Fine mapping of bacterial stalk rot resistance loci in tropical white maize

Date

2015

Abstract

The research project aimed to address the limitation of the existing QTL map for maize bacterial stalk rot resistance (BSRR). Although a major QTL for BSRR was identified in chromosome 2 of the maize genome, the flanking markers are not yet tightly linked (5 cM) to be useful for MAS. The general objective of the project was to fine-map the bacterial stalk rot resistance (BSRR) quantitive trait loci (QTL) regions with DNA markers. Specifically, the research project aimed to 1)screen new polymorphic simple sequence repeat (SSR) and resistance gene analog (RGA) markers by bulk segregant analysis (BSA); b)saturate the QTL for BSRR in P8 x YIF62 cross with SSR and RGA markers and 3)re-map/analyze the QTLs using the saturated linkage/QTL map. The research have significant accomplishments/findings. In DNA marker polymorphism survey, a total of 99 SSR and RGA primer pairs were screened for polymorphism between P8 and YIF62 parental genotypes and BSR resistant and susceptible DNA bulks and 8(23%) SSR markers were polymorphic between the parental inbred lines. No SSR markers were identified to be polymorphic between the DNA bulks. A total of 57 RGA primers were screened for polymorphism between the parental lines and 12 were polymorphic between the BSR tail DNA bulks. In DNA marker segregation and linkage analysis, of the 23 (2 SSR and 21 RGA) polymorphic markers, 17 (74%) followed the expected Mendelian segregation ratios. The remaining six markers 26% showed distorted segregation at 0.01P0.05. A total of 23 (2 SSR and 21 RGA) markers were added to the previous 77 marker loci analyzed wherein 14 linkage groups were established. Eleven of these linkage groups were assigned to each corresponding chromosome number of the maize genome. In the mapping of BSRR-QTL regions, single marker analysis detected putative QTLs for BSRR in chromosome 2. Sux of (2 SSR and 4 RGA) the eight markers were significantly associated with BSRR. Based on composite interval mapping (CIM), at a very high LOD of approx 9, two putative QTLs were identified in chromosomes 2. The flanking markers detected in chromosome 2 are not yet tightly linked (5 cM) to be useful as starting points to clone and characterized the underlying resistance genes.

Language

English

Document Type

Article

Pages /Collation

19 leaves

En – AGROVOC descriptors

ZEA MAYS; MAIZE; VARIETIES; DISEASE RESISTANCE; GENOMES; QUANTITATIVE TRAIT LOCI; DNA; GENETIC MAPS; GENETIC MARKERS; GENETIC POLYMORPHISM

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