Genetic diversity and geographic pattern of wild lotus (Nelumbo nucifera) in Heilongjiang Province

摘要

Based on 47 accessions from Ussuri River Valley, Songhua River Valley and Heilong River Valley together with 2 accessions from Russia and 27 accessions of cultivated lotus from other provinces in China, genetic diversity of wild lotus (Nelumbo nucifera) were revealed using RAPD and ISSR markers. Twenty RAPD primers generated 113 loci, of which 71.68 percent were polymorphic across all samples. The expected heterozygosity was 0.1583. The percentage of polymorphic loci and expected heterozygosity in the wild lotus were 50.44 percent and 0.1241, respectively. The parameters of the cultivated lotus were slightly higher, 53.98 percent and 0.1651 correspondingly. Sixteen ISSR primers produced 90 loci. The percentages of polymorphic loci and expected heterozygosity were 41.11 percent and 0.0851 at species level, 28,89 percent and 0.0661 for the wild lotus, and 32.22 percent and 0.0963 for the cultivated lotus. AMOVA analysis of the wild lotus showed that a small number of variances exist among the 3 river valleys (21.68 percent for RAPD with G_(st)=0.1312 and 15.11 percent for ISSR with G_(st)=0.1352). The molecular variances of both the wild and the cultivated lotuses came predominantly from within the 3 river valleys and the cultivated samples (73.25 percent for RAPD and 81.11 percent for ISSR). Variance components from the wild and the cultivated lotus accounted for 19.17 percent for RAPD and 13.17 percent for ISSR, and variations among the valleys and the culta seemed the least important (7.585 for RAPD and 5.725 for ISSR). Neighbor-joining analysis demonstrated that considerable differentiation happened between the wild and the cultivated lotus. The wild lotus at middle reaches of the Songhua River Valley seemed to be the centre of remnants, from which it spread to the Ussuri River Valley and the Heilong River Valley. The very limited genetic diversity suggests that the wild lotus has experienced severe bottleneck effect, founder effect and rebirth effect. Considering its long evolutionary history, scarcity of genetic variations and importance in wetland ecosystems, we appeal to take lawful measures to protect the wild lotus. For conservation purpose, special attention should be paid to the lotus at the middle reaches of the Songhua River Valley.