Molecular tools for marker-assisted breeding of buffelgrass

摘要

The increasing availability of molecular tools is facilitating marker-assistedselection (MAS) in plant improvement programs. The objectives of this research wereto: 1) populate the framework buffelgrass genome map with additional molecularmarkers, 2) develop polymerase chain reaction (PCR)-based markers from selected,informative restriction fragment length polymorphism (RFLP) markers on thebuffelgrass genome map, and 3) increase marker resolution near the locus conferringapomixis (PApo1). Buffelgrass [Pennisetum ciliare (L.) Link syn. Cenchrus ciliaris L.](2n=4x=36), a highly polymorphic, apomictic, perennial forage grass, is well-suited forgenetic linkage analyses. One hundred and seventy one probes from an apomictic,spikelet-specific, complementary deoxyribonucleic acid (cDNA) library and 70expressed sequence tag simple sequence repeats (EST-SSRs) from apomictic pistilcDNAs were evaluated and added to the framework buffelgrass genome map. Theimproved linkage map contains 851 markers from 11 grass species and coversapproximately 80-85% of the buffelgrass genome. Two RFLPs from the buffelgrassgenome map were converted to PCR-based markers for both the identification of hybrids and quantification of sexual versus apomictic reproduction. A gel-free, high-throughputtechnique was developed to analyze these markers directly in 96-well plates. Fiveadditional markers were placed onto the buffelgrass linkage group with the PApo1apomixis locus through comparative mapping of candidate orthologs from the sorghumgenome map and bulked-segregant analysis of amplified-fragment-lengthpolymorphisms(BSA-AFLP). Increasing the mapping population size did not increasemap resolution in the PApo1 region. Association mapping revealed that therecombination suppression near PApo1 is moderate and would complicate comparativemap-based cloning efforts of the orthologous region in sorghum.