Three oxanthrones from Aloe littoralis

The leaf exudate of Aloe littoralis yielded, in addition to the known 10-hydroxyaloin B, two new C-glucoside oxanthrones namely 10-hydroxy-15-O-(2R,3S-nilyl)(6′-O-acetyl)aloin B (littoraloin) and 10-hydroxy-15-O-(2R,3S- nilyl)aloin B (deacetyllittoraloin). Their structures were determined by spectroscopic methods as well as by conversion to the known 10-hydroxyaloin B and nilic acid.     

黄土高原丘陵区生物结皮土壤的斥水性

采用滴水穿透时间法和酒精溶液入渗法,研究了黄土高原丘陵区浅色藻结皮、深色藻结皮、藻+少量藓结皮、藓+少量藻结皮、藓结皮5种不同发育阶段的原状生物结皮土壤的斥水性及其与土壤含水量的关系.结果表明: 生物结皮增加了土壤的斥水性,其斥水强度和持久性均显著增加.生物结皮土壤的斥水性随生物结皮的演替逐渐降低,当生物结皮中藓类植物盖度在20%以上时,斥水持久性显著低于藻结皮.生物结皮土壤的斥水性与土壤含水量及优势种密切相关,藓类生物结皮土壤的斥水性随着含水量的降低逐渐增加,藻类生物结皮土壤的斥水性随含水量的变化呈双峰曲线.     

Improvement of the recessive genic male sterile lines with a subgenomic background in Brassica napus by molecular marker-assisted selection

Both the pollination control system and genetic distance are major factors in the utilization of crop heterosis. The recessive genic male sterile line (RGMS) 7-7365A (Bnms3ms3ms4ms4) has been widely applied to hybrid seed production because it can generate a completely male sterile population by crossing with the 7-7365C temporary line (Bnms3ms3rfrf). In this study, the sterile genes of 7-7365A were transferred to the new Brassica napus lines 7-749 and 7-750 with a high content of subgenomes by backcross breeding. We used the amplified fragment length polymorphism (AFLP) technique combined with bulk segregant analysis (BSA) to identify markers linked to the BnMs4 gene. Twelve AFLP markers linked to the BnMs4 gene were identified. Of them, SA06MG09 and P08MG16 were the closest makers, which were on either side of the gene at a distance of 0.9 and 0.8?cM, respectively. Twenty AFLP primer combinations were used to screen the F2, BC1F3, and BC2F4 populations from the breeding program, and the markers linked to the BnMs3 and BnMs4 genes were used to screen the BC2F4 populations. As a result, we obtained two types of improved sterile lines, 7-749A and 7-750A, and their indexes of subgenomic components (ISG) were 44.2?C49.8 and 20.2?C26.6%, respectively. The combining ability analyses of seed yield character were conducted in the crosses from the three sterile lines and ten restorers within a random block design in three environments for two successive years. The general combining ability (GCA) of the two improved sterile lines were significantly higher than the GCA of 7-7365A in every environment tested. The two improved sterile lines had stability in seed yield, and they will be used in the future for hybrid seed production.     

Genetic and phylogenetic studies of Chinese native sheep breeds (Ovis aries) based on mtDNA D-loop sequences

To determine the genetic diversity and the origin of Chinese sheep, we analyzed 83 complete sequences of mtDNA D-loop from nine Chinese sheep breeds and a foreign breed, together with nine sheep and cattle available sequences from GenBank. The length of the sequences was considerably variable between 1103 and 1225 bp. The hapolotype diversity was 92.7%. The nucleotide diversity was 3.058%. And the mean nucleotide composition of the 83 sequences was 32.9% A, 29.8% T, 22.9% C and 14.4% G, respectively. The NJ phylogenetic tree (the number of replications of bootstrap test is 1000) revealed that there were three distinct major domestic sheep lineages (termed as lineages A–C) in the 10 breeds. The result indicated that Chinese native sheep breeds derive from three different maternal sources. The mismatch distribution analysis showed that the Fs values were −25.15, −12.28, −8.60 for the lineages A–C, respectively (P < 0.01), which suggested that atleast one population expansion events occur in the demographic history of Chinese sheep breeds.