Location: Sustainable Perennial Crops LaboratoryTitle: Molecular and morphophysiological responses cocoa leaves with different concentrations of anthocyanin to variations in light levels
|ARAUJO, ROMARIA - University Of Santa Cruz - Brazil|
|ALMEIDA, ALEX-ALAN - University Of Santa Cruz - Brazil|
|BARROSO, JOEDSON - University Of Santa Cruz - Brazil|
|OLIVEIRA, ROSILENE - University Of Santa Cruz - Brazil|
|GOMES, FABIO - University Of Santa Cruz - Brazil|
|AHNERT, DARIO - University Of Santa Cruz - Brazil|
Submitted to: Horticulture Scientia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2017
Publication Date: 7/11/2017
Citation: Araujo, R.P., Almeida, A.F., Barroso, J.P., Oliveira, R.A., Gomes, F.P., Ahnert, D., Baligar, V.C. 2017. Molecular and morphophysiological responses cocoa leaves with different concentrations of anthocyanin to variations in light levels. Horticulture Scientia. 224:188-197.
Interpretive Summary: Theobroma cacao is an understory rainforest tree and is the source of chocolate. The trees are typically grown under shade but in recent times cacao has been cultivated under varying levels of shade including full sunlight. Excessive exposure to sun light can cause damage to cacao growth and development. Some plant species have adopted strategies to cope with excessive exposure to light such as an accumulation of anthocyanins in the leaves. Anthocyanins are known to reduce oxidative stress induced by intensive light exposure. In this paper we report the responses of three cacao genotypes that differ in their levels of leaf anthocyanins to varying levels of light. No differences were observed in the evaluated molecular, physiological and morphological traits for these genotypes under the light levels tested. The presence of anthocyanins had no effect on the plants’ ability to mitigate light induced stress. This information will be useful to plant breeders and agronomists when selecting cacao genotypes suitable for growth under full sunlight.
Technical Abstract: Theobroma cacao gives higher yield when cultivated in full sun under irrigation system with fertilization. On the other hand, T. cacao is usually cultivated under shade conditions in ‘Cabruca’ and agroforestry systems with no irrigation but yields are low. 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 UV-absorbing compounds in the leaf epidermis is one of the most important mechanisms plants have adapted to screen 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), which differed in levels of accumulation of anthocyanins in young leaves. At harvest photosynthesis, activity of guaiacol peroxidase (GPX), chloroplastid pigment contents and vacuolar (anthocyanins) flavonoids contents, anatomical characteristics and gene expression were evaluated. In summary, (i) the anthocyanins contents in leaf 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 invested more in the flavonoids content and hsp70 gene expression; and (iii) the relative expression of the genes psbA and psbO, did not vary between genotypes under irradiance stress condition.