Variation and probability grading of main quantitative traits of male flowers for Eucommia ulmoides germplasm.

To make better evaluation and utilization, 14 main quantitative traits of 193 male flowers of Eucommia ulmoides germaplasm were studied through variation analysis and probability grading. The results showed that a large variation was observed in the quantitative traits of the flowers, coefficients of variation of the 14 quantitative traits were all above 12%, in which the highest occurred in geniposide content (112.00%), followed by astragaline content (89.56%) and geniposidic acid content (88.60%), and the smallest occurred in amino acids content (12.52%). According to the K-S test, flower height, stamen length, stamen number, aucubin content, chlorogenic acid content, isoquercitrin content, total flavonoids content and amino acid content all conformed to the normal distribution; flower diameter, fresh weight and dry weight that followed skewed distribution could be regarded and treated as those conforming to normal distribution; geniposidic acid content, geniposide content and astragaline content did not conform to normal distribution. Eleven quantitative traits that conformed to the normal distribution could be divided into 5 grades by 4 dividing points: X-1.281 8S, X-0.524 6S, X+0.524 6S and X+1.281 8S, while other 3 traits could be divided into 5 grades according to the actual distribution. The occurrence probability of grade 1-5 was 10%, 20%, 40%, 20% and 10%, respectively. An index system of probability grading for 14 quantitative traits was built, which could provide important guidelines for E. ulmoides breeding program and quality control of male flower related products, and meanwhile, it could provide a reference for specification and data standardization of E. ulmoides male flowers descriptor system.