Molecular and morphophysiological responses cocoa leaves with different concentrations of anthocyanin to variations in light levels

Theobroma cacao gives higher yield when cultivated in full sun under irrigation system with fertilization, because is a species little conservative in relation the efficiency of water use. On the other hand, T. cacao is usually cultivated under shade conditions in ‘Cabruca’ and agroforestry systems but with low yield. It has been observed under field conditions that the genotypes of T. cacao with high concentration of anthocyanins in young leaves are more tolerant to high irradiance stress when grown in full sun. The accumulation of flavonoids or other UVabsorbing compounds in the leaf epidermis is one of the most important mechanisms to screening out UV-B radiation. The aim of this study was to evaluate the effects of different levels of light on three clonal cacao genotypes (‘Catongo’, SCA-6 and SJ-2), contrasting in relation to accumulation of anthocyanin levels in young leaves, by evaluations of photosynthesis, activity of guaiacol peroxidase (GPX), chloroplastid pigment contents and vacuolar (anthocyanins) flavonoids contents, anatomical characteristics and gene expression of the leaf. In summary, (i) the anthocyanins contents in leaf level did not provide protection against photoinhibition in T. cacao, (ii) the ‘Catongo’ and SJ-2 genotypes showed greater phenotypic plasticity to the morphology and the chloroplastidic pigment contents in the leaf, while the SCA-6 genotype allocated more in the flavonoids content and hsp70 gene expression; (iii) the relative expression of the genes psbA and psbO, did not vary between genotypes under irradiance stress

Genetic structure and molecular diversity of cacao plants established as local varieties for more than two centuries: the genetic history of cacao plantations in Bahia, Brazil

ahia is the most important cacao-producing state in Brazil, which is currently the sixth-largest country worldwide to produce cacao seeds. In the eighteenth century, the Comum, Pará and Maranhão varieties of cacao were introduced into southern Bahia, and their descendants, which are called ‘Bahian cacao’ or local Bahian varieties, have been cultivated for over 200 years. Comum plants have been used to start plantations in African countries and extended as far as countries in South Asia and Oceania. In Brazil, two sets of clones selected from Bahian varieties and their mutants, the Agronomic Institute of East (SIAL) and Bahian Cacao Institute (SIC) series, represent the diversity of Bahian cacao in germplasm banks. Because the genetic diversity of Bahian varieties, which is essential for breeding programs, remains unknown, the objective of this work was to assess the genetic structure and diversity of local Bahian varieties collected from farms and germplasm banks. To this end, 30 simple sequence repeat (SSR) markers were used to genotype 279 cacao plants from germplasm and local farms. The results facilitated the identification of 219 cacao plants of Bahian origin, and 51 of these were SIAL or SIC clones. Bahian cacao showed low genetic diversity. It could be verified that SIC and SIAL clones do not represent the true diversity of Bahian cacao, with the greatest amount of diversity found in cacao trees on the farms. Thus, a core collection to aid in prioritizing the plants to be sampled for Bahian cacao diversity is suggested. These results provide information that can be used to conserve Bahian cacao plants and applied in breeding programs to obtain more productive Bahian cacao with superior quality and tolerance to major diseases in tropical cacao plantations worldwide1012CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP620239/2008-5; 555432/2009-2PROCAD-NF20082008/52197-4; 2010/50033-4; 2013/08086-

Diversidade genética entre acessos de cacau de fazendas e de banco de germoplasma na Bahia

The objective of this work was to assess genetic diversity of farm cacao accessions, previously selected as productive and resistant to witch broom in Bahia, Brazil, and to study their interrelationship with reference genotypes on germplasm bank. DNA samples from 120 cacao accessions, collected on 17 farms in seven counties in Southern Bahia, were amplified by RAPD technique (random amplified polymorphic DNA). The coefficients of genetic dissimilarity, calculated from the RAPD bands by Jaccard method, allowed to show by cluster analysis that most farm selections (89.2%) grouped with accessions from germplasm bank considered representatives of the cacao genetic diversity (hybrids, Trinitarian, Scavina, Amazon and common cacao). The other selections were distributed in seven distinct groups. There is high genetic diversity among farm selections, and some of them may have originated from other progenitors not included in this analysis. These materials present potential for clone selection with higher diversity for new crossings or direct use by agriculturists.O objetivo deste trabalho foi avaliar a diversidade genética de acessos de cacau, selecionados previamente como produtivos e resistentes à vassoura-de-bruxa na Bahia, e estudar suas inter-relações com genótipos no banco de germoplasma. Amostras de DNA de folhas dos 120 acessos, coletados em 17 fazendas de sete municípios do Sul da Bahia, foram amplificadas pela técnica de RAPD ("random amplified polymorphic DNA"). Os coeficientes de dissimilaridade genética, calculados pelo método de Jaccard a partir das bandas RAPD, permitiram evidenciar, pela análise de agrupamento, que a maioria das seleções das fazendas (89,2%) agrupou-se com acessos do banco de germoplasma considerados representativos da diversidade de cacau (híbridos, trinitários, Scavinas, amazônicos e cacau-comum). As demais seleções distribuíram-se em outros sete grupos distintos. Há elevada diversidade genética entre as seleções das fazendas, e algumas delas devem ter-se originado de genitores não incluídos nesta análise. Esses materiais apresentam potencial para seleção de clones com maior diversidade para novos cruzamentos ou uso pelos agricultores

Microsatellite markers related to resistance of cocoa tree against witches'-broom

Os objetivos deste trabalho foram caracterizar a resistência à vassoura-de-bruxa de plantas de cacau originadas do cruzamento entre TSH 1188 e CCN 51 (população segregante), por meio de dois métodos de inoculação em condições de campo, e identificar marcadores microssatélites específicos para grupos de plantas resistentes e suscetíveis. As plantas-controle avaliadas pelos métodos de inoculação natural e inoculação artificial em campo produziram os mesmos padrões de sintomas. As plantas da população segregante também coincidiram os padrões de sintomas em 90%, por esses dois métodos. O método de inoculação artificial em campo permite detectar falso-resistentes. Dos 18 pares de primers microssatélites amplificados, 15 foram polimórficos entre os genitores, e seis entre os grupos de plantas segregantes contrastantes quanto à resistência à vassoura-de-bruxa. Foram confirmadas três marcas previamente associadas a QTL (locos para características quantitativas) relacionados com a resistência à vassoura-de-bruxa, comuns a outras populações. Também foram identificados três novos QTL para esta característica, típicos desta população, o que comprova sua utilidade para o melhoramento genético do cacaueiro.The objectives of this work were to evaluate cocoa tree resistance against witches'-broom, in plants originated from the crossing between TSH 1188 and CCN 51 (segregating population), by means of two methods of inoculation in field conditions, and to identify microsatellite markers specific for resistant and susceptible plants. The control plants bore identical symptoms as the plants of the segregating population in 90% of the cases under the two methods. The method of artificial inoculation in the field allows the detection of false resistance to the disease. Of the 18 pairs of microsatellite primers amplified, 15 were polymorphic between genitors and six were polymorphic between the two groups of plants evaluated for resistance to witches'-broom. Three previously characterized markers were confirmed as associated to QTL (quantitative trait loci) related to resistance to the witches'-broom, which is common in other populations. Three new QTL for this characteristic, typical of this population, were also identified, which proves the utility of this population for cocoa breeding

Molecular and morphophysiological responses cocoa leaves with different concentrations of anthocyanin to variations in light levels

Theobroma cacao gives higher yield when cultivated in full sun under irrigation system with fertilization, because is a species little conservative in relation the efficiency of water use. On the other hand, T. cacao is usually cultivated under shade conditions in ‘Cabruca’ and agroforestry systems but with low yield. It has been observed under field conditions that the genotypes of T. cacao with high concentration of anthocyanins in young leaves are more tolerant to high irradiance stress when grown in full sun. The accumulation of flavonoids or other UVabsorbing compounds in the leaf epidermis is one of the most important mechanisms to screening out UV-B radiation. The aim of this study was to evaluate the effects of different levels of light on three clonal cacao genotypes (‘Catongo’, SCA-6 and SJ-2), contrasting in relation to accumulation of anthocyanin levels in young leaves, by evaluations of photosynthesis, activity of guaiacol peroxidase (GPX), chloroplastid pigment contents and vacuolar (anthocyanins) flavonoids contents, anatomical characteristics and gene expression of the leaf. In summary, (i) the anthocyanins contents in leaf level did not provide protection against photoinhibition in T. cacao, (ii) the ‘Catongo’ and SJ-2 genotypes showed greater phenotypic plasticity to the morphology and the chloroplastidic pigment contents in the leaf, while the SCA-6 genotype allocated more in the flavonoids content and hsp70 gene expression; (iii) the relative expression of the genes psbA and psbO, did not vary between genotypes under irradiance stress

Altered physiology, cell structure, and gene expression of \u3ci\u3eTheobroma\u3c/i\u3e cacao seedlings subjected to Cu toxicity

Seedlings of Theobroma cacao CCN 51 genotype were grown under greenhouse conditions and exposed to increasing concentrations of Cu (0.005, 1, 2, 4, 8, 16, and 32 mg Cu L−1) in nutrient solution. When doses were equal or higher than 8mg Cu L−1, after 24 h of treatment application, leaf gas exchange was highly affected and changes in chloroplasts thylakoids of leaf mesophyll cells and plasmolysis of cells from the root cortical region were observed. In addition, cell membranes of roots and leaves were damaged. In leaves, 96 h after treatments started, increases in the percentage of electrolyte leakage through membranes were observed with increases of Cu in the nutrient solution. Moreover, there was an increase in the concentration of thiobarbituric acid-reactive substances in roots due to lipid peroxidation of membranes. Chemical analysis showed that increases in Cu concentrations in vegetative organs of T. cacao increased with the increase of the metal in the nutrient solution, but there was a greater accumulation of Cu in roots than in shoots. The excess of Cu interfered in the levels of Mn, Zn, Fe, Mg, K, and Ca in different organs of T. cacao. Analysis of gene expression via RTq-PCR showed increased levels of MT2b, SODCyt, and PER-1 expression in roots and of MT2b, PSBA, PSBO, SODCyt, and SODChI in leaves. Hence, it was concluded that Cu in nutrient solution at doses equal or above 8 mg L−1 significantly affected leaf gas exchange, cell ultrastructure, and transport of mineral nutrients in seedlings of this T. cacao genotype

Diversidade genética com base em características morfológicas e de marcadores moleculares (RAPD) em passifloras silvestres ornamentais

Objetivando conhecer a diversidade genética para auxiliar na seleção de genitores para obtenção de híbridos ornamentais interespecíficos, procedeu-se à caracterização morfológica e ao uso de marcadores moleculares para o estudo de diversidade genética em Passiflora spp., por permitir um rápido estudo da variabilidade presente

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 (0.6 mg kg−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 0.1 g kg−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