Stela Dalva Vieira Midlej Silva

Novel sources of witches’ broom resistance (causal agent Moniliophthora perniciosa) from natural populations of Theobroma cacao from the Brazilian Amazon

Witches’ broom is a severe disease of Theobroma cacao L. (cacao), caused by the basidiomycete Moniliophthora perniciosa. The use of resistant cultivars is the ultimate method of control, but there are limited sources of resistance. Further, resistance from the most widely used source (‘Scavina 6’) has been overcome after a few years of deployment. New sources of resistance have been intensively searched for in the Amazon basin. Here, we evaluated for witches’ broom resistance, cacao accessions from various natural cacao populations originally collected in the Brazilian Amazon. Resistance of 43 families was evaluated under nursery and/or field conditions by artificial or natural infection, respectively, based on disease incidence. Screening for resistance by artificial inoculation under nursery conditions appeared to be efficient in identifying these novel resistance sources, confirmed by natural field evaluation over a nine-year period. The increase in natural field infection of ‘Scavina 6’ was clearly demonstrated. Among the evaluated families with the least witches’ broom incidence, there were accessions originally collected from distinct river basins, including the Jamari river (‘CAB 0371’; ‘CAB 0388’; ‘CAB 0392’; and ‘CAB 0410’); Acre (‘CAB 0169’); Javari (‘CAB 0352’); Solimões (‘CAB 0270’); and from the Purus river basin, the two most outstanding resistant accessions, ‘CAB 0208’ and ‘CAB 0214’. The large genetic diversity found in cacao populations occurring at river basins from Acre and Amazonas states, Brazil, increased the chance that the selected resistant accessions would be genetically more dissimilar, and represent distinct sources of resistance to M. perniciosa from ‘Scavina 6’.

Resistência de progênies de cacaueiro à murcha-de-Ceratocystis

Resistance of progenies of cacao to Ceratocystis wilt Seedlings from open-pollinated progenies of 20 clones of cocoa (Theobroma cacao) were inoculated with the fungus Ceratocystis cacaofunesta, the causal agent of Ceratocystis wilt, and their response was assessed based on the percentage of dead plants. Open pollinated progeny of clones TSH1188 and VB1151 were used as standards for resistance, while CCN51 and SJ02 for susceptibility. Contrasts between these benchmarks and the progenies studied were estimated and evaluated by Dunnett’s t test (α = 0.05). The progenies showed different responses to C. cacaofunesta, and it was possible to classify them into three groups: resistant (FCB01, CSG70, BOBA01, VB902, TSH1188, VB1151, PS1319 and MAC01), moderately susceptible (HW25, PM02, FA13, PH15, M05 and BJ11) and susceptible (CCN51, FB206, PH16, SJ02, CCN10 and FSU77).

Reação de genótipos de cacaueiros a isolados de Ceratocystis cacaofunesta

Seventeen genotypes of cocoa (Theobroma cacao) were tested for reaction to Ceratocystis wilt caused by Ceratocystis cacaofunesta, using the three most virulent isolates among five isolates tested. In greenhouse conditions, a suspension containing 3.0 x 104 CFU/mL of each isolate was inoculated on six-month-old seedlings. The assay was carried out using a randomized complete block with 17 treatments, three replications and five seedlings per experimental unit. Assessments were made at 60 days after the inoculation date, by counting the number of healthy seedlings per plot unit. The data were analyzed by SAS statistical procedure and treatment averages were tested by Dunnett test at 5% significance level, using the cultivar Theobahia as control. From the genotypes analyzed, VB 1159 showed high resistance to the pathotype. The genotypes MUC 43, FL 78, VB 681, FC 101, VB 184, LP 06, ICS1, VB 902, FA 13, NO 34, PS 5784 and Theobahia showed moderate resistance, while CA 1.4, VB 206, LCT 37A and SJ 02 were the most susceptible genotypes. The new resistance source to Ceratocystis wilt identified in this work may be used in cocoa breeding programs and as a source of rootstock selection by farmers.

Phytophthora cinnamomi na rizosfera de cultivos agrícolas no Sul da Bahia

Setor de Fitopatologia, Centro de Pesquisas do Cacau, CEPLAC, CEP 45600-970, Ilheus-BA, Brasil. 1Parte da Dissertacao de Mestrado em Producao Vegetal/UESC do primeiro AutorAutor para correspondencia: Marcos Vinicius Oliveira dos Santos (marcosvos@ymail.com)Data de chegada: 16/10/2013. Aceito para publicacao em: 18/02/2014. 1943Aproximadamente 24 especies de

Aspectos histopatológicos da interação Phytophthora palmivora com a pupunheira

Aiming to study the interaction Phytophthora palmivora and pejibaye palm (Bactris gasipaes Kunt.) with the aid of scanning electron microscope (SEM), sections were made of the stem base of pejibaye plants in the sites where six-month-old pejibaye seedlings were inoculated. The inoculation methods used were: i. inoculation with 5 µL drops of zoospore suspension (1x106 zoopores/mL); ii. irrigation around the stem base of seedlings, with 5 mL of a suspension of 1 x 106 zoospores/mL; and iii. inoculation with a 7-mm-diameter disk of mycelium. Tissue sections were made 6 and 12 hours after inoculation, following the conventional process of fixation, dehydration and metallization steps for SEM. Encysted zoospores and sporangia attached to host epidermis were seen 6 and 12 hours after inoculation, with the pre-infection phase occurring before that stage. Independently of the inoculation method employed, host tissue colonization could be observed in all inoculated plants.