Bernard Anthony, Hamdy Sherif, Le Corre Laurence, Dirlewanger Elisabeth, Lheureux Fabrice
Univ. Bordeaux, INRAE, Biologie du Fruit et Pathologie, UMR 1332, 33140 Villenave d'Ornon, France.
CTIFL, centre opérationnel de Lanxade, 24130 Prigonrieux, France.
Plant Methods. 2020 Aug 26;16:115. doi: 10.1186/s13007-020-00657-7. eCollection 2020.
Walnuts are grown worldwide in temperate areas and producers are facing an increasing demand. In a climate change context, the industry also needs cultivars that provide fruits of quality. This quality includes satisfactory filling ratio, thicker shell, ease of cracking, smooth shell and round-shaped walnut, and larger nut size. These desirable traits have been analysed so far using calipers or micrometers, but it takes a lot of time and requires the destruction of the sample. A challenge to take up is to develop an accurate, fast and non-destructive method for quality-related and morphometric trait measurements of walnuts, that are used to characterize new cultivars or collections in any germplasm management process.
In this study, we develop a method to measure different morphological traits on several walnuts simultaneously such as morphometric traits (nut length, nut face and profile diameters), traits that previously required opening the nut (shell thickness, kernel volume and filling kernel/nut ratio) and traits that previously were difficult to quantify (shell rugosity, nut sphericity, nut surface area and nut shape). These measurements were obtained from reconstructed 3D images acquired by X-ray computed tomography (CT). A workflow was created including several steps: noise elimination, walnut individualization, properties extraction and quantification of the different parts of the fruit. This method was applied to characterize 50 walnuts of a part of the INRAE walnut germplasm collection made of 161 unique accessions, obtained from the 2018 harvest. Our results indicate that 50 walnuts are sufficient to phenotype the fruit quality of one accession using X-ray CT and to find correlations between the morphometric traits. Our imaging workflow is suitable for any walnut size or shape and provides new and more accurate measurements.
The fast and accurate measurement of quantitative traits is of utmost importance to conduct quantitative genetic analyses or cultivar characterization. Our imaging workflow is well adapted for accurate phenotypic characterization of a various range of traits and could be easily applied to other important nut crops.
核桃在全球温带地区种植，生产者面临着不断增长的需求。在气候变化的背景下，该行业也需要能产出优质果实的品种。这种品质包括令人满意的饱满度、更厚的外壳、易于开裂、外壳光滑以及核桃形状圆润，还有更大的坚果尺寸。到目前为止，这些理想性状一直使用卡尺或千分尺进行分析，但这需要大量时间且需要破坏样本。面临的一个挑战是开发一种准确、快速且无损的方法，用于核桃与品质相关和形态特征的测量，这些特征用于在任何种质管理过程中对新品种或种质进行表征。
在本研究中，我们开发了一种方法，可同时测量多个核桃的不同形态特征，如形态特征（坚果长度、坚果面直径和轮廓直径）、以前需要打开坚果才能测量的特征（外壳厚度、果仁体积和果仁饱满度/坚果比率）以及以前难以量化的特征（外壳粗糙度、坚果球形度、坚果表面积和坚果形状）。这些测量是通过X射线计算机断层扫描（CT）获取的重建3D图像获得的。创建了一个工作流程，包括几个步骤：噪声消除、核桃个体化、特性提取以及果实不同部分的量化。该方法应用于对法国国家农业食品与环境研究院（INRAE）核桃种质资源库中一部分的50个核桃进行表征，这些核桃来自161个独特的种质，收获于2018年。我们的结果表明，使用X射线CT对50个核桃进行分析足以对一个种质的果实品质进行表型分析，并找到形态特征之间的相关性。我们的成像工作流程适用于任何核桃大小或形状，并提供了新的、更准确的测量。
快速准确地测量数量性状对于进行数量遗传分析或品种鉴定至关重要。我们的成像工作流程非常适合对各种性状进行准确的表型特征分析，并且可以很容易地应用于其他重要的坚果作物。
