| Maize (Zea mays L.) is an important food and forage crop. Recently, steps towards high yield, good quality and resistance in maize breeding programs have been limited due to a reduced genetic background in the maize germplasm. Maize breeders have been exploring different maize germplasm varieties for suitable genes to further enhance maize yield and in doing so, anticipate a breakthrough in maize breeding advancements. Stay-green is a generalterm applied to a variant in which senescence is delayed, compared to a standard reference genotype, and is regarded as a desirable character closely related to yield, forage character and resisitance. The stay-green maize varieties is the most valuable one nowadays. The inheritance of stay-green were studied focused on stay-green germplasm certification, genetic analysis and quantitative trait loci (QTL) mapping. The main results were as follows:1. Thirty elite maize inbred lines were evaluated for stay-green. The results showed that 4 lines (Shen3195, Shen137, Q319 and 178 ) had good stay-green trait, and others had normal or bad stay-green trait. The cluster analysis by SSR markers showed that 30 inbreds could be classified into 6 distinct groups. The 4 stay-green inbreds were found in 2 sources (B and E), respectively and could be used to improve the bad stay-green lines in the same group.2. The inheritance of stay-green was studied in progenies derived from four crosses between two stay-green lines, Q319 or 178, and two non-stay-green lines, Mo17 and BM. The results showed that additive and dominant gene effect as well as gene interactions could be found in the inheritance of stay-green. The broad heritability for stay-green ranged from 59.93% to 76.82% and the ratio of narrow heritability to genetic heritability ranged from 40.70% to 60.10%. Q319 and 178 were estimated to contain at least two and one stay-green genes, respectively.3. A genetic linkage map containing 115 SSR markers and 10 linkage groups was constructed, which spanned a total of 1431.0 cM with an average maker interval of 12.44 cM. Compared with other published maize linkage map in chromosome bin locus, the linkage map established in this study was consistent with them. The SSR linkage map can be used for QTL mapping.4. The major traits(stay-green degree, number of green leaf, chlorophyll content of leaf, emergence-anthesis interval, emergence-pollination interval, emergence-pollination interval, antheisis-silking interval, plant height, ear height, ear length, bald tip length, ear diameter, ear rows, row grains, percent grain, 1000-grain weight, individual plant yield) related to stay-green of 166 F2:3 family lines were surveyed an analysed. The results showed that the average values of all traits are significant among family lines. Correlation analysis showed significant correlations between stay-green traits at different days after flowering (DAF) and some yield-related traits such as ear diameter, 1000-grain weight and plant yield.5. By composite interval mapping(LOD≥2.5), 80 QTLs were detected for traits related to stay-green, in wich 31 QTLs were major effect QTLs(R2≥10%). Each traits have been identified 1–8 QTLs, which were responsible interpreting 4.68–24.75% of phenotypic variance individually, and showed partial dominant effect and over dominant.6. This results also showed that some QTLs trend to cluster the same chromosome region. The six key chromosome regions for stay-green mostly lie on following chromosome: chromosome 1, 115.0–125.0 cM and 140.0– 155.0 cM; chromosome 2, 95.0–110.0 cM; chromosome 5, 50.0–55.0 cM; chromosome 8, 0–10.0 cM; chromosome 9, 50.0–60.0 cM.7. Compared with the results of previous study, our study not only detected the similar stay-green QTLs reported previously, but also found out many new QTLs. The QTLs got in this study not only offered new information for understanding stay-greeen traits of maize, but also provided a potential starting point for marker assisted selection of maize stay-green .
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