A Study On Pathogenic Fungi On Main Gramineous Weeds In Northern Part Of China

In growing seasons of 2007 and 2008, 254 samples were collected from diseased plants of 6 common gramineous weeds, including Setaria viridis, Digitaria sanguinalis, Eleusine indica, Chloris virgata, Echinochloa crusgalli, and Eragrostis cilianensis, growing in farmfield, lawn and wasteland in Beijing, Hebei, Qinghai, Henan, Shaanxi, Shanxi, Jilin and Liaoning. Four hundred and thirty-four strains of pathogenic fungi were isolated, out of which 332 strains produced spores.Based on morphological characteristics and sequence alignments of rDNA ITS region of 183 typic strains, 26 species of 9 genera were identified: Alternaria alternata, A. astragali, A. citri, A. compacta, A. longipes, Bipolaris australiensis, B. maydis, B. peregianensis, B. sacchari, B. setariae, B. sorokiniana, Cladosporium cladosporioides, Colletotrichum gloeosporioides, Curvularia affinis, C. cymbopogonis, C. heteropogonicola, C. heterostrophus, C. lunata, Exserohilum monoceras, E. fusiforme, E. rostratum, Fusarium equiseti, F. incarnatum, F. proliferatum, Nigrospora oryzae, Phoma glomerata. In which, Alternaria and Bipolari were isolated from all the 6 gramineous weeds and were dominant genera.There are some reports about pathogenic fungi on common monocotyledonous and dicotyledonous weeds in farm field in an area or screening of potential strains for biocontrol of a weed in China, but not any special report about pathogenic fungi on main Graminous weeds in a large geographical area. This research preliminarily proved up the kinds and distribution of the pathogenic fungi on the weeds Setaria viridis, Digitaria sanguinalis, Eleusine indica, Chloris virgata, Echinochloa crusgalli, and Eragrostis cilianensis in eight provinces in northern part of China, which provided resources and information for further research on and utilization of the fungal resources.Pathogenicity to the seedlings of common gramineous weeds and crops and host-range were tested for a part of strains with artificial inoculation under controlled conditions. Five gramineous weeds were inoculated with 62 strains, including species of the genera of Bipolaris, Alternaria, Curvularia, and Exserohilum. There were 11 strains that caused different notable symptoms, in which 7 strains had pathogenicity to S. viridis, 2 strains had pathogenicity to D. sanguinalis, 1 strain had pathogenicity to E. indica, 1 strain had pathogenicity to C. virgata. Pathogenicity tests were repeated for the 11 strains with some more kind of plants. We found that ZXL07289a, one strain of C. lunata from E. crusgalli in Nanyang of Henan province, had strong pathogenicity to C. virgata, but had no or little pathogenicity to other plants, and showed some specificity for host. The strain ZXL07290a of B. setariae from S. viridis in Nanyang of Henan provinc had strong pathogenicity to S. viridis, D. sanguinalis, and C. virgata, and notable pathogenicity to Sorghum vulgare and Setaria italic, but it had no or little pathogenicity to dicotyledonous crops such as soybean and cotton, and showed relatively wide host-range. Preliminary tests indicated that the strain ZXL07289a of C. lunata and the strain ZXL07290a of B. setariae had the potential to be developed as microbial herbicides. There were 19 B. setariae strains in the 62 strains tested for pathogenicicy, The results indicated that the strains from different hosts had different pathogenicity to S. viridis. The strains from S. viridis had stronger pathogenicity than those from other hosts to S. viridis. The strain from A. fatua had no pathogenicity to S. viridis. The pathogenicity of the strains from different geographical areas and different samples of S. viridis was notably different.