A simple method for the extension of shelf life of cultures of Phytophthora species causing black pod disease of cacao (Theobroma cacao L.)

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

Efficacy Ofclove ( Syzygium Aromaticum (L.) Merr And Perry) Powder As A Protectant Of Groundnut Kernels In Storage

Fungi and insects infestation of groundnut kernels in storage is a serious post-harvest problem. It leads to quality deterioration and loss of market value and kernels may become contaminated with aflatoxin (AF), which has many negative health implications when consumed. Currently, botanical pesticides are highly preferred to synthetic ones during storage. Effectiveness of preserving groundnut kernels against fungi and insect damage with Syzygium aromaticum cloves (fruits) powder were assessed in the laboratory. Another experiment was conducted under farmer's storage conditions to evaluate potential of Syzygium powder to protect kernels against AF contamination. In the laboratory assessment, 3 kg kernel samples from sun-dried and undried pods were protected with 2 % (w/w) Syzygium powder. Kernels were kept under ambient conditions in sanitised and non-sanitised rooms for six months during the dry season. Unprotected kernels were kept as control and costs of applying the treatments were estimated. The experiment was repeated in the wet season. Under farmer's storage, 50 kg kernel lots of 6 and 9 % initial storage moisture contents were protected with 2 % (w/w) Syzygium powder. Kernel lots stored without Syzygiumpowder served as control. These were packaged in interlaced polypropylene bags (IPPB) or polyethylene bags (PB) and stored in a farmer's barn on farm. In dry and wet seasons, fungi colonised all kernels stored in laboratory from undried pods completely at three months. Pod drying costs GH¢ 8.99 (GH ¢0.82 = $ US1) and it was cost effective against fungi infection in dry season. Protecting kernels with Syzygium powder was estimated at GH¢ 17.87/100 kg lot and under the humid conditions in wet season, it proved cost effective against fungi infection. However, insect damage to the kernels was always higher after three months. Insects damage and fungi colonisation of kernels packaged in either PB or IPPB were reduced significantly (P ≤ 0.05) at three months storage under farmer's conditions, when they were protected with Syzygium powder. Aflatoxins do not use abbreviation at beginning of sentence were not detected in the kernels prior to storage. At three months, however, Syzygium-protected kernels had AF levels ranging between 0 and 29.30 μg/kg compared to 27.5-84.0 μg/kg associated with unprotected kernels. Syzygium powder applied at 2 % (w/w) was effective against fungi colonisation, insect infestation and subsequent AF contamination of kernels in storage. However, the kernels should be stored for three months

Cost effectiveness of selected post harvest pod handling techniques against damage, mouldiness and aflatoxin contamination of shelled groundnut in Ghana

Some post harvest pod handling methods were evaluated at Ejura and at KNUST, Kumasi to determine the costs and effectiveness of the methods in minimising post harvest damage, mouldiness and aflatoxin (AF) contamination of shelled groundnut. The study was conducted in 2002 (dry season) and repeated in 2003 (wet season). Four treatments were imposed on pods from 180 m2 plots at harvest. The treatments were (i) inverted windrowing (1wk) followed by drying of the pods on mats (3wk) (ii) random windrowing (1wk) followed by drying of the pods on mats (3wk) (iii) stripping and drying of pods on mats (4wk) and (iv) storage of pods without drying (control). Costs involved in carrying out the treatments were estimated. Fungi associated with the kernels and AF levels were also determined at harvest and at 4 weeks. In both seasons, Aspergillus niger was the most common fungus associated with kernels at harvest and after the 4 wk pod handling periods. Aspergillus flavus was also encountered at both periods. When pods were dried for 4 wk, the amounts of damaged/mouldy ones that were rejected were low (2.7-13.1%; av. 8.6 %) compared with undried pods where 18.9-25.94% (av. 22.08%) were rejected. Aflatoxins were not detected in kernels at harvest and generally, dried pods had lower levels of AFs (0 - 0.7µg/kg) than the undried control pods (7278.1µg/kg). Visibly healthy pods sorted from the dried lots had kernel AF levels of 0.2 - 0.6µg/kg which were similar to the 0 - 0.7µg/kg levels associated with the unsorted lots. Sorting, however, cost an extra ¢31,354/100 kg lot (¢8,200 = $ US1), making the practice uneconomical for well dried pods. Total cost of pod drying up to 4 wk was the same for the random and the inverted windrowed crops (¢89,980/100 kg pod) but was ¢95,440 when pods were dried on mats immediately after stripping. When pods were not dried, cost of handling was ¢69,600/100 kg pods but due to the high AF contamination (7278.1µg/kg), kernels from such pods constitute total loss. Thus, both windrow and mat drying of groundnut pods are cost effective in controlling damage/mouldiness and AF contamination but costs are lower when windrowed. Journal of Science and Technology(Ghana) Vol. 27 (1) 2007: pp. 17-2