Islam Nishat S, Bett Kirstin E, Pauls K Peter, Marsolais Frédéric, Dhaubhadel Sangeeta
London Research and Development Centre Agriculture and Agri-Food Canada London ON Canada.
Department of Biology University of Western Ontario London ON Canada.
Plants People Planet. 2020 Nov;2(6):663-677. doi: 10.1002/ppp3.10132. Epub 2020 Aug 19.
Pinto bean () is one of the leading market classes of dry beans that is most affected by postharvest seed coat darkening. The process of seed darkening poses a challenge for bean producers and vendors as they encounter significant losses in crop value due to decreased consumer preference for darker beans. Here, we identified a novel allele of the gene, , responsible for the slow darkening seed coat in pintos, and identified trait-specific sequence polymorphisms which are utilized for the development of new gene-specific molecular markers for breeding. These tools can be deployed to help tackle this economically important issue for bean producers.
Postharvest seed coat darkening in pinto bean is an undesirable trait that reduces the market value of the stored crop. Regular darkening (RD) pintos darken faster after harvest and accumulate higher level of proanthocyanidins (PAs) compared to slow darkening (SD) cultivars. Although the markers cosegregating with the SD trait have been known for some time, the () gene identity had not been proven.Here, we identified as a candidate for controlling the trait. Genetic complementation, transcript abundance, metabolite analysis, and inheritance study confirmed that is the gene. is another allele of the () gene, whose loss-of-function alleles result in a white seed coat. encodes a bHLH transcription factor with two transcript variants but only one is involved in PA biosynthesis. An additional glutamate residue in the activation domain, and/or an arginine to histidine substitution in the bHLH domain of the transcript in the SD cultivar is likely responsible for the reduced activity of this allele compared to the allele in a RD cultivar, leading to reduced PA accumulation.Overall, we demonstrate that a novel allele of , , is responsible for the SD phenotype, and describe the development of new, gene-specific, markers that could be utilized in breeding to resolve an economically important issue for bean producers.
斑豆（Phaseolus vulgaris L.）是受收获后种皮变黑影响最大的主要干豆市场类型之一。种皮变黑过程给豆类生产者和销售商带来了挑战，因为消费者对颜色较深的豆子偏好降低，导致作物价值大幅损失。在此，我们鉴定出一个控制斑豆种皮缓慢变黑的基因（Ppd）的新等位基因（PpdSD），并鉴定了性状特异性序列多态性，这些多态性被用于开发新的基因特异性分子标记以用于育种。这些工具可用于帮助解决豆类生产者面临的这一经济重要问题。
斑豆收获后种皮变黑是一种不良性状，会降低储存作物的市场价值。与种皮缓慢变黑（SD）的品种相比，常规变黑（RD）的斑豆收获后变黑更快，原花青素（PA）积累水平更高。尽管与SD性状共分离的标记已经存在一段时间，但Ppd（Phaseolus vulgaris darkening）基因的身份尚未得到证实。在此，我们鉴定出PpdSD是控制该性状的候选基因。遗传互补、转录本丰度、代谢物分析和遗传研究证实PpdSD是Ppd基因。PpdSD是Ppd（PpdRD）基因的另一个等位基因，其功能缺失等位基因导致白色种皮。PpdSD编码一个bHLH转录因子，有两个转录变体，但只有一个参与PA生物合成。与RD品种中的等位基因相比，SD品种中PpdSD转录本的激活域中额外的谷氨酸残基和/或bHLH域中精氨酸到组氨酸的取代可能导致该等位基因活性降低，从而导致PA积累减少。总体而言，我们证明Ppd基因的一个新等位基因PpdSD导致了SD表型，并描述了新的、基因特异性标记的开发，这些标记可用于育种，以解决豆类生产者面临的一个经济重要问题。
