Molecular Phylogenetic Analysis of Grifola frondosa (Maitake) and Related Species and the Influence of Selected Nutrient Supplements on Mushroom Yield
Open Access
- Author:
- Shen, Qing
- Graduate Program:
- Plant Pathology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 23, 2001
- Committee Members:
- David Robert Huff, Committee Member
Daniel J Royse, Committee Chair/Co-Chair
Charles Peter Romaine, Committee Member
John Ayers, Committee Member
David Michael Geiser, Committee Member - Keywords:
- quality
nutrient
yield
genotype
rDNA
Grifola
beta-tubulin
molecular phylogeny - Abstract:
- Grifola frondosa (Dickson: Fr.) S.F.Gray (maitake) is a choice edible mushroom and has been marketed in Asia in recent years for medicinal use. Production and consumption of this mushroom is increasing rapidly in the world. There was a 41-fold increase from 1988-97 worldwide and a 38% increase in the United States (1999-2000). While this mushroom has enjoyed increased popularity among consumers, scientists know little about the genetics and life history of this species. I, therefore, sought to quantify genetic diversity among available isolates and to establish a taxonomic position for this mushroom and some of its allies. To accomplish these goals, the internal transcribed spacers 1 and 2 (ITS-1 and 2) and 5.8S regions of the nuclear ribosomal DNA (rDNA) transcriptional unit and a portion of the b-tubulin gene were PCR-amplified. Then, rDNA and b-tubulin amplicons from 52 isolates of Grifola frondosa, one isolate of Grifola sordulenta, Polyporus umbellatus and Meripilus giganteus were sequenced. In both rDNA and b-tubulin sequences, nucleotide variation within isolates of G. frondosa (5.4% in rDNA and 12.2% in b-tubulin) was relatively small compared to that observed between isolates of G. frondosa and G. sordulenta (14.3% in rDNA and 30.2% in b-tubulin). Molecular phylogenetic analysis of rDNA, b-tubulin and combined sequences revealed two major clades within G. frondosa. Clade I (U.S. clade) included all the U.S. isolates, while Clade II (Asian clade) consisted only of Asian isolates. The major commercial isolate (unknown origin) used on most U.S. mushroom farms grouped within the Asian clade and is apparently of Asian decent. Based on partial b-tubulin sequence, phylogenetic analyses indicated that G. frondosa and its allies (G. sordulenta and P. umbellatus) share a common ancestor. To assist with the demand of commercial growers for isolates with improved yield and quality characteristics, I evaluated 23 genotypes of Grifola frondosa for crop cycle time, biological efficiency (BE; ratio of fresh weight of mushroom harvested to dry weight of substrate x 100) and quality. Significant differences among lines were found for these parameters when mushrooms were produced on nutrient supplemented sawdust substrates. Four isolates (WC828, M036, M037 and M040) were found to have the most consistent and highest BEs (38.5%, 39.5%, 35.8% and 38.9%, respectively) and quality (1.2, 1.3, 1.4 and 1.2, respectively). In order to determine the effects of nutrient supplements on mushroom crop cycle, BE and quality, different combinations of wheat bran, rye, millet and corn meal were evaluated. Combinations of two or three nutrients selected from wheat bran, millet and rye were found to be the most desirable formulations with short crop cycle, high quality and high BE. Significant differences for crop cycle times, BEs and quality also were found when different combinations of wheat bran, rye and millet at different levels (10%, 20% and 30% of total dry substrate wt) were used. The combination of 10% wheat bran, 10% millet and 10% rye (BE 47.1%, quality 1.8 and crop cycle 12 weeks) and the combination of 10% wheat bran plus 20% rye (BE 44%, quality 1.7 and crop cycle 10 weeks) gave the most consistent yields and basidiome quality over time.