| Ginger rhizome rot was a soil-borne diseases caused by Pythium survived extended periods in naturally infested ginger rhizosphere soil. In recent years, ginger rhizome rot occurred in most ginger-growing areas in the Shandong Province, and caused varying degrees of destruction and economic loss. At present, the pathogens have not yet clear, and the occurrence regularity and control methods were still in its infancy. So the pathogens and biological control were researched systemically in this experiment, in order to offer theoretical basis to the control of ginger rhizome rot.The main results were as follows:1. All of 607 isolates from 56 gingers with rhizome rotting symptoms obtained in 2009-2010 from ginger field in Pingdu, Tai'an, Anqiu, Changyi, Laiwu and Juxian areas, Shandong Province, were identified as Pythium spp. The pathogenicity of the 96 strains typical pathogens of Pythium and Koch rule validation were made. The results showed that all of the pathogens had the pathogenicity to ginger, and the morbidity was 100%. The pathogens could re-isolated from the infected ginger.2. The 14 strains of Pythium were identified as P. myriotylum Drechsler by morphological method and nr DNA-ITS technology. The phylogenetic tree based on ITS sequence has showed that 14 Pythium were divided into 3 subgroups:The strains Py01, Py02, Py03, Py04, Py05, Py06, Py07, Py09, Py11, Py12, and Py13 were in a sub-group; the strains Py08 and Py10 in another sub-group; Py14 as an individually sub-group. This indicates that although all of the 14 Pythium were identified as P. myriotylum Drechsler, but there were still some differences within species.3. The inhibition effect of thirteen fungicides and nine herbicides on two kinds of Pythium pathogens causing ginger rhizome rot was determined by using mycelial growing rate method in door. Among thirteen tested fungicides, 98% Hymexazo, 60%Pyraclostrobin·metiram, 25%SYP-Z048 and 25%Pyraclostrobin showed strong toxicity, and the EC50 for mycelial growth was 1.9518 mg/L, 2.8952 mg/L, 4.2275 mg/L and 4.7926 mg/L, respectively. Moreover, the results showed that the inhibition of 5%quizalof op-p-ethyl, 48%oxyfluorfen and 50%prometryn were stronger than other herbicides.4. The inhibition effect of three Bacillaceae (P. polymyxa, B. vallismortis, B. sp.) and two different molecular weight chitosan on Pythium pathogens causing ginger rhizome rot was determined in lab culture dish. The results showed that all of the three tested Bacillaceae showed strong toxicity, and the P. polymyxa with strongest toxicity. At the different concentration, the inhibition rates of P.polymyxa on pathogens were 54.23%～96.76% and 62.25%～93.57%, respectively. B. vallismortis was less strong than P.polymyxa, and B.sp.was the weakest among them. In addition, there was obvious difference in inhibition effect of two different molecular weight chitosan on pathogens. The inhibitive effect of the low molecular weight chitosan was higher than that of the middle molecular weight, and the EC50 for mycelial growth of the pathogens was 771.8694 mg/l and 487.3678mg/l, respectively.5. The water culture method was used to collect garlic root exudates. The inhibitive effects of garlic root exudates on mycelial growth of the pathogens from garlic (P.violae, P.heterothal, P. sylvati) and from peanut (P.helicoide, P.irregular, P.ultimum) were studied in lab culture dish. The results showed that the inhibitive effect of the root exudates from the 30-, and 40-day old garlic was highest during the growth stages of garlic, and the inhibitive effects on pathogen mycelia growth were increased with increasing of garlic root exudates concentration. The reaction of the pathogens from garlic (P.violae, P.heterothal, P.sylvati) were more sensitive than that from peanut (P.helicoide, P.irregular, P.ultimum).6. The population fluctuation of Pythium in ginger field was researched during the growth stages of garlic. The quantity dynamics of Pythium in the soil of pot and field was as follows:the quantity of Pythium increased gradually during May and June, and then sharp decline in July and August, but began to rise in Septembe. Overall, the population dynamics of Pythium was: increased in spring and autumn, and declined in summer.7. The biocontrol effects of 4 biological agent treatments on ginger rhizome rot were performed in field experiments. The results showed that the control efficiency of P. polymyza and P. oligandrum on ginger rhizome rot were 57.4% and 55.55%, that higher than others. However, the biocontrol effects of four biological agents were not significant and less than 60%. Therefore, the selection and application method of the biological agents remains to be researched and improved in the future. |
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