Brazil has a range of fruit species, especially native ones, which play an important role in the life of local populations, but are still little studied, as is the case of bacuri (Platonia insignis Mart.). P. insignis is a fruit tree species native from Amazon region and has great economic potential, mainly due to its excellent organoleptic and nutritional characteristics. Therefore, there is a need for research that seeks the proper use of the species, as well as the selection of superior genotypes. Thus, the objective of this study was to characterize biometric and chemically fruits of eight selections of native P. insignis plants, from the municipalities of Presidente Juscelino and Santa Rita both located in Lower Munim region, state of Maranhão, Brazil. For the biometric characterization, 20 fruits, individually, were analyzed as to mass, longitudinal diameter, transverse diameter, conformation index, seed number, parthenocarpic segments number, pulp yield and bark mass, and for the chemical characterization, samples composed of six fruits were analyzed as to soluble solids (°Brix), total acidity (% citric acid), soluble solids/acidity ratio and pH. There was significant difference for all characteristics evaluated. High coefficients of variation were observed, indicating variability among the selections and possibility of taking advantage for the genetic improvement. The results allow to indicate the fruits analyzed, both for the industrial market and for the in natura consumption, especially for the ‘Domingão’ and ‘Mamão’ selections.

Guava rootstocks can be multiplied by minicuttings in environment with a high relative humidity, being necessary an acclimatization period. Certain growth regulators favor the acclimatization, with brassinosteroids being successfully used in other fruit plants. This study aimed to shorten the multiplication time of the BRS Guaraçá hybrid by applying Biobras-16 (BB-16) during the acclimatization of seedlings obtained from minicuttings. The treatments consisted of five BB-16 concentrations (0, 0.1, 0.3, 0.5 and 1.0 mg L-1), applied in a randomized block design, in a split-plot arrangement, with four replications and five seedlings per plot, repeated at two seasons: winter and spring/summer. After 60 days of acclimatization, shoot and root growth indicators increased as a function of the BB-16 application, particularly at concentrations between 0.3 and 0.6 mg L-1. The brassinosteroid can be used to stimulate the growth of BRS Guaraçá seedlings obtained from minicuttings, shortening its production time and improving its seedling quality.

Changes in the structure of the vegetation reflect on the biodiversity and dynamics of the ecosystem. The objective of the study was to characterize and compare the structure of fragments of vegetation with the occurrence of Platonia insiginis, in different stages of regeneration, with 6, 10, 25 and 100 years of fallow period in western Brazilian Amazon. The study was conducted in a completely randomized design, with four treatments, consisting of 6, 10, 25 and 100 years of fallow period, and five replications, consisting of demarcated temporary plots for each fallow period, with dimensions of 2 m x 2 m for the regenerating stratum of vegetation and 10 m x 10 m for the adult stratum of vegetation. Phytosociological parameters evaluated were number of individuals and species, total density, total height, stem diameter and Shannon DiversityIndex (H’), Pielou Equability (J) and Jaccard Similarity Index (JSI). The data were subjected to the Analysis of Variance, followed by the Tukey Test (p <0.05) and Principal Component Analysis. There was low species diversity for the sampled areas, with (H’) rates ranging from 0.65 to 2.46 nats ind-1. The vegetation fragments with 100 years of fallow period showed a floristic similarity of 10% with the others, while those of 6 and 10 years of fallow period, reached similarity of 40%. For the regenerating strata only, the number of individuals and total density differed, with the lowest averages, respectively, of 5 and 1,400 individuals ha-1 at 100 years of fallow period. For the adult strata, there was a difference between all parameters corroborating the results obtained in the Principal Component Analysis, at 100 years of fallow period, a lower average was obtained for the number of individuals (7), and higher averages of plant height (22.1 m) and diameter at breast height (36.45 cm). As conclusion, the time required for the complete natural regeneration of secondary vegetation fragments in the Brazilian Amazon is over 100 years

The production of grafted seedlings requires longer periods of time. The technique of mini-grafting onto rootstocks previously obtained from herbaceous cuttings can guarantee the genetic fidelity of scion and rootstock and allows grafting onto smaller-diameter stems, accelerating the time required to obtain seedlings. The aim of this study was to anticipate the formation of ‘Paluma’ guava seedlings grafted onto clonal rootstocks with smaller-diameter stems. Treatments consisted of grafting onto rootstocks with five stem diameter classes. The experimental design was randomised blocks with three replicates and five seedlings per plot. Rootstocks were produced from cuttings of herbaceous branches of mother plants originating from crossing between P. guineense and P. cattleianum. Mini-grafts were obtained from a clonal ‘Paluma’ guava mini-garden . Seedlings grafted onto rootstocks with stem diameters from 3.7 to 10.3 mm presented the same success rate however the greatest seedling vigour was observed when grafted onto larger-diameter rootstocks. Grafting success and seedling height show that mini-grafting onto clonal rootstocks with diameters from 3.7 to 5.5 mm allows producing seedlings suitable for transplanting 300 days after cutting.

The viability of the mini-cutting technique requires seedling regrowth ability and continuous propagule production. It is hypothesized that the application of gibberellic acid (GA) can stimulate vegetation and increase the production of mini-cuttings. The aim of this study was to increase the mini-cutting yield of Psidium guajava (L.) × Psidium guineense (Sw.) (‘BRS Guaraçá’) as a function of foliar application of GA and season of the year. The experiment was laid out in a randomized-block design with split-plots in time, in which the plots consisted of different GA concentrations applied (0, 50, 100, 150 and 200 mg L-1) and the subplots were represented by two application periods or seasons (summer and winter). Four replicates were used, with two plants per plot. After the seedlings were topped, GA was applied at different concentrations and the emerged shoots were evaluated over 30 days. Mini-stump yield was assessed by collecting and evaluating the potential number of mini-cuttings. Shoot length and mini-stump yield increased linearly with the increasing GA concentrations during the summer. In the winter, this response was quadratic, with optimal concentrations estimated at 65.3 mg L-1 for shoot length and 76 mg L-1 for mini-stump yield. The GA concentration of 200 mg L-1 provided shorter internodes in the summer, whereas in the winter the use of GA did not interfere with this trait. The increasing applications of GA induced a linear increase in stem diameter at both seasons of the year. Gibberellic acid did not interfere with the rooting of the mini-cuttings. The highest rooting percentage occurred in the summer, with an average of 95%. In the winter, this value was 77.2%, demonstrating that mini-cuttings are a promising technique for ‘BRS Guaraçá’. Foliar spraying of GA promoted an increase in mini-cutting production, without interfering with their rooting.