Detection of genetic resistance to cocoa black pod disease caused by three Phytophthora species

Black pod disease of cacao caused by Phytophthora palmivora and Phytophthora megakarya in Ghana take heavy toll of cacao production in the field. Intensive research has been carried out worldwide on these pathogens. However, viability of the cultures during prolonged storage has remained a major challenge in the research. This paper reports findings of assessment of six storage media viz sterilised distilled water (SDW), sterilised and unsterilized soil suspension (SSS and USS), vegetable 8 juice broth (V8JB), Oat Meal Agar slant under mineral oil (at 4°C) and empty tube. Viability of the cultures was assessed on V8JA and in tetrazolium chloride test. Ability of zoospores of the cultures to infect cacao leaf discs was used to assess growth vigour and pathogenicity. Phytophthora cultures stored in SDW (26 ± 2°C; alternating day light and night) were preserved for 60 days (5 years). Both P. palmivora and P. megakarya performed better on SDW and SSS than on USS due to removal of staling substances in the soil medium by the sterilisation. Vigour of growth and pathogenicity of the stored cultures required re-inoculation of host tissue (cacao pod) in order to maintain potency to continually infect host.

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Genetic diversity of native cultivated cacao accessions (Theobroma cacao L.) in Nicaragua

Plant Genetic Resources ◽

10.1017/s1479262112000238 ◽

2012 ◽

Vol 10 (3) ◽

pp. 254-257

Author(s):

Erwin Aragon ◽

Claudia Rivera ◽

Helena Korpelainen ◽

Aldo Rojas ◽

Paula Elomaa ◽

...

Keyword(s):

Genetic Diversity ◽

Theobroma Cacao ◽

Phytophthora Palmivora ◽

Genetic Composition ◽

Breeding Programmes ◽

Black Pod ◽

Black Pod Disease ◽

Parental Lines ◽

Resistant Genotypes ◽

Theobroma Cacao L

A total of 60 farmers' cacao accessions (Theobroma cacao L.) from Nicaragua were investigated using microsatellite markers to reveal their genetic composition and to identify potentially resistant genotypes against the black pod disease caused by Phytophthora palmivora. These accessions were compared with 21 breeders' accessions maintained locally, two Criollo accessions from Costa Rica and two accessions from Ecuador. The analyses showed a low level of differentiation among groups of farmers' accessions (FST = 0.06) and that six Nicaraguan accessions were genetically closely related to the two Criollo accessions used as a reference. In addition, seven distinct genotypes were found to have allelic composition that may indicate linkage to resistance alleles, thus being potential parental lines in future breeding programmes.

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HERITABILITY OF SINGLE PLANT YIELD AND INCIDENCE OF BLACK POD DISEASE IN COCOA

Experimental Agriculture ◽

10.1017/s0014479707005352 ◽

2007 ◽

Vol 43 (4) ◽

pp. 455-462 ◽

Cited By ~ 15

Author(s):

G. LOCKWOOD ◽

F. OWUSU-ANSAH ◽

Y. ADU-AMPOMAH

Keyword(s):

Large Scale ◽

Mass Selection ◽

Single Plant ◽

Plant Yield ◽

Clone Selection ◽

Level Data ◽

Family Level ◽

Black Pod ◽

Black Pod Disease

Broad sense heritabilities were estimated in three long-term cocoa clone trials in Ghana, with 20, 18 and 15 entries. They were 0.15, 0.05 and 0.15 for yield in pods per plant, and 0.26, 0.19 and 0.40 for incidence of ‘bad’ pods, mostly due to black pod disease, caused by infection with Phytophthora spp. The low heritability of single plant yield, which has been known for 80 years, has been widely overlooked in cocoa research and extension, compromising the success of clone selection programmes. The heritability of the incidence of black pod disease is high enough to justify mass selection where family level data are not available. The findings will be applied in a new large-scale programme in Ghana to select clones that are high yielding in the presence of P. megakarya.

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Growth Inhibition of Cocoa Pod Rot Fungus Phytophthora palmivora byPseudomonas fluorescence and Bacillus subtilis bacteria

Pelita Perkebunan (a Coffee and Cocoa Research Journal) ◽

10.22302/iccri.jur.pelitaperkebunan.v29i2.59 ◽

2013 ◽

Vol 29 (2) ◽

Author(s):

Sakti Widyanta Pratama ◽

Sri Sukamto ◽

Lis Nur Asyiah ◽

Yeni Vida Ervina

Keyword(s):

Bacillus Subtilis ◽

Fungal Growth ◽

Petri Dish ◽

Phytophthora Palmivora ◽

Fungal Treatment ◽

Pure Cultures ◽

Black Pod ◽

Black Pod Disease ◽

First Time ◽

Important Disease

Black pod disease caused by Phytophthora palmivorafungus is one of the important diseases on cocoa crop. Pod rot is the most important disease because it may cause loss of cocoa pod. Until now, the fungal pathogen of cocoa black pod disease is still a crucial problem and there is no fungicide that is really effective against the disease. One alternative to control the cocoa black pod disease is by using biological agents as biofungicide, including utilizing Pseudomonas fluorescenceand Bacillus subtilis bacteria. The research was done by isolation of P. palmivora from infected pods of Kaliwining Experimental Station to obtain pure cultures of fungus and by multiplication of P. fluorescence and B. subtilis. Antagonist test was performed by inoculating P. palmivora into a petri dish in a distance of 3 cm from the edge. P. fluorescenceand B. Subtilis were inoculated into petridishes in three days after the fungal treatment. Control was inoculated with isolate of P. palmivora only. Fungal growth was measured everyday by measuring radius of fungal colonies first time 24 hours after inoculation. Growth of Phytophthora palmivora in the two treatmens were used to calculate the percentage of inhibition. The results of this study indicated that P. fluorescence and B. subtiliswere able to inhibit fungal growth of P. palmivora. Both bacterial antagonists had the same effectiveness in inhibiting the growth of P. palmivora fungus based on the percentage of inhibition and effectiveness criteria. Based on the results of translucent zones indicated that B. subtiliswas more powerfull in inhibiting growth of P. Palmivora compared to P. fluorescence. Key words: Black pod disease of cocoa, biological control, Phytophthora palmivora, Pseudomonas fluorescence, Bacillus subtilis

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