Banca de DEFESA: PEDRO PAULO FARIA CONDE

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : PEDRO PAULO FARIA CONDE
DATE: 27/03/2026
TIME: 13:30
LOCAL: PPGF - Sala 2
TITLE:

Genetic diversity in Brazilian peppertree (Schinus terebinthifolius Raddi.) based on leaf characteristics and ISSR markers

KEY WORDS:

Plant breeding; molecular marker; hierarchical clustering; polymorphic information content (PIC); diversity indices.

PAGES: 50
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Fitotecnia
SPECIALTY: Melhoramento Vegetal
SUMMARY:

In Brazil, the Brazilian peppertree (Schinus terebinthifolius) stands out mainly for its medicinal properties and the production of pink peppercorns. Despite its agronomic potential, only one cultivar of the species has been registered with the Ministry of Agriculture. Genetic improvement work is of paramount importance for developing cultivars adapted to production areas. Therefore, the first step is to understand the available genetic diversity. The general objective of this work was to understand and estimate the genetic diversity among Brazilian peppertree genotypes of agronomic interest, considering morphological aspects of the leaf and DNA, using ISSR markers. For this purpose, 20 genotypes were considered. For each genotype, 25 fully developed leaves were collected and digitized using a desktop scanner. In the ImageJ software, the leaves were analyzed for 20 variables related to their length, width, area, apex shape, and number of leaflets. With these variables, all genotypes were subjected to botanical classification at the variety level. Also, descriptive statistical parameters were obtained from the leaf variables. Concomitantly, genomic DNA from all plants was extracted from leaves. After quantification, different ISSR primers were tested. The 15 most polymorphic primers were used. After performing the PCRs, the amplified products were subjected to electrophoresis on a 5% agarose gel. All gels were photodocumented and analyzed. The presence of bands was recorded with a value of 1 (one), and the absence, zero. From the molecular variables, the polymorphic information content (PIC) was estimated. Both leaf morphological variables and molecular variables were subjected to UPGMA hierarchical cluster analysis, respectively, based on Euclidean distance and Jaccard dissimilarity. Subsequently, the respective cophenetic correlations were estimated. Finally, dendrograms were obtained. In the case of morphological variables, the dendrogram was accompanied by a heatmap. For both types of variables, the number of optimal genotype groups in the dendrogram was estimated using the kgs algorithm. Considering the leaf morphological variables, radar charts were constructed for each of the genotype groups formed. In addition, the relative contribution of leaf variables to the genetic diversity found was estimated. Shannon and Pielou diversity indices were also estimated from the morphological and molecular variables. All statistical analyses were performed using the R program. With the exception of the UFRRJ ARO071-F and UFRRJ ARO078-F genotypes, which had five leaflets per leaf, all others had seven leaflets. In any case, the genotypes were classified as *Schinus terebinthifolia* var. *raddiana*, given that, among other parameters, the central leaflet was larger than the others. On average, leaf length ranged from 8.51 to 14.18 cm. Cophenetic correlation was estimated at 0.91 and 0.72, respectively, for leaf and molecular variables. Genotypes were grouped into six distinct groups, both in relation to leaf and DNA variables. Despite this, there were no genotype matches within the groups. These results were expected, since the ISSR primers used hybridize broadly and randomly across the genome, and are therefore not specific to the DNA sequences that code for morphological aspects in leaves. Regarding the leaves, the clustering patterns obtained indicated broad genetic diversity. This is corroborated by the estimates of the Shannon (H’) and Pielou (J) indices, respectively, of 2.85 and 0.90. The leaf variables that contributed most to diversity were those related to leaflet area. Together, they contributed 68.87% of the diversity found. The UFRRJ ARO078-F and UFRRJ ARO071-F genotypes were the most dissimilar in relation to leaf characteristics. Molecular diversity was also considered high, given that, despite the irregular distribution of plants in the groups, the minimum and maximum distances obtained were high, with an average estimated at 0.76. The diversity indices indicated that molecular diversity was very high (H´= 6.0; J = 0.97). The estimated average PIC (0.33) pointed to the use of highly informative loci. Based on the results found for leaf morphology and genomic DNA analysis among the analyzed genotypes, it is concluded that the genetic diversity among the genotypes was high. These results may indicate that the plants in the studied population tend to diverge for several agronomic traits, such as fruit production and the synthesis of active principles of medicinal interest.

COMMITTEE MEMBERS:
Presidente - 1712769 - PEDRO CORREA DAMASCENO JUNIOR
Externo ao Programa - 2582213 - MARCO ANDRE ALVES DE SOUZA - UFRRJExterno à Instituição - GUSTAVO TORRES DOS SANTOS AMORIM