Liu Qingchang

Development of AFLP markers linked to stem nematode resistance gene in sweet potato ( Ipomoea batatas (L.) Lam.)

Amplified fragment length polymorphism (AFLP) markers linked to the stem nematode resistance gene were developed in sweet potato ( Ipomoea batatas (L.) Lam.). Using bulked segregant analysis (BSA), 800 AFLP primer combinations were screened in the resistant and susceptible bulked DNA from the 186 progeny of an F 1 single-cross population of Xu781 (resistant parent)×Xushu18 (susceptible parent), and 245 of these AFLP primers showed polymorphic bands between resistant and susceptible DNA. Primer combinations detecting polymorphism between the two bulks were used to screen the parents and eight individuals from each of the bulks. The results showed that E2M23 and E33M20 produced a specific band of about 500 bp and 200 bp in length, respectively, in the resistant plants but not in the susceptible plants, suggesting that the markers named E2M23 500 and E33M20 200 linked to a gene for stem nematode resistance. Amplified analysis of the 186 F 1 individuals indicated that the genetic distance between these two markers and the stem nematode resistance gene was 6.9 cM and 11.1 cM, respectively, measured with Mapmaker 3.0. These two AFLP markers were used to identify ten sweet potato varieties planted widely in China and the results were consistent with those of conventional resistance identification, indicating that the two markers can be used in molecular marker-assisted breeding for stem nematode resistance in the sweet potato.

Cloning and sequence analysis of rolC gene affecting ginsenoside content in hairy roots of Panax ginseng C.A. Mey

Ginseng hairy roots were induced from root explants of ginseng by the co-culture of Agrobacterium rhizogenes and ginseng ( Panax ginseng C. A. Mey) roots through direct inoculation. The content of ginsenosides in the ginseng hairy roots after 4 weeks of culture reached the same level as in 3-year-old cultivated ginseng roots, and the content of one ginsenoside (Rb 1 ) increased, showing that left transferred DNA (T L -DNA) has a function of influencing the biosynthesis of ginsenosides. Based on analysis of the RiA 4 T L -DNA sequence, the rolC gene affecting the synthesis of ginsenosides was amplified and cloned from the ginseng hairy roots by PCR. Comparison with a previously published nucleotide sequence showed that the homology was 99.9%.