Core Collection Formation in Guatemalan Wild Avocado Germplasm with Phenotypic and SSR Data

Guatemala's wild avocado germplasm holds vital genetic value, but lacking conservation strategies imperils it. Studying its diversity is pivotal for conservation and breeding. The study aimed to comprehensively assess the wild avocado germplasm in Guatemala by combining phenotypic and genotypic data and to create a core collection for conservation and future breeding programs. A total of 189 mature avocado trees were sampled across Guatemala's northern, southern, and western regions. Morphological characteristics were documented, and genetic diversity was assessed using 12 SSR loci. The investigated germplasm revealed three distinct genetic clusters, exhibiting an average gene diversity of 0.796 and a 7.74% molecular variation among them. The samples showed various morphological characteristics that indicate the presence of three avocado races in Guatemala. The weak correlation between phenotypic and genotypic distances highlighted their independence and complementary nature. The joint matrix effectively integrated and captured genotypic and phenotypic data for comprehensive genetic diversity analysis. A core collection comprising 20% of total accessions that captured maximum genetic diversity was formed. This study exposed wild Guatemalan avocados' genetic diversity, morphological traits, and conservation significance. Integrated data capture via clustering validates holistic genetic insight for conservation and breeding strategies

Botanical diversity, structure and composition in cocoa agroforest systems in Alta Verapaz, Guatemala

The tree composition in cocoa agroforestry systems (CAFS) in Guatemala is valued for providing a number of ecosystem services. Despite the importance of the trees in these systems, little is known about the tree species richness and its contribution to the conservation of diversity. We studied the botanical composition of CAFS of different ages in the Alta Verapaz department of Guatemala. In total, 70 survey plots with a size of 2500 m2 were established. An inventory was carried out in each sampling unit, recording the tree species present and measuring the diameter at breast height (DBH 1.30 m) and the height of each tree. The Importance Value Index (IVI) was calculated and species richness and the similarity between sites were evaluated. A total of 2519 trees, belonging to 59 species and 34 families were identified. The species with the highest IVI was Gliricidia sepium (Jacq.) Kunth. The CAFSs with the highest and lowest species richness were those of 9-12 and 27 years old, respectively (H´=1.99, H´=0.34). This behavior can be explained by the fact that growers work to enrich the agroforestry systems with a broad diversity of species in the first years which they then begin to harvest at around 16 years of age. A discriminant analysis of principal components (DAPC) and the Jaccard Similarity Index were used to show that several AFS were similar in terms of composition and botanical diversity. Given the tree diversity within the CAFS, these can be acknowledged as areas with good potential for the conservation of overall biodiversity. We recommend education programs for local growers about the benefits of shade management during the production cycle of cocoa to preserve the botanical composition and structural complexity of the AFS

Genetic Diversity and Population Structure of Myanmar Rice (<i>Oryza sativa</i> L.) Varieties Using DArTseq-Based SNP and SilicoDArT Markers

Myanmar is well known as a primary center of plant genetic resources for rice. A considerable number of genetic diversity studies have been conducted in Myanmar using various DNA markers. However, this is the first report using DArTseq technology for exploring the genetic diversity of Myanmar rice. In our study, two ultra-high-throughput diversity array technology markers were employed to investigate the genetic diversity and population structure of local rice varieties in the Ayeyarwady delta, the major region of rice cultivation. The study was performed using 117 rice genotypes with 7643 SNP and 4064 silicoDArT markers derived from the DArT platform. Genetic variance among the genotypes ranged from 0 to 0.753 in SNPs, and from 0.001 to 0.954 in silicoDArT. Two distinct population groups were identified from SNP data analysis. Cluster analysis with both markers clearly separated traditional Pawsan varieties and modern high-yielding varieties. A significant divergence was found between populations according to the Fst values (0.737) obtained from the analysis of molecular variance, which revealed 74% genetic variation at the population level. These findings support rice researchers in identifying useful DNA polymorphisms in genes and pinpointing specific genes conferring desirable phenotypic traits for further genome-wide association studies and parental selection for recombination breeding to enhance rice varietal development and release

Tree diversity in cacao agroforests in San Alejandro, Peruvian Amazon

Cacao (Theobroma cacao) cultivation maintaining a high proportion of shade trees in a diverse composition (agroforestry) is currently being viewed as a sustainable land use practice. Our research hypothesis was that cacao agroforests (AF) can support relatively high tree diversity, as compared to surrounding primary and/or secondary forests. The objective of this study was to assess the impact of forest conversion on tree communities by comparing tree composition, community characteristics (richness and diversity) and spatial structure (density, canopy height, basal area) among primary forest, secondary forest, and cacao AF. In total, we collected data from 30 25 x 25 m plots on three land use systems (20 in cacao AF, five in secondary, and five in primary forests) in San Alejandro, Peruvian Amazon. All trees with DBH >= 10 cm were counted, identified to species, and their height and DBH were recorded. Our results support the hypothesis that cacao AF present a relatively high tree species richness and diversity, although they are no substitute for natural habitats. We identified most common species used for shading cacao. Tree species composition similarity was highest between cacao AF and secondary forest. Vegetation structure (density, height, DBH) was significantly lower compared to primary and secondary forest. Species richness and diversity were found to be highest in the primary forest, but cacao AF and secondary forests were fairly comparable. The tree species cultivated in cacao AF are very different from those found in primary forest, so we question whether the relatively high tree diversity and richness is able to support much of the diversity of original flora and fauna