Abstract
Leaf morpho-anatomical characteristics directly reflect photosynthetic performance and the ability to adapt to different environmental conditions. The study of biometric traits is essential for the selection of promising plant materials for breeding purposes. To identify new varieties of coffee plants with desirable traits for genetic improvement programs, this study investigated the variability of leaf morpho-anatomical traits in 43 genotypes of Coffea canephora (as the species under study is hypostomatous). Seven leaf characteristics were used: epidermal cell density (ECD), stomatal length (SL), stomatal width (SW), stomatal density (SD), stomatal size (SS), stomatal index (SI), and stomatal length/width. Morphological traits (plant height, internodal distance, and leaf area) and grain production were also assessed. The data analyzed multivariate analysis of variance grouped by the unweighted pair group the arithmetic mean hierarchical method, and data were also subjected to a Pearson linear correlation and principal component analyses (PCAs). The results showed wide morphological variability reflecting six morphological groups, which is relevant for the genetic divergence analysis and for breeding purposes, as the results have the potential to identify superior genotypes. Within the groups, genotypes were mainly separated by the number of epidermal cells and the number and size of the stomata, reflecting a high genetic heterogeneity within genotypes. Positive and negative correlations were found, with levels of significance ranging from weak to strong among the analyzed traits. The highest correlation levels were found for SL × SS, SW × SS, and SI × SD. In addition, the PCA indicated that plant height, distance between nodes, and leaf area were positively correlated and associated. The greater the number and width of stomata, the higher the rate of gas exchange. Both characteristics are favorable for the development and production of coffee plants, explaining the positive correlation observed in this study. These results emphasize the usefulness of trait evaluations for the identification and breeding of genotypes to compose new C. canephora cultivars suitable for changing environments.
Highlights
Leaf characteristics are among the most important groups of plant functional traits and are a robust proxy for the features of the entire plant [1,2]
When analyzing the images generated by the Anati Quanti program we found that the stomata were present only in the abaxial of the coffee leaves
The morphological traits of stomata, such as size, shape, frequency, and distribution, are considered species dependent, but they can greatly vary among genotypes under the same environmental conditions, or within the same genotype when subjected to different environmental factors, with the latter demonstrating the ability of plants to adjust to external pressures, namely increased temperature [21], lower water availability [26,41], elevated atmospheric CO2 [37,42], high relative air humidity [43,44], and differing irradiance levels [40]
Summary
Leaf characteristics are among the most important groups of plant functional traits and are a robust proxy for the features of the entire plant [1,2]. Leaf traits have been extensively analyzed to discern how plant species coexist within a community and adapt to changing environments [3] and to understand genotype variability in crop breeding lines [4]. Studies show that changes in leaf thickness and increased chlorophyll content, for example, contribute to the enhancement of the light capture and, as a result, to photosynthesis [6]. Coffee is one of the most valuable agricultural products in the global economy, being cultivated over an area exceeding 11 million hectares and distributed across ca. The production and the demand of C. canephora have significantly increased due to its use in blends with C. arabica (both for espresso and soluble coffees) because of its higher content of soluble solids, greater industrial yield, and its contribution to a full-bodied beverage [9]. Some authors argue that this can provide up to 60% of the blend percentage without compromising the final beverage quality [10]
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