Andréa M.A. Gomes

Bacterização de sementes e desenvolvimento de mudas de pepino

Epiphytic and endophytic bacteria were isolated from healthy cucumber plants, collected in several counties of Pernambuco State, Brazil, and evaluated for seedling growth promotion under greenhouse conditions. Three bioassays were performed. In the first, 93 strains were tested; in the second, 32, and, in the third, eight from cucumber plus 10 bacterial epiphytic strains from other crops were used. The cucumber seeds were bacterized by immersion in the bacterial suspension adjusted to A580 = 0.7, sown in polystyrene trays filled with organic substrate and analyzed ten days after sowing in relation to shoot (MSPA), root (MSR), and total (MST) dry matter. In the third bioassay the epiphytes PEP52, PEP8, PEP82, PEP91, and C22 were selected because they significantly (P=0.05) elevated MSR and MST in relation to the control reaching higher values than 70 and 40%, respectively. After compatibility tests the five isolates applied separately and in mixtures efficiently increased the index of MSPA, MSR, and MST in cucumber seedlings, without differing among them. It is worth noticing that PEP81 (Bacillus amyloliquefaciens) and PEP91 (Enterobacter cloacae) increased 55.5 and 34.5% (MSPA), 42.9 and 37.2% (MSR), and 41.6 and 34.0% (MST), respectively. The production of indolacetic acid, hydrogen cyanide, phosphate solubilization and changes in foliar levels of N, P, K, Ca, and Mg were evaluated as putative mechanisms of action for theses isolates, but they showed negative results. Seed bacterization with B. amyloliquefaciens PEP81 and E. cloacae PEP91 could improve quality of cucumber seedlings.

Isolamento, seleção de bactérias e efeito de Bacillus spp. na produção de mudas orgânicas de alface

ABSTRACT Isolation, selection of bacteria, and effect of Bacillus spp. inthe production of organic lettuce seedlings Epiphytic and endophytic bacterial strains isolated from healthylettuce plants were evaluated for growth promotion of seedlings andplants respectively under greenhouse and field conditions of organicproduction of lettuce, in Brazil. The cultivar Veronica was utilized inthe greenhouse experiments and cvs. Veronica and Verdinha wereevaluated in the field. The strains were applied by simultaneousbacterization of seed and substrate. In the field the most efficient strainsC25 ( Bacillus thuringiensis subvar. kenyae ) and C116 ( Bacilluspumilus ) were utilized separated and in mixture after the compatibilityassay. In greenhouse root fresh weight (MFR), shoot fresh weight(MFPA) and total fresh weight (MFT) were evaluated 21 days afterbacterization. In field the total fresh weight of commercial plants wasdetermined 21 and 28 days after transplant, respectively for cvs.Verdinha and Veronica. The mechanisms of BPCP studied wereproduction of indolacetic acid, cyanidric acid, phosphate solubilizationand alterations of N, P, K, Ca and Mg foliar levels. In the greenhouse,seedlings treated with C116 showed significant increase in relation tocontrols for MFR, MFPA and MFT as well as those treated with C25for MFR and MFT. In the field cvs. Verdinha and Veronica treatedwith C25, C116 or mixture did not significantly differ from control.None of the analyzed mechanisms were positive but strain C25significantly increased the level of foliar N.

Tratamento pós-colheita com cálcio e microrganismos para controle da podridão-mole em tomate

The effect of three calcium sources [CaCl2, Ca (CO3)2 and Ca (SO4)2] at 1; 2; 4; 6 and 8% (w/v) were evaluated on control of soft rot caused by Pectobacterium carotovorum subsp. carotovorum (Pcc) in tomato fruits. The calcium sources were applied using vacuum infiltration. Fruits were inoculated with pathogen 24 h later by deposition of 10 ml of a bacterial suspension containing 108 CFU/ml, on artificial wounds. Fruits were incubated in a moist chamber at 92±4% relative humidity during 48 h and evaluated by measuring the lesion diameter in two opposite sides. The disease severity reduction (DSR) was calculated in relation to the control with calcium application. The best calcium source and concentration was CaCl2 8% which reduced the disease severity by 69.5%. The antagonists Rhodotorula sp. (LD-19) and a fluorescent Pseudomonas sp. (P-2) were tested separately and along with CaCl2 8%. The antagonist was applied by pouring 10 ml of suspensions (DO580=0.7) on the wounds 24 h after calcium treatment and 2 h before Pcc inoculation. The difference was significant among treatments and, the combination CaCl2 8% + LD19 showed 90% DSR. Isolates P-2 and LD-19 applied separated showed lower percentage of DSR.

Identificação de progênies de tomateiro resistentes à murcha-bacteriana

Six hundred and sixty F6 plants obtained from the crossing of cultivars CL5915-93 (moderately resistant) and IPA-6 (susceptible) were screened for resistance to bacterial wilt (Ralstonia solanacearum) under field conditions (28 ± 4oC and RH 70 ± 5,5%) in March 1996 at UFRPE. Twenty-day-old seedlings were inoculated with biovar III of the pathogen by pouring 5 ml of a suspension (5x108 UFC/ml) at the base of each seedling, two hours prior to transplanting. Evaluations were performed at weekly intervals until 70 days after inoculation. At the end of the crop cycle, 151 symptomless plants were selected and from this material one progeny was backcrossed with the cultivar IPA-6. 40 progenies (F2) from this backcross were screened for resistance under greenhouse conditions (35 ± 5,5oC and RH 77 ± 2,5%) in September 1997, using the inoculation method previously described. Evaluations of disease incidence and severity were made four, seven, ten, thirteen and 16 days after inoculation. The resistance reaction was also evaluated through incubation and latency periods. Twenty-eight days after inoculation the existence of latent infection in the resistant progenies was evaluated through vascular discoloration and pathogen isolation from processing material. Disease incidence was observed in 95% of the progenies. Eight progenies were ranked as moderately resistant and eight as resistant. The average incubation and latency periods were short (4.5 at 4.8 days) for control susceptible progenies and long (11.6 at 12.9 days) for resistant progenies. Latent infection was detected in 45% of resistant progenies.

Intensidade da cercosporiose da alface em cultivos convencionais e orgânicos em Pernambuco

Surveys of the intensity of cercospora leaf spot of lettuce caused by Cercospora longissima were performed in 25 conventional and 25 organic farming areas in 2 planting periods, January-April (I) and June-September (II) 2002, in State of Pernambuco (Brazil). Disease prevalence was high (> 88%) in all evaluated situations. Disease severity ranged from 0.0 to 16.9% in conventional farming areas and from 0.0 to 22.5% in organic farming areas. In both systems, disease severity was significantly higher in period I when precipitation was almost 3 times higher to that in period II. However, only in period II, significant differences in disease severity were found between farming systems, with high values in the organic system. There were no significant correlations among disease severity levels in the areas in both evaluated periods inside each farming system.

Biocontrole da mancha-aquosa do melão pelo tratamento de sementes com bactérias epifíticas e endofíticas

Epiphytic and endophytic bacteria (96 strains) and endophytic fungi (69 strains) were isolated from symptomless melon plants and tested for control of fruit blotch under greenhouse conditions, by treating seeds previously inoculated with Acidovorax avenae subsp. citrulli or treating healthy seeds in order to protect the plant challenged later with the pathogen. Melon seeds were microbiolized by immersion in suspensions (A570= 0,7), sown and evaluated for incubation period (PI), incidence (INC), disease severity (SEV) and disease severity reduction (RSD). Only microbiolization of artificially infected seed using the endophytic ENM5 (not identified), ENM9 (Bacillus cereus), ENM13 (Bacillus sp.), ENM16 (Bacillus cereus), ENM32 (Bacillus subtilis) and ENM43 (Bacillus sp.), showed potencial for disease control. After in vitro compatibility tests, these strains were reevaluated separately and in pairs, in relation to PI, INC, SEV, RSD, disease index (IDO) and area under disease progress curve (AACPD). All treatments differed significantly (P= 0.05) from the control reaching 93.6% of RSD, with emphasis for ENM13 and ENM9 with 7.5 and 7.25 days of PI, 0.22 and 0.22 of SEV, 2.59 and 2.59 of IDO, and 0.22 and 0.39 of AACPD, respectively. In vitro tests to determine the putative mechanisms of action involved in biocontrol were performed. ENM13 and ENM9 solubilized phosphate, ENM5 presented antibiose against A. avenae subsp. citrulli, and ENM43 produced HCN while ENM16 and ENM32 did not show any of the tested mechanisms.

Caracterização de isolados de Colletotrichum lagenarium de pepino com base em marcadores isoenzimáticos

The knowledge of genetic variability of Colletotrichum lagenarium isolates is highly important for the success of the breeding programs for resistance to cucumber anthracnosis. Nineteen isolates of C. lagenarium obtained from commercial fields of cucumber in Zona da Mata and Agreste of Pernambuco State, Brazil, were compared by isoenzyme electrophorectic analysis in polyacrylamide gel at 7%, using the systems esterase, acid phososphatase, alkaline phosphatase and malic dehydrogenase. The evaluation was based on the number and position of observed bands, calculating the relative motility. The genetic distances and similarities were summarized by grouping analysis, using the software NTSYS. The analysis showed variation in number and position of the bands on gel, for each studied system, revealing phenotypic differences in the population. The enzymes malic dehydrogenase and alkaline phosphatase showed lower polymorphism, while sterase and acid phosphatase were more polymorphic. The grouping analysis allowed to separate the genotypes in five different groups: 1 (CL1, CL3 and CL22), 2 (CL14), 3 (CL4, CL38, CL15, CLl7, CL5, CL8, and CL10), 4 (CL28) and 5 (CL23, CL20, CL34, CL36, CL35, CL37, and CL16). The lower genetic similarity index (27.3%) was observed among isolates CL1 and CL20, CL35, CL37 and CL16 and the higher (100%), was observed among isolates CL5 and CL8; CL5 and CL10; CL8 and CL10; CL35 and CL37; CL35 and CL16 and, CL37 and CL16.