Resistance to witches’ broom in adult plants and progeny of local varieties of cacao in Southern Bahia

Abstract

Plants of local cacao variety from Southern Bahia were evaluated in order to verify if there are different levels of resistance to witches' broom disease in the study population and if the evaluation of adult plants in the field is a good predictor of these resistance levels. The seedlings were maintained under greenhouse conditions and inoculated with the fungus Moniliophthora perniciosa. Evaluations of symptoms occurred 60 days after inoculation. In the field, the same genotypes were evaluated by counting the number of dry brooms per plant, per year, and assessing trunk diameter size. The data were subjected to analysis of variance and averages grouped by the Scott-Knott test, differentiated by Tukey's test and compared by Student's T test. The Scavina-6 and CCN51 clones as well as the Catongo variety were used as resistance, moderate resistance and susceptibility patterns, respectively. Twenty-eight percent of the genotypes were among the most resistant and the genotypes 4119 and 4033 were considered the most susceptible to the disease in both field and greenhouse evaluations. Field evaluation was promising as a predictor of resistance level. The selected materials presented good characteristics for witches' broom resistance, with different levels deserving special attention in the context of reducing the vulnerability of Brazilian cacao cultivation to the effects of the disease, especially in the cacao region of Bahia.

Early selection for resistance to cacao witches’ broom in new parental combinations

“…In Brazil, the most adopted resistant pattern is SCA 6 and the susceptible Catongo (a mutation of 'Comum' variety with white seeds) and/or SIC 23 (a 'Comum' selection at the Cacao Institute). In previous inoculation studies, all three patterns performed as expected (2, 5, 13,18,21,23,5,21,13).…”

Há variabilidade para resistência à Murcha de Ceratocystis em variedades locais de cacau na Bahia

“…Ao selecionar os genótipos com médias inferiores ou iguais estatisticamente ao controle resistente, foram identificadas 86 plantas resistentes para o primeiro ciclo de seleção. No entanto, a combinação dessa seleção com os resultados prévios da resistência à Vassoura de bruxa (24), na busca de resistência a múltiplas doenças, levou à redução do número total de plantas selecionadas.…”

“…Fonte: dados desta pesquisa.Dentre estas, MA apresentou maior número de plantas resistentes à Murcha de Ceratocystis no presente trabalho, como também nos estudos prévios de resistência à Vassoura de bruxa do cacaueiro(24). Parte desses genótipos, quando previamente analisados quanto à resistência à Podridão parda (causada por Phytophthora palmivora) e genotipados com marcadores moleculares, apresentou diversidade genética molecular dentro dos grupos resistentes e suscetíveis à podridão parda, bem como dentro de cada uma das três variedades(26).…”

Cacao genotypes cultivated in agroforestry systems in Bahia have wide genetic variability in morpho-agronomic characters

“…All cacao plantations were covered by native trees with around 50% insolation, mechanical mowing of spontaneous plants three times a year, and pruning undesirable cacao shoots once or twice a year in the last four years. These genotypes are locally recognized and commercially available in the region, and most of their resistance capacity against Moniliophthora perniciosa was previously assessed (Pinto;Pires, 1998;Marssaro et al, 2020). In total, 51 genotypes were evaluated: Comum, Maranhão, Pará, Parazinho, Redondo, and clones CCN51 and PS1319.…”