Genomic regions associated with salinity tolerance in lowland switchgrass

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Abstract
Switchgrass (Panicum virgatum L.) is a promising candidate species for sustainable biofuel feedstock production on marginal land. Soil salinity is one of the significant factors that limits sustainable agricultural production worldwide including a substantial reduction in biomass yield of switchgrass. This study was designed to assess genetic variation in lowland switchgrass and identify genomic regions contributing to an increased level of salinity tolerance using a subset (550 pseudo F2) of a nested association mapping (NAM) population. Salinity tolerance was evaluated based on salt injury score (SIS) using a 1 to 9 scale (1 = the most tolerant, 9 = the most sensitive) and stress tolerance index (STI) calculated from plant height measurements. Substantial variation among NAM families and genotypes within families was observed (p < .05) for SIS. However, no variation was evident among NAM families and genotypes within families for STI. The switchgrass plant accessions EG 1104–1, and EG 1104–2 displayed a high level of salinity tolerance based on SIS which can be used as source material for cultivar development. A total of five quantitative trait loci (QTL) associated with SIS were detected by composite interval mapping on four chromosomes 2B, 6B, 7B, and 9B. The phenotypic variation explained by an individual QTL ranged from 1.4 to 6.5%. The additive genetic effects of individual QTL ranged from −0.07 to 0.63. Homologs of five candidate genes were identified, which were reported to be associated with salinity tolerance.

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