Plant Protect. Sci., 2018, 54(2):74-82 | DOI: 10.17221/124/2016-PPS

Effect of MgSO₄ nutrition on Theobroma cacao L. susceptibility to Phytophthora megakarya infectionOriginal Paper

Emile Minyaka^1,3,*, Collette Vanessa Madina Banen¹, Barbara Kusznierewicz⁴, Oumar Doungous^2,3, Soungouna Haouni¹, Joseph Hawadak¹, Nicolas Niemenak³, Denis Ndoumou Omokolo³

¹ Biochemistry Laboratory, Faculty of Science, University of Douala, Douala, Cameroon

² Biotechnology Laboratory, Institute of Agricultural Research for Development, IRAD Ekona Regional Research Centre, Buea, Cameroon

³ Laboratory of Plant Physiology and Biochemistry, Department of Biological Science, Higher Teachers Training College of Yaoundé, Yaoundé, Cameroon

⁴ Department of Food Chemistry, Technology and Biotechnology, Faculty of Chemistry, Gdańsk University of Technology, Gdańsk, Poland$2

A new strategy to reduce the severity of black pod disease (BPD) in T. cacao plants using MgSO₄ nutrition was investigated. The dynamics of the tolerance to BPD of 18 susceptible T. cacao plantlets coming from the cross (♀SNK64 × ♂UPA14) was monitored during weekly (8 weeks) supply of MgSO₄ into the soil. Prior to MgSO₄ application, disease scores of the 18 plantlets (in six sets of three plantlets per set) were varying between 3.5 (susceptible) and 5 (highly susceptible). After MgSO₄ application, a substantial decrease in disease scores was observed compared to the control. The percentage of disease tolerance gain of plantlets versus MgSO₄ supplied (0-2.96 g) presented a quasi-hyperbolic curve with asymptotic line corresponding to 60% (day 28) and 70% (day 56). Cysteine content was not significantly different between the six triplets before MgSO₄ nutrition. On days 28 and 56 of MgSO₄ supplementation, cysteine content presented a pattern similar to the tolerance gain of plantlet sets. The monitoring of glutathione content versus MgSO₄ supplementation (compared to day 0) showed sigmoid (day 28) and hyperbolic (day 56) curves which were associated with defined mathematical laws determined by MALAB software. Negative and highly significant correlations were observed between disease scores, cysteine and glutathione contents in leaves while positive and highly significant correlations were observed between cysteine and glutathione contents in leaves. These data might mean that MgSO₄ nutrition significantly improved the tolerance of T. cacao. The mechanism of tolerance improvement might be associated with the synthesis of sulphur-containing compounds (cysteine and glutathione) which might be directly or indirectly used by T. cacao against P. megakarya.

Keywords: cocoa; profitability; sulphur; defence; pathogen

Published: June 30, 2018  Show citation