Grain morphological characterization and protein content of sixty-eight local rice (Oryza sativa L) cultivars from Cameroon

Rice (Oryza sativa L.) cultivated in Cameroon is appreciated by consumers for its nutritive quality and good taste. Diversity of 68 local rice cultivars was investigated via grain morphology and protein content characterization. The size and shape of grains were determined and used with yield parameters to classify the cultivars and perform Principal Component Analysis (PCA). Total protein content and glutelin content of eight selected cultivars (CMRGNd, CMRGDn, CMRGTï, CMRTBa, CMRDWb, CMRDTc3, CMRDTx5 and CMRDTx6) were evaluated by Bradford assay and correlation analysis of all the parameters studied was performed. Long size grains (42) were predominant over extra-long (16), medium (9) and short (1) grains. Slender shaped grains (36) were distinguished as well as medium (28) and bold (4) grains. The 68 cultivars were grouped into four clusters independent of their origins. PCA revealed three principal components accounting for 74.4% of total variation. Highest total protein content was observed in CMRGNd (14.3%) and highest glutelin content in CMRGDn (10.1 mgEqvBSA/g DW). Pearson correlation of the different variables revealed no significant correlation between total protein and glutelin contents with the agro-morphological parameters evaluated in this study. This suggests that none of these parameters could be descriptor for protein content. Positive correlation between grain length and yield (r = 0.7) suggests grain length as yield descriptor

Phenolic content and heritability of resistance in four hybrid populations of Theobroma cacao L. after leaves inoculation with Phytophthora megakarya Bras. et Grif

Cocoa is cultivated in Cameroon for its broad beans. The commercialization of cocoa seeds constitutes a major source of income to farmers. Nevertheless, cacao black pod disease caused by Phytophthora megakarya is responsible of about 80% of cocoa production loss in Cameroon without any protection method. To assess the resistance of cocoa plants against this pathogen, necrotic lesions and phenolic content were conducted on 3 clones (SNK16, ICS40, Sca12) and their progenies (families F40, F12, F20 and F25) after leaves inoculation. The existence of strong hybrid vigour has been shown. All hybrid genotypes manifested a positive heterosis effect for this symptom suggesting the existence of hybrid vigour. Some hybrids like F40.6, F40.7, F40.8, F40.9, F40.10, F12.10, F12.15, F20.7, F20.10, F25.2, F25.5 and F25.7 were characterized by localized lesions. A negative correlation between the size of necrotic lesions and the total phenolic compound was demonstrated. Three genotypes of the F40 family (F40.8, F40.9 and F40.13), one of the F12 (F12.15) and two of the F25 (F25.2 and F25.8) had small lesions and high concentrations of phenols. These six genotypes can be considered as elite clones with high tolerance to P. megakarya. The values of the heritability of lesion size and the total phenolic content in offsprings don’t show the maternal effect.Keywords: Cocoa, Phytophthora megakarya, heterosis, heritability, necrosis, phenol

Assessing relationship between phenolic compounds and resistance tPhytophthora megakarya using two cocoa (Theobroma cacao) families

Black pod disease is an important fungal infection in cocoa (Theobroma cacao L.) which causes high production losses. In Cameroon, these losses reached 80% of cocoa production depending on ecological zones. In order to contribute to the efficiency of selection methods used in resistance or tolerance to black pod disease with the aim of improving on cocoa farming, the content of phenolic compounds was analyzed on the genotypes of two hybrid families (F79:♀T79/467x♂SNK13 and F13:♀SNK13x♂T79/467) of cocoa which are different in productivity and vulnerability to black pod disease. After artificial inoculation of the pods by mycelium of Phytophthora megakarya, the content of the phenolic compounds significantly increased in all genotypes of the two families. The heterosis effect of each family revealed a higher variability within both families. These results alike showed that productive and tolerant genotypes (F1307, 1314, F7902 and F7928) have a high phenols content and positive heterosis meanwhile the less tolerant and productive genotypes (F1321, F1326, F7904 and F7911) have a weak content and negative heterosisKeywords: Cocoa, disease, tolerance, heterosis effect, phenolic compounds, hybrid progeniesAfrican Journal of Biotechnology Vol 13(29) 2956-296

Variation of β-1,3-Glucanase, Chitinase and Polyphenoloxidase Activities in Cacao Pods upon Phytophthora megakarya Inoculation

Cacao (Theobroma cacao L.) clones that differ in susceptibility to black pod disease were analysed for response to stress induced by pod inoculation with the fungus Phytophthora megakarya Braz. Et Griff. Fungal inoculation significantly stimulated β-1,3-glucanase activity in both soluble and ionically-bound fractions of the less susceptible clones. No significant correlation was found in the other clones. Chitinase activity in both soluble and ionically-bound fractions was generally reduced upon pod inoculation with the fungus, but this pattern did not correlate with disease severity. Polyphenoloxidase activity, following pod inoculation, was genotype dependent in the soluble fractions, whereas in the ionically-bound fractions, stimulation of this activity was recorded in the less susceptible clones. Moreover, pod inoculation was characterised by the appearance of a new polyphenoloxidase isoform A\'2 in the less susceptible clones. Key Words: Absorbance, cortex, ionically-bound, Theobroma cacao, wonding Résumé Les réponses aux stress induits par innoculation de gousses de cacao (Theobroma cacao L.), aux susceptibilités differentes à la maladie de Blackpod, par le Phytophthora megakarya Braz étaient analysées. L\'inoculation de fungi a significativement stimulé les activités de « glucanase » β-1,3 dans les deux fractions solubles et à liaison ionique des clones moins susceptibles. Pas des corrélations significatives étaient observées dans d\'autres clones. L\'activité de la chitanase dans les deux milieux était generalement reduite juste après l\'inoculation par le fongi, mais cette tendance n\'a pas corrélée avec la sévérité de la maladie. L\'activité du polyphenoloxidase, après inoculation de gousses, était généralement dependante du génotype dans la fraction soluble, alors que la stimulation de cette activité était observée dans les clones moins susceptibles. En plus, l\'inoculation des gousses était caracterisée par l\'apparition de nouveau polyphenolosidase isoformes A\'2 dans les clones les moins susceptibles. Mots Clés: Absorbance, cortex, ionically-bound, Theobroma cacao, wonding (Af Crop Sci J 2003 Vol 11 No 2 pp.97-106

VARIATION OF b-1,3-GLUCANASE, CHITINASE AND POLYPHENOLOXIDASE ACTIVITIES IN CACAO PODS UPON Phytophthora megakarya INOCULATION

Cacao (Theobroma cacao   L.) clones that differ in susceptibility to black pod disease were analysed for response to stress induced by pod inoculation with the fungus Phytophthora megakarya   Braz. Et Griff. Fungal inoculation significantly stimulated β-1,3-glucanase activity in both soluble and ionically-bound fractions of the less susceptible clones. No significant correlation was found in the other clones. Chitinase activity in both soluble and ionically-bound fractions was generally reduced upon pod inoculation with the fungus, but this pattern did not correlate with disease severity. Polyphenoloxidase activity, following pod inoculation, was genotype dependent in the soluble fractions, whereas in the ionically-bound fractions, stimulation of this activity was recorded in the less susceptible clones. Moreover, pod inoculation was characterised by the appearance of a new polyphenoloxidase isoform A'2 in the less susceptible clones

Plant Cell wall polysaccharides: immunomodulators of the immune system and source of natural fibers

International audienc

Plant Cell wall polysaccharides: immunomodulators of the immune system and source of natural fibers

International audienc

Characterization of endophytic Streptomyces strains from roots of cocoyam (Xanthosoma sagittifolium L. Schott) in the South West Region of Cameroon, their in vitro plant growth promoting abilities and biocontrol efficacy against Pythium myriotylum

The focus of this study was to isolate, evaluate and characterize endophytic actinobacteria from cocoyam roots collected in the localities around Mount Cameroon for their potential antagonistic activities against Pythium myriotylum (the major pathogen that limits growth and productivity of this crop in Cameroon) and their ability to promote plant growth. A total of 171 actinobacteria were isolated from healthy cocoyams and were screened for their antagonistic activities against P. myriotylum, Phytophthora megakarya, Fusarium oxysporum and Colletotrichum gloeosporioides. Four isolates (PERM1, PERM2, PERM4 and PERM5) were selected based on of their strongest antagonistic activity in vitro against P. myriotylum. These four isolates were subsequently identified using phenotypic and molecular tests, characterized for extracellular hydrolytic enzymes, plant growth-promoting (PGP) traits, and their effects were evaluated on tissue culture-derived cocoyam plantlets. The sequencing of the 16S rRNA genes and alignment with sequences retrieved through the EzTaxon program indicated that PERM2, PERM4 and PERM5 have low similarity percentages with S. samsunensis EU077190 (92.4% sequence similarity), S. roietensis KX394336 (81% sequence similarity), S. flavoviridis AB184842 (91% sequence similarity) respectively. The comparison of some physiological and biochemical properties of PERM2,PERM4 and PERM5 with the most closely related Streptomyces species showed that these strains differ phenotypically. PERM2, PERM4 and PERM5 might represent new species. All selected Streptomyces were able to produce siderophores, indole-3-acetic acid (IAA), aminocyclopropane-1-carboxylate (ACC) deaminase, and solubilized tricalcium phosphate. With 20.30 μg/ml of IAA, the PERM2 isolate significantly increased the length of roots as compared to the positive control. These results suggest the possibility of using endophytic Streptomyces strains, especially isolate PERM2 in the protection of cocoyams against root rot disease and the promotion of root growth

Compositional, spectroscopic and rheological analyses of mucilage isolated from taro (Colocasia esculenta L. Schott) corms

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