John Silva Porto

Common scab caused by Streptomyces spp., causes considerable potato yield losses worldwide. Here, we aimed to study the correlation between common scab severity, and soil chemical characteristics and leaf nutrient contents. Data on potato yield, scab incidence, and soil characteristics obtained from 26 sampling points were subjected to multivariate analysis and then analyzed for spatial dependence. For most soil nutrients and pH, there was a inverse relationship with scab severity. Conversely, organic matter, S, Ca, and Mg contents positively correlated with scab damage. Leaf N, P, K, Ca, Mg, S, Cu, Mn, and Fe contents were inversely related severity, whereas B and Zn concentrations were closely associated with the disease. Differences in the relationship between foliar and soil nutrient contents greatly contribute to the complexity with which soil conditions affect the growth of Streptomyces spp. in the soil, and the plant chemical-physiological conditions. Our findings revealed that soil and foliar nutrient status affected the incidence of scab. Although most nutrients suppressed the disease, B and Zn showed a complex association with severity. These discrepancies likely arose from soil conditions, as pH and organic matter drive Streptomyces activity, while plant physiology modulates nutrient uptake and infection resistance.

Bixa orellana L., also known as achiote, is a shrub native to tropical regions. It has been arousing the interest of the industrial sector due to the film that covers its seeds, which is rich in a reddish carotenoid called bixin. Although, traditionally, it is sexually propagated through seeds, this process can also take place in a vegetative manner. Given the economic and social relevance of this species, the aim of the current study is to assess both the vegetative and reproductive development of achiote plants, based on their propagation process, to help finding the best association between plant growth and early production. The experiment was conducted in a farm, in Porto Seguro City – Bahia State. Treatments were based on two genotypes (A and B), which were multiplied through asexual (plant cutting) and sexual (seeds) reproduction. The experimental design was based on randomized blocks, at 2x2 factorial arrangement, with 5 repetitions and 7 useful plants per plot. The following parameters were assessed at 59, 154, 284, 383, 497, 656 and 840 days after planting: incidence of flowers and/or capsules, stem diameter, plant height and canopy diameter. Collected data were compared to each other through Tukey’s test, at 5% probability level. Asexually propagated treatments were the first to start the reproduction stage, whereas sexually propagated treatments recorded higher vegetative development rate; no difference in vegetative development and in reproductive stage onset was observed between the investigated genotypes.

Potato common scab causes significant economic losses worldwide, and current control methods remain ineffective. However, biological control methods have been effective in controlling phytopathogens in several other crops. Trichoderma spp. and Bacillus subtilis are the most studied microorganisms in agriculture for controlling plant diseases. However, interactions between these biological control agents and the organic matter present at the cultivation site have not been extensively studied. Therefore, the objective of this study was to evaluate the action of biological agents in controlling potato common scab using different soil mulch compositions. Two field experiments were performed simultaneously: one tested T. longibrachiatum (TL) and T. asperellum (TA) treatments in the control of potato scab, and the other tested two types of soil mulch (vetch and palisade grass) and four microorganism treatments (TL, TA, B. subtilis + Enterococcus faecium + Lactobacillus plantarum (BSEFLP), and B. subtilis + B. licheniformis + T. longibrachiatum (BSBLTL)). In the first experiment, TL and TA decreased the disease severity from 80% in the control to 34%, and 56% in the control to 5%, respectively, based on yield losses caused by the potato scab. In the second experiment, TA and BSEFLP reduced the disease severity to 61% and 62%, respectively, compared with that in the control (98%), and losses caused by the common scab to 38% and 40%, respectively, when combined with vetch mulch (control: 98%), demonstrating that microbial response can be influenced by the cover crop. Therefore, this work provides evidence that biological control of potato common scab is a viable alternative for disease control.

Organomineral fertilizer has great potential to replace synthetic fertilizers. The goal of this study was to determine an optimal substitution rate of organomineral fertilizer for mineral fertilizer to increase potato yield and quality. The experimental design was a randomized complete block with four replicates and six treatments, namely four substitution rates of organomineral fertilizer application (25, 50, 75, and 100% of mineral fertilizer demand), one rate of mineral fertilizer application (100% of mineral fertilizer demand), and the control (no fertilizer application). The organomineral application rates were tested as an alternative to substitute 25 to 100% of mineral fertilizer. The potato yield (total and in-class) and quality and plant and soil nutrient contents were monitored. The pH and total soluble solid contents had positive correlations with yield. Potatoes accumulated higher contents of K > N > P in the leaves, stems, and tubers. The organomineral fertilizer application rate of 3.7 t ha-1 (equivalent to 100% of mineral fertilizer demand) was the optimal rate to increase potato yield and quality. Organomineral fertilizer is a viable alternative to increase potato quality and yield and to increase plant and soil nutrient contents.

O nematoide das galhas (Meloidogyne spp.) tem sido um fator limitante ao cultivo da goiabeira no Brasil, pois restringe a produção e a qualidade dos frutos. O controle biológico vem sendo empregado para suprimir nematoides fitopatogênicos e a inoculação com Trichoderma spp. e Pochonia chlamydosporia é um método promissor, contudo poucas pesquisas são relatadas com estes fungos à cerca da cultura da goiabeira. Objetivou-se avaliar a eficiência de Trichoderma harzianum, Trichoderma longibrachiatum e Pochonia chlamydosporia na modulação morfológica do crescimento inicial de mudas de goiabeira ‘Paluma’ em solo naturalmente infestado com Meloidogyne spp. A pesquisa ocorreu na Universidade Estadual do Sudoeste da Bahia – UESB, Campus de Vitória da Conquista - BA em telado experimental. Foram realizadas as análises morfológicas altura da planta, diâmetro do caule, comprimento de raízes, massa fresca e seca da parte aérea e das raízes. Foi possível observar que os fungos de biocontrole não foram eficientes na supressão dos nematoides juvenis durante o período de avaliação, no entanto a inoculação com Trichoderma harzianum, promoveu incremento nas massas fresca e seca da parte aérea e na massa seca das raízes, Pochonia clamydosporia mostrou-se menos eficiente quanto a promoção de crescimento inicial das mudas quando comparadas a Trichoderma spp. Palavras-chave: Psidium guajava; Trichoderma spp.; Pochonia spp.; Meloidogyne spp. USE OF BENEFICIAL FUNGI IN DEVELOPMENT OF GUAVA SEEDLINGS IN NEMATODES INFESTED SOILS ABSTRACT: Root-knot nematode (Meloidogyne spp.) has been a limiting factor to growing guava in Brazil since it restricts yield and fruit quality. Biological control has been employed to suppress phytopathogenic nematodes. The inoculation with Trichoderma spp. and Pochonia chlamydosporia is a promising method; however, studies on the impact of these fungi on guava trees are lacking. This work aimed to assess the efficiency of Trichoderma harzianum, Trichoderma longibrachiatum and Pochonia chlamydosporia in morphological modulation at the early development of ‘Paluma’ guava seedlings grown on a soil naturally infested by Meloidogyne spp. The study took place at the State University of Southeastern Bahia – UESB, campus Vitória da Conquista, Bahia state, Brazil, in a net house. The following morphological traits were evaluated: plant height, stem diameter, root length, and fresh and dry weights of shoots and roots. These fungi as biocontrol agents were not efficient in suppressing juvenile nematodes over the evaluation period; nonetheless, inoculation with Trichoderma harzianum increased fresh and dry weights of shoot as well a root dry weight. Pochonia clamydosporia was less efficient in promoting the early development of seedlings compared to Trichoderma spp. Keywords: Psidium guajava; Trichoderma spp.; Pochonia spp.; Meloidogyne spp.

Tomatoes are an important component of the human diet because they are rich in minerals and antioxidants that sequester free radicals in cells, preventing various disorders that affect human health. Here, we aimed to evaluate the effects of different nitrogen sources and concentrations on antioxidant capacity and physical and chemical quality of tomato fruit. The experiment was conducted in Vitória da Conquista, state of Bahia, Brazil, in the experimental field of Universidade Estadual do Sudoeste da Bahia. The experimental setup included a randomized block design with four replicates in a factorial layout of 3 × 3 + 1 (control), for a total of 40 plots. The three treatments comprised different nitrogen sources (calcium nitrate, urea, and ammonium sulfate), applied in three doses (140, 280, and 420 kg ha^-1). We evaluated firmness, pH, titratable acidity - TA, soluble solid - SS, SS/TA ratio, ascorbic acid, carotenoids, flavonoids, phenolic compounds and DPPH inhibition, were evaluated after samples were harvested. However, increasing concentrations of N adversely affected the acidity and led to an increase in the SS/TA ratio. Increasing the N concentration also reduced the content of bioactive compounds. excluding carotenoids, which consequently impaired antioxidant activity.

This work aimed to evaluate the influence of green fertilization and the compost on the production of radish, cv. ‘Cometa’. The experimental design was randomized blocks with 6 treatments and 4 replicates: T1 - Leucaena, T2 - ‘Madeira-nova’, T3 - Compost (maize straw and composted cattle manure), T4 – ‘Sempre verde’ grass + compost and T5 – ‘Sempre verde’ grass and T6 - control without fertilization, totaling 24 experimental plots. The total area of the experimental plot was 1.44 m², with useful area of 0.80 m² and 21.0 t ha^-1 of fertilizer (dry basis) were incorporated in each treatment. The radish crop was directly sown in the beds, in 2- to 3-cm-deep holes, leaving one plant at spacing of 20 cm between rows and 5 cm between plants. Twenty-nine days after planting, plants were evaluated for total yield, commercial yield, percentages of commercial roots (%) and waste roots (%), fresh and dry matter of shoots and roots, total and individual leaf area and the SPAD index. The incorporation of Leucaena at the amount of 21.0 t ha^-1 (dry basis) promoted the highest increments for the analyzed characteristics.

Diversas alternativas vêm sendo estudadas e utilizadas no controle de doenças de plantas, no intuito de suprir as necessidades dos produtores e consumidores no desejo de reduzir o uso de defensivos agrícolas. Assim, o objetivo deste trabalho foi avaliar a atividade de extratos vegetais de Azadirachta indica A. Juss., Anonna muricata L. e de Lippia alba (Mill) N. E. Brown. no controle de Colletotrichum gloeosporioides Penz. in vitro. O experimento foi conduzido na Universidade Estadual do Sudoeste da Bahia, Câmpus de Vitória da Conquista, Bahia, Brasil. Extratos aquosos de folhas de graviola e erva-cidreira, e extratos aquosos de sementes de nim e graviola foram usados visando à inibição do crescimento micelial do patógeno causador da antracnose em frutos de mamão. A atividade antifúngica dos extratos foi mensurada mediante a medição do crescimento micelial das culturas. O delineamento adotado foi o DIC em esquema fatorial (3x3x3), com quatro repetições, nos dois experimentos. Os resultados obtidos indicam maior inibição ao crescimento micelial do patógeno com o uso dos extratos de folhas de erva-cidreira e de sementes de graviola.