National Maize Improvement Center of China, China Agricultural University, 2 West Yuanmingyuan Road, Beijing, 100193, People's Republic of China.
Theor Appl Genet. 2010 Aug;121(4):673-87. doi: 10.1007/s00122-010-1339-0. Epub 2010 Apr 17.
Fusarium graminearum Schwabe, the conidial form of Gibberella zeae, is the causal fungal pathogen responsible for Gibberella stalk rot of maize. Using a BC(1)F(1) backcross mapping population derived from a cross between '1145' (donor parent, completely resistant) and 'Y331' (recurrent parent, highly susceptible), two quantitative trait loci (QTLs), qRfg1 and qRfg2, conferring resistance to Gibberella stalk rot have been detected. The major QTL qRfg1 was further confirmed in the double haploid, F(2), BC(2)F(1), and BC(3)F(1) populations. Within a qRfg1 confidence interval, single/low-copy bacterial artificial chromosome sequences, anchored expressed sequence tags, and insertion/deletion polymorphisms, were exploited to develop 59 markers to saturate the qRfg1 region. A step by step narrowing-down strategy was adopted to pursue fine mapping of the qRfg1 locus. Recombinants within the qRfg1 region, screened from each backcross generation, were backcrossed to 'Y331' to produce the next backcross progenies. These progenies were individually genotyped and evaluated for resistance to Gibberella stalk rot. Significant (or no significant) difference in resistance reactions between homozygous and heterozygous genotypes in backcross progeny suggested presence (or absence) of qRfg1 in '1145' donor fragments. The phenotypes were compared to sizes of donor fragments among recombinants to delimit the qRfg1 region. Sequential fine mapping of BC(4)F(1) to BC(6)F(1) generations enabled us to progressively refine the qRfg1 locus to a ~500-kb interval flanked by the markers SSR334 and SSR58. Meanwhile, resistance of qRfg1 to Gibberella stalk rot was also investigated in BC(3)F(1) to BC(6)F(1) generations. Once introgressed into the 'Y331' genome, the qRfg1 locus could steadily enhance the frequency of resistant plants by 32-43%. Hence, the qRfg1 locus was capable of improving maize resistance to Gibberella stalk rot.
镰刀菌禾谷种（Schwabe），即玉蜀黍赤霉（Gibberella zeae）的分生孢子形式，是引起玉米赤霉茎腐病的致病真菌。利用来自“1145”（供体亲本，完全抗性）和“Y331”（轮回亲本，高度敏感）杂交的 BC(1)F(1)回交群体，已经检测到了两个赋予对玉米赤霉茎腐病抗性的数量性状位点（QTLs），qRfg1 和 qRfg2。主要的 QTL qRfg1 在双单倍体、F(2)、BC(2)F(1)和 BC(3)F(1)群体中得到了进一步确认。在 qRfg1 置信区间内，利用单/低拷贝细菌人工染色体序列、锚定表达序列标签和插入/缺失多态性，开发了 59 个标记来饱和 qRfg1 区域。采用逐步缩小策略来进行 qRfg1 基因座的精细作图。从每个回交世代中筛选出 qRfg1 区域内的重组体，与“Y331”回交以产生下一个回交后代。这些后代个体进行基因型分析并评估对玉米赤霉茎腐病的抗性。在回交后代中，纯合和杂合基因型之间的抗性反应有显著（或无显著）差异，表明供体片段“1145”中存在（或不存在）qRfg1。将表型与重组体中供体片段的大小进行比较，以确定 qRfg1 区域的范围。通过对 BC(4)F(1)到 BC(6)F(1)世代的连续精细作图，我们能够将 qRfg1 基因座逐渐精确定位到 SSR334 和 SSR58 标记之间的~500-kb 区间。同时，还在 BC(3)F(1)到 BC(6)F(1)世代中研究了 qRfg1 对玉米赤霉茎腐病的抗性。一旦被导入“Y331”基因组，qRfg1 基因座就可以通过 32-43%的频率稳定提高抗性植株的频率。因此，qRfg1 基因座能够提高玉米对玉米赤霉茎腐病的抗性。
