre-treatment periods were calculated (Snedecor, 1946). Urediniospores of M. larici-populina incubated under the conditions outlined, on leaf di sks of poplar, can germinate in as little as 30 min (Spiers 1978 ). Germination after 6 h may exceed 90 % , and penetration can occur in less than 2'5 h after deposition (Omar, 1978). It can be assumed, therefore, that all viable urediniosp ores had germinated and that penetration of the leaf d isks was complete within 10 h of th e pretreatment period. D eposition of conidia of C. tenuissimum , immediately follow ing inoculatio n with uredinio spores of the three races of M , larici-populina, resulted in a 60 % reduction in the ULD (T able 1), Depending on the race employed a pre-treatment period of 12 or 24 h, resulted in a reduction of 47 to 44 % or 31 to 17 % respectively in the ULD . The reductions in ULD after pre-treatment pe riod s of 12 or 24 h would seem to be the result of hyperparasitism or antibiosis by the con id ia of C. tenuissimum to the post-penetrative phase of infection of the leaf disks by the rust. This appears to be the first report
of such a phenomenon . Irrespective of the pretreatment period , the C. tenuissimum colonised 85 to 95 % of the uredinia produced and this should reduce cons iderably the infectivity of urediniospores subsequently dispersed (Sharma & Heather, 1981). Pre-treatment period was the most significant, and the race employed a lesser, but nev ertheless highly significant, contributor to variation in the ULD aft er 15 da ys of incubation. W ith in a pre-treatment period, mean ULD d iffered sign ificantly (P = 0 '01) between races in most instances, and in all cases within a race the mean ULD differed significantly (P = 0 '01 ) between pretreatment period s (T able 1). While C .tenuissimum penetrates and subsequently fru its on the urediniosp ore s of M . larici-populina (Sharma & Heather, 1981), the mycelium of the hyperparasite grows in contact with, but doe s not seem to proliferate within, the living germ tubes of its host (Sharma, unpubl. ). Thus the antagonism of C. tenuissimum to uredinial production, following a pr e-treatment of 12 or 24 h, possibl y re sults from antibiosis rather than colonisation of the rust mycelium within the host tissue . The hi st ology of th is relation ship is being inv estigated further. REFERENCES
OMAR, M , B. (1978). Aspects of pre- and post-penetration phenomena of M elamp sora larici-p opulina Kl eb . Ph.D. Thesis, The Australian National University. SHARMA, 1. K . & HEATHER, W . A. (1981), Antagonism by three species of Clad osporium to three races of Me lampsora larici-popultna Kleb. A ustralian Forest Research 11 , 283- 293, SINGH, S, J. & HEATHER, W, A, (1981). An improved method for detached leaf culture of Melampsora leaf rust of Populus speci es. Transactions of the British Mycological Socie ty 77, 436-437. SNEDECOR, G , W. (1946). Statistica l M ethods. Am es : Iowa State College Pre ss. SPIERS, A. J. (1978). Effect of light , temperature, and relative humidity on germination of urediniospo res of, and infection of poplars by, M elampsora larici-populina and M, medusae. N ew Z ealand J ournal of S cience 21, 393-400,
A COMPARISO N OF METHODS TO SUR FACE STERILIZE WHEAT SEEDS BY
J. B. S P EA K M AN
AND W . KR U GER
Biologis che Bundesanstalt fur Land- und Fors uoirtschaft, S chlosshoppelioeg 8, D-2305 Heikendorf-Kitz eberg, We st Germany
In the course of a study to investigate perithecial production by isolates of the Gaeumannomy ces] Phialophora complex (Speakm an, 1982), it was necessary to find a method which satisfacto rily Trans . Br. my col. Soc . 80 (2), (1983).
ste rilized the surface of wheat seeds. St eril izing agents reported to have been used with wheat seeds include ethanol (Reinecke & Fokkema, 1981 ), mercuric chloride (H gCI2 ) (D om sch & Gams,
Printed in Great Britain
KHAN, R. S. & CAIN, R. F . (1977). The occurrence of amyloid plugs in the asci of A scotricha erinacea. Mycotaxon S, 409-4 14. MINTER, D. W., KIRK, P. M . & SUTTON, B. C. (1982). Holoblastic phialides. Transacrions of the British Mycological Society 79, 75--93. MINTER, D. W., KIRK, P. M. & SUTTON, B. C. (1983). Thal1ic phialides. Transactions of the British Mycological S ociety 80, 39-66.
373
MULLER, E . (1959) . Uber die Stel1ung der Ascornycetengattung Wa welia Namyslowsky. In Omagiu lui Traian Sd oulescu, pp. 515-518. Editura Acad . Rep . Pop. Romine. MOLLER, E. & ARX, J. A. VON ( 1973) . Pyrenomycetes : Meliolales, Coronophorales, Sphaeriales. In The Fungi, 4A (ed. G. C. Ainsworth, F. K. Sparrow and A. S. Su ssman ), pp . 87-132. New York , London, Academic Press. NAMYSLOWSKI, B. (1908). Sur la structure et Ie developpernent de Wawelia regia nov. subfan. gen.sp. Bull etin international de Academie des sciences et des lettres de Cracovie (Classe des sciences mathematiques et naturelles : S erie B ) Sciences naturelles, 597-603 . WALKER, J. C. & MINTER, D. W. (1981). Taxonomy of Nematogonum, Gonatobotrys , Gonatobotryum and Gonatorrhodiella. Transactions of the British Mycological S ociety 77, 299-3 1 9. WEBSTER, J. (1970). Coprophilous fungi. Transactions of the British Mycological Society 54, 161-180.
r
POST-PENETRATION ANTAGONISM BY CLADOSPORIUM TENUISSIMUM TO UREDINIAL INDUCTION BY MELAMPSORA LARICI-POPULINA BY 1. K. SHARMA AND W . A. HEATHER
Department of Forestry, Australian National University , P.O. Box 4, Canberra , A.C.T. Australia Cladosporium tenuissimum Cooke is antagonistic to the production of uredinia by races of Melampsora larici-populina Kleb. on leaf disks cut from Populu s x euramericana (D ode) Guinier cv. 1-488 (Sharma & Heather, 1981). It has been suggested that this antagonism results from two prepenetration phenomena; (a) the antibiosis by conidia of C. tenuissimum to urediniospores of M .larici-populina and (b) hyperparasitism of the germ tubes of the rust by the mycelium of C. tenuissimum (Sharma & Heather, 1981). This communication reports an experiment designed to test whether C. tenuissimum affects also the post-penetration phase of the parasitism of leaf disks of cv. 1-488 by three races of M. larici-populina. Procedures for raising plants in a rust-proof glasshouse, selection of leaves, preparation and inoculation of the leaf disks with urediniospores and conidia have been described (Sharma & Heather,
Fig .
1.
1981). Incubation of the inoculated disks used the procedure of Singh & Heather (1981). Following the deposition of urediniospores of the three races on groups of separate leaf disks, ten replicate disks inoculated with each race were incubated for 0, 12, 24 or 48 h (the pre-treatment period) at 20°C under cool, fluorescent lights, (int ensity 100 pEm- 2 s" , 16 h photoperiod). Following pre-treatment, groups of disks were returned to the spore settling tower and conidia of C. tenuissimum deposited on the abaxial surface (Sharma & Heather, 1981). Conidia were not deposited on 40 disks (four groups, each of 10 replicates, inoculated with the separate races) which served as controls. The disks were then reincubated, and the number ofuredinia per leaf disk (U L D ) was assessed at 15 days after inoculation with the urediniospores. The data were analysed using the ANOVA procedures detailed elsewhere (Sharma & Heather, 1981) and least significant differences (L SD) in mean ULD for
Rabbit pellets with str omata, some of which bear perithecia (actual size).
Fig . 2. Detail of single pel1et with stromata ( x 4). Fig. 3. Str oma and peritheciurn in vertical section . Fig . 4. Detail of anamorph. Fig . 5. Paraphyses, asci and ascospores. Tran s. Br . my col. Soc. 80 (2) , ( 1983).
Printed in Great Britain
Notes and brief articles
374
Table 1. Number of uredinia developed on leaf disks of P , x euramericana cv , 1-488 when inoculated separately with urediniospores of thr ee races of M, larici-populina and incubated fo r certain pretreatm ent periods prior to deposit ion of conidia of C. tenuissimum
P re-treatment per iod (h) 0
12 24 48 Control
N umber of uredinia produ ced per leaf disk (U L D) : race of M , larici-populina A
D
E
27'6 37'7 52 '9 5 8 'S 67'3
22' 2 29 '2 4 6 '2 5° '7 55'S
23'9 33 '9 42 9 53' 1 61 8
L.S.D. (P = 0 '01 ) for races period = 1,88.
= 2'43,
for pr e-t reatment
race s and for pre-treatment periods were calculated (Snedecor, 1946). Urediniospores of M. larici-populina incubated under the conditions outlined, on leaf di sks of poplar, can germinate in as little as 30 min (Spiers 1978 ). Germination after 6 h may exceed 90 % , and penetration can occur in less than 2'5 h after deposition (Omar, 1978). It can be assumed, therefore, that all viable urediniosp ores had germinated and that penetration of the leaf d isks was complete within 10 h of th e pretreatment period. D eposition of conidia of C. tenuissimum , immediately follow ing inoculatio n with uredinio spores of the three races of M , larici-populina, resulted in a 60 % reduction in the ULD (T able 1), Depending on the race employed a pre-treatment period of 12 or 24 h, resulted in a reduction of 47 to 44 % or 31 to 17 % respectively in the ULD . The reductions in ULD after pre-treatment pe riod s of 12 or 24 h would seem to be the result of hyperparasitism or antibiosis by the con id ia of C. tenuissimum to the post-penetrative phase of infection of the leaf disks by the rust. This appears to be the first report
of such a phenomenon . Irrespective of the pretreatment period , the C. tenuissimum colonised 85 to 95 % of the uredinia produced and this should reduce cons iderably the infectivity of urediniospores subsequently dispersed (Sharma & Heather, 1981). Pre-treatment period was the most significant, and the race employed a lesser, but nev ertheless highly significant, contributor to variation in the ULD aft er 15 da ys of incubation. W ith in a pre-treatment period, mean ULD d iffered sign ificantly (P = 0 '01) between races in most instances, and in all cases within a race the mean ULD differed significantly (P = 0 '01 ) between pretreatment period s (T able 1). While C .tenuissimum penetrates and subsequently fru its on the urediniosp ore s of M . larici-populina (Sharma & Heather, 1981), the mycelium of the hyperparasite grows in contact with, but doe s not seem to proliferate within, the living germ tubes of its host (Sharma, unpubl. ). Thus the antagonism of C. tenuissimum to uredinial production, following a pr e-treatment of 12 or 24 h, possibl y re sults from antibiosis rather than colonisation of the rust mycelium within the host tissue . The hi st ology of th is relation ship is being inv estigated further. REFERENCES
OMAR, M , B. (1978). Aspects of pre- and post-penetration phenomena of M elamp sora larici-p opulina Kl eb . Ph.D. Thesis, The Australian National University. SHARMA, 1. K . & HEATHER, W . A. (1981), Antagonism by three species of Clad osporium to three races of Me lampsora larici-popultna Kleb. A ustralian Forest Research 11 , 283- 293, SINGH, S, J. & HEATHER, W, A, (1981). An improved method for detached leaf culture of Melampsora leaf rust of Populus speci es. Transactions of the British Mycological Socie ty 77, 436-437. SNEDECOR, G , W. (1946). Statistica l M ethods. Am es : Iowa State College Pre ss. SPIERS, A. J. (1978). Effect of light , temperature, and relative humidity on germination of urediniospo res of, and infection of poplars by, M elampsora larici-populina and M, medusae. N ew Z ealand J ournal of S cience 21, 393-400,
A COMPARISO N OF METHODS TO SUR FACE STERILIZE WHEAT SEEDS BY
J. B. S P EA K M AN
AND W . KR U GER
Biologis che Bundesanstalt fur Land- und Fors uoirtschaft, S chlosshoppelioeg 8, D-2305 Heikendorf-Kitz eberg, We st Germany
In the course of a study to investigate perithecial production by isolates of the Gaeumannomy ces] Phialophora complex (Speakm an, 1982), it was necessary to find a method which satisfacto rily Trans . Br. my col. Soc . 80 (2), (1983).
ste rilized the surface of wheat seeds. St eril izing agents reported to have been used with wheat seeds include ethanol (Reinecke & Fokkema, 1981 ), mercuric chloride (H gCI2 ) (D om sch & Gams,
Printed in Great Britain