Assessment of tolerance to bud rot in oil palm under field conditions

Abstract

Bud rot (BR), caused by Phytophthora palmivora, is one of the most devastating diseases affecting oil palm. It has destroyed oil palm plantations in countries throughout Latin America. To assess their resistance to BR, two cultivars of African oil palm (Elaeis guineensis Jacq.) and two interspecific OxG (E. oleifera × E. guineensis Coari × La Me and Coari × Pobe) hybrids were planted under field conditions in a plantation with a strong presence of BR. Incidence and severity data were recorded for 1812 days from the date of planting; the disease index was estimated, and progress curves were constructed and adjusted to monomolecular, logistic and Gompertz models. Severity progression and incidence progression rates for each cultivar were estimated using a simple linear regression. Statistical comparisons of the parameters were performed using Student's t-tests. Survival analyses were performed for each of the cultivars. Log-rank statistics were used to compare the responses of the cultivars to BR. Severity progression in the interspecific hybrids was significantly slower than that in the E. guineensis cultivars. No statistically significant differences were found in the progression rates among the hybrids; however, the survival analysis did show statistically significant differences. The Coari × Pobe hybrid had the longest survival time. Considering that partial resistance does not prevent plants from becoming infected but does slow disease progression, the two evaluated hybrids may have commercially valuable levels of resistance.