Switchgrass (Panicum virgatum), a C4 perennial grass native to North America and developed as a sustainable biofuel feedstock, occurs in two ecotypes, lowland and upland, which vary in their architecture as well as their range of adaptation. In this study, we assessed single nucleotide polymorphism (SNP) variation in 372 switchgrass genotypes for nine genes involved in lignin and pectin biosynthesis. STRUCTURE results at K = 3 differentiated the genotypes into three genetic subpopulations that corresponded largely to the previously characterized upland C1 and lowland C2 and C3 subpopulations. Out of the 146 SNPs identified, 19 SNPs were non-synonymous, including two non-conservative and common SNPs in cinnamyl alcohol dehydrogenase (CAD, Chr01N) and p-coumarate3-hydroxylase (C3H, Chr09N), two genes in the lignin biosynthesis pathway. Allele status at seven of the 19 non-synonymous SNPs, including the non-conservative SNP in C3H, was significantly associated with four dry matter traits within subpopulations. Dry matter traits appeared to be mostly dominant and three of them (acid detergent fiber, non-fiber carbohydrate, water-soluble carbohydrates) were the most frequently differentiated traits. In addition, a heterosis effect was detected at the non-conservative SNP in phenylalanine ammonia-lyase (PAL) for neutral detergent fiber. Association analysis revealed the CAD gene on Chr01N, its homoeolog on Chr01K and cinnamate 4-hydroxylase (C4H, Chr03K) as potential candidates associated with dry matter traits. Further analyses are needed to determine whether these candidate genes play a role in switchgrass lignin content and could be exploited to reduce recalcitrance in this bioenergy crop.

中文翻译：

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柳枝L（Panicum virgatum L.）木质素和果胶生物合成相关基因的自然变异以及SNP变异与干物质性状的关联

柳枝（（Panicum virgatum）是北美原生的一种C4多年生草，作为可持续的生物燃料原料而开发，有两种生态型，低地和高地，其结构和适应范围各不相同。在这项研究中，我们评估了372柳枝switch基因型中9个参与木质素和果胶生物合成的基因的单核苷酸多态性（SNP）变异。K = 3时的结构结果将基因型分为三个遗传亚群，这些亚群主要对应于先前鉴定的高地C1和低地C2和C3亚群。在鉴定出的146个SNP中，有19个SNP不是同义词，包括肉桂醇脱氢酶（CAD，Chr01N）和Cn中的两个非保守和常见SNP。对香豆酸3-羟化酶（C3H，Chr09N），木质素生物合成途径中的两个基因。19个非同义SNP中的7个（包括C3H中的非保守SNP）的等位基因状态与亚群中的4个干物质性状显着相关。干物质性状似乎占主导地位，其中三个（酸性洗涤剂纤维，非纤维碳水化合物，水溶性碳水化合物）是最常见的性状。此外，在中性洗涤剂纤维的苯丙氨酸解氨酶（PAL）中的非保守SNP处检测到杂种优势。关联分析显示，CAD基因位于Chr01N上，其同源于Chr01K和肉桂酸4-羟化酶（C4H，Chr03K）可能与干物质性状相关。需要进一步分析以确定这些候选基因是否在柳枝switch木质素含量中发挥作用，并可以用来减少这种生物能源作物的顽固性。