| Summary: | 碩士 === 國立臺灣大學 === 農藝學系 === 81 === Rice blast fungus Magnaporthe grisea has been known to have a
high degree of variability in the field. In this study,
hermaphroditic rice isolate Guy11 was crossed to four local
races (II-1, IH-1,IF-4,IG-2) and one isolate MAT1 that is
pathogenic to grass.Young asci that were dissected from fertile
perithecia were stained with lactic-orcein for counting
chromosomes at meiosis. The chromosome number in M. grisea is
nine. Chromosome-size DNA molecules from seven M. grisea
isolates were separated by pulsed- field gel electrophoresis(
CHEF II). Nine bands could be resolved at most. Chromosomal
polymorphisms for both length and number were observed among
seven isolates. Genomic DNA isolated from six M. grisea
isolates were used as template in polymerase chain reaction
(PCR) to get random amplified polymorphic DNA (RAPD) markers in
order to establish a preliminary electrophoretic karyotype for
M. grisea. Among the 60 arbitrary 10-mer primer used, 56.7 %
could generate polymorphic fragment, 73 RAPD markers were
obtained by reamplifying those primarily polymorphic fragments.
To find chromosome-specific marker, 15 RAPD markers were
radioisotop labelled with 32p and used as probes in Southern
blot analysis of chromosomal DNA bands separated by CHEF. 93 %
of RAPD markers that were hybridized to multiple bands showed
that they are dispersed repeatitive sequences. One RAPD marker
M08-M2 was hybridized to single band of about 4.6 Mb in length
in all the isolates used. It showed that this marker is
chromosome- specific. The seresults suggest that random
oligomer could generate useful RAPD markers to construct
physical map of M. grisea in the near future.
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