Variability, Inheritance, And QTL Mapping Of Output Of Tofu And Soymilk Of Soybean From Huang-Huai-Hai And Southern China

Tofu and soymilk are always the most important sources of traditional food and vegetable protein of China. In recent years, soybean food is increasing by degrees as 10%, and the consumption of tofu and soymilk goes up 15% every year in America. Several studies have indicated that tofu output of landraces have significant diversity. The variation of tofu output from Southern China and Huang-Huai-Hai Area was large enough and the mean values of tofu output from Southern China were significantly larger than that from Huang-Huai-Hai Area. There is possible to select specific germplasm from landraces for tofu production. Special cultivars of high output of tofu and soymilk are required to be raw materials due to the development of producing modernization of tofu and soymilk. The main objectives of this study were: (1) On the base of improving the measurement technology of tofu and soymilk output for large amount of mini-specimen in laboratory, probing the variation of output of tofu and soymilk of cultivars and part of excellent landraces from Huang-Huai-Hai and Southern China, and expecting cultivars with high output selected as raw materials for production and elite germplasms as breeding parents to further improvement; (2) revealing inheritance mechanism and mapping QTLs of output of tofu and soymilk related genes. The results of this study will be helpful for high ouput of tofu and soymilk in soybean breeding.A sample consisted of 176 accessions, including 126 cultivars, 16 lines and 34 landraces being the main ancestor parents of cultivars, was used to study the variation of output of dried tofu, wet tofu and dried soymilk and used in this experiment carried out in summer, 2005 in Nanjing. The standard of elite accessions is that output of dried tofu, wet tofu and dried soymilk are with mean values more than 10 percent, supplying varieties for processing tofu and soymilk from source of Great Wall, and searching elite germplasms for high output of tofu and soymilk. The results were as follows: (1) There existed large variation of output of dried tofu, wet tofu and dried soymilk, of soybean from Huang-Huai-Hai and Southern China, with a range of 45.60～73.53g, 368.74～622.14g and 58.05～83.33g, and the highest values being with mean values more than 31.14%, 17.33% and 17.71%. The results in Huang-Huai-Hai and Southern China showed a similar tendency as in low values of the three traits, with varieties of high values in Southern China being more than that in Huang-Huai-Hai Area. Cultivars of high output of tofu and soymilk were mainly in summer planting season type, with averages of the highest values being in autumn planting season type. Cultivars of high output of tofu and soymilk after 1995 were similar as that before 1995; (2) 29 cultivars with high output of tofu and soymilk were selected, with more materials from Southern China than that from Huang-Huai-Hai Area, including 17 and 12 cultivars, respectively, with 3 elite accessions with three high outputs, Nannongcaidou No.5, Narmongcaidou No. 1 and Xiangchundou 16 from Southern China.The RIL population NJRISX with 176 families was derived from the cross Su88-M21×Xinyixiaoheidou providing by National Center for Soybean Improvement to reveal the genetic mechanism of output of dried tofu, wet tofu and dried soymilk in soybean. Genetic analysis were performed under major gene + polygene mixed inheritance model in the P₁, P₂, RIL of the cross Su88-M21×Xinyixiaoheidou which was tested in two cropping years (2005 and 2006). The gene loci of the three traits might decentralize different parents since the segregation of over-parents in RIL population with the wide range of 44.31～66.48, 330.42～509.56 and 56.34～77.00 g/100 g, respectively. The results showed that mean values of dried tofu and soymilk output were controlled by one major genes plus polygenes, with the major gene heritability of 52.63% and 51.88%, respectively, and polygene heritability of 8.32% and 24.63%, respectively. Output of wet tofu was controlled by two major genes plus polygenes, with the major gene heritability of 53.29%, and polygene heritability of 25.76%. Correlation analyses between the three traits showed that positive correlations with significant level of 1% were found among output of dried tofu and wet tofu, dried soymilk (0.62,0.73), between output of wet tofu and dried soymilk (0.49) in 2005; and among output of dried tofu and wet tofu, dried soymilk (0.67,0.51), between output of wet tofu and dried soymilk (0.58) in 2006.Based on the genetic research above, QTL mapping for output of tofu and soymilk in soybean was carried out as following. The RIL population NJRISX with 176 families of the cross Su88-M21×Xinyixiaoheidou was tested for their genetic variation, and then used to construct a genetic linkage map, containing 131 SSR markers, spanning 24 linkage groups (LG) at a total distance of 2044.6 cM, with an average distance of 15.6 cM between the flanking markers by using MAPMAKER 3.0 procedure. QTLs were mapped with both composite interval mapping (CIM) and multiple interval mapping (MIM) of the software Win QTL Cartographer Version 2.5 on output of dried tofu, wet tofu and dried soymilk. The major QTL qODT-A2-1 associated with dried tofu output, explaining 15.7%～28.2% of the total phenotypic variation was identified between Satt424 and Sat₁62 on LG A2; the major QTL qODS-A2-1 related to dried soymilk output, explaining 30.0%～34.8% of the phenotypic variation was also between Satt424 and Sat₁62 on LG A2; and two major QTLs qOWT-A2-1 and qOWT-L associated with wet tofu output, explaining 20.7%～30.7% and 19.0%～27.4% of the total phenotypic variation were identified between Satt424 and Sat₁62 on the Linkage group A2 and between Satt481 and Sat₃97 on linkage group L, respectively. The results from segregation analysis showed that dried tofu and soymilk output were controlled by one major gene plus polygenes, respectively, and wet tofu output was by two unlinked major genes plus polygenes. By comparison, the number of major genes, explained proportion of phenotypic variation by the major genes, and relative contribution of major gene vs. ploygene from segregation analysis and QTL mapping were similar, and both analyses could be used for verification each other. Both major genes and polygenes should be emphasized in breeding for output of tofu and soymilk.But the results of this research are preliminary and tentative. For the number of output of dried tofu, wet tofu and dried soymilk of genes and their exact positions are still to be known. Therefore, further research work on this field should be continued. Elite accessions of cultivars with high output of tofu and soymilk haven't been applied to production.