Bulletin Spring‧Summer 1996

X i a n g g u M u s h r o om How to Make it Palatable to Both the Taste Buds and the Pocket The tasty and versatile Xianggu mushroom is a favourite on Chinese dinner tables, in haute cuisine as in more homely fare. It can cost from under a hundred dollars to a few hundred dollars per catty, depending on the quality. Different grades of Xianggu are the result of differences in the strains or in the cultivation processes. To Develop a Breeding Programme for Xianggu There have not been, however, any breeding programmes for Xianggu similar to plant breeding programmes. Traditionally the better strains have been selected only after time-consuming and labour-intensive screening, which adds to the overall production cost. But since 1993 ， Prof. H.S. Kwan of the Xianggu mushroom molecular biology research programme at The Chinese University of Hong Kong has striven to make Xianggu more palatable to both the taste buds and the pocket. The programme tries to develop and apply state-of-the-art molecular biological technology for the improvement o f Xianggu mushroom strains, and three of its projects have received funding from the Research Grants Council three years in a row since 1993 (see box). The projects have different focuses but share in common two objectives: (1) to plot a molecular genetic map of the Xianggu mushroom, and (2) to isolate and manipulate genes that are important for the cultivation of quality Xianggu mushroom. To Plot a Genetic Map To facilitate the construction of strains with desirable qualities, researchers need the help of a molecular genetic map to identify and locate the agronomically important genes in the Xianggu mushroom genome. Prof. Kwan and his team have so far generated over 70 molecular markers and located two mating-factor genes. A molecular genetic map has been plotted based on this information (see p. 27). It is hoped that eventually genes that are conducive to tastiness, succulence, and rapid growth can be identified, isolated, and reshuffled into a single strain. Plentiful yields of quality Xianggu mushroom may thus result. Gene Manipulation Researchers set their eyes on two types of genes in particular: those involved in fruiting body development, and those involved in the degradation of lignocellulosic materials in the growth substrate. Once such genes have been identified, they will be cloned for further analysis. Gene cloning is the process by which a vector inserted with an isolated gene is placed inside a suitable organism, often some bacterium, to produce multiple copies o f that gene. RGC-supported Research P r o j e c t Generation of Molecular Markers for Construction of a Genetic Map and Characterization of Genetic Determinants of Some Phenotypic Traits in Shiitake Mushroom ( L e n t i n u l a e d o d e s ) 1993 RGC g r a n t HK$756,000 P r o j e c t Identification and Molecular Cloning of Differentially Expressed Genes Involved in Lignocellulose Utilization in Shiitake Mushroom ( Lentinulae d o d e s ) 1994 RGC g r a n t HK$583,000 P r o j e c t Molecular Cloning and Time Course Studies of Genes Specially Expressed during Fruit Body Development in Shiitake Mushroom ( L e n t i n u l a e d o d e s ) 1995 RGC g r a n t HK713,000 26