Quantitative Trait Locus Analysis Of Stalk Strength In Maize

Maize (Zea mays L.) is a grain crop in Gramimeae, Maudeae. Maize has been one of the most vitalcrops in the world from the aspect of cultivated area and gross product. But lodging is always one of themain limited factors in maize high and stable yield. Systematic research on the genetics of stalk strengthis essential for lodging resistance breeding and increasing maize yield. To elucidate the genetic basis ofthe rind penetrometer resistance, two populations had been constructed. PopulationⅠwas formed bycrossing inbred lines B73with By804, and populationⅡderived from a cross between inbred linesZheng58and HD568. RPR was determined for competitive plants with an electronic rind penetrometer,and plants were probed in the middle of the flat side of the third-internode over ground. Data werecollected over multiple locations and growth periods. Individuals in each population were genotypedwith single nucleotide polymorphisms (SNP), and means combined over environments and periods wereused as trait data to detect major QTL. The main results were as follows:1. As the growth period goes, the value of rind penetrometer resistance(RPR) enhanced distinctlyfrom big trumpet stage to silking stage, and it had a little change at other stages. Stalk strength ofparents and RIL population reached maximum value from30to40days after anthesis period, moreover,transgressive segregation was seen in both populations. The result of complex analysis of varianceindicated that environments, families and periods had significant influence on RPR, and the interactioneffect among different factors had powerful impact on RPR. The narrow sense heritabilities were71.53%and75.58%in each population. Both populations had a similar result indicated a strong geneticbasis of RPR.2. The result of joint analysis of multiple generations in each population implied that theinheritance of maize RPR trait fitted the genetic model of three pairs of additive-epitasis major genesplus additive polygene (G-1model), and the major gene and polygene had equally genetic effects oncontrolling RPR trait in certain environment.3.20,17and18single-effect QTL were detected for RPR of populationⅠ(B73×By804RIL) ineach year with genetic contribution from4.98%to13.81%. Some QTL had a lower contribution, soRPR may be controlled by micro-effect polygene. The BLUP prediction data were used as trait data todetect QTL, and6of24single-effect QTL were detected for RPR at the period of20days after silkingstage.11episitatic interactions were found in that population, only seven of the22loci involved inthese interactions were detected as single-effect QTL. That indicated that certain QTL had complicatedeffect in RPR. There were11QTL which control RPR on chromosome3between marker intervalSNP1950-SNP1953at different period, the genetic contribution of five QTL were more than10%.There may be a major QTL controlling RPR in this marker interval.4.37single-effect QTL were detected for RPR of populationⅡ(Zheng58×HD568RIL) with thegenetic contribution from4.08%to12.67%. The BLUP prediction data were used as trait data to detectQTL, and10of31single-effect QTL were detected for RPR at the period of30days after silking stage, and these can accounted for59.20%of the phenotypic variation. Three of five epistatic interactionswere located on the chromosome7and8. In the populationⅡ, most QTL were detected on thechromosome4and5.5. One QTL was detected for RPR at the30days after silking stage in both populationⅠandpopulationⅡ, and the QTL allele that increased RPR originated form parent which has phenotypic traitof stiff stalk.