Villalta I, Reina-Sánchez A, Cuartero J, Carbonell E A, Asins M J
Instituto Valenciano de Investigaciones Agrarias, Apdo. Oficial, 46113, Moncada-Valencia, Spain.
Theor Appl Genet. 2005 Mar;110(5):881-94. doi: 10.1007/s00122-004-1906-3. Epub 2005 Feb 3.
A population of recombinant inbred lines (RILs) has several advantages over its F2 population counterpart with respect to quantitative trait loci (QTLs) and genomic studies. The objective of the investigation reported here was the comparative characterization by simple sequence repeat (SSR) and sequence characterized amplified region (SCAR) markers of two populations of F6 lines derived from Lycopersicon pimpinellifolium (P population, consisting of 142 lines) and L. cheesmanii (C population, consisting of 115 lines) and sharing the female parent, L. esculentum var. cerasiforme. Almost the same percentage of polymorphic markers was found for each population although a different set of markers was involved. The proportion of SSR primer pairs (93 in total) that resulted in polymorphism for the main band was larger (55-56%) than for SCAR ones (13-16%). The C population showed the largest proportion of markers with zygotic and gametic segregation distortion, which is in agreement with the larger genetic distance reported between L. esculentum and L. cheesmanii than with the former and L. pimpinellifolium. Zygotic distortion corresponded primarily to an excess of heterozygotes in both populations, suggesting that the increment of homozygosity was the main factor limiting viability/self-fertility of the lines. Despite both populations sharing the female parent, P alleles were slightly favored in the P population while E alleles were the most frequently fixed in the C population. A linkage map for each population was obtained, with the average distances between consecutive markers being 3.8 cM or 3.4 cM depending on the population. Discrepancy between the maps for the location of only four markers on chromosomes 3, 6 and 10 was observed. Two possible causes of this discrepancy were investigated and can not be discarded: (1) the presence of duplicated markers and (2) segregation distortion caused by the selective advantage of gametes carrying one of the two alleles. This marker characterization of both populations will continue and will enable the comparative QTLs and candidate gene analysis of complex traits towards a more efficient utilization of genetic resources and breeding strategies.
在数量性状基因座（QTL）和基因组研究方面，重组自交系（RIL）群体相较于其对应的F2群体具有若干优势。本文所报道的研究目的是，通过简单序列重复（SSR）和序列特征化扩增区域（SCAR）标记，对源自微小番茄（P群体，由142个株系组成）和契斯曼尼番茄（C群体，由115个株系组成）且共享母本樱桃番茄的两个F6株系群体进行比较特征分析。尽管涉及的标记不同，但每个群体中发现的多态性标记比例几乎相同。导致主带出现多态性的SSR引物对（总共93对）比例（55 - 56%）高于SCAR引物对（13 - 16%）。C群体中具有合子和配子分离畸变的标记比例最大，这与报道的番茄与契斯曼尼番茄之间的遗传距离大于番茄与微小番茄之间的遗传距离一致。合子畸变主要对应于两个群体中杂合子过量，这表明纯合度的增加是限制株系活力/自交育性的主要因素。尽管两个群体共享母本，但P等位基因在P群体中略占优势，而E等位基因在C群体中最常被固定。获得了每个群体的连锁图谱，根据群体不同，相邻标记之间的平均距离为3.8 cM或3.4 cM。观察到3号、6号和10号染色体上仅四个标记的图谱位置存在差异。对这种差异的两个可能原因进行了研究且无法排除：（1）存在重复标记；（2）携带两个等位基因之一的配子的选择优势导致的分离畸变。这两个群体的标记特征分析将继续进行，并将有助于对复杂性状进行比较QTL和候选基因分析，以更有效地利用遗传资源和育种策略。
