Dynamic QTL Analysis Of Sugar Content In Stalk At Different Developmental Stages Of Maize

Improving the quality of silage is very important for the development of animal husbandry. For silage maize, sugar content in the stem is one of important factors that affect quality and palatability. However, the sugar content of stalk in maize is a complicated quantitative trait. Conventional static mapping(SM) can not reveal the gene number completely and some important information about dynamic expression. Dynamic mapping method can use genetic information at different developmental stages, greatly improve the power and accuracy of QTL mapping, and reveal the dynamic expression of QTL. In this research, in order to have deep understanding for the sugar content of genetic variation patterns and breeding high sugar content of stalk in maize, we made systematic researches on constructing recombinant inbred lines (RILs) population and used dynamic mapping (DM) methods to estimate the QTL effects at different developmental stages in maize.In this research, two hundred and two F7recombinant inbred lines population derived from the cross of stalk high sugar maize inbred line’YXD053’and stalk low sugar maize inberd line ’Y6-1’and a high-density genetic map which contain180SSR and10AFLP marker were used for the identifcation of QTL underlying sugar content of stalk from the0day to40day stages after flowering, at Yangzhou in2011and2012.To provide theoretical base and practical guide for subservient and marker-assisted selection (MAS) breeding of high quality varieties and cloning of genes of high quality traits in maize of our country, we discuss the hereditary basis of sugar content of stalk in maize.Main conclusion as follows:1. Using200pairs SSR molecular markers that polymorphism were good and the bands were clear (polymorphic rate was29.63%) and12AFLP markers to construct a genetic linkage map, the linkage map contains180SSR markers and10AFLP markers, the total length is1648.6cM, the average distance between markers was8.68cM, maximum distance was45.9cM.2. Using WinQTLCart2.5software conforms which is based on composite interval mapping (CIM) method, to analysis unconditional QTL mapping of sugar content of stalks in mazie. A total of37unconditional QTLs were detected in four development period,, except the chromosome7detected no unconditional QTL, the rest of the chromosomes all detect the unconditional QTL which were controlled sugar content of stalks in mazie. One QTL, qWSC-2-1, in bin2.05have been detected during the same period (20days after flowering) in two years, the LOD value was3.64-4.52, which can explain the phenotypic variation of10.03%-11.47%. Three unconditional QTLs, qWSC-2-1, qWSC-9-1, and qWSC-9-3were detected in2011and 2012during different periods. Seven QTLs, qWSC-2-1, qWSC-4-1, qWSC-9-2, qWSC-1-1, and qWSC-2-4, and qWSC-1-3, qWSC-6-1were detected in the same year during different periods. All detected unconditional QTL can explain the phenotypic variation of1.07%-17.73%.3. Using condition variables analysis method combined with interval mapping method to analysis conditional QTL of sugar content of stalks in mazie.Result shows that22conditional QTL were detected in three periods, covering10chromosomes in mazie, and explained1.05%-9.70%phenotypic variations. Every period were all have conditional QTLs, but there is no conditional QTL can express in all periods, the expression of genes have space-time obviously.4. Using QTLNetwork analysis Epistatic epistasis (AA) effect and spistasisxenvironment interaction (AAE) effect of QTL. A total of six epistatic pairwise QTL were identifed in different developmental stages and none of six epistatic parewise QTL had AAE effect. All the epistatic parewise were only identifed at one stage, epistatic effects existed mostly for a short time period.5. Using the markers bnlg1909and umc1635which located the QTL qWSC-2-1on two sides to analysis the effect of Marker-assisted selection of the group. The effect of using unilateral markers and bilateral markers to select sugar content of stalks in mazie all reached significant level (P<0.01). All in above show that the two markers can be used for Marker-assisted selection breeding, cultivating varieties of high sugar content of stalks in mazie.