Effects of high temperature after casing on mushroom production

Effects of high temperature after casing on mushroom production1 M. H. JODON,D. J. ROYSE,AND L. C. SCHISLER Department of Plant Pathology, The Pennsylvania State University, University Park, PA, U.S.A. 16802 Received July 22, 1980

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JODON, M. H., D. J. ROYSE,and L. C. SCHISLER. 1981. Effects of high temperature after casing on mushroom production. Can. J. Bot. 59: 735-741. Composts spawned with two cultivars of Agaricus bisporus (Lange) Sing. were subjected to a temperature of 28 + 0.5"C for 48 h at four time intervals after casing. Response to heat treatment varied with time of application relative to fruiting induction (pinning). High temperature imposed prior to pinning, while the mycelium was primarily in the vegetative state, resulted in little or no delay in onset of production and significant increases in mushroom size associated with fewer mushrooms per tray. High temperature applied when the mycelium was undergoing primordial formation and extending into pin development resulted in considerable delay in onset of production with no significant effect on mushroom size. Abnormal pins and misshapen caps were observed on all heat treatments. There were significant cumulative yield reductions from most heat treatments after 3 weeks of harvest. Production recovery occurred during the 4th and subsequent weeks of the harvest period with final yields not adversely affected. JODON,M. H., D. J. ROYSEet L. C. SCHISLER. 1981. Effects of high temperature after casing on mushroom production. Can. J. Bot. 59: 735-741. Des composts lardis avec deux cultivars d'Agaricus bisporus (Lange) Sing. ont CtC soumis a une tempirature de 28 + 0,5"C pendant 48 h ? quatre i moments aprbs le gobetage. La reaction a la chaleur varie selon le moment oh la chaleur est appliquCe par rapport i I'induction de la fructification (dCveloppement des boutons). Une temperature ClevCe avant le dCveloppement des boutons, alors que le mycClium est surtout a 1'Ctat vCgCtatif, provoque un retard faible ou nu1 dans le dCbut de la production et augmente significativement la grosseur des champignons, mais ceux-ci sont moins nombreux par boite. Une tempirature ClevCe au moment oh le mycClium forme des primordiums jusqu'au moment du dCveloppement des boutons retarde considCrablement le debut de la production, mais n'affecte pas la grosseur des champignons. On observe des boutons anormaux et des chapeaux difformes aprbs tous les traitements i la chaleur. Pour presque tous ces traitements, le rendement cumulatif est significativement rCduit aprbs 3 semaines de rCcolte. La production se rCtablit durant la 4bme semaine de la pCriode de rCcolte et durant les semaines suivantes et le rendement final n'est pas affect6 dCfavorablement. [Traduit par le journal]

stressed by emphasis on the possible consequences of Introduction during spawn run and after casing. Several researchers have reported on the detrimental L. R. Kneebone and M. H. Jodon (unpublished data) effects of cropping mushrooms, Agaricus bisporus conducted a preliminary experiment in which four (Lange) Sing., at temperatures above 18°C ( 1 , 4 , 5 , 6 , 9 , 10). In addition to reduced quantity, mushroom quality cultivars of A. bisporus (white, off-white, light cream, is lowered, and growth of competitive or disease- brown) were subjected to an air temperature of 27 causing organisms is enhanced. During spawn run 0.s0C for 48 h at three periods after casing. They found (mycelial growth throughout the compost), it is gener- that heat tI-eatment at 8-10 days after casing affected ally recommended that temperatures above 27°C be only the b~-owncultivar, which produced no mushrooms room avoided (1, 14). However, there is only one report On the first break (cyclic Pattern of ~ ~ ~ ~ s h ~roduction). Heat treatment at 13-15 da$ after casing reduced concerning the effects of an air temperature above 2 7 0 ~ during the interval between casing and primordium first break yields of all cultivars, and reduced second formation on mushroom production (6). crop manage- break yields of the white and brown cultivars. Treatment ment during this critical period involves control ofmany at 15-17 days after casing resulted in a reduced first the cultivar Third break environmental conditions, including ventilation, air and break yield compost temperature, relative humidity, casing rnois- yields wed production recovery in all cultivars ture, etc. Suggestions on management vary consider- except the In a second preliminary (M. H. ably (I), but the importance of temperature control is unpublished data), two brown cultivars were subjected 'contribution No. 1198, Department of Plant Pathology, to an air temperature of 27 0.5"C for48 h on days 6-8, and 12-14 after casing. Approximately The Pennsylvania Agricultural Experiment Station. Author- 8-10, ized for publication July 1980 as Journal Series paper NO. 24 h were required to equilibrate compost temperature and air temperature. The results showed (i) a delay or 6023. J0d0n7

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reduction in yield or both in the first two breaks for all treatments, (ii) death of many mushrooms at the pin or button stage, (iii) a greater percentage of larger mushrooms when trays were heat-treated 6-8 days after casing, and (iv) an increase in production from the heat-treated trays during breaks four through seven. Final yields indicated that only trays heat-treated at 8- 10 days after casing were significantly lower in yield than the nonheated (control) trays. As a result of these preliminary findings, a more in-depth study was undertaken to obtain definitive data on the effects of "high" temperature on spawned compost after casing and its relation to mushroom quantity and quality. The objectives of this study were (i) to determine if there is a critical time after casing when overheating is most detrimental, (ii) to define the effects or abnormalities associated with overheating, and (iii) to determine if these effects are temporary or irreversible. This information could be very useful in terms of crop management, particularly during periods of hot weather. It might also be useful in assessing potential damage to the crop in case of cooling equipment failure. Materials and methods Cultures and medium Two brown cultivars of A . bisporus were obtained from The Pennsylvania State University (PSU) Mushroom Culture Collection. Mushroom cultivar No. 344 is a monospore isolate obtained in 1974 and cultivar No. 321 is a multispore isolate obtained in 1967. The isolates have been maintained on potato dextrose yeast extract agar (infusion from 250 g potatoes, 10 g dextrose, 1.5 g yeast extract, and 15 g agar per litre) and transferred to fresh agar medium at least every 60 days (8). Rye grain spawn was prepared as outlined by Jodon and Royse (8). Mushroom production Methods of compost preparation, spawning, casing, and production followed the standard practices used at the PSU Mushroom Research Center as outlined by Carroll and Schisler (3). Trays having an area of 0.3 m2 and a depth of 14 cm were spawned at the rate of 110 g spawn per tray. A uniform compost was used for 30 trays of each cultivar, at a fill rate of 20.4 kg (45 lb) fresh compost per tray. The nitrogen content of the compost after pasteurization was 2.25%, NH3 was 0.036%, with a moisture of 72% (on a wet weight basis) at spawning. After spawning, all trays of both cultivars were placed in a controlled-environment room for growth of the mycelium throughout the compost. The relative humidity was maintained at 95-100% and the compost temperature at 22-24°C with minimum ventilation. After a spawn run of 13 days, the trays were cased with a pasteurized (70°C for 2 h) Hagerstown siltyclay loam soil at a depth of 3.0-3.5 cm. A thin layer (5 mrn) of limestone-neutralized (pH 7.5) peat moss was broadcast on the soil surface to help preserve soil aggregation. Following casing, 30 trays of each cultivar were placed in separate production rooms. Ambient air temperatures of the production rooms were adjusted to maintain compost temperatures of 22-24°C. The casing soil was adjusted to field

capacity (26% on a dry weight basis) by frequent light waterings during the first 4 days after casing. Introduction of outside fresh air was minimal (0-10%) during the time period from casing until the mushroom mycelium became visible over approximately 40% of the casing surface. This occurred at 9 days after casing. The production room then was ventilated with fresh air to reduce the carbon dioxide level, and the ambient air temperature was reduced to 15°C to induce fruiting. This temperature was maintained throughout the production cycle except where otherwise specified. The relative humidity was maintained at about 85% and fresh air introduced as required. Trays were watered as necessary between breaks. Temperature treatments Treatment intervals were selected to cover the period of mycelial growth into the casing layer through the time of fruiting initiation. Figure 1 illustrates the pattern of heat treatments applied to the spawned compost after casing. The treatments were carried out in ~roductionrooms similar to those previously described. Two rooms were necessary owing to the overlapping time sequence of one treatment. The physical design and environmental control systems of these rooms were identical. Treatment 1 (controls), consisted of six randomly selected trays per cultivar which were not removed from the two production rooms. On the 4th day after casing, treatment 2 trays were moved to the first heat-treatment room. The ambient air temperature of this room was 28-29OC with the relative humidity at 95-98%. Compost temperatures were monitored twice daily in the center of each tray using a single channel thermistor telethermometer (Yellow Springs Instrument Co., Inc., Yellow Springs, OH). After 24 h (the 5th day after casing), the compost temperature of treatment 2 had reached an average of 28°C. This temperature was maintained for 48 h (days 5 through 7 after casing). On the 7th day, the Heat Treatment Room No.

Treatment

I

2 I

2

DAYS AFTER CAStNG

FIG. 1. Time sequence of heat treatments applied to spawned compost after casing. (a) Normal production room environment with compost temperature between 22 and 24°C until 9 days after casing, and 15-16°C thereafter; (b) 24-h equilibration period to raise compost temperature to ambient air temperature of heat-treatment room (28-29°C); (c) compost temperature held at 28 2 O.S°C for 48 h.

JODON ET AL

Treatment I = I Treatment 2=Q Treatment 3- [7


Cultivar No. 344

HARVEST WEEK

FIG.2. Mushroom size as affected by compost temperature after casing. Treatment 1: control, normal compost temperature of 22-24°C until 9 days after casing, and 15- 16°C thereafter. Treatment 2: compost temperature raised to 28 + O.S°C on days 5-7 after casing. Treatment 3: compost temperature raised to 28 O.S°C on days 7-9 after casing. Data for each week were analyzed separately. Means with different letters are significantly different according to the Waller-Duncan K-ratio t-test (P = 0.05).

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heat-treated trays were returned to their respective production rooms where the compost temperature dropped to the ambient air temperature within 24 h. Treatment 3 was carried out similarly in a second heat-treatment room starting on the 6th day after casing to increase compost temperatures to an average of 28°C. This temperature was maintained for 48 h during days 7 through 9 after casing. Treatment 4 was initiated on the 8th day after casing in the first heat-treatment room. The 48-h treatment period of high temperature occurred on days 9 through I1 after casing. Treatment 5 was begun on the 10th day after casing in the second heat-treatment room with the 48-h high compost temperature treatment occumng during the I lth through 13th day after casing. Trays were arranged in the production room in a completely randomized design following each treatment. All mushrooms were harvested before the veil was broken and the bottom end cut off to remove adhering soil. The number and weight of mushrooms harvested per tray were recorded daily during the 56-day production period. Observations were made daily for abnormalities. Experimental data were subjected to analysis of variance using the within-room error term, and means were separated by the Waller-Duncan K-ratio t-test (2).

significantly ( P = 0.05) larger than the controls during the 5th week only, hence were omitted from Fig. 2. Cultivar No. 321 showed no significant differences in mushroom size from any of the heat treatments. Analysis of the total number of mushrooms produced showed that the treatments which produced the largest mushrooms also produced the fewest per tray as compared with the controls.

Mushroom abnormalities In addition to the unusually large size of many mushrooms, one consistent abndrmality was noted. Mushrooms in the prebutton stage (cap tissue not fully differentiated) tended to have a bulbous base with the pileus diameter about half that of the stipe (Fig. 3). As these mushrooms enlarged, the stipe became barrel shaped; the pileus and stipe diameters were approximately equal. At harvest, these mushrooms tended to have a very short, squat stipe with a large, heavy pileus (Fig. 4). The pileus was frequently elliptical, triangular, Results or irregular in shape (Fig. 5). This abnormality was seen to some extent in all treatments except the control. Mushroom size and number Heat treatment of cultivar No. 344 on days 5-7 and However, it was more often observed in treatments 2 7-9 after casing resulted in significant ( P = 0.05) and 3 in association with fewer but larger mushrooms increases in mushroom size, particularly during the 2nd per tray. The frequency of these abnormal mushrooms through 5th weeks (Fig. 2). Treatments 4 and 5 were decreased after the 5th week of harvest.


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FIG. 3. Mushroom in the prebutton stage showing enlarged stipe as a result of heat damage.

FIG. 4. Comparison of nontreated (control) mushrooms (344- 1(ck) ) and those from trays subjected to overheating after casing (344-2). The latter have a larger pileus with a very short, stocky stipe.

Yield delay and reduction High casing, air, and compost temperatures after casing resulted in a delay in onset of production, or first harvest day, in certain treatments as compared with the controls. Treatments 4 and 5 for cultivar No. 344 were delayed by 7 and 6 days, respectively. Treatment 2 was not affected while production was delayed 2 days in

treatment 3. Cultivar No. 321 showed a delay of 2 and 4 days for treatments 4 and 5 . Treatments 2 and 3 were not adversely affected. Figure 6 illustrates the effects of high temperature after casing on yield. All four heat treatments imposed on cultivar No. 344 resulted in significant cumulative yield reductions after 3 weeks of harvest. However,


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FIG. 5. Mushroom having large, misshapen pilei and short, heavy stipe associated with overheated compost after casing.

Week I =

5

Week 2 = Week 3 =

4

W

Week 4 = 1

3

Week 5 = Week 6 =

2

Week 7 =

I

&

Week 8 = k

LSD = 458

z W

I

k

a

W

u +

5

CUMULATIVE

MEAN WEEKLY WEIGHT (9)

FIG. 6. Effect of "high compost temperature after casing on yield of two cultivars of Agaricus bisporus. Treatment 1: controls, with compost temperature of 22-24°C until 9 days after casing and 15- 16°C thereafter. Compost temperature raised to 28 0 5 ° C for 48 h on: days 5-7 after casing (treatment 2); days 7-9 after casing (treatment 3); days 9-1 1 after casing (treatment 4); and days 11-13 after casing (treatment 5). Each treatment was replicated six times. A, cultivar No. 344; B, cultivar No. 321. Individual weekly yields are represented within the cumulative weekly yield (see legend on the figure). Horizontal bar at end of the 3-week cumulative yield indicates significant differences by Waller-Duncan K-ratio t-test (P = 0.05).

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shaped pinheads that developed into mushrooms with elongated stipes and small pilei that opened early associated with C 0 2 concentrations of 0.4-0.2%. Although the pinheads he illustrated are similar to those observed in heat-treated trays, subsequent development of the mushroom was distinctly different in our experiments. Mushroom size is dependent on many variables, environmental as well as genetic. Sinden et al. (13) state that "the size of the mushrooms produced by a strain is dependent first and foremost on the number of fruit body initials formed on the bed surface and the yield is then Discussion dependent on the amount of nutrient stored in the The results of this study revealed differential re- mycelium and available for growth." This supports the sponses to time of high temperature exposure on observation in this study that larger mushrooms were spawned, cased compost. It should be noted that the consistently associated with fewer mushrooms per tray time of the treatments and their effects must be related to and no significant change in yield. The reason for fewer fruiting induction rather than the actual number of days fruit bodies per tray from heat treatment during the after casing. The latter may be misleading in that under vegetative phase (5-7, 7-9 days after casing) is not differing environmental conditions, especially commer- clear. Preliminary studies on spawn and spawned cial ones, time of pinning may be as early as 7 days or compost indicated that the mycelium is not necessarily much later than the 9 days which occurred in this damaged beyond recovery by the temperature used in particular study. Heat treatments applied while the this experiment. Nevertheless, it is apparent that the mechanism for primordium formation was disrupted in mycelium was primarily in the vegetative state (5-7, 7-9 days after casing) showed little or no delay in onset that fewer pins were formed. This phenomenon perof production. However, significant increases in mush- sisted through the 5th week of harvest. The lack of room size, associated with fewer mushrooms per tray competition for water and nutrients may account for the and anomalous pins and malformed pilei were observed. large size as these pins developed. The benefits of using greater compost density and These treatments may have reduced the number of mycelial aggregates formed in the casing. Flegg (7) depth of fill are well known. However, this practice demonstrated that maximum aggregation occurred at considerably increases the possibility of overheated 24°C as opposed to lower temperature. Higher'tempera- compost during spawn run or after casing. Supplementatures, therefore, may also reduce mycelial aggregation. tion of compost may also produce undesirably high It should be noted, however, that C 0 2 and other gases temperatures (12). The production recovery exhibited and volatiles were not monitored during this study and by both test cultivars in the later weeks of the cropping may have influenced primordial formation and develop- period is an extremely important aspect of this study. It suggests that crop damage or loss due to overheating of ment. When treatments were applied at the beginning of spawned compost after casing might be recovered by an primordial formation and extending into pin develop- extension of the harvest period. However, it should be ment (9- 11, 11- 13 days after casing), a considerable recognized that under the conditions of this study, there delay in the onset of production with sparse and slow pin were no disease or insect problems observed which may initiation was observed. There was no effect on mush- have affected yield. Under '"commercial conditions, these factors could contribute further damage to that room size. Abnormal pins and malformed pilei were observed on from heat and might prevent production recovery. The all heat treatments. Although final yields were not association of specific signs, such as bulbous pins and affected, these deformed and misshapei mushrooms malformed pilei, with heat damage may assist in could result in crop losses through reduction of quality. diagnosis of the problem. In view of increasing costs of In one study on conditions affecting fructification, energy and materials, information on heat and CO2 Mader (1 1) described abnormally large, misshapen tolerance of a cultivar may be very useful to the grower mushrooms with elongated stipes and fruit bodies with for prudent crop management. onionlike bulges at the base. These developing mush1. ATKINS, F. C. 1974. Guide to mushroom growing. Faber rooms were present on the trays before being placed in and Faber Ltd., London, England. air-tight chambers; therefore, the relationship of the 2. BARR,A. J., J. H. GOODNIGHT, J. P. SALL,and J. T. HELWG.1976. A user's guide to SAS-76. Sparks Press, abnormalities observed by Mader (11) to C 0 2 conRaleigh, NC. centration is not clear. Vedder (14) reported onionanalysis of yields per individual week showed that production from all heat treatments increased significantly above the controls during the 4th week with smaller gains distributed throughout the remaining weeks. Final yields were not significantly affected. Yields from treatments 4 and 5 for cultivar No. 321 were significantly reduced after 3 weeks of harvest. Production from these treatments during later weeks tended towards a gradual increase so that final yields were not significantly different. Yields from treatments 2 and 3 closely followed that of the controls.


JODON ET AL.

3. CARROLL,A. D., JR., and L. C. SCHISLER.1976. Delayed release nutrient supplement for mushroom culture. Appl. Environ. Microbial. 31: 499-503. 4. FLEGG,P. B. 1968. Response of the cultivated mushroom to temperature at various stages of crop growth. J. Hortic. Sci. 43: 441-452. 5. FLEGG,P. B. 1970. Response of the cultivated mushroom to temperature during the 2-week period after casing. J. Hortic. Sci. 45: 187-196. 6. FLEGG,P. B. 1972. Response of the cultivated mushroom to temperature with particular reference to the control of cropping. Mushroom Sci. 8: 75-84. 7. FLEGG,P. B. 1979. Effect of temperature on sporophore s Mushinitiation and development in ~ ~ a r i c ubispo/us. room Sci. 10: 595-602. 8. JODON,M. H., and D. J. ROYSE.1979. Care and handling of cultures of the cultivated mushroom. Bull. Pa. Agric. Exp. Stn. No. 258.

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9. KLIGMAN, A. M. 1950. Handbook of mushroom culture. 2nd ed. J. B. Swayne, Kennett Square, PA. 10. LAMBERT,E. B. 1938. Principles and problems of mushroom culture. Bot. Rev. 4: 397-426. 1I . MADER,E. 0. 1943. Some factors inhibiting the fructification and production of the cultivated mushroom, Agaricus campestris L. Phytopathology, 33: 1134- 1145. 12. SINDEN,J. W., and L. C. SCHISLER.1962. Nutrient supplementation of mushroom compost at casing. Mushroom Sci. 5: 267-280. and E. HAUSER.1962. 13. SINDEN,J. W., H. J. TSCHIERPE, Transplantation of sporophores as a new method for studying growth and nutritional factors of mushrooms. Mushroom Sci. 5: 250-266. 14. VEDDER,P. J. C. 1978. Modern mushroom growing. Educaboek, Culemborg, Netherlands.