Zhang L P, Khan A, Niño-Liu D, Foolad M R
Department of Horticulture, The Pennsylvania State University, University Park 16802, USA.
Genome. 2002 Feb;45(1):133-46. doi: 10.1139/g01-124.
A molecular linkage map of tomato was constructed based on a BC1 population (N = 145) of a cross between Lycopersicon esculentum Mill. line NC84173 (maternal and recurrent parent) and Lycopersicon hirsutum Humb. and Bonpl. accession PI126445. NC84173 is an advanced breeding line that is resistant to several tomato diseases, not including early blight (EB) and late blight (LB). PI126445 is a self-incompatible accession that is resistant to many tomato diseases, including EB and LB. The map included 142 restriction fragment length polymorphism (RFLP) markers and 29 resistance gene analogs (RGAs). RGA loci were identified by PCR amplification of genomic DNA from the BC1 population, using ten pairs of degenerate oligonucleotide primers designed based on conserved leucine-rich repeat (LRR), nucleotide binding site (NBS), and serine (threonine) protein kinase (PtoKin) domains of known resistance genes (R genes). The PCR-amplified DNAs were separated by denaturing polyacrylamide gel electrophoresis (PAGE), which allowed separation of heterogeneous products and identification and mapping of individual RGA loci. The map spanned 1469 cM of the 12 tomato chromosomes with an average marker distance of 8.6 cM. The RGA loci were mapped to 9 of the 12 tomato chromosomes. Locations of some RGAs coincided with locations of several known tomato R genes or quantitative resistance loci (QRLs), including Cf-1, Cf-4, Cf-9, Cf-ECP2, rx-1, and Cm1.1 (chromosome 1); Tm-1 (chromosome 2); Asc (chrromosme 3); Pto, Fen, and Prf (chromosome 5); 01-1, Mi, Ty-1, Cm6.1, Cf-2, CF-5, Bw-5, and Bw-1 (chromosome 6); I-1, 1-3, and Ph-1 (chromosome 7); Tm-2a and Fr1 (chromosome 9); and Lv (chromosome 12). These co-localizations indicate that the RGA loci were either linked to or part of the known R genes. Furthermore, similar to that for many R gene families, several RGA loci were found in clusters, suggesting their potential evolutionary relationship with R genes. Comparisons of the present map with other molecular linkage maps of tomato, including the high density L. esculentum x Lycopersicon pennellii map, indicated that the lengths of the maps and linear order of RFLP markers were in good agreement, though certain chromosomal regions were less consistent than others in terms of the frequency of recombination. The present map provides a basis for identification and mapping of genes and QTLs for disease resistance and other desirable traits in PI126445 and other L. hirsutum accessions, and will be useful for marker-assisted selection and map-based gene cloning in tomato.
基于番茄栽培种（Lycopersicon esculentum Mill.）品系NC84173（母本及轮回亲本）与多毛番茄（Lycopersicon hirsutum Humb. and Bonpl.）种质PI126445杂交产生的BC1群体（N = 145）构建了番茄分子连锁图谱。NC84173是一个先进的育种品系，对几种番茄病害具有抗性，但不包括早疫病（EB）和晚疫病（LB）。PI126445是一个自交不亲和的种质，对许多番茄病害具有抗性，包括早疫病和晚疫病。该图谱包含142个限制性片段长度多态性（RFLP）标记和29个抗病基因类似物（RGA）。通过使用基于已知抗病基因（R基因）的保守富含亮氨酸重复序列（LRR）、核苷酸结合位点（NBS）和丝氨酸（苏氨酸）蛋白激酶（PtoKin）结构域设计的10对简并寡核苷酸引物，对BC1群体的基因组DNA进行PCR扩增来鉴定RGA位点。PCR扩增的DNA通过变性聚丙烯酰胺凝胶电泳（PAGE）进行分离，这使得能够分离异质产物并鉴定和定位各个RGA位点。该图谱覆盖了12条番茄染色体的1469厘摩，平均标记间距为8.6厘摩。RGA位点被定位到12条番茄染色体中的9条上。一些RGA的位置与几个已知的番茄R基因或数量抗性位点（QRL）的位置重合，包括Cf-1、Cf-4、Cf-9、Cf-ECP2、rx-1和Cm1.1（第1染色体）；Tm-1（第2染色体）；Asc（第3染色体）；Pto、Fen和Prf（第5染色体）；01-1、Mi,、Ty-1、Cm6.1、Cf-2、CF-5、Bw-5和Bw-1（第6染色体）；I-1、I-3和Ph-1（第７染色体）；Tm-2a和Fr1（第9染色体）；以及Lv（第12染色体）。这些共定位表明RGA位点要么与已知R基因连锁，要么是其一部分。此外，与许多R基因家族类似，发现几个RGA位点成簇存在，表明它们与R基因可能存在进化关系。将本图谱与其他番茄分子连锁图谱（包括高密度的番茄栽培种×潘那利番茄图谱）进行比较表明，图谱长度和RFLP标记的线性顺序吻合良好，尽管某些染色体区域在重组频率方面不如其他区域一致。本图谱为鉴定和定位PI126445及其他多毛番茄种质中抗病性和其他优良性状的基因及QTL提供了基础，并且将有助于番茄的标记辅助选择和基于图谱的基因克隆。
