Genetics Of Fusarium Section Liseola

Studies on gene loci of molbdcmum containing cotactor, the genetic relationship between molvhdernurn containing cofactor and nitrite reductase, the genetic stability of heterokaryon. the ability of pigment formation and its inheritance, as well as population structure of I2uxuriuni rnonihforrnL?isolated from different hosts and collecting places. were carried out by physiological complementation test, sexual cross, heterokaryon formation and RAPD analysis, respectively.Complernentation analysis of forty-two molybdemum containing cofactor mutants (nitB) obtained from the same strain 慡C5O?revealed that at least seven different genes were involved. Likewise, the results of complementation tests of all nitrate ruductase mutants (nitA) and all nitrite reductase mutants (nitC) obtained from the same strain ~SC50?also revealed that apart from single gene, there were other genes to regulate the two enzymes, nitrate reductase and nitrite reductase. The result of studies on two major nitrogen regulatory loci mutants (nitD) revealed that, with the occurrence of this type of mutants, they often deleted the ability of female fertility.The analysis results of sexual progenies between molybdemum containing cofactor mutants (nitB) and nitrite reductase mutants (nitC) showed that there were two kinds of gene to control the enzymes, molybdernurn containing cofactor and nitrite reductase, in different mating populations and in different hosts in the same mating population of the pathogen. It is the first time to propose the hypothesis that3J~j~nuclear gene and cytogene co-control the enzymes related to nitrate utilization pathway. If the ratio of segregation is 1:1:1:1 to four different phenotypes (nitD,nitB,nitC,wt), they were under the control of nuclear genes; Otherwise, two phenotypes were emerged by female parent phenotype and wild type, with ratio of 1:1, male parent phenotype was disappeared, there were two set of gene (nuclear gene and cytogene) controlled the two enzymes (molybdemum containing cofactor and nitrite reductase).The inheritance of heterokaryon between two isolates which belong to the same vegetative compatibility group (VCG) was unstable, the trait of heterokaryon was disappeared during 3~-~5 generations. These revealed that parasexuality and heterokaryosis were not the main reasons including genetic variation and diversity in F moni1~fornie.The ability to secrete pigment is stable in asexual stage, according to sexual crossing, it is the first time to propose the hypothesis that there were a pair of alleles (A, a) controlling the production of pigment precursor, but the pigment production relied on the presence of a number of numerical trait genes, however, the number of these genes is related to quantity and time of pigment production.Nine primers were used to amplify DNA of F moniljforme isolates in this study. 88 RAPD markers were obtained, 97.73% were polymorphisms. Based on the genetic distance from the result of RAPD fingerprinting showed that polymorphyism of strains were not obviously related to their collected place or hosts. However, system cluster analysis based on hosts and mating populations showed that the difference between A and D mating populations is rather small, the variation being 0.0348; while it抯 more big between strains isolated from rice and maize, the variation being 0.2412. and there was a certain correlation to the host of maize in A, D mating populations.