A disease and production index (DPI) for selection of cacao (Theobroma cacao) clones highly productive and tolerant to pod rot diseases

Abstract

Frosty pod rot (FPR) (Moniliophthora roreri), along with black pod rot (Phytophthora species) and witches’ broom disease (Moniliophthora perniciosa) constitute the main phytosanitary problems limiting cacao (Theobroma cacao) production causing severe yield losses. One of the main sought after methods of pod rot management is the selection of tolerant cacao genotypes. Typically, the selection is carried out through the quantification of the percentage of diseased pods (PDP). However, PDP does not consider the relative productivity, or production potential (PT) of the genotype. Production potential can vary among cacao genotypes. Consequently, genotypes with similar PT can have similar or vastly different disease tolerance levels as measured by PDP. The disease and production index (DPI) was developed to integrate a genotype's tolerance to M. roreri and other diseases as measured by PDP, with its PT. Here, we evaluated the number of healthy pods, number of diseased pods, and weight of fresh seed for 29 clones grown in replicated five‐tree plots over 4 years. The data obtained was used to calculate PDP and DPI for each clone for three different disease combinations: frosty pod rot alone, pod rots other than frosty pod rot, and the combination of all pod rots. Multivariate analysis verified that DPI discriminated between clones based on productivity and disease tolerance. Surprisingly, there was a close ranking of clones between resistance to FPR and resistance to all other pod rots. The DPI can be used in breeding programmes focused on the selection of high yielding disease‐tolerant cacao genotypes.

Physiological and root morphological responses in different combinations of rootstock-scion of cacao to water deficit

“…The first two were recently released by INIAP (Loor et al, 2019), and the last ones were obtained from crosses of pre-selected National-type clones based on characteristics of productivity and tolerance to diseases with CCN 51 clone. These clones are still under evaluation of yield and disease tolerance (Jaimez et al, 2018;Jaimez et al, 2020). At 126 days after sowing, when the seedlings had between six to eight leaves, seedlings of each rootctock were grafted with different scions using the bud grafting method.…”

“…Los dos primeros fueron lanzados recientemente por el INIAP (Loor et al, 2019), y los últimos se obtuvieron a partir de cruces de clones tipo National, preseleccionados en función de características de productividad y tolerancia a enfermedades con el clon CCN 51. Estos clones aún están bajo evaluación de rendimiento y tolerancia a enfermedades (Jaimez et al, 2018: Jaimez et al, 2020. A los 126 días después de la siembra, cuando las plántulas tenían entre seis y ocho hojas, las plántulas de cada portainjerto fueron injertadas con los diferentes clones utilizando el método de injerto lateral.…”

Challenges to Cocoa Production in the Face of Climate Change and the Spread of Pests and Diseases

“…Multi-criteria selection is therefore necessary to develop varieties that meet the various objectives of the production chain. Selection indexes can be constructed for this purpose in order to jointly improve several characteristics [54,55], and molecular markers could be also developed in order to reduce breeding/selection cycles.…”

Theobroma Grandiflorum Breeding Optimization Based on Repeatability, Stability and Adaptability Information

“…Variation throughout years can create different environments, which, in turn, will influence genotypes differently (Jaimez et al 2020). The evaluation of genotypes across several harvests is crucial in perennial fruit trees as it enables the quantification of the genotype x measurement (GM) interaction effect and estimates of the repeatability coefficient to determine the optimal number of harvests necessary to conduct effective genetic selection (Resende 2015;Ferreira et al, 2020).…”