Genetic Diversity Of Curvularia Lunata (Wakk.) Boed. And Evaluation Of Maize Germplasm On Disease Resistance

Maize Curvularia leaf spot . caused by Curvularia lunata (Wakk.) Boed. ,has been found in the most of maize production regions in China. The disease incidence and severity has been rising in recent years, especially in northern and the north-eastern China. The disease is becoming one of the most important diseases in maize production, and has aroused concern of plant pathologists and crop breeders. In the study, many diseased maize plants were collected from different regions, and pathogens were isolated, purified, identified and conserved. Pathogenieity and virulence of the isolates were assessed; Soluble mycoprotein and esterase etc isoenzynie patterns of 43 isolates were analyzed; Genetic diversity among 40 isolates of Curvularia lunata was evaluated by random amplified polymorphic DNA (RAPD) fingerprint. Maize germplasm were evaluated for resistance to Curvularia leaf spot. The major results are as follows: 1. 40 isolates isolated from maize and 3 isolates from rice, wheat, adzuki bean in ten provinces were identified as Curvularia lunata. Based on the culture characters, such as color of colony, aerial myeelia, the number of conidia, there were some difference among 43 isolates. Meanwhile, five types of conidium were compared in culture characters and virulence. In each single conidia culture there were different morphic conidia also and no difference in virulence was found among five single-conidium cultures. 2. Pathogenicity and virulence of 43 isolates were tested by inoculation on five inbreeding lines. All isolates infect maize, but successional diversification of virulence was appeared from weakness to strength. According to the average of disease index and reaction of five inbreeding lines, to pathogen isolates difference of virulence in the isolates was conspicuous. Briefly, there was extremly diversity on virulence of Curvularia lunata. 3. The Esterase, Catalase, PPO isoenzyme and soluble mycoprotein patterns of 43 isolates were analyzed by polyacrylamide gel electrophoresis. There were distinct differences on electropheretic patterns among 43 isolates. The similar coefficient (sc) among 43 isolates was 0.368?.000. 96-12 and 96-14 isolates are farther in relation to other isolates. The results indicated that the polymorphism of isoenzyme was correlateed with virulence difference of most isolates, but there were difference in some isolates. 4. Genetic variation in 40 isolates was analyzed by RAPD assay. Using 12 oligonucleotide primers, fingerprint patterns were generated for each isolate, Of 94 RAPD markers, 60 (63.8%) were polymorphic. The similar coefficient (sc) among 40 isolates was 0. 298?.000. 96-12 and 96-14 isolates were farther in relation to other isolates. The result showed that substantial genetic diversity was existed among isolates. The virulence was correlateed with RAPD groups obtained with 12 primers, but there were differences in some isolates. 5. The resistance to maize curvularia leaf spot of 1475 maize accessions , 25 special lines including different cytoplasm lines, inbreeding lines and sterile lines were evaluated during 1998?999. Of 1475 varieties, 4 were high resistant (HR), no immunity (I) variety had been found, 28 resistant (R), 1260(85.4%) were moderately susceptible (MS), susceptible (5) and high susceptible. Except three inbreeding lines, Shengl37 ,Shengl3S and CN165, other special lines were susceptible(S). In 1475 maize accessions, most of resistant germplasm were in Guizhou, Sichuan provinces and the nor...