We examined the possibility of cultivating Agaricus bisporus (Ab) on various grains and agricultural by-products. with the objective of improving yield capacity of substrate pre-colonized by Scytalidium thermophilum (St). Radial growth rate (RGR) of St at 45 degrees C ranged from no growth on sterile wheat grain to 14.9 mm/d on whole oats. The linear extension rate (LER) of Ab, grown on St-colonized substrate (4 days at 45 degrees C), ranged from a low of 2.7 mm/d on 100% corncobs to 4.7 mm/d on a 50/50 mixture of ground corncobs/millet grain. Several other substrates containing wheat straw + ground corncobs + boiled millet and pre-colonized by St (4 days at 42 +/- 3 degrees C), were evaluated for production of Ab. The biological efficiency (BE) of production increased linearly with the addition of millet to the formula. However, substrates with millet levels >= 84% often were contaminated before mushroom harvest. Maximum BE (99%) and yield (21.6 kg/m(2)) were obtained on St-colonized wheat straw + 2% hydrated lime supplemented with 9% commercial supplement added both at spawning and at casing. (C) 2008 Elsevier Ltd. All rights reserved.