scholarly journals Phosphates solubilizing bacteria like promoters agent of cocoa-tree growth and biocontrol of Phytophthora megakarya Brasier and M.J. Griffin, agent of black pod disease

2019 ◽  
Vol 11 (2) ◽  
pp. 8-21
Author(s):  
Sani Maryam ◽  
Claude Simo ◽  
Souleymanou Adamou ◽  
Hélène Laure Mafokoua ◽  
Tchakounte Gylaine Vanissa Tchuisseu ◽  
...  
Keyword(s):  
Tree Growth ◽  
Black Pod ◽  
Phytophthora Megakarya ◽  
Black Pod Disease ◽  
Cocoa Tree

scholarly journals Effect of MgSO4 nutrition on Theobroma cacao L. susceptibility to Phytophthora megakarya infection

2018 ◽  
Vol 54 (No. 2) ◽  
pp. 74-82
Author(s):  
Minyaka Emile ◽  
Banen Collette Vanessa Madina ◽  
Kusznierewicz Barbara ◽  
Doungous Oumar ◽  
Haouni Soungouna ◽  
...  
Keyword(s):  
Theobroma Cacao ◽  
Substantial Decrease ◽  
Asymptotic Line ◽  
New Strategy ◽  
Hyperbolic Curve ◽  
Cysteine Content ◽  
Black Pod ◽  
Phytophthora Megakarya ◽  
Black Pod Disease ◽  
Theobroma Cacao L

A new strategy to reduce the severity of black pod disease (BPD) in T. cacao plants using MgSO<sub>4</sub> 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 MgSO<sub>4</sub> into the soil. Prior to MgSO<sub>4</sub> 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 MgSO<sub>4 </sub>application, a substantial decrease in disease scores was observed compared to the control. The percentage of disease tolerance gain of plantlets versus MgSO<sub>4</sub> 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 MgSO<sub>4 </sub>nutrition. On days 28 and 56 of MgSO<sub>4</sub> supplementation, cysteine content presented a pattern similar to the tolerance gain of plantlet sets. The monitoring of glutathione content versus MgSO<sub>4</sub> 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 MgSO<sub>4</sub> 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.

scholarly journals Maximum Entropy Niche Modelling to Estimate the Potential Distribution of Phytophthora megakarya (Brasier & M. J. Griffin) in Tropical Regions

2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Maxwell Obiakara ◽  
Peter Etaware ◽  
Kanayo Chukwuka
Keyword(s):  
West Africa ◽  
Geographic Distribution ◽  
Goodness Of Fit ◽  
Small Sample ◽  
Data Types ◽  
Niche Modelling ◽  
Tropical Regions ◽  
Black Pod ◽  
Phytophthora Megakarya ◽  
Black Pod Disease

Background: Phytophthora megakarya is an invasive pathogen endemic to Central and West Africa. This species causes the most devastating form of black pod disease. Despite the deleterious impacts of this disease on cocoa production, there is no information on the geographic distribution of P. megakarya. Aim: In this study, we investigated the potential geographic distribution of P. megakarya in cocoa-producing regions of the world using ecological niche modelling. Methods: Occurrence records of P. megakarya in Central and West Africa were compiled from published studies. We selected relevant climatic and edaphic predictor variables in the indigenous range of this species to generate 14 datasets of climate-only, soil-only, and a combination of both data types. For each dataset, we calibrated 100 candidate MaxEnt models using 20 regularisation multiplier values and five feature classes. The best model was selected from statistically significant candidates with an omission rate ≤ 5% and the lowest Akaike Information Criterion corrected for small sample sizes, and projected onto cocoa-producing regions in Southeast Asia, Central and South America. The risk of extrapolation in model transfer was measured using the mobility-oriented parity (MOP) metric. Results: We found an optimal goodness-of-fit and complexity for candidate models incorporating both climate and soil data. Predictions of the model with the best performance showed that nearly all of Central Africa, especially areas in Gabon, Equatorial Guinea, and southern Cameroon are at risk of black pod disease. In West Africa, suitable environments were observed along the Atlantic coast, from southern Nigeria to Gambia. Our analysis suggested that P. megakarya is capable of subsisting outside its native range, at least in terms of climatic and edaphic factors. Model projections identified likely suitable areas, especially in Brazil and Colombia, from southwestern Mexico down to Panama, and across the Caribbean islands in the Americas, and in Sri Lanka, Indonesia, Malaysia, and Papua New Guinea in Asia and adjacent areas Conclusion: The outcomes of this study would be useful for developing measures aimed at preventing the spread of this pathogen in the tropics.  

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