QTL Identification for Plant Height in a New Dwarf Germplasm of Maize

Abstract

Dwarf germplasm is important for both breeding programs and basic researches in maize (Zea mays L.). Previously we found a naturally occurred dwarf mutant from the inbred "K36" and developed a new dwarf germplasm, "Ai 2003", with good agronomical performance. Classical genetic analysis showed that this dwarfing character was controlled by a major single reces-sive nuclear gene. However, the character of plant height in the germplasm is also likely associated with other genetic loci. There-fore, quantitative trait locus (QTL) analysis was conducted to elucidate the genetic basis of plant height of this dwarf germplasm by using a segregating population consisting of 255 F2:3 lines derived from a cross between Ai 2003 and a normal inbred, Ji 257. A genetic linkage map was constructed by 114 polymorphism simple sequence repeat (SSR) markers covering the entire maize genome. The total map length was 2 852.1 cM, with an average distance of 27.4 cM between markers. Composite interval map-ping (CIM) was used to identify the genes/QTLs controlled plant height based on the phenotypic characterization of 255 F2:3 fami-lies in Beijing and Hainan in 2006. The same three QTLs located on chromosomes 1 and 2 were identified under both environ-ments, explaining 4.8% to 50.5% of the phenotypic variances, among which, one major QTL located in the region of bin 1.10–1.11 explained 50.5% and 37.5% of the phenotypic variation in Beijing and Hainan, respectively. A further sequences analy-sis revealed that the QTL is located in the 20–30 cM interval downstream of dwarf plant8 (d8), a well-known maize dwarf gene, implying that the locus is a gene newly discovered for controlling plant height in maize.