Development of candidate gene sequence-specific DNA marker for downy mildew resistance in corn, Zea mays L.

Date

4-2012

Degree

Bachelor of Science in Agricultural Biotechnology

College

College of Agriculture and Food Science (CAFS)

Adviser/Committee Chair

Galvez, Hayde F.

Abstract

Re-optimization of the map positions of the markers in the previous genetic linkage map (Galvez, 2006) was done by genotyping the whole 142 (Pi23 x P345) BC1F1 individuals using three (3) EST-SSR and three (3) RGA markers mapped in chromosomes 4, 7 and 8. The resulting re-optimized linkage map has an additional marker and shorter average marker distance in chromosome 4, shorter total length and average marker distance in chromosome 7, and rearrangement of marker order and shorter total length and average marker distance in chromosome 8. QTL analysis using composite interval mapping (CIM) showed that there are two (2) putative QTL regions for downy mildew resistance (DMR) in maize located in chromosomes 7 and 8, which are different from the regions identified in previous QTL analysis (Galvez et al., 2011). To clone and characterize the validated QTL markers, colony PCR of the transformed E. coli cells showed that there was no effective ligation of the RGA1_01 fragment in the pGEM cloning vector. Troubleshooting experiment showed that there was indeed a failure in the ligation reaction. However, the srga3 and RGA1_01 markers were successfully isolated among the degenerate bands generated by a RGA marker system. The isolated fragments are ready for sequencing once the limitations in the cloning experiment would be addressed. The results of this study contributed in the identification and mapping of new markers for downy mildew resistance in corn. Previous QTL markers were also validated, as well as the isolation of candidate gene fragments derived from RGA markers. The markers that would be eventually developed based from the sequence information of these DMR-QTLs will be invaluable in future marker assisted breeding (MAB) in maize for downy mildew resistance.

Language

English

Location

UPLB Main Library Special Collections Section

Call Number

Thesis

Document Type

Thesis

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