Morphophysiological changes in melon and cucumber plants, quality of melon fruits and protection of cucumber against Colletotrichum lagenarium, caused by paclobutrazol

Apesar do potencial do Paclobutrazol (PBZ), tanto como fitorregulador e agente elicitor, pesquisas sobre sua utilização em cucurbitáceas ainda são escassas. Este trabalho consistiu de quatro experimentos e objetivou: avaliar o efeito do PBZ sobre as características morfofisiológicas de plantas e sobre a qualidade de frutos de meloeiro; detectar e quantificar a possível presença de resíduo de PBZ na polpa de melão por meio da Cromatografia Líquida de Alta Eficiência (HPLC); e verificar as alterações morfofisiológicas e o potencial elicitor do PBZ contra Colletotrichum lagenarium em plantas de pepino, agente causal da antracnose nesta cultura. No experimento 1, os tratamentos consistiram de 11 doses de PBZ (2; 4; 8; 12; 16; 20; 30; 40; 50; 60 e 70 mg PBZ planta-1) e o controle (plantas não tratadas). No experimento 2, foram utilizadas quatro doses de PBZ (0,4; 0,8; 1,2 e 1,6 mg PBZ planta-1) e o controle. No experimento 3, oito frutos por tratamento foram coletados para a detecção e quantificação de resíduo de PBZ na polpa do melão. No experimento 4, foram testados dois isolados de C. lagenarium (CLKJ11 e CLKJ25) em 7 tratamentos: meio BDA puro (testemunha) e acrescidos com concentrações dos compostos PBZ (50, 100, 200 e 400 mg PBZ L-1), FTT (Tebuconazole + Trifloxystrobin) (100 mg L-1) e FTB (Tebuconazole) (200 mg L- 1) para o bioensaio. Para a avaliação das alterações morfofisiológicas e o potencial elicitor do PBZ, as plantas de pepino foram tratadas com 4 doses de PBZ (50, 100, 200 e 400 mg PBZ planta-1) e suas folhas inoculadas com a suspensão de conídios do isolado CLKJ25, na concentração 1x10-8 conídios mL-1. O PBZ é extremamente efetivo na redução do porte de plantas de melão e de pepino, demonstrando ser uma alternativa eficaz no manejo dessas plantas no cultivo em casa de vegetação. Além disso, o PBZ não afetou a produtividade, a aparência e os atributos de qualidade dos frutos do meloeiro e não foram detectados resíduos deste fitorregulador na polpa dos melões. O PBZ também revelou-se eficaz na inibição do crescimento micelial de C. lagenarium e na redução da área foliar lesionada por este patógeno. Todavia, este fitorregulador não pode ser considerado um agente indutor de resistência de plantas devido ao efeito tóxico sobre o patógeno avaliado.Despite the potential of Paclobutrazol (PBZ) as a plant growth regulator and elicitor agent, researches about its use in cucurbits are still scarce. This study was divided in 4 experiments and aimed: to evaluate the PBZ effects on development of melon plants; to evaluate the PBZ effect on morphophysiological features and quality of melon fruits; to detect and quantify PBZ residue in melon pulp using High Performance Liquid Chromatography (HPLC); and finally, verify morphophysiological changes and its elicitor potential against C. lagenarium in cucumber plants, causal agent of anthracnose in this culture. At first, treatments consisted of 11 PBZ doses (2, 4, 8, 12, 16, 20, 30, 40, 50, 60 and 70 mg PBZ plant-1) and the control (untreated plants). In the second experiment 4 PBZ doses were used (0.4, 0.8, 1.2 and 1.6 mg PBZ plant-1) and the control. To the third experiment, 8 fruits per treatment were collected to detect and quantify PBZ residues on melon pulp. In the fourth experiment, two C. lagenarium isolates (CLKJ11 and CLKJ25) were tested in 7 treatments: pure BDA medium (control) and plus with PBZ concentrations (50, 100, 200 and 400 mg L-1), FTT (Tebuconazole + Trifloxystrobin) (100 mg L-1) and FTB (Tebuconazole) (200 mg L-1) to the bioassay. To evaluate the morphophysiological changes and elicitor potential of PBZ, cucumber plants were treated with 4 PBZ doses (50, 100, 200 and 400 mg PBZ plant-1) and its leaves inoculated with suspension of isolate CLKJ25 at concentration of 1x10-8 conidia mL-1. PBZ is extremely efficient in reducing the size of melon and cucumber plants proving to be an effective alternative for management in green house crop. In addition, PBZ did not affect the productivity, appearance and quality attributes of melon fruits and no residue was found in melon pulp. The PBZ also proved to be effective in inhibiting the C. lagenarium mycelial growth and in the reduction of lesioned leaf area by this pathogen. Even so, this phytoregulator can not be considered a plant resistance inducer due to the toxic effect on the tested pathogen.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Potential role of weather, soil and plant microbial communities in rapid decline of apple trees.

An unusual decline and collapse of young established trees known as "rapid apple decline" (RAD) has become a major concern for apple growers, particularly in the northeastern United States. This decline is characterized by stunted growth, pale yellow to reddish leaves, and tree collapse within weeks after onset of symptoms. We studied declining apple trees to identify potential involvement of abiotic and biotic stresses. We used 16S and ITS to profile bacterial and fungal communities in the soil, rhizosphere, roots, and shoots and tested for the presence of six viruses in scions and rootstocks of symptomatic and asymptomatic trees. The viruses detected were not associated with RAD symptoms. Bacterial and fungal populations were highly variable in plant tissue, soil and rhizosphere samples, with bacteroidetes, firmicutes, proteobacteria, acidobacteria, and actinobacteria the predominant bacterial classes in various samples. 'Alphaproteobacteria-rickettsiales', a bacterial class usually reduced in water-limiting soils, had significantly low abundance in root samples of symptomatic trees. Basidiomycota and Ascomycota fungal classes were the most common fungal classes observed, but neither showed differential enrichment between symptomatic and asymptomatic trees. Analyzing weather data showed an extremely cold winter followed by drought in 2015-2016, which likely weakened the trees to make them more susceptible to varied stresses. In addition, similar physical and nutritional soil composition from symptomatic and asymptomatic trees rules out the role of nutritional stress in RAD. Necrotic lesions and wood decay symptoms dispersing from bark or vascular cambium towards the heartwood were observed primarily below the graft union of declining apple trees, suggesting that the rootstock is the originating point of RAD. We speculate that differences in abiotic factors such as moisture levels in declining roots in combination with extreme weather profiles might cause RAD but cannot clearly rule out the involvement of other factors

Differential gene regulatory pathways and co-expression networks associated with fire blight infection in apple (Malus × domestica)

Disease resistance: How apples fight blight Different apple varieties, such as ‘Gala’ and ‘Empire,’ defend themselves against fire blight in different ways, and studying how they do it may help in breeding varieties with better resistance. Fire blight is a devastating bacterial disease that can destroy entire orchard blocks in a single season. Breeding for increased resistance is one of the most efficient ways to combat it. Some apple varieties are naturally more resistant than others, but the underlying genetics are not well understood. Awais Khan at Cornell University in New York and co-workers investigated how the ‘Gala’ and ‘Empire’ varieties defend themselves in the first 72 h after infection. ‘Empire’ showed stronger resistance than ‘Gala,’ with many distinct resistance mechanisms. The researchers identified several resistance genes in each variety, which may eventually be used in breeding more blight-resistant apple varieties

Monosporascus cannonballus: AGENTE CAUSAL DO COLAPSO OU MORTE SÚBITA DO MELOEIRO

O fungo Monosporascus cannonballus destaca-se como um dos principais fitopatógenos envolvidos no Colapso ou Morte Súbita do meloeiro. Trata-se de um fitopatógeno habitante natural do solo, termófilo e bem adaptado às condições áridas e semi-áridas, e por isso, responsável por grandes perdas, limitando o cultivo de melão em diversas regiões do mundo. Inúmeras medidas de controle têm sido estudadas, entretanto, estas ainda são pouco eficazes. Apesar da importância desta síndrome, poucos são os estudos sobre o potágeno. Desta forma, informações epidemiológicas da doença constituem importantes aspectos no desenvolvimento de estratégias para seu manejo integrado

Plant Growth-Promoting (PGP) Traits of Endophytic Bacteria from In Vitro Cultivated <i>Tectona grandis</i> L.f

Tectona grandis L.f. (teak) is a tropical tree cultivated mainly due to its resistance, valuable wood and tolerance to biotic and abiotic factors. An abundant bacteria community exists in teak tissues and knowledge of the functional roles of teak endophytic bacteria, from in vitro tissue culture, is essential for improving micropropagation techniques. In this study, we isolated endophytic bacteria with plant growth-promoting (PGP) traits from two teak clones (Proteca® A3 and E4) in calli, leaves, and stems segments in a culture medium. We analyzed colony pigmentation, gram reaction, and evaluated PGP traits (phosphorous solubilization, nitrogen fixation and indol-acetic acid production) of 54 colonies from clone A3 and 50 colonies from clone E4. A total of 35 colonies of clone A3 and 42 colonies of clone E4 were capable of fixing nitrogen. Four isolated bacteria from clone A3 were capable of solubilizing phosphorous (P-Ca3(PO4)2), while no strain of E4 clone showed that capacity. Furthermore, 49 endophytic bacteria from clone A3 showed capacity to synthesize indol-acetic acid, while only 4 bacteria from the E4 clone presented that characteristic. We also identified six teak endophytic bacteria, by analysis of the 16S-23S rDNA intergenic spacer region, showing high identity with the genera Curtobacterium sp., Ochrobactrum sp., and Bacillus spp. Therefore, we demonstrate here that the abundant bacterial community existing in teak tissues, including those of in vitro cultivated plants, have PGP traits that can be further harnessed for preparation of bioformulations, for example. Our findings open the possibility for studying these isolated endophytic bacteria more closely in order to understand their association with teak growth

USO DE DIFERENTES SUBSTRATOS E DO SUPERFOSFATO SIMPLES NA PRODUÇÃO DE MUDAS DE NESPEREIRA (Eriobotrya japonica Lind)

It was carried out, in the nursery area located at Campus of Federal University of Lavras (UFLA) Minas Gerais, an experiment aiming to evaluate different doses of simple super phosphate and two substrates in plant production of loquat tree. It was tested four doses of simple super phosphate (0; 2.5; 5; 10 kg m-3 of substrate) and two substrates: A (organic compost + sand + soil in 1:1:3 volume proportion) and B ( Plantmax + sand + soil 1:1:3 volume proportion) A randomized block design was used with a 4 x 2 factorial scheme, with four replications and four plants per plot. The following characteristics were evaluated: high of plants (cm); length of root (cm); number of leaves/plant, dry matter of above ground part, roots and total (g/plant). The results showed that for seedlings of loquat tree, it is recommended to mix to substrate the super phosphate fertilizer in doses until 6 kg m-3. Between the substrates, the one the showed more viable was the substrate A (organic compost + sand + soil in 1:1:3 volume proportions)

The Arabidopsis ELP3/ELO3 and ELP4/ELO1 genes enhance disease resistance in Fragaria vesca L.

Abstract Background Plant immune response is associated with a large-scale transcriptional reprogramming, which is regulated by numerous transcription regulators such as the Elongator complex. Elongator is a multitasking protein complex involved in diverse cellular processes, including histone modification, DNA methylation, and tRNA modification. In recent years, Elongator is emerging as a key regulator of plant immune responses. However, characterization of Elongator’s function in plant immunity has been conducted only in the model plant Arabidopsis thaliana. It is thus unclear whether Elongator’s role in plant immunity is conserved in higher plants. The objective of this study is to characterize transgenic woodland strawberry (Fragaria vesca L.) overexpressing the Arabidopsis Elongator (AtELP) genes, AtELP3 and AtELP4, and to determine whether F. vesca carries a functional Elongator complex. Methods Transgenic F. vesca and Arabidopsis plants were produced via Agrobacterium-mediated genetic transformation and characterized by morphology, PCR, real-time quantitative PCR, and disease resistance test. The Student’s t test was used to analyze the data. Results Overexpression of AtELP3 and AtELP4 in F. vesca impacts plant growth and development and confers enhanced resistance to anthracnose crown rot, powdery mildew, and angular leaf spot, which are caused by the hemibiotrophic fungal pathogen Colletotrichum gloeosporioides, the obligate biotrophic fungal pathogen Podosphaera aphanis, and the hemibiotrophic bacterial pathogen Xanthomonas fragariae, respectively. Moreover, the F. vesca genome encodes all six Elongator subunits by single-copy genes with the exception of FvELP4, which is encoded by two homologous genes, FvELP4–1 and FvELP4–2. We show that FvELP4–1 complemented the Arabidopsis Atelp4/elo1–1 mutant, indicating that FvELP4 is biologically functional. Conclusions This is the first report on overexpression of Elongator genes in plants. Our results indicate that the function of Elongator in plant immunity is most likely conserved in F. vesca and suggest that Elongator genes may hold potential for helping mitigate disease severity and reduce the use of fungicides in strawberry industry

FORMATION OF CASHEW AND TAMARIND ROOTSTOCKS INFLUENCED BY NITROGEN LEVELS

The purpose of this study was to assess the seedling growth of cashew and tamarind rootstocks with nitrogen fertilization. To this end, two experiments were conducted in the Production Sector of the State University of Mato Grosso do Sul (UEMS), at the University Unit of Cassilândia (UUC), Brazil. Five nitrogen levels were tested: 0, 400, 800, 1600 and 3200 mg/dm3 of N in the substrates. The experimental design was in randomized blocks with 4 repetitions and ten plants per parcel. 20 ml of urea solution were added to each application from each treatment containing 45% nitrogen. The application was repeated four times. Ninety days after planting, we assessed plant height (cm), number of leaves/seedling, plant diameter (mm), roots, aerial part, root and total dry matter (g/seedling). Nitrogen fertilizer in doses of up to 2000 mg/dm3 of N in the substrate ensures better cashew and tamarind rootstock seedling quality. A 3200 mg/dm3 dose of N in the substrate had a growth depression effect on the rootstock seedlings