Reassessing the genetic variability of Tectona grandis through high-throughput genotyping: Insights on its narrow genetic base.

Teak (Tectona grandis Linn. f.) is considered one of the most expensive hardwoods in the world. The dispersion of the species over the years has taken the teak beyond its first sources of diversity and little is known about the genetic origin and genetic variability. Thus, this study aimed to investigate the genetic diversity and genetic population structure existing in a representative teak germplasm bank collection. DNA was extracted from young leaves and each sample were genotyped by whole genome sequencing at 3 giga bases per sample, the sequences are aligned using the genome, and SNPcalls and quality control were made. To study the population structure of the genotypes, Bayesian variational inference was used via fastStructure, the phylogenetic tree was based on the modified Euclidean distance and the clustering by the UPGMA hierarchical method. Genetic diversity was analyzed based on the pairwise genetic divergence (Fst) of Weir and Cockerham. Genotyping by sequencing resulted in a database of approximately 1.4 million of variations SNPs were used for analysis. It was possible to identify four populations with considerable genetic variability between and within them. While the genetic variability in teak is generally known to be narrow, this study confirmed the presence of genetic variability scale in teak, which is contrary to what was initially expected.

Application of Near-Infrared Reflectance Spectroscopy for Predicting Damage Severity in a Diverse Panel of Tectona grandis Caused by Ceratocystis fimbriata.

Tectona grandis Linn., also known as teak, is a highly valued species with adaptability to a wide range of climatic conditions and high tolerance to soil variations, making it an attractive option for both commercial and conservation purposes. In this sense, the classification of cultivated teak genotypes is crucial for both breeding programs and conservation efforts. This study examined the relationship between traits related to damage in the stem of teak plants caused by Ceratocystis fimbriata (a soil-borne pathogen that negatively impacts the productivity of teak plantations) and the spectral reflectance of 110 diverse clones, using near-infrared spectroscopy (NIRS) data and partial least squares regression (PLSR) analysis. Cross-validation models had R2 = 0.894 (ratio of standard error of prediction to standard deviation: RPD = 3.1), R2 = 0.883 (RPD = 2.7), and R2 = 0.893 (RPD = 2.8) for predicting stem lesion area, lesion length, and severity of infection, respectively. Teak genotypes (clones) can benefit from the creation of a calibration model utilizing NIRS-generated data paired with PLSR, which can effectively screen the magnitude of damage caused by the fungus. Overall, while the study provides valuable information for teak breeding and conservation efforts, a long-term perspective would be essential to evaluate the sustainability of teak genotypes over various growth stages and under continuous pathogen pressure.

Multivariate analysis for the detection of Passiflora species resistant to collar rot / Análise multivariada na distinção de espécies de Passiflora resistentes à podridão do colo

Collar rot is a disease difficult to control that has hindered passion fruit cultivation in many regions of Brazil. Therefore, this study aimed to find genetic resistance to the fungus Fusarium solani in Passiflora species using the multivariate analysis methodology to discriminate the most resistant species. The following fourteen Passiflora species were assessed: P. quadrangularis, P. nitida, P. foetida, P. tenuifila, P. alata, P. setacea, P. cincinnata, P. mucronata, P. micropetala, P. suberosa, P. morifolia, P. eichleriana, P. edulis and P. coccinea. These plants were arranged in a casualized block design with 14 treatments (species), three replications and three plants per plot. The reactions of the inoculated species of Passiflora were evaluated with the use of 12 resistance traits. The generalized Mahalanobis distance was used to form groupings by the UPGMA method. 3D projection with the canonical variables and quantification of the relative contribution of characters were also conducted. The UPGMA method revealed the formation of three distinct groups of species, which composed the susceptible, moderately resistant and resistant groups. The groups formed by threedimensional dispersion were similar to those formed by the dendrogram. The following traits contributed most to genetic diversity: inoculation time until the lesion reached more than 50% of the circumference of the injured stem and area under the curve of the expansion of the lesion width. The use of the set of traits and their joint assessment through multivariate analysis allowed greater accuracy in the inference of the most resistant species, mainly P. nitida and P. cincinnata.

A podridão do colo é uma doença de difícil controle e que em muitas regiões do Brasil tem dificultado o cultivo do maracujazeiro. Neste contexto, este estudo teve por objetivos avaliar resistência genética em espécies de Passiflora ao fungo Fusarium solani utilizando análise multivariada como metodologia para distinguir as espécies quanto à resistência. Foram avaliadas 14 espécies de Passiflora, sendo elas: P. quadrangularis, P. nitida, P. foetida, P. tenuifila, P. alata, P. setacea, P. cincinnata, P. mucronata, P. micropetala, P. suberosa, P. morifolia, P. eichleriana, P. edulis e P. coccinea. Estas plantas foram dispostas em blocos ao acaso com 14 tratamentos (espécies), três repetições e três plantas por parcela. A reação das espécies de Passiflora inoculadas foi avaliada utilizando 12 características de resistência. Através dessas características, por meio da distância generalizada de Mahalanobis, foram realizados agrupamentos pelo método UPGMA, projeção 3D com as variáveis canônicas e também foi quantificada a contribuição relativa dos caracteres. Verificou-se, por meio do método de agrupamento UPGMA, a formação de três grupos distintos de espécies, e estes foram classificados como sendo suscetíveis, moderadamente resistentes e resistentes. Os agrupamentos formados pela dispersão tridimensional se assemelharam aos formados pelo dendrograma. As características que mais contribuíram para a diversidade genética foram período da inoculação até a lesão atingir mais que 50% da circunferência do caule lesionado e área abaixo da curva de expansão da largura da lesão. O uso do conjunto de características e a avaliação conjunta das mesmas através de análise multivariada possibilitaram maior acurácia na inferência das espécies mais resistentes, destacando-se P. nitida e P. cincinnata.