Napus New Yellow-seeded Germplasm Resources Identified

The genetic basis of Brassica napus L. (2n=38,AACC), one of the most important oilseed crops worldwide, is quite narrow. As an allopolyploid with a short phylogeny, the specie was originated in Europe and then introduced into China, thus it is important to improve B.napus germplasm.Previous studies showed that yellow seed resource does not exist in natural B.napus, amounts of yellow-seed B.napus obtained were derived from interspecific gene flow between B.napus and B.rapa, B.juncea, B. carinata , whereas yellow-seed related gene introgression from relative genus have never been found. Furthermore, B.napus with yellow seed character obtained by conventional methods behaves common feature—khaki or ginger seed capsule with black spots and brown circular fringe, which is genetically instable and hard to pure by selfling, unlike the delicate yellow of B.rapa and orange yellow of B.juncea. Thus, it is important to carry out germplasm enhancement and expand genetic basis of B.napus, which is significant to broaden yellow seed resources.Distant hybridization, as a valuable measure to germplasm reformation, may overcome genus boundary, enlarge genetic variation, and ultimately resulting the creation of new variants and species. On the other hand, the progenies of hybrids are exempt of bio-safety and available for B.napus breeding and production. In this study, somatic hybrids obtained by protoplast fusion of B.napus and S.alba were applied for meaningful creation of new B.napus germplasm. Through successive backcrossing with B.napus, several progeny lines with advantageous agronomic characters were received, such as yellow-seeded germ, which were taken for further identification and of great value to B.napus breeding. The major findings of this research are as follows:1,Progenies with improved characters from S.alba, such as high pod density, yellow seed, disease resistance, longer silique, multi-seed, were obtained through successive backcrossing, which may greatly contribute to enrichment of B.napus germplasm and act as materials for B.napus breeding of high output, quality and resistance varieties. Our research firstly obtained novel rapeseed with yellow seed color via intergeneric hybridization, which is interested for mechanism discussion of B.napus seed color and yellow seed breeding.2,Comparative anatomy analysis of novel yellow seed resulted that seeds of yellow seed progenies not only resemble to B.napus in anatomic structure, but behave some characters of S.alba. The seed coat pigments were mainly distributed in the palisade layer, the highest quantity of seed coat pigmentation was observed in B.napus and some backcross lines. On the other hand, the seeds of S. alba and several backcross progenies exhibited nearly no pigmentation. The thickness of palisade layer was highest in B.napus, thinnest in S.alba and intermediate in the hybrid progenies. Ornamentation characters of progeny seed surface is reticulation-carve shaped, the same as B.napus, whereas S.alba seed coat manifests the appearance of groove or blister. Cellular area and protein body area of scutellum from backcrossing progeny lines are intermediate of the parents. Oil body exists as two forms—big or small oil body, and its discrepancy is obvious between progenies and parents. These results indicate that introgression of S.alba chromosome or gene fragment is the cause of seed structural mutations in progeny lines.3,GISH analysis with S.alba genome as probe showed that chromosome of B.napus behaves normal pairing and segregation in every generation. While S.alba chromosome mostly exists as univalents, and occasionally form trivalents with B.napus chromosomes, making it possible for chromosome recombination between B.napus and S.alba. GISH of both meiotic and mitotic chromosomes from BC3F1 showed normal chromosome number and no hybrid signal was detected, demonstrating these materials are not addition lines or substitution lines. In addition, we used minisatellite core sequence 33.6 as primer also obtained a specific band of S.alba. Primers TT2-2 designed according to flavonoid biosynthetic genes of Arabidopsis thaliana and Sal resulted from specific product of TT2-2 resulted same sequences between S.alba and yellow seed progenies, illuminating our yellow seed germplasm possess DNA sequences of S.alba. The developed molecular marker Sal of yellow seed may contribute to B.napus breeding.4,Analysis of economical characters, yield traits, quantitative characters and disease resistance of six yellow seed progenies showed that, the dominant degree and uniformity of yellow seed line D244-18 is higher, as well as earlier age of maturity, bigger seeds, higher yield per plant, higher oil content, mediate Sclerotinia selerotiorum resistance. This line is proximal to the double-low quality standards and of great utility value. Line D244-6 possess earlier age of maturity, more effective branches, higher pod density, et al, also next to the nation quality standard, high Sclerotinia selerotiorum resistance,but the dominant degree, uniformity of yellow seed is not up to scratch. Further improvement of D244-6 is needed for making it valuable as breeding material.