Cacao Genotypes Research Articles

Selection of putative relic cacao (Theobroma cacao L.) genotypes in farmers' fields in Trinidad and Tobago

Trinidad and Tobago is a repository of putative relic cacao genotypes, given its long history of cultivating cacao from the 1700s onwards. As part of a project conducted between 2009 and 2011, funded by the World Bank Development Market Place, World Bank Project TF 093747 (DM 2008), 106 putative, ancient cacao varieties were collected from farms throughout Trinidad and Tobago to be conserved and utilized to preserve traditional quality (flavour) attributes. The objective of this article is to provide information on agronomic and phenotypic traits of 94 of these 'relic' accessions collected in farmers' fields (FA). These are presumed to be relic Criollos or Trinitarios (selected pre-and post-1930s), and were selected over six cocoa production zones in Trinidad and Tobago. In addition, data for 31 regional Trinitario cacao accessions, which are conserved at the International Cocoa Genebank Trinidad (ICGT) were assessed. Morphological assessment of the selections was based on 22 phenotypic traits including characteristics of economic interest, viz. bean number (BN), individual dried bean weight (DBW), total wet bean weight (TWBW) and pod index (PI), which ranged from 26.4 to 58.0 (CV 16.3%); 0.6g to 2.12g (CV 22.6%); 42.5 to 228g (CV 24.2%) and 10 to 57 (CV 27.5%), respectively. Significant differences (p < 0.0001) were found among the production zones for BN and DBW only. Four zones had selections with significantly higher BN and all six had selections with superior TWBW relative to the ICGT clones studied. No association between cotyledon colour and leaf petiole hairiness was found, suggesting independent inheritance of these traits used for preliminary identification of 'Criollo-like' genotypes in the field. FAs from Tobago generally had selections with paler cotyledons, implying relatively more pronounced Criollo ancestry. Principal Component (PC) scores 1 and 2 accounted for 74.7% of the phenotypic variation expressed by the accessions studied in terms of five traits, based on Principal Component Analysis (PCA). PI and TWBW were major contributors to PC 1, while for PC 2, the major contributors were BN and DBW. The results of PCA and cluster analyses suggest that a phenotypically diverse and unique selection of genotypes was collected from the farmers' fields, relative to studied ICGT types, several of which displayed 'Criollo-like' and Trinitario characteristics (large, plump seeds/beans with pale cotyledons) and favourable yield potential. These can be utilized to enhance the genepool at the ICGT, for breeding to introgress favourable Trinitario genes into national recurrent breeding programmes and for commercial cultivation.

Selection of putative relic cacao (Theobroma cacao L.) genotypes in farmers’ fields in Trinidad and Tobago

Trinidad and Tobago is a repository of putative relic cacao genotypes, given its long history of cultivating cacao from the 1700s onwards. As part of a project conducted between 2009 and 2011, funded by the World Bank Development Market Place, World Bank Project TF 093747 (DM 2008), 106 putative, ancient cacao varieties were collected from farms throughout Trinidad and Tobago to be conserved and utilized to preserve traditional quality (flavour) attributes. The objective of this article is to provide information on agronomic and phenotypic traits of 94 of these ‘relic’ accessions collected in farmers’ fields (FA). These are presumed to be relic Criollos or Trinitarios (selected pre-and post-1930s), and were selected over six cocoa production zones in Trinidad and Tobago. In addition, data for 31 regional Trinitario cacao accessions, which are conserved at the International Cocoa Genebank Trinidad (ICGT) were assessed. Morphological assessment of the selections was based on 22 phenotypic traits including characteristics of economic interest, viz. bean number (BN), individual dried bean weight (DBW), total wet bean weight (TWBW) and pod index (PI), which ranged from 26.4 to 58.0 (CV 16.3%); 0.6g to 2.12g (CV 22.6%); 42.5 to 228g (CV 24.2%) and 10 to 57 (CV 27.5%), respectively. Significant differences (p < 0.0001) were found among the production zones for BN and DBW only. Four zones had selections with significantly higher BN and all six had selections with superior TWBW relative to the ICGT clones studied. No association between cotyledon colour and leaf petiole hairiness was found, suggesting independent inheritance of these traits used for preliminary identification of ‘Criollo-like’ genotypes in the field. FAs from Tobago generally had selections with paler cotyledons, implying relatively more pronounced Criollo ancestry. Principal Component (PC) scores 1 and 2 accounted for 74.7% of the phenotypic variation expressed by the accessions studied in terms of five traits, based on Principal Component Analysis (PCA). PI and TWBW were major contributors to PC 1, while for PC 2, the major contributors were BN and DBW. The results of PCA and cluster analyses suggest that a phenotypically diverse and unique selection of genotypes was collected from the farmers’ fields, relative to studied ICGT types, several of which displayed ‘Criollo-like’ and Trinitario characteristics (large, plump seeds/beans with pale cotyledons) and favourable yield potential. These can be utilized to enhance the genepool at the ICGT, for breeding to introgress favourable Trinitario genes into national recurrent breeding programmes and for commercial cultivation.

Pseudomonas chlororaphis CP07 strain reduces disease severity caused by Phytophthora palmivora in genotypes of Theobroma cacao

Black pod rot is the most important disease affecting Theobroma cacao in Cuba. Plant growth promoting bacteria (PGPB) are considered an alternative for controlling plant disease in the context of the integrated management. The present work was aimed to evaluate Pseudomonas chlororaphis strain CP07, isolated from T. cacao rhizosphere, as potential PGPB against P. palmivora in cacao plants cultivated under controlled conditions. Three genotypes of Cuban traditional cacao of the group Trinitario and the genotype UF 677 were used. The effect of CP07 was evaluated by using detached leaf tests and in planta assays with plants obtained in vitro from both seeds and micrografting. Inoculation of P. palmivora in control plants showed that genotypes EICB-371, EICB-384 and UF 677 were highly susceptible to the disease (71.4 to 99% disease severity) while EICB-385 was significantly less susceptible (39 to 54.5%). In EICB-371 and EICB-385 genotypes, disease symptoms were significantly reduced in presence of CP07 compared to the control plants in all assays. In contrast, for EICB-384 and UF 677 genotypes, there was not reduction of disease severity in plants pre-treated with CP07. Results show the protective effect of treating cacao plants with CP07 against P. palmivora. Plant genotype significantly influenced the protective ability of bacteria affecting the CP07-mediated disease control. Results suggest that depending on cacao genotype, CP07 has a potential for inducing plant defense against P. palmivora which can be used in the control of black pod rot.

Field evaluation of the impact of Sahlbergella singularis Haglund infestations on the productivity of different Theobroma cacao L. genotypes in the Southern Cameroon

Mirids (Sahbergella singularis and/or Distantiella theobroma) are the major pests of cacao farms in Africa. Cocoa production losses due to these species have been widely documented in West Africa. However, their impact on cocoa production is unknown in Central Africa, especially in Cameroon. Moreover, no data are available on the threshold level of fruits tolerance to mirid attacks. For these reasons, we assessed the effect of S. singularis on the productivity of ten cacao genotypes as well as the threshold number of the lethal feeding punctures to fruits under a randomized experimental design. Observations were made on three categories of fruits (cherelle, immature and mature/ripe). A control trial was also set up per batch. The overall results showed that 68.0% and 0.4% of fruits aborted, respectively, in mirid and control trials. The percentages of aborted fruits were significantly (p < 5%) different between cacao genotypes and ranged from 20 to 100%. Bonferroni test revealed six homogenous groups for cacao genotypes susceptibility to mirid attacks; SNK52 proved to be most tolerant/resistant, whereas two genotypes (UPA138 and SNK67) revealed more sensitive. In contrast, six genotypes (SNK07, IMC60 × SNK417, T60/887 × PA7, T79/501 × SNK479, UPA143 × ICS84, UPA143 × NA33) displayed similar sensitivity to mirid attacks. ANOVA showed that the threshold tolerance of tested fruits, expressed by the mean numbers of lethal feeding punctures, to S. singularis attacks was comparable between cacao genotypes. This new quantitative database improves our knowledge on the (i) threshold tolerance of fruits to S. singularis attacks and (ii) economic impact of this pest on cocoa production in Cameroon.

Resistant and susceptible cacao genotypes exhibit defense gene polymorphism and unique early responses to Phytophthora megakarya inoculation

Key genes potentially involved in cacao disease resistance were identified by transcriptomic analysis of important cacao cultivars. Defense gene polymorphisms were identified which could contribute to pathogen recognition capacity. Cacao suffers significant annual losses to the water mold Phytophthora spp. (Oomycetes). In West Africa, P. megakarya poses a major threat to farmer livelihood and the stability of cocoa production. As part of a long-term goal to define key disease resistance genes in cacao, here we use a transcriptomic analysis of the disease-resistant cacao clone SCA6 and the susceptible clone NA32 to characterize basal differences in gene expression, early responses to infection, and polymorphisms in defense genes. Gene expression measurements by RNA-seq along a time course revealed the strongest transcriptomic response 24h after inoculation in the resistant genotype. We observed strong regulation of several pathogenesis-related genes, pattern recognition receptors, and resistance genes, which could be critical for the ability of SCA6 to combat infection. These classes of genes also showed differences in basal expression between the two genotypes prior to infection, suggesting that prophylactic expression of defense-associated genes could contribute to SCA6's broad-spectrum disease resistance. Finally, we analyzed polymorphism in a set of defense-associated receptors, identifying coding variants between SCA6 and NA32 which could contribute to unique capacities for pathogen recognition. This work is an important step toward characterizing genetic differences underlying a successful defense response in cacao.

Residual Effects of Moisture Stressed Seedlings in the Nursery on Field Performance of Cacao Genotypes

Residual Effects of Moisture Stressed Seedlings in the Nursery on Field Performance of Cacao Genotypes

Effect of Biofertilizers on the Phenolic Content in a Hybrid Family of Cacao After Leaf Infection with &amp;lt;i&amp;gt;Phytophthora megakarya&amp;lt;/i&amp;gt; and Exogenous Application of Salicylic Acid

In order to protect cacao against <i>Phytophthora megakarya</i>, the most aggressive pathogen of this plant in Cameroon, a study was carried out on hybrid genotypes of the family F79SA of cacao (<i>Theobroma cacao</i> L.) to investigate the effect of inoculation of the biofertilizers <i>Gigaspora margarita</i> and <i>Acaulospora tuberculata</i> on the phenolic compound content in hybrid genotypes after leaf infection with <i>Phytophthora megakarya</i> and treatment of salicylic acid (SA). Thus, the phenolic compound content of hybrid genotypes of the family F79SA of <i>T. cacao</i> was evaluated after artificial infection of leaves with <i>P. megakarya</i> and treatment of salicylic acid without control and under control of biofertilizers. The artificial infection of <i>P. megakarya</i> and exogenous application of salicylic acid resulted in an increase in the accumulation of phenolic compounds (PC) in all genotypes. This increase was more important under the control of <i>Gigaspora margarita</i> and <i>Acaulospora tuberculata</i> and varied from one genotype to another. The PC content analysis map of these genotypes at different treatment conditions under the control of biofertilizers showed a gradual evolution of black coloration, a sign of the increase in phenolic compound content related to concentrations of salicylic acid and infected leaves in all hybrid genotypes thus expressing high tolerance. This map allowed to classify hybrid genotypes according to their level of tolerance. A negative and significant correlation (P = 0.05) was observed between the development of necrosis and the accumulation of phenolic compounds on one hand and between salicylic acid and the accumulation of phenolic compounds on the other hand. Salicylic acid can therefore be used in the cacao selection program in the absence of the pathogen for the identification of hybrid cacao genotypes as well as in other similar breeding programs.

Mode of Inheritance and Combining ability studies on Epicuticular wax Production in Resistance to Black pod disease in Cacao (Theobroma cacao L.)

Abstract Black pod caused by Phytophthora species is a devastating disease of cacao (Theobroma cacao L.) in production regions worldwide. Breeding for cacao genotypes resistant to black pod disease is crucial for sustainable cocoa production and profitability. Although breeding programmes in the past have made considerable efforts in improving resistance of cocoa genotypes with diverse genetic background, the disease continues to cause unacceptable yield losses in cacao production. To understand the mode of inheritance of epicuticular wax on the surface of cocoa pod known to play a major role in resistance to black pod disease, a 6 × 6 full diallel and a M x N (6 × 4) mating designs were used and data was analysed using Griffing’s method I model I approach and the North Carolina design –II approach, respectively. The results of the two mating designs were consistent and showed that epicuticular wax on leaf and pod surfaces of cacao were under the control of additive genetic effects. The non-additive effects were generally much smaller compared to the additive genetic effects. The significant association between GCA estimates of parents and their means indicates that parental values could be used as indicators of progeny performance. The best general combiners for epicuticular wax load on leaf and pod surfaces were Pa7/808, T60/887 and Pa 150. The larger additive components and heritability observed in this study, indicates that pedigree selection could be used to develop cacao cultivars with high amount of epicuticular wax on pod surface to enhance resistance to black pod disease.

Effects of silicon on biochemical and physiological aspects in Theobroma cacao under inoculation with Moniliophthora perniciosa

This study aimed to verify the efficiency of silicon leaf application in the physiological and biochemical characteristics in a&nbsp;Theobroma cacao&nbsp;genotype inoculated with&nbsp;Moniliophthora perniciosa&nbsp;fungus, which causes the witches’ broom disease, important cocoa disease in Brazil and worldwide. Seedlings of Catongo genotype were used.&nbsp; The experimental design used was a randomized block design with four replicates, including two inoculation factors (inoculated and non-inoculated plants), each one with two levels of silicon application (0.0 mg and 1.0 mg mL-1&nbsp;with AgriSil containing 98% of SiO2). We observed that plants that were inoculated with&nbsp;M. perniciosa&nbsp;and subjected to leaf application with silicon presented enhanced photosynthesis, peroxidases, chitinase, polyphenoloxidases activities and stomatal density. Results have shown that silicon application is beneficial and increases the defenses against&nbsp;Moniliophthora perniciosa&nbsp;in cocoa seedlings.

Physiological, ultrastructural, biochemical and molecular responses of young cocoa plants to the toxicity of Cr (III) in soil

The objective of this study was to evaluate Cr toxicity in young plants of the CCN 51 Theobroma cacao genotype at different concentrations of Cr3+ in the soil (0, 100, 200, 400 and 600 mg kg−1) through physiological, ultrastructural, antioxidant and molecular changes. Doses of 400 and 600 mg Cr3+ kg−1 soil severely affected foliar gas exchange, promoted by damages in photosynthetic machinery evidenced by the decrease in CO2 fixation. Decreased expression of psbA and psbO genes, changes in enzymatic activity and lipid peroxidation also affected leaf gas exchange. A hormesis effect was observed at 100 mg Cr3+ kg−1 soil for the photosynthetic activity. As a metal exclusion response, the roots of the cocoa plants immobilized, on average, 75% of the total Cr absorbed. Ultrastructural changes in leaf mesophyll and roots, with destruction of mitochondria, plasmolysis and formation of vesicles, were related to the oxidative stress promoted by excess ROS. The activity of the antioxidant enzymes SOD, APX, GPX and CAT and the amino acid proline coincided with the greater expression of the sod cyt gene demonstrating synchronicity in the elimination of ROS. It was concluded, therefore, that the tolerance of the cocoa plants to the toxicity of Cr3+ depends on the concentration and time of exposure to the metal. Higher doses of Cr3+ in the soil promoted irreversible damage to the photosynthetic machinery and the cellular ultrastructure, interfering in the enzymatic and non-enzymatic systems related to oxidative stress and gene expression. However, the low mobility of the metal to the leaf is presented as a strategy of tolerance to Cr3+.

Analisis Sebaran Tipe dan Performa Mutu Fisik Kakao pada Tiga Rentang Elevasi

&lt;em&gt;Cacao genotype most cultivated in Indonesia divided into three main groups, namely &lt;/em&gt;&lt;em&gt;Criollo&lt;/em&gt;, &lt;em&gt;Forastero&lt;/em&gt;, and &lt;em&gt;Trinitari. Beside genetical factor, the pod and beans qualities are also strongly influenced by the environment in which the plant grows. The research aimed to analyze the types and physical qualities of the pod and bean from Patuk, Gunungkidul at three elevations range (154.00–267.20, 302.00–401.00, and 469.20–657.90 m above sea level/asl). The research was conducted at smallholder plantations in Patuk District, Gunungkidul, Yogyakarta from September until Desember 2017. As many as 40–42 samples were randomly taken from each elevation range and analyzed by descriptive statistic and one-way anova. The parameters observed were cocoa types identification (Criollo, Forastero, and Trinitario), pod’s physical quality (fresh weight of fruits, length to width ratio, fresh weight of beans, number of beans, and fresh weight of one bean), and bean’s physical quality (thickness, length/width ratio, dry weight of one bean, and number of beans in 100 g). The results showed that Trinitario cacao type dominates at elevation range of 154.00–267.20 m asl, while Forastero dominates at elevation range of 302.00–401.00 and 469.20–657.90 m asl. The pod physical qualities of Criollo, Forastero, and Trinitario showed highest fresh weight per bean at 469.20–657.90 m asl compared to those at lower elevation (increased 19.05%–31.94%). At elevation of 469.2–657.9 m asl, Forastero shown higher beans physical quality at all variables, whereas Criollo was significantly higher dry weight per bean and number of beans per 100 g, and Trinitario shown significantly higher bean thickness.&lt;/em&gt;

Selection of cocoa progenies for resistance to witches’ broom

Witch’s broom (WB) and frost pod rot (FPR) are devastating fungal diseases and responsible for severe losses in cacao trees grown in tropical America. To expand and stabilize the resistance to WB in cacao progenies, as well as to incorporate resistance genes to FPR, 17 genotypes were selected from a structured population. These were used in a second selection cycle, in which four gene donors of FPR resistance were included. All but one of the 59 and 52 progenies differed significantly (P < 0.05) from the susceptible controls Catongo and SIC 23, respectively. Nineteen progenies differed significantly (P < 0.05) from the resistance control SCA 6, suggesting high WB resistance. The direct descendants of cacao genotypes from the Brazilian Amazon and from clones carrying FPR resistance showed lower disease index than the resistant control SCA 6, except for some of the progenies of clone ICS 95, which behaved similarly to the susceptible control. The study highlights nine progenies carrying WB resistance genes from several sources and seven of them from parents carrying frosty pod resistance genes.

Characterization of the Sexual Self- and Cross-Compatibility in Genotypes of Cacao

Cacao is a tree crop of high economic importance and the subject of several studies aiming the genetic improvement of the species with the incorporation of characteristics that are agronomically important to create superior genotypes. In this context, this study aimed to characterize 22 genotypes of cacao for sexual compatibility, which is a trait that is strongly associated with yield. Additionally, we identify genotypes incompatible with clone TSH-1188 through controlled intercrosses, due to the great importance of this clone in cocoa breeding. Fifteen genotypes were characterized as self-incompatible and other seven as self-compatible, considering the retention index (20%) of self-pollinated flowers. Nine genotypes were characterized for the first time: CCN-16, COCA-3310, COCA-3370/5, EB-1017, IMC-119, IMC-97, LCTEEN-37A, NA-45, and UF-612. Cacao genotypes showed flower retention index ranging from 0.0% to 55.1% after 15 days of self-pollinations. The number of retained flowers varied after self-pollination of cacao genotypes at 1, 5 and 15 days after pollination. CCN-51, Catongo, CCN-10 and P-4B, were the genotypes with minor losses of flowers after 15 days of pollination, while IMC-119 and TSH-516 had 100% of loss of flowers between 1 and 5 days after pollination. Moreover, the flower retention index 15 days after cross-pollination with TSH-1188 ranged from 0.0% to 87.5% among the tested genotypes. The results of cross-pollinations identified two genotypes that are incompatibles, EB-1017 and IMC-119. This result is important for future allelic studies of incompatibility in cacao, because it might indicate that these genotypes share the same self-incompatibility allele(s). We conclude, therefore, that this study enable the characterization of this working collection of cocoa germplasm for sexual compatibility and this information is important for subsequent crosses between cacao genotypes.

Desempeño fisiológico de nueve genotipos de cacao (&lt;i&gt;Theobroma cacao&lt;/i&gt; L.) bajo la sombra de tres especies forestales en Santander, Colombia

En la actualidad, Colombia tiene 173.000 ha cultivadas con Theobroma cacao, de las cuales la mayoría están establecidas en asocio con árboles frutales o maderables, además de proveer sombra pueden generar ingresos para el cacaocultor. Para seleccionar especies que conforman el arreglo agroforestal, es necesario considerar los requerimientos ecofisiológicos de los genotipos de cacao y la interacción con su entorno agroecológico, incluido el sombrío. El objetivo de esta investigación fue evaluar el rendimiento fisiológico de nueve clones de cacao establecidos en sistema agroforestal con Cariniana pyriformis, Hevea brasiliensis en El Carmen de Chucurí y C. pyriformis, Tectona grandis en Rionegro, Santander. Se realizó seguimiento a la tasa de fotosíntesis, transpiración, conductancia estomática y uso eficiente del agua, tanto en la época húmeda, como en la seca. Los resultados mostraron que los sistemas de sombrío influyen sobre las tasas de fotosíntesis que presentan las plantas de cacao. Estos clones establecidos bajo el sistema de sombrío con C. pyriformis, presentan mayores tasas de fotosíntesis (5,39 μmoles CO2 m-2 s-1), en la época húmeda y seca. Lo anterior se atribuyó al tipo de crecimiento y sombra proveída por esta especie, que ofrece mejores condiciones ambientales para el desempeño fisiológico del cacao. Se recomienda esta especie forestal como sombrío, para el establecimiento de nuevas áreas de cacao en el departamento de Santander. Individualmente, los clones de cacao con el mejor comportamiento ecofisiológico fueron TCS19 y TCS13, por lo que se constituyen en genotipos de importancia agronómica.

Genetic control, combining ability and heritability of resistance to stem canker in cacao (Theobroma cacao L.)

Stem canker caused by Phytophthora palmivora and Phytophthora megakarya is a serious disease of cacao (Theobroma cacao L.). Studies of the genetics of resistance to this disease is important to identify an effective procedure to use in breeding resistant varieties. The objective of this study was to determine mode of inheritance, combining ability and heritability of resistance to stem canker in cacao. A 6 × 6 full diallel mating design was used to generate 36 F1 hybrids which were evaluated for resistance to stem canker with three replications under artificial inoculation with 1 mm2 agar plug taken from actively growing colonies of 10-day old cultures of P. palmivora and P. megakarya. Twelve months later, the canker lesions on outer bark of the stem of the seedlings were measured and the canker lesions inside was also measured after scraping the bark. There were significant (p 50%) of GCA suggest that additive gene effects were more important than non-additive gene effects. The overall direction of results showed that using one of the following parents: P1 (Alpha B36), P4 (T17/524) and P5 (T65/238) as the female produced progenies with better resistance to stem canker disease than when they were used as the male parent. The majority reflected the resistance level of the female parent, suggesting that resistance to stem canker in cacao is influenced by maternal inheritance. Cacao genotypes Alpha B36, T17/524 and T65/238 showed significant negative GCA effects for resistance to stem canker suggesting that these genotypes will transmit the trait to their progenies and therefore recommended for cacao breeding. Narrow sense heritability for stem canker resistance was low indicating large component of dominance effects and influence of environment in inheritance of resistance to stem canker in cacao. However, the very high broad sense heritability (0.99) coupled with large variation within the cacao tree population indicate that progeny testing and within family selection would be appropriate in breeding against stem canker in cacao.

Heavy metal accumulation in leaves and beans of cacao (Theobroma cacao L.) in major cacao growing regions in Peru

Peru is one of the leading exporters of organic cacao beans in the world. However, the accumulation of heavy metals in cacao beans represents a problem for cocoa bean export and chocolate quality. The aim of this study was to investigate the distribution and accumulation of heavy metals in cacao leaves and cocoa beans in three major cacao growing regions of Peru. The study was conducted in cacao plantations of 10 to 15years old in three regions of Peru: North (Regions of Tumbes, Piura, Cajamarca, and Amazonas); Center (Regions of Huánuco and San Martin) and South (Junin and Cuzco). Samples of leaf and cacao beans were collected from 70 cacao plantations, and the nature of cacao clone or genotype sampled was recorded. The concentrations of heavy metals such as Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in leaves and beans were determined using atomic absorption spectrophotometer. Overall, concentrations of heavy metals were below the critical limits; however, the presence of high levels of Cd in cacao grown in Amazonas, Piura, and Tumbes regions is of primary concern. Plantations of cacao with different cacao clones show differences in Cd accumulation both in leaves and cocoa beans. Therefore, it is promising to screen low Cd accumulator cacao genotypes for safe production of cacao on lightly to moderately Cd contaminated soils. Also, synergism between Zn and Cd present both in plant and soil suggests that Zn has a direct effect on Cd accumulation in cacao.

Inheritance of foliar resistance to Phytophthora species in cacao (Theobroma cacao L.): can it be influenced by CSSV infection?

Studies on quantitative genetics of foliar resistance to black pod disease in cacao could inadvertently use cocoa swollen shoot virus (CSSV) infected leaves which could bias the results especially in West Africa where the virus is prevalent. However, effects of CSSV on inheritance and heritability of foliar resistance to Phytophthora species is not known. Choice of an efficient breeding method requires an accurate estimation of genetic effects in selection schemes for foliar resistance to Phytophthora species in cacao. The objective of this study was to investigate the effect of CSSV infection on quantitative genetic parameters of foliar resistance to cocoa black pod disease in a population of 36 F1 hybrids developed by mating six cacao genotypes using a diallel method. The generated F1s and their parents were evaluated for foliar resistance to P. palmivora and P. megakarya using a randomized complete block design (RCBD) with three replications. 1A CSSV and Nsaba CSSV strains were used to infect the cacao genotypes using the patch graft method. The parents chosen showed significant variations for scores of leaf discs after inoculation with P. palmivora and P. megakarya. The leaf disc scores of CSSV infected crosses were lower than leaf disc scores of CSSV-free crosses. Genetic component analysis showed that the effects of GCA and SCA was significant for both CSSV-free and CSSV-infected crosses in resistance to P. palmivora and P. megakarya. The significant GCA and SCA for both CSSV-free and CSSV-infected crosses strongly suggest that both additive and non-additive genetic effects play an important role in the determination of inheritance of foliar resistance to Phytophthora species in cacao. There was significant variability in mean squares of GCA and SCA of CSSV-free and CSSV-infected crosses indicating that CSSV infection modifies GCA and SCA of affected plants. Narrow sense heritability was relatively low (0.31) for foliar resistance to P. palmivora and P. megakarya under CSSV-free and 1A CSSV strain infected conditions. However, heritability for foliar resistance to P. palmivora (0.43) and P. megakarya (0.36) was significantly higher under Nsaba CSSV infected condition. The modifications of mean squares of GCA and SCA and narrow sense heritability due to CSSV infection could mislead in choice of breeding methods indicating that attention must be paid to the infection status of plants when conducting quantitative genetics studies using diseased and healthy plants. CSSV status of leaf samples should be known before using them in leaf disc test. Genotypes Pa7/808 and Pound 7 had high negative GCA effects and are promising parents for enhancement of resistance to black pod disease in cacao.

Photosynthetic, antioxidative, molecular and ultrastructural responses of young cacao plants to Cd toxicity in the soil

Cadmium (Cd) is a highly toxic metal for plants, even at low concentrations in the soil. The annual production of world cocoa beans is approximately 4 million tons. Most of these fermented and dried beans are used in the manufacture of chocolate. Recent work has shown that the concentration of Cd in these beans has exceeded the critical level (0.6mgkg−1 DM). The objective of this study was to evaluate the toxicity of Cd in young plants of CCN 51 cacao genotype grown in soil with different concentrations of Cd (0, 0.05 and 0.1gkg−1 soil) through photosynthetic, antioxidative, molecular and ultrastructural changes. The increase of Cd concentration in the soil altered mineral nutrient absorption by competition or synergism, changed photosynthetic activity caused by reduction in chloroplastidic pigment content and damage to the photosynthetic machinery evidenced by the Fv/Fm ratio and expression of the psbA gene and increased GPX activity in the root and SOD in leaves. Additionally, ultrastructural alterations in roots and leaves were also evidenced with the increase of the concentration of Cd in the soil, whose toxicity caused rupture of biomembranes in root and leaf cells, reduction of the number of starch grains in foliar cells, increase of plastoglobules in chloroplasts and presence of multivesiculated bodies in root cells. It was concluded, therefore, that soil Cd toxicity caused damage to the photosynthetic machinery, antioxidative metabolism, gene expression and irreversible damage to root cells ultrastructure of CCN 51 cocoa plants, whose damage intensity depended on the exposure time to the metal.

Cacao Phylloplane: The First Battlefield against Moniliophthora perniciosa, Which Causes Witches' Broom Disease.

The phylloplane is the first contact surface between Theobroma cacao and the fungus Moniliophthora perniciosa, which causes witches' broom disease (WBD). We evaluated the index of short glandular trichomes (SGT) in the cacao phylloplane and the effect of irrigation on the disease index of cacao genotypes with or without resistance to WBD, and identified proteins present in the phylloplane. The resistant genotype CCN51 and susceptible Catongo presented a mean index of 1,600 and 700 SGT cm-2, respectively. The disease index in plants under drip irrigation was reduced by approximately 30% compared with plants under sprinkler irrigation prior to inoculation. Leaf water wash (LWW) of the cacao inhibited the germination of spores by up to 98%. Proteins from the LWW of CCN51 were analyzed by two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by tandem mass spectrometry. The gel showed 71 spots and identified a total of 42 proteins (28 from the plant and 14 from bacteria). Proteins related to defense and synthesis of defense metabolites and involved in nucleic acid metabolism were identified. The results support the hypothesis that the proteins and water-soluble compounds secreted to the cacao phylloplane participate in the defense against pathogens. They also suggest that SGT can contribute to the resistance of cacao.

Pengaruh Tetua Jantan terhadap Komponen Buah dan Biji Hasil Persilangan Enam Genotipe Kakao Mulia

&lt;em&gt;In cacao crossing process, the genetic symptoms of direct effect of male parent as a pollen source on pod and beans performances generated from their crossing are called as the xenia effect. The aim of this study was to investigate the effect of male parents on characters of pod and bean components generated from the crossing of several genotypes of fine cacao. The research was conducted at Kalikempit Afdeling of PTPN XII, Tulungrejo Village, Glenmore District, Banyuwangi Regency, East Java Province, at an altitude of 340 m asl, Latosol type of soil, and C type of climate, from May until December 2014. Crossing combinations were (1) DR 38 x DR 1, (2) DR 38 x DR 38, (3) DR 2 x DR 1, (4) DR 2 x DR 2, (5) DRC 16 x DR 38, and (6) DRC 16 x DRC 16. Variables observed were the quantitative and qualitative characters of pod and bean component. The results showed that male parent DR 1 crossed with female parent DR 2 contributed in increasing fresh bean weight (34.70%), fresh bean/pod weight (44.32%), fresh single bean weight (31.00%), pod apex and base constriction shapes. Meanwhile DR 38 crossed with DRC 16 showed xenia effect on fresh bean weight (47.01%), bean (31.22%), and qualitative characters i.e. the colour of mature pod and the availability of bottle neck. All of crossing combinations produced white colour beans above 85% thus qualified as good. DR 2 and DR 38 are potential male parents to enhance the number of white bean.&lt;/em&gt;