Rotting wood samples were collected in two areas of Yunnan Province, China. The areas were located in the Xishuangbanna Primeval Forest Park of Jinghong (21°98'N, 100°88'E) and Zixi Mountain of Chuxiong (25°03'N, 101°41'E). The predominant vegetation is characterised as tropical and subtropical forest biome. The climate is hot and humid, with annual precipitation between 1,000 to 1,600 mm and an average temperature that ranges from 14.8 to 21.9 °C. Sixty decayed wood samples were collected during July to August in 2016–2018. The samples were stored in sterile plastic bags and transported under refrigeration to the laboratory over a period of no more than 24 h. The yeast strains were isolated from rotting wood samples in accordance with the methods described by Morais et al. (2013) (link) and Lopes et al. (2016). Each sample (1 g) was added to 20 ml sterile d-xylose medium (yeast nitrogen base 0.67%, d-xylose 0.5% and chloramphenicol 0.02%, pH 5.0 ± 0.2) in a 150 ml Erlenmeyer flask and then cultured for 3–10 days on a rotary shaker. Subsequently, 0.1 ml aliquots of the enrichment culture and appropriate decimal dilutions were spread on d-xylose agar plates and then incubated at 25 °C for 3–4 days. Different yeast colony morphotypes were then isolated by repeated plating on yeast extract-malt extract (YM) agar (1% glucose, 0.5% peptone, 0.3% yeast extract and 0.3% malt extract, pH 5.0 ± 0.2) and then stored on YM agar slants at 4 °C or in 15% glycerol at -80 °C.
The morphological, physiological and biochemical properties were determined according to those used by Kurtzman et al. (2011) (link). The beginning of the sexual stage was determined by incubating single or mixed cultures of each of the two strains on corn-meal (CM) agar, 5% malt extract (ME) agar, dilute (1:9) V8 agar or yeast carbon base plus 0.01% ammonium sulphate (YCBAS) agar at 15 and 25 °C for 6 weeks (Kurtzman 2007 (link); Huang et al. 2018 (link)). The assimilation of carbon and nitrogen compounds and related growth requirements were tested at 25 °C. The effects of temperature from 25–40 °C were examined in liquid and agar plate cultures.
Free full text: Click here