| Piriformospora indica is a root endophytic fungus, which was isolated from Thar Desert in India, forms an association with roots of many plant species. The fungus has captable to stimulate growth, increase biomass and enhance seed production of the hosts. It also confers the host resistance against abiotic and biotic stress.Brassica napus L. belongs to Cruciferae Brassica, and it is one of the world’s most important oil crops. The planting area of B. napus accounts for more than40%of the total area of the oil crops growth in China, and the production is accounted for more than35%of the total oil crops. However, the cultivation of B. napus has been always affected by various biotic and abiotic stresses. The co-cultivation system between P. indica and B. napus (Gaoyou605) was established and optimized in this thesis. The growth promotion, stress tolerance and the quality of rapeseed improvement in B. napus conferred by P. indica and their mechanisms were preliminary studied. The main results are as follows:1Established and optimized the co-cultivation system between P. indica and B. napus. The co-cultivation of P. indica and B. napus seedlings on petri dish showed that the PNM medium is much better than MS medium for root colonized by P. indica, and the chlamydospores can be detected in root of seedlings after co-cultivation for15days. Furthermore, the treatment with two plugs of P. indica on PNM medium is much better than one plug, the lateral root number were increased by120.04%and76.35%over control after co-cultivation for7days and10days, respectively. The fresh weight and dry weight of shoot were increased by33.19%and21.96%, and the fresh weight and dry weight of root were increased by71.62%and40.14%over control after co-cultivation for15days, respectively.2P. indica promoted the growth and biomass of B. napus. Two year’s (2010and2011) consecutively pot culture experiment showed that P. indica can obviously promote the growth of B. napus. The growth status of B. napus colonized by P. indica was much better than un-colonized ones after transplantion for4weeks. The growth promotion was more obviously after transplantion for9weeks. The petiole length, length and width of the largest leaf, the fresh weight and dry weight of the shoot, and fresh weight and dry weight of the root were increased by26.41%,20.92%,38.52%,94.36%,93.43%,138.32%,105.06%and20.01%,15.39%,19.47%,74.67%,76.57%,128.74%,132.91%over control in2010and2011, respectively. P. indica also promoted B. napus9days earlier bolting and8days earlier flowering than control plants in2010, and3days earlier bolting in2011. The branch number was increased by20.83%and16.39%in2010and2011, respectively. The pod number per plant, the pod length, the pod diameter and the seed weight were increased by68.71%,35.66%,23.40%,93.99%and36.74%,32.40%,22.92%,41.43%over the control when harvested in2010and2011, respectively.3P. indica conferred drought tolerance in B. napus. The20%polyethylene glycol (PEG)6000solution was used to imitate drought stress. The results showed the leaves of un-colonized B. napus began to curl, shrink and deformation after treatment by PEG solution for48hours, but the colonized ones did not performance drought stress state. The concentration of malondialdehyde (MDA) in the leaves of P. indica colonized plants significantly lower than that in un-colonized plants, and the degree of membrane lipid peroxidation was reduced. The Proline content in the leaves of B. napus colonized by P. indica was significantly higher than that in un-colonized ones, and it was1.3folds of that after PEG treatment for72hours. While the activity of SOD, POD and CAT was significantly higher than un-colonized plants, the activity of SOD, POD and CAT was1.17,1.38and1.27folds of the control ones after PEG treatment for24hours. RT-PCR analysis showed that the expression of drought-related gene575which codes lipid-transfer protein was upregulated in leaves of colonized plants, and the expression level was3.2folds of control plants after PEG treatment for9hours.4P. indica promoted uptake of mineral element in B. napus, and improved rapeseed quality. P. indica promoted uptake of N, P, S, Mg and Zn and other mineral elements, the accumulation of N, P, S, Mg and Zn in rapeseed and in leaves were increased by23.34%,30.83%,37.25%,24.51%,41.36%and17.68%,6.23%,4.58%,31.04%, 7.68%over control, respectively. Rapeseed quality analysis indicated that P. indica improve rapeseed oil content (10.27%), reduce erucic acid (10.95%) and glucosinolate (11.96%) content. Further research found that the expression of Bn-FAE1and BnECR, which encode two key enzymes (β-ketoacyl-CoA synthase and trans-2,3-enoyl-CoA reductase) responsible for the regulation of erucic acid biosynthesis, are down-regulated at mid and late life stages during seed development in colonized plants, the expression level of Bn-FAE1and BnECR in seed of colonized B. napus8weeks after pollination were0.32folds and0.42folds over control, respectively. |
PDF Full Text Request