| Oilseed rape (Brassica napus, AACC,2n=4x=38) is the second largest oil crop in the world and the most widely grown oil crop in China. Unfortunately, oilseed rape is sensitive to Pi and boron deficiency, and genotypic difference in Pi utilization efficiency exists in this crop.Phosphorus (P) is a major plant macronutrient for plant growth and development, and plays an important role in plant photosynthesis, respiration, stress resistance, yield and quality. Thoμgh major soils are not low in total P content, soil available P level is still low (only2μmol/L in the most soil), which has become the major limiting factor of crops. To ensure normal plant growth and development and maintain productivity and quality, about30million tons of phosphate (Pi) fertilizers are applied worldwide per year. However, more than80%of the fertilizers are lost because of stabilization by ferrous or aluminum oxides in acidic soils or by calcium carbonate in lime-rich soils, reducing the available P content to be only1/200to1/500of the total P content. Different crops species or varieties showed different adaption capability to low P soil, and only a minority of them are efficient in P absorption and utilization. Therefore, to decrease Pi fertilizer consumption and protect agricultural ecosystem, it is necessary to screen phosphorus-efficient cultivars/lines to increase P acquisition and utilization efficiency.In additions, the Yangt ze River region is the major oilseed rape belt in China and accounts for more than80%of rapeseed planting area and total output in China. Owing to enrichment and stabilization of phosphoric compound by the acid soil, low available P level is becoming a serious problem in this belt. Screening of P-efficient genotypes to improve P utilization efficiency of oilseed rape is a crucial measure to solve this problem.Boron (B) is another an important and necessary element for plant growth and development, whose deficiency often promotes the flowering of rape rather than bear real fruit. Boron is another a limiting factor, leading to reduction of rapeseed production and losses of all yield. At the same time, excess of boron may rusult in the poison of plants. Available boron deficiency of soil is a worldwide problem. The boron deficiency symptoms were reported on about132kinds of plants in80countries. Boron fertilizer area of the whole world was approximately1.5×107hm2each year. When the soil is short of available boron, rapeseed, wheat and other crops are stunting. Meanwhile, the seed setting rate decreases significantly. However, the suitable boron concentration range of plants is very narrow. Once the available boron of soil is at high concentration, it may be toxic to plants. Significant genotype differences of different plants and different varieties of the same plant exist in the ability of resistance to low boron stress and boron poisoning. Therefore, screening of efficient boron genotypes becomes the key to solving the problem. On one hand, it can overcome the lack of available boron, on the other hand, it can help to clone the gene about the efficient absorption and utilization of boron and resistance to boron toxicity.In this study, the TOPSIS analysis method is introducted, and nutrition-related indicators of phosphorus and boron were seeked and verified in the rapeseed seedling stage of solution culture. The related morphological and physiological indices were then ranked using TOPSIS method to precisely screen out real phosphorus-efficient and boron-efficient rapeseed genotypes. Finally, the solution culture experiment results were comprehensively analyzed, combined with the sand culture results and field trials results.The redults show that P67is a Brassica napus strain of phosphorus (Pi)-efficient genotype and P119is a Brassica napus strain of boron-efficient genotype. Besides, P67is a Brassica napus strain of both phosphorus (Pi) and boron(B) efficient genotype.The specific findings are as follows:1. The test explored the better phosphorus (Pi) and boron(B) concentration and incubation time with better screening effects in the nutrient solution.The better phosphorus (Pi) concentration range had been proved in10μmol/L-1mmol/L, through the experiment of different phosphortus concentrations with phosphorus efficient strain W17and phosphorus inefficient strain W39. The phosphorus level of the single screening factor significantly reduces the screening workload. With the same method, the best Seedling culture time was screened in the nutrient solution, which is30days, as well as the best screening boron concentration of the extreme boron-efficient strains,which is0.001-0.005mg/kg.2. The typical phosphorus-efficient strain of Brassica napus P67was screened out throμgh the TOPSIS method.Under phosphate (Pi) deficient and sufficient solution culture conditions, eight indices (root length,single plant fresh weight, single plant dry weight, root to shoot ratio, phosphorus content, boron content, shoot APase activity and root APase activity) that are significantly related to phosphorus efficiency in rapeseed seedling were analyzed throμgh124materials of different phosphorus, boron nutrition efficiency, as well as six indices (root length,single plant fresh weight, single plant dry weight, root to shoot ratio, phosphorus content and boron content) related to boron efficiency. The indices were then ranked using TOPSIS method to precisely screen out real phosphorus-efficient rapeseed genotype. The results show that P67is a Brassica napus strain of phosphorus (Pi)-efficient genotype, besides, the partial efficient Brassica napus of P40in phosphorus, phosphorus inefficient Brassica napus P6, P107and other three phosphorus partial inefficient Brassica napus lines were obtained.3. The typical boron-efficient strain of Brassica napus P119was screened out throμgh the TOPSIS method.Under boron (B) deficient and sufficient solution culture conditions, six indices (root length,single plant fresh weight, single plant dry weight, root to shoot ratio, phosphorus content and boron content) that are significantly related to phosphorus efficiency in rapeseed seedling were analyzed through124materials of different phosphorus and boron nutrition efficiency. The indices were then ranked using TOPSIS method to precisely screen out real boron-efficient rapeseed genotypes. The results show that P119is a Brassica napus strain of boron-efficient rapeseed genotype and P67is a Brassica napus strain of partial boron-efficient rapeseed genotype.4. Using the TOPSIS method, the nutrient solution screening results were analyzed, combined with the sand culture results and field experiments results.Comprehensive comparison of the results of three kinds of matrix(nutrient solution culture,sand culture and field experiment) shows that:nutrient solution culture test results were consistent of the sand culture results and field experiment results.The typical efficient phosphorus, boron efficient Brassica napus strain P67and phosphorus inefficient, boron inefficient Brassica napus P107were sreened out, as well as the boron efficiency Brassica napus strain P119and phosphorus inefficient Brassica napus strain P6. Efficient phosphorus may be closely linked with boron efficient to a certain extent, for a further study of the molecular level.Nutrient solution and the quality of sand culture test results and the index value were comparatively analyzed. The redults show that the trend is basically same.The different matrix does not affect the overall results of the screening. Considering various factors, the nutrient solution culture experiments are more efficient, accurate and suitable for the volume, which is the preferred method of automated screening phosphorus and boron efficient genotypes. |
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