LINKAGE MAP CONSTRUCTION AND MAPPING QTLs FOR IMPORTANT AGRO-MORPHOLOGICAL TRAITS IN OIL PALM (Elaeis guineensis Jacq.)
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Date
2018
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Publisher
Acharya N.G. Ranga Agricultural University
Abstract
The present investigation was carried out during 2017-18 at ICAR-IIOPR, Pedavegi, Andhra Pradesh, India. Two oil palm genotypes i.e. DURA 240D and DURA 281D which differ in yield and oil yield content were selected as parents which were developed at Regional Agricultural Research Station, Palode, Kerala. From this cross 70 F1 progenies were generated and raised at DURA block of IIOPR, Pedavegi, Andhra Pradesh. Morphological characters such as Bunch number, Bunch weight, Bunch index, Oil to dry mesocarp and Oil to wet mesocarp were recorded as per the standard procedures. The phenotypic and genotypic data of 70 palms were used for construction of linkage maps and QTL mapping.
In Parental analysis study, a total of 400 SSR markers of Elaeis guineensis were used to screen two parental genotypes. Out of 400 SSR markers analyzed for polymorphism, 19 SSR markers (4.75%) were polymorphic and these 19 polymorphic SSRs were used to genotype the 70 F1 progenies of the 240D x 281D cross. Then the genotypic data was scored as ‘A’-homozygous allele to parent 240D, ‘B’-homozygous to parent 281D and ‘H’-which has both the alleles.
In Linkage Mapping studies 70 F1 progenies of 240D x 281D cross genotypes were screened with the co-dominant subset of 19 putative polymorphic SSRs. Data for SSR markers was obtained in the form of A,B and H scoring which was then used for Linkage Map construction and QTL analysis. Linkage analysis and map construction were performed using Mapmanager software. Out of 19 SSRs, 13 SSRs were found linked with chromosome 1,6,8 and 15. Each chromosome was linked with 3 SSR markers, except the 8th chromosome which was linked with 4 markers. A total of 13 SSRs were mapped to 4 linkage groups (C1, C6, C8 and C15) of Elaeis guineensis genome. Map was drawn with the help of QTL Cartographer after determining the best possible order by Mapmanager. The map covered four linkage groups with 13 polymorphic SSR markers.
In QTL mapping study three different methods were used i.e. Simple regression analysis, Simple interval mapping and Composite interval mapping for QTL detection. In Simple regression analysis (SRA) by WinQTL Cartographer 2.0 revealed two markers for bunch number on chromosome 1 and chromosome 8. Bunch weight, oil to dry mesocarp, oil to wet mesocarp and bunch index could not show any association with the QTL. In Simple Interval mapping (SIM) analysis by WinQTL Cartographer 2.0 revealed a total of 4 QTLs for various yield traits. Out of these identified QTLs, one QTL (qBN1.1) was for bunch number, two QTLs (qODM1.1, qODM1.2) for oil to dry mesocarp and one QTL (qOWM1.1) for oil to wet mesocarp in E.guineensis in the population under study. Bunch weight and Bunch index were not associated with any QTL. Composite Interval Mapping (CIM) analysis by WinQTL Cartographer 2.0 revealed a total of 5 QTLs for various yield traits. Out of these identified QTLs, one QTL (qBN1.1) was for bunch number, two QTLs (qODM1.1, qODM1.2) for oil to dry mesocarp and two QTLs (qOWM1.1, qOWM1.2) for oil to wet mesocarp. No QTLs were identified for bunch weight and bunch index.
This study confirmed that QTLs can be detected in homozygous and heterogenous populations successfully in perennial crops like oil palm in limited time span by using SSR markers. At the same time linkage map studies in oil palm through morphological marker needs data for several years. However, this work provided valuable information and detected some important QTLs in oil palm, which can be used as parent material in oil palm breeding for yield improvement programmes as well as any intra-specific hybridization programme. Therefore the knowledge of QTLs in relation to yield and oil quality data would help in searching and pin-pointing palms as parent material. Therefore using the phenotypic data and genotyping it with various SSR Markers and performing QTLs analysis would be useful to link the phenotype to genotype for developing appropriate tools and methodologies for marker–assisted breeding. This knowledge will also provide a better understanding of the biological basis of various traits.
Description
D5588
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