Study of Potassium Silicate Spraying in Coffee Plants to Control <i>Oligonychus ilicis</i>(McGregor) (Acari: Tetranychidae)

The southern red mite, Oligonychus ilicis (McGregor) (Acari: Tetranychidae) can cause a significant reduction in the photosynthesis potential and the growth of new coffee plants (Coffea spp., Rubiaceae). Studies suggest that the leaf spraying of silicon (Si) leads to increase plants resistance in order to reduce infestations of insect pests such as herbivores, borers, sucking insects and mites. The objective of this study was to evaluate the effect of leaf spraying of potassium silicate (K2SiO3) to control the southern red mite in coffee plants. Experiments were conducted in coffee plants (Coffea arabica L.), grown in a greenhouse, by means of completely randomized design with six treatments: Dose 0 (control), 2, 4, 6, 8 and 10 liters of silicate potassium ha-1 and five replications. Plants treated with potassium silicate, regardless of the applied dose, had a lower O. ilicis infestation compared to the control, not allowing the population increase, thus a smaller damage in coffee leaves. The silicon content in leaves was higher in plants treated with the highest dose of potassium silicate. It was observed that there was induction of defense molecules such as tannins and lignin in plants sprayed with potassium silicate. It was concluded that the potassium silicate applied in leaf spraying had positive effect on reducing O. ilicis attack in coffee plants, even being a dicot. Therefore, the applications of potassium silicate by leaf spraying can be used in programs of integrated management of the southern red mite in coffee, with a view to sustainable management and environmental protection.

Progeny selections of coffee cultivar'Mundo Novo'with potential for the specialty coffee market

Coffee is one of the most popular beverages in the world with a global market worth over$USD 100 billion.In Brazil,the Arabica coffee(Coffea arabica)cultivar'Mundo Novo'is one of the most planted cultivars due to its high yield,growth vigor and stability.However,this traditional cultivar is generally not considered a good production source for specialty coffee.Exploring intra-cultivar variation and selecting'Mundo Novo'progenies with superior sensory quality may provide a viable option for coffee producers targeting the rapidly expanding specialty coffee market.The present study analyzed cup quality attributes,agronomic characteristics and genetic identities of 14 genotypes selected from the putative progenies of'Mundo Novo'and assessed their potential as specialty coffee in Brazil.Beverage quality was assessed using chemical and sensory analysis according to the methodology proposed by the Specialty Coffee Association(SCA)in six selected genotypes.High sensory quality,with sensory scores above 80 points was observed which qualified them in the very good and excellent quality categories.Genetic identities of the 14 selections were verified using 96 SNP markers,based on 57 reference cultivars from the coffee collection of EPAMIG(Empresa de Pesquisa Agropecuária de Minas Gerais),Brazil.Multivariant and Bayesian clustering analysis generated consistent results and confirmed that all the 14 selections were progenies of'Mundo Novo'.Among them,the top three genotypes(SGAB 1,SGAB 7 and SGAB 8)were selected as promising genotypes,either for future genetic improvement or for direct use in the production of specialty coffee.

Biological Control of Southern Red Mite,Oligonychus ilicis(Acari:Tetranychidae),in Coffee Plants

The species of mite Oligonychus ilicis (McGregor) (Tetranychidae) is an important pest of dicotyledonous plants, cosmopolitan and polyphagous, reported in seven countries from four continents, feeding on 34 plant species of 15 families. The spider mite O. ilicis is known in Brazil as coffee red spider mite, and as southern red mite most in other countries. In Brazil O. ilicis has been reported as the second most important pest of “Conillon” coffee, Coffea canephora Pierre & Froehner, in the state of Espírito Santo. Depending on the number of mites per leaf of arabica coffee, Coffea arabica L., the rate of potential photosynthesis can be reduced by 37% to 50%. In the present study, it was investigated the potential of the two predatory mites which, among others, naturally occurs in coffee plantations, Euseius alatus DeLeon and Amblyseius herbicolus (Chant) (Phytoseiidae), in the control of O. ilicis in coffee plants. It was used potted coffee plants in this research, with approximately 100 cm high, growing in a greenhouse covered with transparent plastic and shading material of 50% sun protection factor, and with fine mesh on all the sides. Results showed that both species of predatory mites, A. herbicolus and E. alatus, are efficient in reducing the mobile phases—larvae, protonymphs, deutonymphs and adults—of the southern red mite O. ilicis. So, the importance of conservation and increase number of these predatory mites in the field coffee growing is essential for implementing the southern red mite integrated management tactic, since these species are of natural occurrence in coffee plants.

AtDREB2A-CA Influences Root Architecture and Increases Drought Tolerance in Transgenic Cotton

Drought is a major environmental factor limiting cotton (Gossypium hirsutum L.) productivity worldwide and projected climate changes could increase their negative effects in the future. Thus, targeting the molecular mechanisms correlated with drought tolerance without reducing productivity is a challenge for plant breeding. In this way, we evaluated the effects of water deficit progress on AtDREB2A-CA transgenic cotton plant responses, driven by the stress-inducible rd29 promoter. Besides shoot and root morphometric traits, gas exchange and osmotic adjustment analyses were also included. Here, we present how altered root traits shown by transgenic plants impacted on physiological acclimation responses when submitted to severe water stress. The integration of AtDREB2A-CA into the cotton genome increased total root volume, surface area and total root length, without negatively affecting shoot morphometric growth parameters and nor phenotypic evaluated traits. Additionally, when compared to wild-type plants, transgenic plants (17-T0 plants and its progeny) highlighted a gradual pattern of phenotypic plasticity tosome photosynthetic parameters such as photosynthetic rate and stomatal conductance with water deficit progress. Transgene also promoted greater shoot development and root robustness (greater and deeper root mass) allowing roots to grow into deeper soil layers. The same morpho-physiological trend was observed in the subsequent generation (17.6-T2). Our results suggest that the altered root traits shown by transgenic plants are the major contributors to higher tolerance response, allowing the AtDRE2A-CA-cotton plants to maintain elevated stomatal conductance and assimilate rates and, consequently, reducing their metabolic costs involved in the antioxidant responses activation. These results also suggest that these morpho-physiological changes increased the number of reproductive structures retained per plant (26% higher) when compared with its non-transgenic counterpart. This is the first report of cotton plants overexpressing the AtDRE2A-CA transcription factor, demonstrating a morpho-physiological and yield advantages under drought stress, without displaying any yield penalty under irrigated conditions. The mechanisms by which the root traits influenced the acclimation of the transgenic plants to severe water deficit conditions are also discussed. These data present an opportunity to use this strategy in cotton breeding programs in order to improve drought adaptation toward better rooting features.