Identification And Physiological Characteristics Studies On Welsh Onion Germplasms

Identifiction of genetic relationship and resistance to Welsh onion Alternaria Leaf Spot of 65 germplasm materials had been studied. Meanwhile physiological characteristics of disease resistance, nutrient metabolism, dynamic growth of plant, photosynthetic potential and factors that contributed to yield had been studied. Physiological characteristics of varieties with high yield or quality or disease-resistance had been expounded.What had been done provided theoretical basis for breeding new varieties and optimizing cultural technique of welsh onion. The research results were as followed.1 There were divided 6 clusters and 14 sub-clusters from 57 different welsh onion materials by RAPD, 6 clusters and 14 sub-clusters by EST and 5 clusters and 9 sub-clusters by morphological charatistics. By combining RAPD and EST, most varieties were divided into 5 clusters.2 There was relationship between morphological division and geographic distribution. It revealed the results of long domestication and cultivation. There were no certain relationship between RAPD or isoenzyme and the geographic region. Compared RAPD with EST , both methods contained similar information in different cluster though EST marker sites were limited.3 By identifying the resistance to Welsh onion Alternaria Leaf Spot of 65 materials on seedling and plant, 4 materials were high-resistant, 33 materials were middle-resistant, 22 materials were resistant, 4 were middle susceptible and 2 were high susceptible.4 Chlorophyll content and carotenoid content were high in resistant materials and dropping scope was low after pathogenesis. POD, SOD, APX and PPO activity of resistant material were higher than the susceptible one, and the degree of increase was bigger after pathogenesis. There was no obvious difference on MDA content between the resistant and susceptible material in normal condition. But MDA content in susceptible material increased higher than the resistant one after pathogenesis. Proline content in resistant material was higher than the susceptible one, and increased more obviously after pathogenesis. After pathogenesis, soluble protein content of resistant one dropped. On the contrary, that of the susceptible one raised slightly. Soluble sugar content dropped, but the degree of the resistant one was smaller than the susceptible one. Free amino acid content of susceptible one increased slightly, and that of the resistant one dropped. Total S content in resistant materials was higher. POD activity, APX activity, proline content and total S content were consided as physiological norms for early identifying Welsh onion Alternaria Leaf Spot.5 Soluble sugar in pseudostem raised after planting,then dropped in the later period of growth, raised swiftly again at the harvest time. Soluble protein in pseudostem dropped after planting, and raised at the harvest time. Amino acid in pseudostem raised after planting, and reached its highest value at the harvest time. Nitrate nitrogen content in pseudostem dropped slowly after planting and raised at the harvest time.6 When harvesting, soluble sugar content and amino acid in pseudostem of clusterâ…¤were higher than other clusters. Soluble protein content of clusterâ…£was highest, the next was clusterâ…¡. Nitrate nitrogen content in clusterâ… was lowest. Total sulfur content of clusterâ…£w as higher. Nitrate nitrogen content in pseudostem were concentrated the third class of nitrate nitrogen content in vegetable of China.7 Plant height, plant weight, pseudostem weight, pseudostem length and pseudostem diameter of different clusters showed"S"growth curve. Soluble protein content, amino acid content and soluble sugar content had close relationship with plant growth in different growing stage. These nutrients were the basics for quality and quantity of welsh onion.8 Clusterâ…¢and clusterâ…¡were high yield types which had higher plant weight, plant height, pseudostem weight, pseudostem length. Dry matter content in pseudostem in clusterâ…¤and clusterâ…£were higher.They were suited for winter storage. Leaf weight in clusterâ… w as higher. And it was suited for procession. Clusterâ…¤had conpacted pseudostem, high dry matter, middle average height and weight. Its leaf colour was deep green, and was suited for sale in supermarked.9 By simple correlation analysis, yield of welsh onion had obvious positive correlation with plant height, plant weight, leaf diameter, pseudostem weight ,pseudostem diameter and scale numbers. Plant height had extremely obviously positive correlation with pseudostem length, pseudostem weight, leaf length and plant weight. So did plant weight with pseudostem weight, leaf diameter, leaf length and pseudostem diameter; and leaf length with pseudostem weight, pseudostem diameter and leaf diameter; pseudostem weight with pseudostem diameter and number of scale; leaf diameter with pseudostem weight and pseudostem diameter; pseudostem with number of scale.By simple regression analysis, pseudostem lengh, leaf lengh more influences on plant height, pseudostem weight, leaf diameter, pseudostem diameter had more influences on plant weight. Pseudostem diameter had more influences on pseudostem weight, and numbers of scale had more influences on pseudostem diameter. By step regression analysis, the most important factors that affected welsh onion yield were pseudostem weight, numbers of function leaf, number of scale and plant weight. The optimum regressive equation was y=-549.204+6.201x₇+124.504x₅+84.126x9+2.751x₂By principal components analysis, the first principal component was weight factor, the second principal component was diameter factor, the third and the fourth principal component were length factor, and the fifth principal component was photosynthetic factor.