The herbicide 2,4-D (2,4-dichlorophenoxyacetic acid) is a plant growth regulator for callus induction and somatic embryogenesis in tissue culture protocols. Research has shown that exposure to 2,4-D causes a number of environmental and health problems. Routine laboratory work involves the use of 2,4-D in the preparation of culture media, thus generating culture media with 2,4-D residues, the disposal of which is often improper. Therefore, this study aimed to determine the residual content of 2,4-D in MS (Murashige and Skoog), agrowth medium used in plant tissue cultures, after callus development. MS media were used from callus cultures of bananeira (Musa sp.) and basil (Ocimum basilicum L.). Callus cultures were supplemented with 2,4-D at concentrations of 1.0 and 0.5 mg.L-1, respectively. MS media were also evaluated in the absence of plant culture at the 0.2; 0.5 and 1.0 mg.L-1 concentrations of 2,4-D under light and dark conditions for a period of one month. Banana callus cultures consumed about 79% ± 0.27% of 2,4-D in the culture medium after two months. After three months of culture, it was not possible to detect 2,4-D in basil callus culture since the values found were below the detection limit (LOD ≤ 0.096 mg.L-1). Light does not appear to influence the degradation of 2,4-D in the culture medium. Results suggest that the concentration of 2,4-D residues depends on the species cultured. Improper disposal of these media might be a source of ignored and, hence, environmental contamination, depending on 2,4-D concentration and volume of mediawaste.

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Guava is of great economic importance in Brazil. The development of new cultivars by obtaining inbreeding lines has been a promising option. The objective of this work was to evaluate the S 2 families of Psidium guajava using seed attributes. Different characters of physiological quality of guava seeds were studied, in addition to performing digital phenotyping of characteristics of geometry, texture and colors of the seeds. The variables were analyzed simultaneously using the Ward-Modified Location Model (MLM) method and carried out individual analyses of variance for estimating genetic parameters of the population. The formation of more than one group of divergent genotypes was observed, the geometry characteristics were more impacting for the discrimination of the genotypes, a high phenotypic correlation was observed with the germination variables and dry matter weight. High heritabilities were verified for the variables related to seed quality, indicating success in selecting vigorous genotypes. The Ward-MLM method is a useful tool to detect genetic diversity among genotypes of inbred guava. Thus, the most divergent genotypes with high germination potential can be recommended for future crosses or self-fertilized to obtain new lines in the guava breeding program.

Guava is an important fruit in Brazil and worldwide. However, research has yet to advance on its breeding and seed technology, an essential factor for the development of productive genotypes with germination potential which would support the continuity of breeding programs. In search of a methodology for routine analysis testing of guava seeds under genetic control, this study examined the effect of temperature and substrate on the germination of guava seeds from full-sib families. The experiment was laid out in a completely randomized design with a 5 × 4 factorial arrangement consisting of the combination of five temperatures (25, 30, 35, 20-30 and 25-35 °C) and four substrates (paper roll, on-paper, in-sand and on-sand), with eight replicates of 50 seeds. Germination, germination speed index and live ungerminated seeds were evaluated. The alternating temperatures of 20-30 and 25-35 °C and the paper roll, on-paper and in-sand substrates are adequate conditions for germination tests with guava seeds.

Guava, Psidium guajava L., is a species of economic importance for several countries. The production of new varieties of guava from seeds with good germination and vigor potential has been investigated. In this scenario, the present study characterized and estimated the genetic diversity of seeds of 42 genotypes of guava from an S2 family based on germination response, vigor tests, and digital phenotyping analysis. The experiment was laid out in a randomized-block design with four replicates. Descriptive statistics were carried out for each of the analyzed variables and multivariate analyses were used to estimate genetic diversity based on Gower's Distance. Digital analysis was performed using the GroundEye S120 system, which extracted color, geometry, texture, and histogram data. In total, three color, two geometry, five texture, four physiological analysis, and 17 histogram variables were used. The physiological variables and those obtained by digital phenotyping were efficient to discriminate the genotypes, indicating that there is genetic variability to be exploited within the guava breeding program. The traits that most contributed to genetic diversity were those related to the histogram. The genotypes belonging to groups I and III had the highest means for germination percentage, thousand-seed weight, and shoot length. Based on the results, two options are viable for conducting the guava breeding program. The most vigorous individuals can be self-pollinated for the development of lines and the superior and most divergent ones from groups I and III can be crossed to exploit heterosis. Thus, crosses between the most vigorous individuals from groups I and III are recommended, as they exhibited higher means for the traits of germination percentage, thousand-seed weight, and shoot length.