Application of high-throughput phenotyping tool Tomato Analyzer to characterize Balkan Capsicum fruit diversity

Abstract

For years, the main emphasis of industrial pepper production has been the creation of large-fruited high-yielding varieties. This has led to the exploitation of pepper (Capsicum annuum L.) varieties with a significantly narrow genetic background. The Balkan region has a range of valuable local landraces that are noticeably decreasing in prevalence and may be lost. In this study, we utilized Tomato Analyzer (TA) to characterize the intra-and intervarietal type fruit diversity using 50 different fruit shape, size, and color descriptors of a Balkan pepper collection. The collection comprised of 168 diverse accessions and collected from 62 locations and 31 districts in six different Balkan countries. Fruit shape was the main trait used for visual accession grouping into 5 different varietal groupings of elongated, round, conical, bell, and pumpkin shape, respectively. Beyond visual grouping, hierarchical cluster analysis grouped the evaluated accessions into eight distinct clusters based on fruit shape, size, surface, and color. In total, 47 TA descriptors were identified to contribute to the total variation, with first two components explaining 54% of variation, and 90% of variation contained in 12 components. Among TA descriptors, fruit size and proximal/distal fruit end shape contributed to component 1 variation whereas fruit perimeter, area and color contributed to component 2. We hope that this research will assist pepper breeding and genetic resources communities to better understand Balkan pepper fruit diversity and develop pepper varieties with desirable fruit traits. Quantification of fruit diversity could be crucial for further investigation into the genetic determinants of fruit shape and size by a genome-wide association study.

Tomato Phenotypic Diversity Determined by Combined Approaches of Conventional and High-Throughput Tomato Analyzer Phenotyping

“…Distinctness analysis of plant and fruit diversity was carried out in tomato [1,17,28,46], pepper [35,48,49], and eggplant [50]. Distinctness, as identified using hierarchical clustering, multivariate and correlation network analyses, explains the impact of fruit shape and size descriptors on overall fruit diversity, and the findings of our study report similar observations, with the exception of clear separation of the varietal groups tested here.…”

Phytochemical Assessment of Native Ecuadorian Peppers (Capsicum spp.) and Correlation Analysis to Fruit Phenomics

“…Furthermore, manually measured fruit width was slightly lower than the maximum width derived from TA. Identical observations were reported by other authors [21,26], who suggested that this inconsistency might be associated to the way both parameters are quantified. Hence, width measured by TA was recorded where longitudinal sections are wider, so it could hardly vary depending on fruit shape.…”

“…Pereira-Dias et al, [25] working on a collection of Spanish peppers, recorded higher percentages of variation when PCA analysis was performed separately for conventional and digital phenotyping, than that obtained when both sets were combined. The most important positively correlated traits for the first PC were conventional descriptors (FWE, FLE, FWI, and FWT) and TA attributes from basic measurements and latitudinal section, although the former contributed more than the latter, accordingly with previous works [20,21,25,26]. In addition, this component was negatively correlated with polyphenols and capsaicinoids, i.e., larger fruits possessed a low content of these compounds.…”

“…Our data partly agreed with other studies dealing with pepper phenomics, with differences likely arising from differences across the groups of accessions investigated. Nevertheless, those descriptors related to fruit size and shape always explained a high level of diversity, regardless of the collection considered [24][25][26]62]. The projection of the accessions on a two-dimensional plot confirmed that each Capsicum species was diverse for morphological and biochemical traits, as accessions of a single group presented a certain degree of dispersion, plotting at different areas of the graph.…”

“…Several studies performing high-throughput phenotyping in different pepper collections have been recently published [23][24][25][26]. However, to the best of our knowledge, no works exist attempting to evidence the impact of morphology on fruit composition for health-promoting compounds.…”