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STAINING ABILITY OF VARIOUS SAPSTAINING FUNGI ON JACK PINE SHORT LOG SECTIONS.

DIAN-QING YANG [*]

ABSTRACT

Ceratocystis and Ophiostoma species are common fungi that cause wood sapstain worldwide. The staining ability of these fungi on wood wafers of different wood species has previously been investigated and the results were published. The present study was conducted to evaluate the growth and stain intensity of 20 isolates of 6 sapstain fungi on jack pine short log sections (billets) under natural environmental conditions. Ceratocysits coerulescens, Ceratocystis piceaperda, Ophiostoma ips, Ophiostoma minus, Ophiostoma piceae, and Ophiostoma piliferum isolated from logs and lumber of various softwoods across Canada were evaluated. The results showed that most of these species caused dark black discoloration of wood, except O. piceae, which caused a brownish stain on this wood species. O. minus rapidly colonized the billets in all three directions, longitudinal, tangential, and radial. O. piliferum, C. coerulescens, and certain isolates of C. piceaperda displayed moderate growth rates. O. ips and O. piceae grew sl owly on billets of jack pine, especially in the radial direction. Information provided in this paper will help develop more effective control strategies for sapstain prevention in jack pine.

There is an increasing interest in the causal agents of wood discoloration, especially Ceratocystis and Ophiostoma spp. [3,9,10]. A recent field survey in Canada showed that 13 species were isolated from stained logs and lumber of various softwoods, including 11 belonging to the genera Ceratocystis and Ophiostoma [9]. This survey also revealed that fungal diversity was greater in logs than in lumber. Ophiostoma piceae, Ophiostoma minus, and Ophiostoma floccosum were most frequently isolated from logs, whereas in lumber, O. piceae, O. floccosum, and Ophiostoma piliferum were most frequently isolated. Ceratocystis coerulescens, Ceratocystis piceaperda, and Ophiostoma ips were only isolated from logs.

Freshly cut logs in Canada are often left in the forest or in sawmills for several weeks to several months before processing. This extended storage period results in increased opportunities for fungal invasion and colonization of wood. Jack pine (Pinus banksiana Lamb.) is increasingly used for value-added wood products in Canada, and sapstain has an important economic impact on this wood species [9,10]. Information on the actual causal fungi producing stain on this wood species will help develop more effective control strategies for stain prevention. This research was performed in conjunction with a similar study on wafers under laboratory conditions [10].

In the summer of 1999, jack pine trees (approx. 30 years old) were felled in Northern Quebec, Canada. Logs (7 to 14 cm diameter) were cut into 20-cm-long short sections (billets). The billets selected had bark on their entire surfaces and were free of any wounds or insect damage. The ends of billets were flame sterilized and immediately covered with a silicone sealant (Silicone II, GE Silicones, Waterford, N.Y) to retard moisture loss and contamination of the sawn surfaces. The billets were numbered and stored at -30[degrees]C until needed.

MATERIALS AND METHODS

PREPARATION 0F BILLETS

SOURCES OF FUNGI

Six fungal species that frequently cause wood stain in North America were selected for the test; 2 to 5 isolates of C. coerulescens (Munch) Bakshi, C. piceaperda (Rumbold) Moreau, O. ips (Rumbold) Nannf., O. minus (Hedge.) Syd. & P. Syd., O. piceae (Munch) Syd. & P. Syd., and O. piliferum (Fr.:Fr.) Syd. & P. Syd. [2] were selected from the Forintek Culture Collection. Most isolates were isolated from logs and sawn lumber of jack pine and black/white spruce across Canada during a previous field survey [9]. Three isolates each of C. coerulescens and O. ips were isolated from local jack pine logs in 1999. These fungi were grown in petri plates containing 2 percent malt extract agar at 25[degrees]C for 2 weeks prior to being used in the test.

INOCULATION OF BILLETS

The billets were thawed at room temperature, then 10 billets were randomly selected, placed in an oven at 103 [degrees]C, and dried to a constant weight. The moisture contents (MCs) of the billets were determined by weighing before and after drying. Two inoculation holes (as deep as the thickness of the bark) were made on opposite sides of the remaining billets and 10 cm away from each end by a 5-mm-diameter corer. Fungal mycelial discs (5 mm diameter) cut from the actively growing edge of the test fungus were placed into the inoculation holes of the billets. The mycelial side of the agar disc was in contact with the wood and the inoculation holes were wrapped with tape (Fig. 1A). Each fungal isolate was inoculated into 10 holes on 5 billets, and a total of 100 billets were inoculated. The inoculated billets were randomly placed in six covered plastic containers, which were then moved to a lumber yard for storage. The temperature and relative humidity (RH) at the test site were monitored using a data logger.

SAMPLING AND STAIN EVALUATION

Stain development on billets was accessed from each inoculation point 8 weeks after inoculation. The billets were debarked and the longitudinal growth of staining fungi emerging from each inoculation point was measured (Fig. 1B). Each billet was then sawn into two pieces across the inoculation points so that radial and tangential growth of fungus could be measured (Fig. 1C). All the assessments were based on 10 measurements for each isolate from 5 replicate billets. Following the assessments, the identities of inoculated fungi on wood wafers were confirmed by microscopic examination. Contaminated samples were not considered in the analysis.

Means and standard deviations of data were calculated. Means of the growth of different fungal species were compared and ranked by Scheffe's test using the Statistical Analysis System [6].

RESULTS AND DISCUSSION

The average MC of the billets was 79.2 [+ or -] 18.2 percent (n =10), which corresponds to a previous report by Cech and Pfaff (1) for this wood species. This level should be adequate for supporting fungal growth.

The billets were inoculated in June and inspected in August. During this period of time, the maximal temperature was 35.7[degrees]C, the minimal temperature was 7.4[degrees]C,. and the average was 20.0[degrees]C. The average RH reached 94.8 percent with the minimal and maximal RH of 49.8 and 100 percent, respectively. These data are representative of summer conditions in Quebec: high temperatures during the day, low temperatures at night, and high RH.

All the fungal isolates inoculated caused stain in jack pine wood (Table 1). All isolates of C. coerulescens grew well in longitudinal and tangential directions and moderately in the radial direction. This species produced a black to greenish black discoloration of the wood. C. piceaperda grew at similar rates both longitudinally and tangentially to C. coerulescens, but caused a darker stain and one isolate grew faster in the radial direction than C. coerulescens. Compared to other species, the growth of O. ips was relatively slow, especially in the radial direction. This fungus generally did not grow beyond 2 cm into the wood 8 weeks after inoculation. This species caused a black discoloration of the wood. Similar to O. ips, O. piceae did not grow as fast as other fungal species and caused a less intensive, brownish black stain. Although the three isolates of O. piliferum were isolated from sawn lumber, they all grew well in the billets, especially in the radial direction. This fungus caused a black stain. Of the six fungi tested, O. minus grew most rapidly. The growth of this fungus in all three directions of the billets was significantly larger than the other five fungi. This fungus produced a large quantity of dark perithecia on the wood and caused the most intensive black stain.

Based on growth rate and stain intensity, O. minus was the most important species on jack pine logs, followed by O. piliferum and C. coerulescens. O. ips and O. piceae were third in importance on this wood species. One isolate of C. piceaperda (DSp 1/5B-3) grew similar to the fungi that were second in importance; another isolate (DPj4/lB-2) grew similar to those that were third in importance; however, C. piceaperda caused an intensive dark stain on the wood.

O. minus is a common species in North America, especially on the west coast. The fungus attacks mainly logs, but may also affect lumber. It was reported from New Mexico, California, Yukon, and up to North Alaska [8]. It affects many pine species (Pinus spp.), as well as Douglas-fir (Pseudotsuga menziesii), and true fir (Abies lasiocarpa) [2,8]. This species was found on six of seven sampling sites located in British Columbia, Alberta, Saskatchewan, Ontario, Quebec, and New Brunswick [9]. Most isolates were obtained from logs located in Saskatchewan. The fungus grew mainly on jack pine and white/black spruce and occasionally was found on balsam fir [9]. This species may become a major cause of log stain in Canada.

O. piliferum causes wood stain on both coniferous and hardwood species and was found mainly in western and central Canada. This species grew moderately on jack pine logs, but in fact, it mainly attacks lumber rather than logs in the natural condition [9].

A comparison of these observations to the previous test on jack pine wood wafers [10] revealed that although both O. piliferum and O. minus can grow on logs and on lumber, O. piliferum grew faster than O. minus on wood wafers, whereas O. minus grew better than O. piliferum on billets. These laboratory testing data support the field survey report [9] that O. piliferum occurred three times more often in lumber than in logs, whereas O. minus was encountered eight times more frequently in logs than in lumber.

C. coerulescens is an important staining fungus of hardwoods such as Acer spp., Quercus, spp., or Fagus spp. It also affects softwood species in North America and Europe [2]. An increasing number of isolates of this fungus have been found in jack pine and white/black spruce logs across Canada [9].

Unlike O. piliferum, O. ips mainly attacks logs of softwoods. This fungus is associated mostly with logs infested with Ips spp. [8]. The fungus did not grow as fast as other Ophiostoma species such as O. minus on jack pine logs in our test.

O. piceae is the most common fungal species on conifer wood in Canada [7,9]. On jack pine logs, we found that it was a less important staining species than the other fungal species tested.

The use of unsterilized freshly cut log sections for tests allowed natural infection by other microorganisms on some sections, but most of the contamination was some distance away from the inoculation points. Therefore, growth of the inoculated fungal colonies was well defined. Although growth of the inoculated fungus might be reduced or limited by competition, the data reflect more closely in viva situations as indicated by Gibbs [4].

Wood MC is another factor that can influence growth and colonization by sapstaining fungi [5]. In our test, MC of the billets was not adjusted. However, all the billets were freshly cut from trees of similar age at the same location. We believe that the influence of MC was minimal in our test.

CONCLUSIONS

All 20 fungal isolates caused stain in jack pine billets. O. minus was the most important species on jack pine logs, followed by O. piliferum, C. coerulescens, and C. piceaperda. O. ips and O. piceae were less important than the other fungi tested on this wood species.

The author is a Research Scientist, Forintek Canada Corp., Eastern Lab., Sainte-Foy, Quebec, Canada G1P 4R4. Forintek Canada Corp. would like to thank its industry members, Natural Resources Canada (Canadian Forest Serv.), and the provinces of British Columbia, Alberta, Quebec, Nova Scotia, New Brunswick, and Saskatchewan for their guidance and financial support of this research. This paper was received for publication in February 2000. Reprint No. 9094.

(*.) Forest Products Society Member.

LITERATURE CITED

(1.) Cech, M.Y. and F. Pfaff. 1977. Kiln Operator's Manual for Eastern Canada. Rept. No. SP504E. Canadian Forest Serv., Ottawa, Ontario, Canada.

(2.) Farr, D.F., G.F. Bills, G.P. Chamuris, and A.Y. Rossman. 1989. Fungi on Plants and Plant Products in the United States. APS Press, St. Paul, Minn.

(3.) Farrell, R.L, E. Hadar, S.J. Kay, R.A. Blanchette, and T.C. Harrington. 1998. Survey of sapstain organisms in New Zealand and albino anti-sapstain fungi. In: Proc. Biology and Prevention of Sapstain. May 25, 1997, Whistler, B.C. Pub. No. 7273. Forest Prod. Soc., Madison, Wis. pp. 57-62.

(4.) Gibbs, J.N. 1993. The biology of Ophiostomatoid fungi causing sapstain in trees and freshly cut logs. In: Ceratocystis and Ophiostoma: Taxonomy, Ecology, and Pathogenicity. M.J. Wingfield, K.A. Seifert, and J.F. Webber, eds. APS Press, St. Paul, Minn. pp. 153-160.

(5.) Lindgren, R.M. 1942. Temperature, moisture and penetration studies of wood-staining Ceratostomellae in relation to their control. Tech. Bull. No. 807. USDA Forest Serv., Washington, D.C.

(6.) SAS Institute Inc. 1989. SAS/STAT user's guide, Version 6 ed. SAS Inst. Inc., Cary, N.C.

(7.) Seifert, K.A. 1993. Sapstain of commercial lumber by species of Ophiostoma and Ceratocystis. In: Ceratocystis and Ophiostoma: Taxonomy, Ecology, and Pathogenicity. M.J. Wingfield, K.A. Seifert, and J.F. Webber, eds. APS Press, St. Paul, Minn. pp. 141-151.

(8.) Upadhyay, H.P. 1981. A Monograph of Ceratocystis and Ceratocystiopsis. The Univ. of Georgia Press, Athens, Ga. pp. 100-102.

(9.) Uzunovic, A., D-Q. Yang, P. Gagne, C. Breuil, L. Bernier, A. Byrne, M. Gignac, and S.H. Kim. 1999. Fungi that cause sapstain in Canadian softwoods. Can. J. Microbiol. 45:914-922.

(10.) Yang, D.Q. 1999. Staining ability of various sapstaining fungi on agar plates and on wood wafers. Forest Prod. J. 49(11/12):78-90.
 Growth and staining ability of various
 sapstaining fungi on jack pine billets.
Fungus Isolate no. Source [a]
Ceratocystis coerulescens DS1/8 J. pine (L), PQ
 TL5/6 J. pine (L), PQ
 TL7/4 J. pine (L), PQ
 Au 123-22-12 J. pine (L), SK
 Au 157-152 W. spruce (L), BC
 Average
Ceratocystis piceaperda DPj4/1B-2 J. pine (L), PQ
 DSp1/5B-3 B. spruce (L), PQ
 Average
Ophiostoma ips DL2/5a J. pine (L), PQ
 TL6/6 J. pine (L), PQ
 TL6/1 J. pine (L), PQ
 Average
Ophiostoma piceae MPj4A-3 J. pine (S), ON
 FpSp2c-3 B. spruce (S), NB
 Au 104-2 B. spruce (S), SK
 Au 86-3 J. pine (S), SK
 Average
Ophiostoma piliferum MSplc-5 B. spruce (S), ON
 MPj7a-1 J. pine (S), ON
 Au 199-4 L. pine (S), AL
 Average
Ophiostoma minus MSp1/1-1 B. spruce (L), ON
 MPj1/3-1 J. pine (L), ON
 Au 58-4 L. pine (S), BC
 Average
 Growth (SD) [b]
Fungus Longitudinal Tangential
 (mm)
Ceratocystis coerulescens 43.6 (14.5) 8.5 (1.1)
 53.5 (23.8) 8.1 (1.1)
 29.4 (14.7) 6.8 (2.5)
 26.9 (19.8) 6.4 (2.4)
 37.7 (23.7) 7.5 (1.0)
 38.2 [+ or -] 10.8 B [c] 7.5 [+ or -] 0.9 B
Ceratocystis piceaperda 31.6 (19.8) 7.6 (0.8)
 51.5 (20.5) 9.8 (2.9)
 41.6 [+ or -] 14.1 B 8.7 [+ or -] 1.6 B
Ophiostoma ips 28.3 (13.6) 7.7 (0.7)
 28.0 (10.5) 7.7 (0.5)
 34.1 (14.6) 7.3 (0.7)
 30.1 [+ or -] 3.4 B 7.6 [+ or -] 0.2 B
Ophiostoma piceae 34.5 (12.0) 8.7 (2.6)
 23.1 (19.3) 5.8 (3.1)
 12.8 (17.4) 2.9 (3.8)
 17.3 (17.2) 4.4 (3.9)
 21.9 [+ or -] 9.4 B 5.5 [+ or -] 2.5 B
Ophiostoma piliferum 40.1 (19.6) 7.9 (0.8)
 47.0 (33.4) 8.5 (5.2)
 43.6 (13.8) 7.7 (0.7)
 43.6 [+ or -] 3.5 B 8.0 [+ or -] 0.4 B
Ophiostoma minus 81.4 (46.0) 25.7 (20.0)
 92.3 (37.5) 21.4 (10.6)
 70.1 (36.4) 17.9 (14.1)
 81.3 [+ or -] 11.1 A 21.7 [+ or -] 3.9 A
Fungus Radial Coloration
Ceratocystis coerulescens 1.8 (0.8) Greenish black
 2.3 (2.2) Black
 1.3 (0.8) Black
 1.5 (1.7) Greenish black
 1.2 (1.0) Black
 1.6 [+ or -] 0.4 B
Ceratocystis piceaperda 1.3 (0.8) Bluish black
 4.8 (6.2) Bluish black
 3.0 [+ or -] 2.5 B
Ophiostoma ips 1.1 (0.7) Black
 1.6 (1.1) Black
 1.0 (0.4) Bluish black
 1.2 [+ or -] 0.3 B
Ophiostoma piceae 1.1 (0.8) Brownish black
 1.3 (1.1) Brownish black
 1.0 (1.9) Brownish black
 1.9 (4.6) Brownish black
 1.3 [+ or -] 0.4 B
Ophiostoma piliferum 3.7 (4.5) Black
 6.3 (7.5) Black
 1.9 (1.1) Black
 3.9 [+ or -] 2.2 AB
Ophiostoma minus 7.2 (6.6) Bluish black
 5.6 (7.8) Bluish black
 3.8 (6.5) Bluish black
 5.5 [+ or -] 1.7 A
(a.)B. spruce = black spruce; J. pine
= jack pine; L. pine = lodgepole pine;
W. spruce = white spruce; (L) = log;
(S) = sawn lumber; AL = Alberta; BC =
British Columbia; ON = Ontario;
NB = New Brunswick; PQ = Quebec;
SK = Saskatchewan.
(b.)Values represent means of 10
replicates. Values in parentheses are
standard deviations.
(c.)Numbers in each column followed by
the same capital letter are not
significantly different according to
Scheffe's test (p = 0.05).
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Author:YANG, DIAN-QING
Publication:Forest Products Journal
Geographic Code:1USA
Date:Feb 1, 2001
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