Chestnut rose (Rosa roxburghii Tratt) is a rare fruit crop of promising economical importance in fruit and ornamental exploitation in China. Isolation of high quality RNA from chestnut rose is difficult due to its high levels of polyphenols, polysaccharides and other compounds, but a modified CTAB extraction procedure without phenol gave satisfactory results. High concentrations of PVP (2%, w/v), CTAB (2%, w/v) and b-mercaptoethanol (4%, v/v) were used in the extraction buffer to improve RNA quality. The average yield was about 200 lg RNA g)1 fresh leaves. The isolated RNA was of sufficient quality for construction of suppression subtraction hybridization (SSH) library, which allowed the isolation of several pathogeninduced defense genes.

Toll and interleukin-1 receptor (TIR) and nonTIR nucleotide binding site-leucine rich repeat (NBS-LRR) resistance gene analogues (RGAs) were obtained from chestnut rose (Rosa roxburghii Tratt) by two PCR-based amplification strategies (direct amplification and overlap extension amplification) with degenerate primers designed to the conserved P-loop, kinase-2, and Gly-Leu-Pro-Leu (GLPL) motifs within the NBS domain of plant resistance gene (Rgene) products. Thirty-four of 65 cloned PCR fragments contained a continuous open reading frame (ORF) and their predicted protein products showed homology to the NBS-LRR class R proteins in the GenBank database. These 34 predicted protein sequences exhibited a wide range (19.5-99.4%) of sequence identity among them and were classified into two distinct groups by phylogenetic analysis. The first group consisted of 23 sequences and seemed to belong to the nonTIR NBS-LRR RGAs, since they contained group specific motifs (RNBS-A-nonTIR motif) that are often present in the coiled-coil domain of the nonTIR NBS-LRR class R genes. The second group comprised 11 sequences that contained motifs found in the TIR domain of TIR NBS-LRR class R genes. Restriction fragment length polymorphic (RFLP) markers were developed from some of the RGAs and used for mapping powdery mildew resistance genes in chestnut rose. Three markers, RGA22C, RGA4A, and RGA7B, were identified to be linked to a resistance gene locus, designated CRPM1 for chestnut rose powdery mildew resistance 1, which accounted for 72% of the variation in powdery mildew resistance phenotype in an F1 segregating population. To our knowledge, this is the first report on isolation, phylogenetic analysis and potential utilization as genetic markers of RGAs in chestnut rose.

采用刺梨‘贵农6号’（抗）ב贵农5号’（感）正反交获得的F1代群体, 对刺梨白粉病抗性的遗传倾向进行研究。结果表明, F1 代杂种的抗病性呈正态分布, 正反交群体病情指数的遗传传递力（Ta）明显高于亲中值, 广义遗传力（H2）分别为61.0%和60.4%; 按病情指数的大小, F1 代群体可明显聚为高抗、中抗和感病等3类, 经X2 检测符合1∶2∶1分离比率, 推测抗病性受2对主效基因控制, 且非等位基因间存在积加效应, 还受多个修饰基因的调控作用。

分子标记是继形态学标记、细胞学标记和生化标记之后发展起来的一种新的遗传标记, 已广泛应用于园艺植物上。本文综述了分子标记技术在园艺植物种质资源遗传多样性评价、遗传变异检测、遗传图谱构建、分子克隆、分子标记辅助选择育种等领域上的研究进展。文中还就分子标记在园艺植物遗传育种上存在的问题进行了探讨。