In-Depth Characterisation of Common Bean Diversity Discloses Its Breeding Potential for Sustainable Agriculture

Evaluation of Cowpea Landraces under a Mediterranean Climate

Cowpea (Vigna unguiculata (L.) Walp.) yield is strongly influenced by environmental conditions. Average seed yield can decrease to a great extent when drought conditions occur, especially when they prevail during flowering and seed filling periods. Identifying genotypes presenting yield stability is one of the most important breeding goals. Local varieties or crop landraces are genetic resources that, despite exhibiting intermediate yield production capacity, present high yield stability in low-input cropping systems. The objective of this study was therefore to evaluate five selected cowpea landraces originated from different Greek islands under Mediterranean climatic conditions. A complete randomized block design with four replications was used during three consecutive cropping seasons. Many phenological and agronomic traits studied showed statistically significant genotype × experimental year interaction, while there was a strong experimental year effect. Among the landraces studied, local population VG23 from Kythira Island was the most productive under the experimental climatic and soil conditions, while local population VG2 from Lemnos Island was characterized by low seed productivity. Conclusively, our study showed that VG23 landrace is a promising genetic material to be used for seed yield improvement.

Towards microalga-based superfoods: heterologous expression of zeolin in Chlamydomonas reinhardtii

Microalgae are unicellular photosynthetic organisms that can be grown in artificial systems to capture CO₂, release oxygen, use nitrogen- and phosphorus-rich wastes, and produce biomass and bioproducts of interest including edible biomass for space exploration. In the present study, we report a metabolic engineering strategy for the green alga Chlamydomonas reinhardtii to produce high-value proteins for nutritional purposes. Chlamydomonas reinhardtii is a species approved by the U.S. Food and Drug Administration (FDA) for human consumption, and its consumption has been reported to improve gastrointestinal health in both murine models and humans. By utilizing the biotechnological tools available for this green alga, we introduced a synthetic gene encoding a chimeric protein, zeolin, obtained by merging the γ-zein and phaseolin proteins, in the algal genome. Zein and phaseolin are major seed storage proteins of maize (Zea mays) and bean (Phaseolus vulgaris) that accumulate in the endoplasmic reticulum (ER) and storage vacuoles, respectively. Seed storage proteins have unbalanced amino acid content, and for this reason, need to be complemented with each other in the diet. The chimeric recombinant zeolin protein represents an amino acid storage strategy with a balanced amino acid profile. Zeolin protein was thus efficiently expressed in Chlamydomonas reinhardtii; thus, we obtained strains that accumulate this recombinant protein in the endoplasmic reticulum, reaching a concentration up to 5.5 fg cell^-1, or secrete it in the growth medium, with a titer value up to 82 µg/L, enabling the production of microalga-based super-food.

The Evaluation of Common Bean (Phaseolus vulgaris L.) Genotypes under Water Stress Based on Physiological and Agronomic Parameters

Drought affects common bean productivity, and the severity of its impact is expected to increase due to climate change. The use of versatile genotypes could contribute to securing future bean production. This study investigates the adaptability of 10 common bean genotypes of indeterminate growth type under water scarcity conditions by measuring agronomic and physiological parameters. The evaluation occurs under irrigation treatments applied at two different phenological stages (anthesis (WDA) and seed filling initiation (WDSF)). The recorded adaptabilities of the genotypes (G) showed that G10 produced the highest overall seed yield in the normal irrigation (NI) (197.22 g plant−1) and WDA (192.78 g plant−1), while the G6 had the highest yield at WDSF (196.71 g plant−1). For the genotype’s average mean, chlorophyll content decreased by 10.5% under drought at WDSF. Net photosynthetic rate (Pn), stomatal conductance (gs), and transpiration rate (E) were reduced at WDA by 53%, 80.8%, and 61.4% and at WDSF by 43.75%, 57.7%, and 36%, respectively, while relative water content (RWC) reduced by 16.48%, on average, for both stages. G10 and G6 showed adaptability when water scarcity occurred at an early (WDA) or later stage (WDSF), respectively, providing insights into using germplasm resources to cope with the drought effect.

Phenotypic and Genotypic Characterization and Correlation Analysis of Pea (Pisum sativum L.) Diversity Panel

Phenotypic and genotypic characterization were performed to assess heritability, variability, and seed yield stability of pea genotypes used in breeding to increase the pea production area. A European pea diversity panel, including genotypes from North America, Asia, and Australia consisting of varieties, breeding lines, pea, and landraces was examined in 2019 and 2020 in Serbia and Belgium using augmented block design. The highest heritability was for thousand seed weight; the highest coefficient of variation was for seed yield. The highest positive correlation was between number of seeds per plant and number of pods per plant; the highest negative correlation was between seed yield and protein content. Hierarchical clustering separated pea germplasm based on use and type. Different Principal component analysis grouping of landraces, breeding lines, and varieties, as well as forage types and garden and dry peas, confirms that there was an apparent decrease in similarity between the genotypes, which can be explained by their different purposes. Pea breeding should be focused on traits with consistent heritability and a positive effect on seed yield when selecting high-yielding genotypes, and on allowing for more widespread use of pea in various agricultural production systems.

Assessment of the Origin and Diversity of Croatian Common Bean Germplasm Using Phaseolin Type, SSR and SNP Markers and Morphological Traits

Landraces represent valuable genetic resources for breeding programmes to produce high-yielding varieties adapted to stressful environmental conditions. Although the common bean (Phaseolus vulgaris L.) is an economically important food legume for direct human consumption worldwide, common bean production in Croatia is based almost exclusively on landraces and there is no common bean breeding program. Information on phaseolin type and results of population structure and genetic diversity obtained by analysis of SSR and SNP markers, in combination with the morphological characterization of 174 accessions of 10 common bean landraces (morphotypes), enabled thorough classification of accessions. The accessions were classified into phaseolin type H1 (“S”) of Mesoamerican origin and phaseolin types H2 (“H” or “C”) and H3 (“T”) of Andean origin. By applying distance- and model-based clustering methods to SSR markers, the accessions were classified into two clusters at K = 2 separating the accessions according to the centres of origin, while at K = 3, the accessions of Andean origin were further classified into two clusters of accessions that differed in phaseolin type (H2 and H3). Using SNP markers, model-based analysis of population structure was performed, the results of which were consistent with those of SSR markers. In addition, 122 accessions were assigned to 14 newly formed true-type morphogenetic groups derived from three different domestication events: (1) Mesoamerican (H1A) (“Biser”, “Kukuruzar”, “Tetovac”, “Trešnjevac”), (2) Andean—indeterminate type (H2B1) (“Dan noć”, “Sivi”, “Puter”, ”Sivi prošarani”, “Trešnjevac”) and (3) Andean—determinate type (H3B2) (“Bijeli”, “Dan noć”, “Puter”, “Trešnjevac”, “Zelenčec”). The rest of the accessions could represent putative hybrids between morphogenetic groups. The differences between the true-type groups of accessions were further analysed based on nine quantitative traits, and the subsets of traits that best distinguish among centres of origin (A: Mesoamerican, B: Andean) and genetic groups (H1A, H2B1, H3B2) were proposed.

European landrace diversity for common bean biofortification: a genome-wide association study

Mineral deficiencies represent a global challenge that needs to be urgently addressed. An adequate intake of iron and zinc results in a balanced diet that reduces chances of impairment of many metabolic processes that can lead to clinical consequences. In plants, bioavailability of such nutrients is reduced by presence of compounds such as phytic acid, that can chelate minerals and reduce their absorption. Biofortification of common bean (Phaseolus vulgaris L.) represents an important strategy to reduce mineral deficiencies, especially in areas of the world where this crop plays a key role in the diet. In this study, a panel of diversity encompassing 192 homozygous genotypes, was screened for iron, zinc and phytate seed content. Results indicate a broad variation of these traits and allowed the identification of accessions reasonably carrying favourable trait combinations. A significant association between zinc seed content and some molecular SNP markers co-located on the common bean Pv01 chromosome was detected by means of genome-wide association analysis. The gene Phvul001G233500, encoding for an E3 ubiquitin-protein ligase, is proposed to explain detected associations. This result represents a preliminary evidence that can foster future research aiming at understanding the genetic mechanisms behind zinc accumulation in beans.

Preserving Biodiversity in Marginal Rural Areas: Assessment of Morphological and Genetic Variability of a Sicilian Common Bean Germplasm Collection

The historical cultivation of common bean (Phaseolus vulgaris L.) has resulted in the development of local populations/cultivars in restricted Italian rural areas. Many common bean landraces, still cultivated in small mountain areas from Sicily, have become outdated and endangered due to the commercial varieties spreading. These accessions are poorly known but often represent a genetic heritage to be preserved and enhanced. The ex situ conservation of fifty-seven Sicilian common bean landraces was carried out at the "Living Plants Germplasm Bank" at Ucria (Messina, Italy), founded by the Nebrodi Regional Park, together with the "Sicilian Plant Germplasm Repository" of University of Palermo (SPGR/PA). To assess the germplasm genetic diversity, nineteen morphological traits and eight Simple Sequence Repeats (SSRs) were used. Genetic distances among landraces were calculated to construct a clustering tree by using unweighted pair group method arithmetic (UPGMA). Seed germplasm diversity of Sicilian common bean varied from 80.7% to 93.3%, based on six seed descriptors and six leaf, flower, and pod descriptors, respectively, while cluster genetic analysis depicted a clear separation among all the 57 landraces. Principal coordinates (PCoA) and STRUCTURE analyses showed a prevalent rate of admixture between Mesoamerican and Andean gene pools in Sicilian common bean collection, confirming its heterogeneity. The observed high level of diversity evidenced the needs to adopt accurate criterion to plan a definitive ex situ germplasm collection to share agrobiodiversity with local farmers and to avoid any further loss of genetic resources in rural and protected areas.