In micropropagation, potassium nitrate (KNO3), an ACS reagent grade chemical, used in the preparation of growing mediums is expensive and its procurement depends on bureaucratic procedures, as it is controlled by the Brazilian Army. This research to assessed the effect of replacing the ACS KNO3 for a commercially available fertilizer (KNO3- based) on the micropropagation of the prickly pear cactus (Opuntia stricta (Haw.) Haw. cv. Elephant Ear. Treatments used six different fertilizer concentrations (0, 0.5, 1, 1.5, 2 and 2.5 g L-1) and a control consisting of 1.9 g L-1 KNO3, as shown in the MS salts. The survival, size and number of sprouts and the value of fresh biomass were evaluated. After seedling acclimation, we assessed the survival, number of sprouts, length, and number of roots, racket formation, average fresh biomass mass, macronutrient absorption and morphological changes of the seedlings. Explants inoculated with fertilizers at concentrations of 0.0; 2.0 and 2.5 g L-¹ did not grow. The response of explants at concentrations of 0.5 and 1.5 g L-1 of the fertilizer were the same as those developed in a KNO3 medium, and at a concentration of 1.0 g L-1, in all variables, the means were higher than those of the control medium. Therefore, it showed the feasibility of using fertilizers in the in vitro cultivation of the prickly pear cactus, which may remove bureaucratic barriers and reduce product costs by 99.12%.

O alecrim-pimenta é uma importante planta medicinal, nativa do nordeste brasileiro, que, devido ao seu óleo essencial, apresenta grande potencial antifúngico e antibacteriano. Um dos fatores que afetam o teor de metabólitos secundários das plantas é o horário de colheita, assim, o conhecimento desse fator subsidia as decisões agronômicas da espécie, favorecendo o aumento do teor de óleo essencial no momento da colheita. Dessa forma, o objetivo do presente trabalho foi avaliar o efeito do horário de colheita na produção de óleo essencial de alecrim-pimenta (Lippia sidoides Cham.). O experimento foi desenvolvido no Instituto de Ciências Agrárias da Universidade Federal de Minas Gerais (ICA/UFMG), Montes Claros, Minas Gerais, Brasil. Utilizou-se o delineamento experimental em blocos casualizados com cinco tratamentos, definidos pelos horários de coleta das folhas (6:00, 9:00, 12:00, 15:00 e 18:00) e seis repetições, sendo esse o número de coletas em cada tratamento. As folhas foram obtidas de plantas matrizes do Horto Medicinal do ICA/UFMG. O óleo essencial foi obtido pelo método de hidrodestilação usando o aparelho de Clevenger. A análise de regressão apresentou um efeito cúbico para o teor de óleo essencial, sendo que o maior valor, 5,78% em relação à matéria seca, foi obtido às 9h59min. Portanto, recomenda-se a colheita das folhas de alecrim-pimenta próximo das 10h.

Meloidogyne enterolobii associated with Fusarium solani causes the guava decay, which is the main factor of yield loss in guava crops and limits guava production in Brazil. Therefore, searching for guava genotypes (Psidium spp.) with resistance to M. enterolobii is important to control this root-knot nematode. The objective of the present work was to evaluate the reaction of Psidium spp. accessions from the Germplasm Bank of the Bahia State University (UNEB) to different levels of inoculation with M. enterolobii. Guava seedlings were inoculated with 600, 1,600, and 2,000 eggs + J2 second stage juveniles of M. enterolobii and the root fresh weight, total number of eggs (TNE), and reproduction factor (RF) were evaluated. The results were subjected to ANOVA and means were clustered using the Scott-Knott test at 5% probability. The diversity of accessions was estimated using the Tocher's clustering and UPGMA methods. The nematode RF reduced in some accessions with increasing inoculation levels of the nematode. However, the RF increased in some accessions with high levels of inoculation. Plants of the Y50 accession were immune or resistant to M. enterolobii, indicating variability of reaction of plants to the nematode within the Psidium genus. The resistance of Psidium accessions to M. enterolobii needs to be measured with different inoculation levels to verify the existence of false-positive results, since the evaluated accessions, including the Paluma cultivar, presented distinct reactions regarding RF in the three levels of inoculation used.

Meloidogyne enterolobii has severely compromised the main guava producing regions in Brazil, thereby stimulating the development of resistant varieties for efficient management of this nematode. This study aimed to assess the penetration, development, reproduction, and induced cellular responses of M. enterolobii in roots of four species of the genus Psidium ( P. guajava ‘Paluma’, P. guineense , P. cattleyanum , and P. friedrichstalianum ) from the Active Germplasm Bank (BAG) of the Center for Agricultural Research of the Semi-arid Tropics (Embrapa Semi-arid) located in Petrolina, PE, Brazil. Three experiments were carried out to assess the penetration, development, and reproduction of the nematode and, subsequently, histological analyses were performed. Nematode penetrated indistinctly in both resistant and susceptible species, but only in ‘Paluma’ an evolution was observed from vermiform juveniles to “sausage” and globose forms in experiment 1. In experiment 2, all species presented “sausage” forms of nematode, but only in ‘Paluma’, these forms reached adult female stages. In experiment 3, only ‘Paluma’ was susceptible to M. enterolobii , with reproduction factor above unity. Histological analyses showed that, except for P. guajava, the other Psidium species presented poorly developed feeding sites at 20 days after inoculation. Index terms Guava root-knot nematode; Psidium cattleyanum; P. friedrichstalianum; P. guajava; P. guineense; resistance

The guava decline, a complex disease caused by the interaction between Meloidogyne enterolobii and Fusarium solani, has caused damage to production and unviable guava producing areas in the Lower Basin of the São Francisco Valley. The management of this disease is difficult due to the facts that cultivated plants are susceptible to nematodes, nematicides have no effective control, and the use of fungicides to control Fusarium still has not been evaluated. However, some Psidium genotypes, such as the araçazeiros, show resistance to the nematodes, and therefore decline resistance. The objective of this study was to evaluate the interaction between genotypes of Psidium spp. and M. enterolobii to identify resistant plants. Three araçazeiro genotypes from the states of São Paulo and Paraná were artificially inoculated with M. enterolobii and compared with the species P. guajava cultivar Paluma, which is a commercial cultivar susceptible to root-knot nematode. All araçazeiro genotypes evaluated were resistant to the disease, with low reproduction factor (0.000 to 0.004) compared to cultivar Paluma (FR = 1,610). These results demonstrate that the araçazeiro genotypes have the potential to be used in the development of rootstocks resistant to guava decline.

The aim of this study was to check the use of the following gelling agents: the xanthan gum “Adicel®” and the stabilizer “Super Liga Neutra®” to replace agar in the in vitro rooting phase of Gerbera hybrida cv. Essandre. Additionally, the possibility of using chemical sterilization of both culture media and glassware with sodium hypochlorite to replace autoclaving was analyzed. The gelling agents, xanthan gum “Adicel®” and the stabilizer “Super Liga Neutra®” were tested at the following concentrations (g L^-1): 7; 9; 11; 13; 15; 17; 19; and 21. No concentrations of Super Liga Neutra® provided effective solidification. Concentrations of 17 and 21 g of Adicel® provided a good gelling of the culture medium, which was compared to the medium containing agar (control) with two types of sterilization: autoclaving (for 20 and 40 minutes) and chemical sterilization. Autoclaving for 20 minutes did not provide effective elimination of contamination in the culture medium containing xanthan gum; this only occurred when autoclaving time increased to 40 minutes. Plant development in culture media containing 17 and 21 g of xanthan gum, either sterilized by autoclaving for 40 minutes or at a concentration of 17 g xanthan gum using sodium hypochlorite, was statistically the same as the control that contained agar. However, plant development at a concentration of 21g of xanthan gum in a sterilized medium using sodium hypochlorite was lower than that observed in media containing agar.