Combining ability, heritability and genotypic relations of different physiological traits in cacao hybrids

Cocoa Apoplastome Contains Defense Proteins Against Pathogens

The apoplast performs important functions in the plant, such as defense against stress, and compounds present form the apoplastic washing fluid (AWF). The fungus Moniliophthora perniciosa, the causal agent of witches' broom disease (WBD) in Theobroma cacao, initially colonizes the apoplast in its biotrophic phase. In this period, the fungus can remain for approximately 60 days, until it changes to its second phase, causing tissue death and consequently large loss in the production of beans. To better understand the importance of the apoplast in the T. cacao-M. perniciosa interaction, we performed the first apoplastic proteomic mapping of two contrasting genotypes for WBD resistance (CCN51-resistant and Catongo-susceptible). Based on two-dimensional gel analysis, we identified 36 proteins in CCN-51 and 15 in Catongo. We highlight PR-proteins, such as peroxidases, β-1,3-glucanases, and chitinases. A possible candidate for a resistance marker of the CCN-51 genotype, osmotin, was identified. The antioxidative metabolism of the superoxide dismutase (SOD) enzyme showed a significant increase (P < 0.05) in the AWF of the two genotypes under field conditions (FD). T. cacao AWF inhibited the germination of M. perniciosa basidiospores (>80%), in addition to causing morphological changes. Our results shed more light on the nature of the plant's defense performed by the apoplast in the T. cacao-M. perniciosa interaction in the initial (biotrophic) phase of fungal infection and therefore make it possible to expand WBD control strategies based on the identification of potential targets for resistance markers and advance scientific knowledge of the disease.

Combining Ability and Molecular Marker Approach Identified Genetic Resources to Improve Agronomic Performance in Coffea arabica Breeding

Plant breeding aims to develop cultivars with good agronomic traits through gene recombination and elite genotype selection. To support Coffea arabica breeding programs and assist parent selection, molecular characterization, genetic diversity (GD) analyses, and circulating diallel studies were strategically integrated to develop new cultivars. Molecular markers were used to assess the GD of 76 candidate parents and verify the crossing of potential F1 hybrids. Based on the complementary agronomic traits and genetic distance, eight elite parents were selected for circulating diallel analysis. The parents and 12 hybrids were evaluated based on 10 morpho-agronomic traits. For each trait, the effects of general and specific combining abilities, as well as the averages of the parents, hybrids, and predicted hybrids, were estimated. Crosses that maximize the genetic gains for the main agronomic traits of C. arabica were identified. Joint analysis of phenotypic and molecular data was used to estimate the correlation between molecular GD, phenotypic diversity (PD), phenotypic mean, and combining ability. The selection of parents that optimize the allele combination for the important traits of C. arabica is discussed in detail.

Genetic combining ability of coriander genotypes for agronomic and phytochemical traits in response to contrasting irrigation regimes

Knowledge of genetic combining ability and gene action would help breeders to choose suitable parents and devise an appropriate breeding strategy for coriander. In the present study, six diverse genotypes of coriander, their 15 F₁s and 15 F₂s were evaluated through randomized complete block design with three replications to study genetic combining ability for agronomic and phytochemical traits in coriander. Plants were subjected to well-watered (WW), mild water-deficit stress (MWDS) and severe water-deficit stress (SWDS) irrigation regimes. The results indicate that water-deficit stress decreased all of the measured traits in both the F₁ and F₂ generations. General combining ability and specific combining ability effects were highly significant for all of the traits in both the F₁ and F₂ generations. Additive gene action was predominant for phonology and fruit yield component traits in all irrigation regimes in both the F₁ and F₂ generations. For fatty acid content and total lipid yield, non-additive gene action was predominant in the F₁ generation while additive gene action was predominant in the F₂ generation under MWDS and SWDS conditions. The P₄ parent had the highest general combining ability for fruit yield components in both the F₁ and F₂ generations. The P₆ parent had the highest general combining ability for phenological and phytochemical traits. The P₄ and P₆ parents are promising material to develop early flowering and early maturing genotypes coupled with high total lipids in advanced generations of segregation.

Cacao biotechnology: current status and future prospects

Theobroma cacao-The Food of the Gods, provides the raw material for the multibillion dollar chocolate industry and is also the main source of income for about 6 million smallholders around the world. Additionally, cocoa beans have a number of other nonfood uses in the pharmaceutical and cosmetic industries. Specifically, the potential health benefits of cocoa have received increasing attention as it is rich in polyphenols, particularly flavonoids. At present, the demand for cocoa and cocoa-based products in Asia is growing particularly rapidly and chocolate manufacturers are increasing investment in this region. However, in many Asian countries, cocoa production is hampered due to many reasons including technological, political and socio-economic issues. This review provides an overview of the present status of global cocoa production and recent advances in biotechnological applications for cacao improvement, with special emphasis on genetics/genomics, in vitro embryogenesis and genetic transformation. In addition, in order to obtain an insight into the latest innovations in the commercial sector, a survey was conducted on granted patents relating to T. cacao biotechnology.