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Biology Of Sexual Reproduction And Genetic Diversity In Phytophthora

Posted on:2001-02-15Degree:DoctorType:Dissertation
Country:ChinaCandidate:J Y WangFull Text:PDF
GTID:1103360002452519Subject:Plant pathology
Abstract/Summary:PDF Full Text Request
Inheritance of biological characters, population genetics, mating type variation and physiology of sexual reproduction were studied in homothallic Phytophlhora cactorum and P boehmeriae. The inheritance and variation of biological characters including growth rate and homothallism of? cactorum were studied in vitro. Six isolates obtained from different localities and host plants were tested. The results showed that there were at least three patterns on inheritance of growth rate in? cactorum: 1. Growth rate steadily inherited in both single-zoospore and single-oospore progenies, which indicated that the genetic factors controlling growth rate in the isolates were homozygous. 2. Growth rate steadily inherited in progenies but showed obvious variation in selfed single-oospore progenies, which suggested that the character of the isolates were controlled by nuclear heterozygous gene. 3. Growth rate showed variation in both single-zoospore and single-oospore progenies, but the variation of growth rate in selfed oospore progenies was significantly different from that in zoospore progenies, which suggested that this character might be controlled by cytoplasmic factors, moreover, the variation of growth rate in selfed oospore progenies also associated with nuclear genetic factors. The results also showed that the homothallic character of all the tested isolates were steadily inherited in both asexual and sexual progenies, which suggested that the genetic factors controlling the character appeared to be homozygous. The inheritance in successive single-zoospore progenies of variation of growth rate following sexual reproduction were studied, the growth rate showed obviously continuing variation in over two successive zoospore generations. The results suggested that except for causing gene recombination the sexual reproduction of? cactorum induced a new mechanism which 134 may engage in regulating and controlling the inheritance and variation of the character. The inheritance of pathogenicity to apple of isolate Ap-14 of? cactorum, which was isolated from apple fruit in Heilongjiang province, in asexual and sexual progenies were studied. The pathogenicity was evaluated by the semidianieters of lesions on the wounded apple fruits by culture block inoculation. The results showed that the pathogenicity of? cactorum to apple was steadily inherited in two successive zoospore progenies but showed obvious variation in first single-oospore generation. The inheritance of sensitivity to metalaxyl of the same isolate in single-zoospore and single- oospore was investigated. The sensitivity was evaluated by the ratio of the growth rate on LBA medium which supplemented with 0.05 1.?gIml metalaxyl to the growth rate on LBA. The sensitivity of P cactorum to metalaxyl also steadily inherited in two successive zoospore progenies but showed obvious variation in first single-oospore generation. The above results indicated the two characters of P cac forum were controlled by nuclear heterozygous genes. A total of 45 isolates of P boehmeriae from different localities and host plants were amplified with 8 RAPD primers which were selected from 126 primers. 68 RAPD markers were obtained. 29.4% of them were polymorphic. The genetic distance and phylogenetic tree were constructed by use of Popgene. Isolates were divided into two groups. Isolates from cotton clustered into one group and isolates from other host plants clustered into another group. The...
Keywords/Search Tags:P cactorum, P boehmeriae, mating type, biological characters, inheritance, sexual reproduction, lipids
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