分子标记辅助选择为选育由多基因控制的或易受环境影响的性状提供了一条有效的途径。番茄分子标记的开发工作已经进行了三十多年，到目前为止已有2300多个不同类型的分子标记被开发和定位到12条染色体上。很多文献对这些分子标记的特点及其在番茄遗传育种中的应用进行了综述，但对其开发过程却很少提及。因此本文就主要类型的番茄分子标记的开发进展进行概括并分析其开发前景。

番茄疮痂病是世界上所有番茄种植地区主要的细菌性病害之一，该病能引起严重的产量损失和品质下降，几十年来一直受到育种界的关注。由于该病病原菌存在多个种和小种以及对该病的抗性呈数量性状遗传，因此通过育种途径来改良抗性进展缓慢。分子标记辅助选择为育种家筛选、聚合或累加对多个小种的抗性提供了一种工具。以前的综述对1997年以前在病害的发生、症状、危害、综合防治、遗传分析和育种等方面的研究进行了较为详尽的总结。近年来，在病原菌种与小种的鉴定、抗源的发掘抗性遗传的分子定位和分子标记辅助选择方面的研究取得了很大进展，传统育种与分子生物学方法有机结合的策略也初见成效。本文将对这些进展进行总结，并对分子标记在番茄疮痂病抗性育种中的应用前景进行讨论。

The lack of resistance to bacterial diseases increases both the fi nancial cost and environmental impact of tomato (Lycopersicon esculentum Mill.) production while reducing yield and quality. Because several bacterial diseases can be present in the same fi eld, developing varieties with resistance to multiple diseases is a desirable goal. Bacterial spot (caused by four Xanthomonas Dowson species) and bacterial speck (caused by Pseudomonas syringae pv. tomato Young, Dye and Wilkie) are two economically important diseases of tomato with a worldwide distribution. The resis-tance gene Pto confers a hypersensitive response (HR) to race 0 strains of the bacterial speck pathogen. The locus Rx3 explains up to 41% of the variation for resistance to bacterial spot race T1 in fi eld trials, and is associated with HR following infi ltration. Both Pto and Rx3 are linked in repulsion phase on chromosome 5. We made a cross between two elite breeding lines, Ohio 981205 carrying Pto and Ohio 9834 carrying Rx3, to develop an F2 population and subsequent inbred generations. Marker-assisted selection (MAS) was applied to the F2 progeny and to F2:3 families in order to select for coupling-phase resistance. Thirteen homozygous progeny from 419 F2 plants and 20 homozygous families from 3716 F3 plants were obtained. Resistance was confi rmed in all selected families based on HR in greenhouse screens using bacterial speck race 0 and bacterial spot race T1 isolates. Resistance to bacterial spot race T1 was confi rmed in the fi eld for 33 of the selected families. All selected families were also resistant to bacterial speck in the fi eld. MAS was an effi cient tool to select for desirable recombination events and pyramid resistance.

Yang, W., Sacks, E. J., Lewis Ivey, M. L., Miller, S. A., and Francis, D. M. 2005. Resistance in Lycopersicon esculentum intraspecific crosses to race T1 strains of Xanthomonas campestris pv. vesicatoria causing bacterial spot of tomato. Phytopathology 95: 519-527. We used molecular markers to identify quantitative trait loci (QTL) that confer resistance in the field to Xanthomonas campestris pv. vesica-toria race T1, a causal agent of bacterial spot of tomato. An F2 population derived from a cross between Hawaii 7998 (H 7998) and an elite breeding line, Ohio 88119, was used for the initial identification of an association between molecular markers and resistance as measured by bacterial populations in individual plants in the greenhouse. Polymorphism in this cross between a Lycopersicon esculentum donor of resistance and an elite L. esculentum parent was limited. The targeted use of a core set of 148 polymerase chain reaction-based markers that were identified as polymor-phic in L. esculentum × L. esculentum crosses resulted in the identifica-tion of 37 markers that were polymorphic for the cross of interest. Previous studies using an H 7998 × L. pennellii wide cross implicated three loci, Rx1, Rx2, and Rx3, in the hypersensitive response to T1 strains. Markers that we identified were linked to the Rx1 and Rx3 loci, but no markers were identified in the region of chromosome 1 where Rx2 is located. Single marker-trait analysis suggested that chromosome 5, near the Rx3 locus, contributed to reduced bacterial populations in lines carry-ing the locus from H 7998. The locus on chromosome 5 explained 25% of the phenotypic variation in bacterial populations developing in infected plants. An advanced backcross population and subsequent inbred back-cross lines developed using Ohio 88119 as a recurrent parent were used to confirm QTL associations detected in the F2 population. Markers on chromosome 5 explained 41% of the phenotypic variation for resistance in replicated field trials. In contrast, the Rx1 locus on chromosome 1 did not play a role in resistance to X. campestris pv. vesicatoria race T1 strains as measured by bacterial populations in the greenhouse or symp-toms in the field. A locus from H 7998 on chromosome 4 was associated with susceptibility to disease and explained 11% of the total phenotypic variation. Additional variation in resistance was explained by plant matur-ity (6%), with early maturing families expressing lower levels of resis-tance, and plant habit (6%), with indeterminate plants displaying more resistance. The markers linked to Rx3 will be useful in selection for resistance in elite × elite crosses.