169 The effects of supraoptimal temperatures upon North American brown-rot fungi in pure culture

JOHN G. PALMER Department ofBiology, Virginia Polytechnic Institute and State University, Blacksburg. VA. U.S.A. 24061 AND

RUTH G. PAYNE Centerfor Forest Research, United States Department ofAgriculture, Forest Service, Forest Products Laboratory,1 Madison. WI, U.S.A. 53705 Received April 19, 19852 Accepted October 7, 1985

PALMER. J. G., and R. G. PAYNE. 1986. The effects of supraoptimal temperatures upon North American brown-rot fungi in pure culture. Can. J. For. Res. 16 169-176. Ninety-one North American brown-rot fungi were exposed in agar culture to four high temperatures for 16 days. Isolates originated from basidiospores, sporophore tissue, or decaying wood. One or more isolates of 58 species grew at 35°C, of 20 species at 41°C and of 4 species at 46°C; none grew at 52°C. Similar inter- and intra-specific variations occurred during recoveries in the absence of growth. Some isolates of two species of Antrodia recovered after exposure to 52°C. The possibility that a brown rotter might be active. alive but inactive, or neither within a wood substrate can be inferred by comparison of ratings derived by mathematical formulae applied to species represented by four or more isolates. Species that destroy wood products made up 73% of those likely to grow at these higher temperatures and 81% of those most likely to recover from exposure to supramaximal temperatures based upon these ratings. Only 2 of the 12 fungi least capable of growth and recovery at high temperatures were associated with forest products. Temperature ratings for two fungi that had been isolated by another worker from western pine slash coincided with the upper and lower portions in which they occurred. However, field data were insufficient for a satisfactory comparison of sapwood and heartwood rotters.

PALMER, J. G.. et R. G. PAYNE. 1986. The effects of supraoptimal temperatures upon North American brown-rot fungi in pure culture. Can. J. For. Res. 16 169-176. Quatre-vingt onze champignons de carie brune de provenance nord-américaine ont été placée sur un milieu gélosé à quatre températures élevées pendant 16 jours. Les isolats provenaient de basidiospores et de cultures obtenues à partir de sporophores. ou de bois carié. Au moins un des isolats appartenant à 58, 20 et 4 espèces ont poussé respectivement à 35, 41 et 46°C. Aucun isolat ne s'est développé à 52°C. Des variations inter- et intra-spécifiques analogues ont été observées durant la période de récupération chez les isolats dont la croissance avait été inhibée. Quelques isolats provenant de deux espèces du genre Antrodia ont repris leur croissance après avoir été placés à 52°C. On peut déduire qu’un champignon sera actif dans le bois, vivant mais inactif ou ni l’un ni l’autre, en comparant des indices calculés au moyen d’une formule mathématique appliquée aux espèces représentées par au moins quatre isolats. D’après ces indices, 73% des espèces capables de croître à des tem­ pératures élevées et 81% des espèces susceptibles de reprendre leur croissance, après avoir été soumises aux températures les plus élevées, sont des champignons qui s’attaquent aux produits du bois. Seulement deux des 12 champignons les moins affectés par des températures élevées sont associés aux produits du bois. Deux champignons, isolés par un autre chercheur dans des déchets de coupe de pin de l’ouest. ont donné des indices correspondant à la position supérieure ou inférieure dans laquelle ils avaient été trouvés. Par contre, les données prises sur le terrain étaient insuffisantes pour comparer adéquatement les champignons de carie d’aubier et de coeur. [Traduit par le journal]

Introduction 1977). Response to a supramaximal temperature is complicated Temperature is an environmental factor that affects the by several factors. Hyphal mortality at a given temperature is a colonization and decomposition of wood in nature (Cartwright function of time exposed and moisture content of the air and Findlay 1958; Snell 1922). Rate of decay in wood blocks surrounding the hyphae whether on agar or in wood (Arita et al. correlates well with mycelial growth in pure culture at compara­ 1980; Chidester 1937; Kurpik and 1978; Loman 1978; ble temperatures for some Hymenomycetes (Grinda 1976; Snell 1922). Although comparable moisture levels are difficult Lindgren 1933; Loman 1962; and Willeitner 1984; to certify, Montgomery (1936) concluded that the time required Wälchli 1977). The optima and maxima are known for many to kill was essentially the same at a given temperature and equal species only in agar culture. Among 60 North American air moisture contents around mycelium on agar and in wood. In isolates, 67% had optima between 20 and 36°C (Humphrey and any case, many wood-decay fungi differ in their abilities to Siggers 1933). Maxima ranged from 28 to 46°C. In only one survive at supramaximal temperatures. isolate was the maximum more than 10°C above the optimum. Brown rotters make up only 6% of the 1669 species of decay Optima and maxima for fungi from other regions in the north fungi that are currently recognized in North America (Gilbert­ temperate zone are similar (Bondartsev 1956; Cartwright and son 1981) and are important ecologically and economically. Findlay 1934; and Willeitner 1984; Robak 1942; Walchli Most are associated with decomposition of softwoods and are considered a major factor in the survival and perpetuation of the 1Maintained in cooperation with the University of Wisconsin, coniferous forest biotype (Gilbertson 1980), especially in Madison, WI, U.S.A. western summer-dry habitats. They also destroy wood being 2Revised manuscript received September 12, 1985. processed for use and in use, much of which is coniferous 170 CAN. J. FOR. RES. VOL. 16. 1986 (Duncan and Lombard 1965). Experiments were undertaken in 46°C, Lentinus lepideus at 40°C, and Phaeolus schweinitzii at agar culture to determine relative growth and survival of 34°C) were higher. We had anticipated an increase in species vegetative mycelia of brown-rot species exposed to four that would grow at 41 and 46°C when represented by a larger high temperatures. Results should suggest the probability that a number of isolates. brown rotter may grow, survive without growth, or be elimi­ Intraspecific variation also exists in growth of brown-rot nated relative to other species at temperatures of 35°C or higher. fungi at high temperatures. Although 64% of the species in Table 1 had one or more isolates that grew at 35°C, in only 41 % Methods and materials did all of the isolates grow. Among the latter, nine species were Ninety-one species of fungi with negative responses in the Baven­ represented by three or fewer isolates (column A, Table 1), dam test (Davidson et al. 1942) were represented in the culture which was considered merely indicative of probable species collections of the Center for Forest Mycology Research, Forest response. Except for Robak (1942), most investigators report­ Products Laboratory, Madison, Wisconsin, in 1980 when the study ing maxima studied only one or two isolates per species was begun. Most are reported to cause brown rots (Gilbertson 1981). (Bondartsev 1956; Cartwright and Findlay 1934; Grinda 1976; Scientific names and numbers of isolates are listed in Table 1. Since Humphrey and Siggers 1933; Lindgren 1933; Spaulding 1929; most specific epithets remain unchanged, except for Latin gender endings, fungus names in older references, including Fries (1821), can Wälchli 1977). A combination of data from these authors show be traced to the names in Table 1 through specific epithets in most cases that maxima vary for individual isolates of five brown rotters ifauthority names are available. Some synonymy, geographic distribu­ (Antrodia serialis, 32-38°C; Coniophora puteana, 30-38°C; tions, substrates, and references are listed for most brown rotters that , 38-45°C; Gloeophyllum trabeum, occur in the United States and Canada (Gilbertson 1981). Species 38-46°C; Lentinus lepideus, 36-40°C). Ranges among isolates associated with wood products have been reported by Duncan and representing four of these five fungi in Table 1 are compatible Lombard (1965) and are indicated in Table 1 (see footnote c). A total of with these figures. In the case of A. serialis, 37% of 30 isolates 1160 isolates were included in the study. Sixty-five percent of the grew at 35°C and 3% grew at 41 and 46°C. The probability of mycelia had been obtained from sporophores, most originating from obtaining an isolate with a higher maximurn in North America polysporsus basidiospore drops. The remaining 35% were mycelia does not appear to be great. Eight of 12 isolates reported by the isolated from decay, mostly in wood products. Each isolate was replicated four times at each of four temperatures aforementioned authors were Norwegian (Robak 1942) and in a single experiment. Disposable 15 × 150 mm borosilicate glass test English (Cartwright and Findlay 1934) with maxima between tubes were filled to one-third capacity with 2% malt agar, plugged with 32 and 35°C. This suggests that isolates of A. serialis may have cotton, autoclaved, and slanted during cooling. Each slant was less tolerance to high temperatures in northern habitats. Data in inoculated with mycelium on an agar plug, left at room temperature for Table 1 indicate that only 1 in 30 isolates of A. serialis should 24h, examined for growth, and then placed at an experimental have a maximum near 41 or 46°C. With respect to growth at temperature for 16 days. Upon removal, tubes were checked for growth high temperatures, isolates in some fungi behaved similarly. All that occurred during exposure. If growth had developed in any one of isolates of Crustoderma flavescens, Fomitopsis meliae, G. the four replicates, the isolate was recorded under “Growth” at that sepiarium, and G. trabeum grew at 35 and 41°C, but none temperature in Table 1. Tubes of isolates considered not to have grown grew at the two higher temperatures. More often within a were incubated at 22°C for 16 days and then examined. Any growth in one tube and the isolate was tallied under "Recovery"in Table 1. species the number of isolates that grew declined at succeed­ The four temperature-control incubators were convection type with a ingly higher temperatures. Fomitopsis cajanderi, Tyromyces water-holding pan underlying the lowermost shelf into which water palustris, and Wolfporia cocos are like A. serialis in this was siphoned for humidification. Temperature settings were 35, 41, respect. Occasionally, a decline can be abrupt like that in 46, and 52°C. These temperatures represent 10°F intervals between 95 Fomitopsis pinicola or Lentinus lepideus. In addition to A. and 125°F, because the initial experiments were so calibrated. The serialis and G. trabeum, only A. carbonica and Tyromyces replicate tubes were placed on the central shelf of each incubator where palustris possessed isolates that grew at both 41 and 46°C. variation was less than one degree centigrade. Species listed in Group A under “Growth” in Table 1 are most likely to have isolates that grow at high temperatures. An Results and discussion internal temperature of 46°C for more than a few minutes or Data for all isolates in each species are unified in Table 1 to hours is undoubtedly rare in temperate zone forest woods, even emphasize responses of species, one of which is interspecific slash (Loman 1962). Consequently, the probability of isolating variation. In earlier experiments, no isolate of a decay fungus growing mycelium of a brown-rot fungus is very low. If, had grown at 52°C (J. G. Palmer, unpublished data) and however, one is isolated, it would likely be T. palustris, G. approximately 60% of isolates had grown at 35°C (Humphrey trabeum, A. carbonica, or A. serialis in this order if no other and Siggers 1933; J. G. Palmer, unpublished data). In these factor is limiting. Twenty-two species represented by four or tests, of the 91 species, 58 grew at 35°C, 20 species grew at more isolates had no growth at any of the temperatures (group D 41oC, and 4 species grew at 46°C (Table 1). No fungus grew at under “Growth,” Table 1). Many in group C had a very low 52°C. The presumption that approximately 60% of the species percentage of isolates that grew. Species in growth group B would grow at 35°C proved valid; 64% of the species grew. The probably are not as highly competitive at high temperatures percentages of species that grew at 41 and 46°C were similar to compared with those in group A, unless exposure is brief. those previously reported for both brown and white rotters Recovery of isolates that failed to grow at high temperatures (Humphrey and Siggers 1933). This similarity suggests that a is recorded in Table 1. These data illustrate that both intra- and large number of white-rot as well as brown-rot species grow at inter-specific variations in this response are also common. high temperatures. Using the data of Humphrey and Siggers Apparently, some fungi may survive for relatively long periods (1933) for the isolate that grew at the highest temperature, the of time in substrates at a temperature above the maximum for maximum temperature for Antrodia serialis was lower than that growth. In the case of Antrodia carbonica, 23 of 26 isolates in Table 1 and maxima for five species (Fomitopsis officinalis at grew at 35°C and the remaining 3 isolates recovered. At 41°C, 2 34°C, quercina at 44°C, Gloeophyllum sepiarium at isolates grew and 22 of the remaining 24 isolates recovered. At PALMER AND PAYNE 171

46°C only 1 isolate grew and 14 recovered. No isolates grew at decay in wood products were represented by four or more 52°C. but one did recover. Isolates of A. carbonica obviously isolates, while only 70 of the total of 91 species had four possess extensive intraspecific variation with regard to both isolates. Of 20 species with 20 or more isolates, 16 occur in growth and recovery at four high temperatures. On the other wood products. Species having four or more isolates (Table 1) hand, Crustoderma flavescens appears to be more likely to grow were subjected to x2 analyses for both growth and recovery at high temperatures but is unlikely to survive exposure to data to compare products fungi with all brown rotters. At the temperatures above its maximum for growth. 10% level, a significantly larger number of fungi from wood Fifteen fungi neither grew nor recovered at any of the high products grew and they had a significantly greater ability to temperatures. Among these were three species represented by recover at the 1% level. They make up 73% of the species in 10 or more isolates each. The chance of obtaining Panus growth group A and 81% of the fungi in recovery group A, but kauffmanii, Poria albobrunnea, or Tyromyces leucospongia compose only 40% of the species in Table 1. These data also from a substrate at any of the high temperatures listed in Table 1 support the view that North American slash fungi isolated from seems less likely than obtaining Coprinus micaceus, which is products are more adapted to habitats with high temperatures represented by only one isolate, or Anomoporia albolutescens, than are their north European counterparts (Cartwright and which is represented by four. In fact, P. kauffmanii occurs Findlay 1934; Wälchli 1977). In contrast, only seven wood along the Pacific coast of North America mostly north of products fungi (20%) did not grow at any of the high California, often on offshore islands (Bier and Nobles 1946; temperatures and only five (14%) had no isolates that recovered. Gilbertson 1981) in the fog belt, which has relatively low Among them, only Panus kauffmanii and Tyromyces fragilis temperatures (J. H. Ginns, personal communication): T. leu­ occur in group D in both growth and recovery categories. The cospongia is a snowbank fungus and psycrophile (Miller 1965). former has occurred in lumber and the latter in the porch of a However, an increase to 10 isolates for the latter species might building (Duncan and Lombard 1965). These two as well as provide one or more that would grow or recover at one or more others intolerant of high temperatures, e.g., Coniophora of these higher temperatures. Antrodia carbonica, Daedalea puteana and Fibroporia vaillantii, may be restricted to sub­ quercina, and Tyromyces palustris seem relatively restricted to strates or loci within substrates at which temperatures of 35°C regions of high temperatures. Antrodia carbonica and T. and higher are rarely if ever attained. Some species that grow palustris occur in areas that have lengthy warm periods in poorly or not at all at and above 35°C. e.g., Antrodia albida, western North America and in the southeastern United States Paxillus panuoides, and Phaeolus schweinitzii. possess strains (Gilbertson 1981). Daedalea quercina occurs over a wider adapted to survive for fairly long periods of time at temperatures north-south range, but is most common in the region between well above the relatively low maximum for growth. Each of North Carolina and New York in the east and Iowa in the west. those listed has been isolated from exposed aboveground woods The possibility that a brown-rot fungus might be (i) active, (Duncan and Lombard 1965). (ii) alive but inactive, or (iii) not alive within a substrate at high Forest substrates are decayed by all species tested (Table 1). temperatures is suggested by comparing its group ratings for Sixty-two of the 70 species represented by four or more isolates “Growth“ and “Recovery” in Table 1. Gloeophyllum sepia­ vary in response to high temperatures, especially with reference rium is likely to be active at temperatures up through 41°C and is to recovery. In forests, these fungi decay heartwood and in growth group A. However, it is unlikely to be recovered at sapwood in stems, stumps, and roots in living trees as well as 46°C and ranks in recovery group C. In comparison, Phaeolus these tissues in dead standing and fallen trees. In some schweinitzii is unlikely to grow (growth group C), but might substrates, external layers of sapwood should insulate heart­ well be recovered from substrates at temperatures of 35 to 46°C wood from high temperatures induced by insolation or incursion (recovery group A). This fungus causes butt and root rots in of hot air currents. Two conjectures seem reasonable. (i) Decay living conifers throughout North America (Gilbertson 1981; fungi in southern forests should be more heat tolerant than those Hepting 1971). Its elimination from forest clear-cuttings by in northern forests at similar elevations. (ii) Heart rotters need exposure to incident sunlight seems improbable. Phaeolus be less tolerant of heat than sap rotters, both in living trees and schweinitzii and other fungi that may inhabit wood-products and slash. Data from two intensive studies of decay in living trees can grow or recover after 16 days at temperatures of 41°C or support the first conjecture. Across central Ontario, Basham and higher might survive improper kiln drying. Six species rank in Morawski (1964) recorded seven brown-rot fungi that were group A for both “Growth” and “Recovery.” In descending isolated from living trees, mostly softwoods, and that were numerical order based on averages of indexes from both groups, represented by four or more isolates in Table 1. Two of these T. palustris, T. sparaguei, Antrodia carbonica, A. oleracea, species occurred in growth and recovery groups A or B. One D. quercina, and Poria placenta are the most temperature was in growth group B; another was in recovery group A. In the tolerant North American brown-rot species among those tested. east central United States, Bery and Lombard (1978) isolated Each of these fungi has been isolated from wood substrates that six brown rotters in living . Five occurred in growth group are often exposed to direct sunlight, high ambient air tempera­ A or B and all six were in recovery group A or B. In other words, ture, or localized heating by some mechanism (Duncan and brown-rot fungi in northern tree species appear less tolerant of Lombard 1965; Gilbertson 1981). Other conditions being equal, high temperatures than those in more southerly species. Nearly exposure for periods shorter than 16 days should increase the all were isolated from the butt rather than the bole portions of number of fungi that can be isolated. Brown-rot species more stems (Basham and Morawski 1964; Berry and Lombard 1978). tolerant to heat may exist in North America but, if so, are Based upon data for their species in Table 1, a very high probably not common. percentage are capable of growth, recovery, or both at high Wood products are decayed by 39% of the species in Table 1. temperatures (100% in the oaks and 70% in northern hardwoods Among these fungi, Serpula incrassata is the only one that has and conifers). The relatively few brown rotters reported in proportionately been reported only rarely from a forest substrate earlier literature leave the second conjecture unresolved. Exten­ (Palmer and Eslyn 1980). All of the 35 fungi associated with sive isolations from specific loci in heartwood and sapwood of 172 CAN. J. FOR. RES. VOL. 16, 1986

TABLE 1. The number of isolates in each of 91 brown-rot fungi that grew during exposure to four high temperatures for 16 days and that recovered when unable to grow PALMER AND PAYNE 173

TABLE 1. (continued) 174 CAN. J. FOR. RES. VOL. 16, 1986

TABLE 1. (continued) PALMER AND PAYNE 175

TABLE 1. (concluded)

logs, standing dead stems, or stems of living trees in at least one recorded. Some decay fungi may be able to moisten relatively forest type will be necessary. dry wood, perhaps of a specific type. during the decay process. One can postulate that dead sapwood in trees and slash, For example, Antrodia carbonica may be isolated from, or its especially small pieces that are exposed to sunlight, are fruiting body associated with, localized moist spots on Douglas- degraded by fungi that can grow or survive at high temperatures. fir logs during lengthy dry periods in western North America. With reference to slash, heat, moisture, and oxygen are At the taxonomic order level no common temperature inextricably interrelated and have been discussed by Spaulding tolerance exists. The only three agarics, Lentinus lepideus, (1929). Loman (1962) recorded very high temperatures in 4 in. Lentinus ponderosus, and Panus kauffmanii, have both intra­ diameter pine slash in Alberta during July. For short periods (up and inter-specific variations. Among genera in the Aphyllopho­ to 4-5h) on a cloudless day, temperatures exceeded 50°C in the rales represented by three or more species and based upon upper portion, 40°C in the middle portion, and 30°C in the indexes similar to those used to group species in Table 1, bottom portion of a piece that was not in contact with soil. Gloeophyllum is more uniformly tolerant to high temperatures Temperatures were only slightly lower in a piece in contact with by a distinct margin in both growth and recovery. Species in the soil. Gloeophyllum sepiarium (growth group A, recovery other genera, e.g., Antrodia, Poria, and Tyromyces, vary more group C; Table 1) frequented the middle portions and Conio­ extensively. Whether a uniformity of responses among species phora pureana (growth group C, recovery group C) the bottom within a genus to this or any other physiological inducer implies portions. Coniophora puteana isolated from this slash was less natural taxonomic clustering is unknown. tolerant of high temperatures than was G. sepiarium. Many of these fungi also degrade wood products. For example, 13 of 16 Acknowledgements brown rotters reported to degrade slash in the northeastern Francis F. Lombard of the Center for Forest Mycology United States (Spaulding and Hansbrough 1944) also occur in Research at the Forest Products Laboratory deserves special wood products. Two restricted to slash, Antrodia hereromorpha thanks for her long-term maintenance of the culture collections, and Antrodia variiformis, are relatively temperature intolerant isolate records, and current taxonomic nomenclature for species (growth groups C and D. respectively, and recovery group D for in the Aphyllophorales, all of which she shared with us. In the both: Table 1). In fact, only 5 ofthe 13 species tested occurin at Department of Biology, Virginia Polytechnic Institute and State least one group A. Among these, Gloeophyllum trabeum is in University, we thank Orson K. Miller for the current nomencla­ growth group A and A. serialis and Laetiporus sulphureus are ture in the Agaricales, Pierre Dery for technical assistance in the in recovery group A. Daedalea quercina occurs in both groups laboratory, and H. Van T. Cotter for great patience during both A. Details are lacking about specific loci of pieces of slash on the computer programming and the essential repetitive instruc­ which these fungi were found. However, those on which group tion in its use. D or group C species occurred may well have been in contact ARITA, I., A. TERATANI, and Y. SHIONE. 1980. The optimal and with moist soil, in the shade, or both. The probability exists that critical temperatures for growth of Pholiota adiposa. Rep. Tottori had indentification of cultures been possible when most slash Mycol. Inst. 18: 107-113. studies were conducted, additional species would have been BASHAM, J. T., and Z. J. R. MORAWSKI. 1964. Cull studies, thedefects 176 CAN. J. FOR. RES. VOL. 16, 1986

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