The effects of different levels of fertilization with nitrogen and potassium (NK), height within the canopy and plant age of Lycopersicon hirsutum f. glabratum (PI 134417) C. H. Mull and L. esculentum on the density of foliar cristalliferous idioblasts and trichomes, and on the levels of 2-tridecanone (2-TD) and 2-undecanone (2-UD) and their influence on the resistance to Myzus persicae (Sulzer) were investigated. NK levels were inversely related to densities of trichomes and cristalliferous idioblasts in L. esculentum, but only to densities of cristalliferous idioblasts in L. hirsutum. Trichome density increased with increasing height within the canopy and with plant age in L. esculentum and L. hirsutum. Density of cristalliferous idioblasts in L. hirsutum increased with canopy height reaching a maximum at mid-height within the canopy in opposition to L. esculentum in which a small decrease in density with height within the canopy was found. There was also a small decrease of idioblast density with increasing plant age for L. esculentum, while a greater and opposite variation took place in L. hirsutum. L. esculentum has mainly non-glandular leaf trichomes (90%), while L. hirsutum has mainly glandular trichomes (97%). The main glandular trichomes of L. hirsutum are producers of 2-TD and 2-UD, whose leaf content increases with increase of trichome density. A negative effect of 2-TD concentration and cristalliferous idioblast density on the survival and longevity of M. persicae was observed. Since L. hirsutum presented much higher levels of 2-TD and cristalliferous idioblast density than L. esculentum, L. hirsutum seems a promising source of resistance to M. persicae for tomato breeding programs.

Studies on the genetic diversity of species with pharmacological potential are essential for the conservation of genetic resources. The genetic characterization of a species can guide efforts to collect and conserve germplasm and, in the future, genetic improvement. Domestic cultivation of medicinal plants is an important strategy for protecting these species from over harvesting. Genetic studies of medicinal species by molecular markers could allow for assessment and management of these species. Croton urucurana Baill. is widely used in Brazilian traditional medicine, but there are practically no data about its genetic patterns. We used 12 ISSR markers to evaluate the genetic diversity levels of 30 trees distributed in three populations of C. urucurana, two of which were located in Brazilian savanna (Cerrado) and one on semi-deciduous tropical forest areas. From a total of 82 bands recorded, 89% were polymorphic and presented a Shannon's diversity index of 0.26. The populations formed two distinct groups: Two populations were divided each into a different genetic group, while the Aquidauana population, which is in a transition area between the Cerrado and the Pantanal, presented a mixture of the two genetic groups. Croton urucurana has G ST values (0.200) similar to those found in species with a mixed mating system, but the lack of detailed studies on the reproductive system of this species makes it difficult to correctly interpret the origin of the population structure observed. Moreover, even using a simpler marker we were able to identify regions that deserve further studies, especially from a chemical point of view, to see whether there are any differences between the populations that could help in defining future conservation strategies, management and genetic improvement plans of the species.

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Assessing the parental genetic differences and their subsequent prediction of progeny performance is an important first step to assure the efficiency of any breeding program. In this study, we estimate the genetic divergence in Eucalyptus camaldulensis based on the morphological traits of 132 progenies grown in a savanna biome. Thus, a field experiment was performed using a randomized block design and five replications to compare divergences in total height, commercial height, diameter at breast height, stem form and survival rate at 48 months. Tocher’s clustering method was performed using the Mahalanobis and Euclidian distances. The Mahalanobis distance seemed more reliable for the assessed parameters and clustered all of the progenies into fourteen major groups. The most similar progenies (86 accessions) were clustered into Group I, while the most dissimilar (1 progeny) represented Group XIV. The divergence analysis indicated that promising crosses could be made between progenies allocated in different groups for high genetic divergence and for favorable morphological traits.