Optimization of map position of resistance gene analogue (RGA) markers associated to downy mildew resistance in Maize (Zea mays L.)

Date

6-2016

Degree

Bachelor of Science in Agricultural Biotechnology

College

College of Agriculture and Food Science (CAFS)

Adviser/Committee Chair

Hayde F. Galvez

Restrictions

Restricted: Not available to the general public. Access is available only after consultation with author/thesis adviser and only to those bound by the confidentiality agreement.

Abstract

The quantitative trait loci (QTL) map for Philippine downy mildew resistance in maize was re-optimized using three (3) RGA markers, one (1) RGA-derived SCAR marker, and using the total 142 individuals of the [(Pi23 x P345) x Pi23] BC1F1 population. Re-optimization was done to validate the RGA markers associated to corn QTL for downy mildew resistance (DMR) as previously mapped through bulk segregant analysis (BSA) (Galvez, 2006 Galvez et al., 2011). With the re-optimized genetic linkage map, the QTL for DMR in chromosome 5 was validated using composite interval mapping (CIM). This is a major QTL specifically against the usm21 isolate of downy mildew, having a R2 of 28.25%, and likelihood (LOD) of QTL-marker linkage of 6.0 and 0.64 cM genetic distance to nearest marker. The SCAR marker, dmrc8_3, is also mapped in this QTL region. The SCAR marker was designed from RGA marker tightly linked to DMR-QTL, which has been validated for its putative biological function based on sequence characterization against the annotated sequences of plant disease resistance genes (Lantican et al., 2014). Along with other highly significant QTLs mapped for corn DMR, tightly linked flanking markers can readily be used in marker-assisted breeding, and/or be converted to SCAR markers for efficiency in routine application. Other DMR-QTLs that were validated in the re-optimized genetic map are: (a) buk21-QTL ? chromosomes 3 and 7 (b) usm21-QTL ? chromosome 4 (c) uplb-QTL ? chromosomes 6 and 8 and (d) isa35-QTL ? chromosomes 8 and 9. The naming of these QTLs is based on which specific isolate of downy mildew the marker-QTL linkage was significantly associated i.e. usm21-QTL refers to DMR QTL against the usm21 isolate of downy mildew. The major QTL in chromosome 5 is also tightly linked to corn DMR against usm21. The usm21 isolate of the pathogen is reported to be the most agressive isolate of Philippine downy mildew.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2016 A127 /F38

Notes

Major in Crop Biotechnology

Document Type

Thesis

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