Effects Of Grafting On The Relieve Of Continuous Cropping Obstacles Of Chrysanthemum

Chrysanthemum, as one of the famous traditional flowers in China, was widely used as cut flower, potted plant and garden ornamental flower. Using Artemisia frigida as root stock,’Jinba’ as scion, grafted chrysanthemum were created. Chrysanthemum cutting seedlings and self-rooted Artemisia frigida were as contrasts. All of the three treatments were grown in two kinds of soils, continuous soil and non-continuous soil respectively. The effects of grafting on microbe group in the rhizosphere soil、soil nutrition of the rhizosphere、soil enzymes of the rhizosphere and nutrients in leaves and stems of plants were investigated through the methods of LSD and variance analysis. We extracted the total community DNA directly from the rhizosphere soil. Fungus universal primers were used to amplify18S rDNA; Rhizoshpere fungus communities of continuous cropping chrysanthemum during seedling stages were detected by DGGE. The main results were as follows:1. The content of bacteria and actinomycetes in the rhizosphere soil of grafted seedlings and self-rooted Artemisia frigida were much more than that of ’Jinba’ cutting seedlings significantly. And the content of bacterium and actinomycetes in the rhizosphere soil of grafted seedlings and self-rooted Artemisia frigida increased gradually, reached the maximum in their vegetable stages, then decreased partly. However, the content of fungi in the grafted seedlings and self-rooted Artemisia frigida decreased gradually, and the differences were significant. The increase amplitudes of bacterium and actinomycetes in the rhizosphere soil of grafted seedlings are15.73times and1.73times, respectively, while fungi decreased11.87%. The content of fungi in the rhizosphere soil of’Jinba’cutting seedlings was increased gradually during the whole growing period, reaching the maximum in the vegetable stage.2. The content of inorganic nitrogen, available phosphorus and available potassium in the soils of self-rooted Artemisia frigida were the lowest, the highest content were in cutting seedlings, while the content of these nutrients in grafted seedlings were in the middle. The contents of inorganic nitrogen, available phosphorus and available potassium in the soils of chrysanthemum grafted seedlings decrease24.75%,22.24%and13.18%respectively than that of cutting seedlings. Variance analysis results showed that the differences of soil available phosphorus in the two soils and of the three treatments (grafted,’Jinba’ cutting seedlings, self-rooted Artemisia frigida) were all very significant; while the content of soil available potassium was just very significant in the three treatments. We could conclude that grafting was the major factor affecting the soil available potassium in our research. The two factors, soil and graft, have no significant interaction effects of soil nutrients.3. The content of catalase, invertase, urease and phosphatase of grafted seedlings and self-rooted Artemisia frigida were mostly higher than cutting seedlings. All of these enzymes presented to increase gradually first, reach the maximum in vegetable stage, then to decrease a little, and again to increase partly in squaring period. The increase amplitudes of the four enzymes are14.14%、32.56%、15.20%and34.54%respectively. Variance analysis results showed that the soil catalase and phosphatase had no significant differences on the two factors (soil and grafting). However, invertase had very significant differences both on soil and grafting. The content of urease in the two soils has significant differences, while no significant differences were discovered among grafting treatments. The two factors, soil and graft, have no significant interaction effects of soil enzymes.4. The content of total nitrogen, total phosphorus and total potassium in the leaves of the plants had decreased gradually during the whole growing period. And the contents in the grafted seedlings were mostly more than that in the chrysanthemum cutting seedlings. Among the grafting treatments, the content of total nitrogen in leaves had significant differences, while total potassium and total phosphorus had no significant difference. There was no significant difference in the two soils also. The increase amplitudes of total nitrogen and total potassium in the leaves are22.44%and29.53%respectively, no in total phosphorus. We concluded that grafting had enhanced the absorbing ability of roots to a certain extent. The two factors, soil and graft, have no significant interaction effects of nutrients in leaves.The content of total nitrogen, total phosphorus and total potassium in the stems of the plants had decreased gradually during the whole growing period. And the contents in the grafted seedlings were mostly more than that in the chrysanthemum cutting seedlings. The increase amplitudes of total nitrogen, total phosphorus and total potassium in the stems are46.91%.9.26%.32.82%respectively. Variance analysis results showed that there was no significant different in the nutrients of stems under the two factors, and also no interaction effects.5. We studied the rhizoshpere fungus communities of continuous cropping chrysanthemum during seedling stages through DGGE. The result showed that there are more bands on continuous cropping soil than that on non-continuous cropping soil. There were some different bands among grafted seedlings, cutting seedlings and self-rooted Artemisia frigida. We found Glomus sp. NBR PP1in the rhizosphere soil of grafted seedlings and Artemisia frigida, which was one kind of AMF, but failed to discover in the rhizosphere soil of cutting seedlings. Rhizoctonia solani was the mainly pathogen of chrysanthemum rhizoctonia disease, which was found in the cutting seedlings and self-rooted Artemisia frigida planted on continuous cropping soil and not in grafted seedlings on continuous cropping soil and all the treatments on non-comtinuous soil. Fusarium would result in chrysanthemum fusarium wilt. We found two species and one kind of varieties of Fusarium in all the treatments of our experiment. According to the bands’brightness, we discovered that Fusarium and Fusarium oxysporum f were more in continuous cropping soil than that in non-continuous cropping soil. The content of the two pathogen fungi were also more in cutting seedlings than that in grafted seedlings and Artemisia frigida. So the continuous cropping of chrysanthemum would increase the kinds and contents of the pathogen fungi. After grafted, because of changing the roots, the fungi community of rhizosphere soil had changed, and the kinds and number of pathogen fungi had decreased. Because AMF could form around the root of Artemisia frigida, it would promote the absorption ability of soil nutrients, strengthen the tolerance of plants and remit the obstacle of continuous cropping of chrysanthemum.