Control of Fungal Pathogens of Postharvest rot of Groundnut ( Arachys Hypogea L . ) using Aqueous and Ethanol Root Extracts of Mahogany ( Khayasenegalensis ) in Hong Local Government Area of Adamawa State Nigeria

Fungi are associated with heavy losses of seeds, fruits, grains, vegetables, and other plant products in transit and storage rendering them unfit for human consumption. The effect of synthetic fungicides on humans is hazardous, hence the need to find a safer means of control. A research was conducted in Hong Local Government Area of Adamawa State of Nigeria (the most prominent groundnut farming community in the state). The following molds were associated with postharvest groundnut rot in the seven districts of Hong local government area in July 2016: Aspergillus niger, Aspergilus flavus, Penicillium chrysogenum, Rhizopus stolonifer, Paecilomyces lilacinus, Pseudallescheria boydii, Cylindrocarponl ichenicola, and Scedosaporium prolificans. Therefore, the research sought to assess the management of rot using plant extracts of mahogany. Control trials were carried out using the extracts of root of mahogany. The growth of pathogens both in-vitro and in-vivo was significantly reduced by the plant extracts.

Introduction he roles of agriculture remain significant in the Nigerian economy despite the strategic importance of the oil sector, agriculture still provides primary means of employment for Nigeria and accounting for more than one-third of total gross domestic product (GDP) and labor force (Ayoade, 2012).
The major food crops of Adamawa State according to Adebayo (1997) are mainly cereals, legumes, and root crops, while the cash crops are mostly cotton, groundnut and sugar cane. The variable climatic and edaphic factors of the state as well as cultural and socio-economic factors, are reportedly responsible for the distribution of food and cash crops in the State.
Groundnut (Arachis hypogaea L.) is an essential oilseed crop in Nigeria and is widely grown in the tropics and sub-tropics (Nigam et al., 1994). It is one of the most significant crops that can flourish on newly reclaimed sandy soils as a legume of high nutritive value as well as being a source of edible oil (Spears et al., 2002). The major groundnut producing countries from the world are China, India, Nigeria, Argentina, USA, Indonesia, and Sudan. Developing countries account for 96 percent of the global groundnut area and 92 percent of the world production (FAOSTAT, 2011).
Fungi such as Aspergillus niger, Aspergillus flavus, Alterneria anthocola, Curvularia lunata, Curvulari apellesecens,Fusarium oxysporum, Fusarium equiseti, Microphomina phaseolina, Rhizopus stolonifer, Penicillium digitatum and Penecillium chrysogenum cause severe damage to stored commodities resulting in discolouration, rotting, shrinking, seed necrosis, loss in germination capacity and toxification to oilseeds according to Chavan and Kakde (2008). Verma et al. (2003) reported that, the action of these fungi resulted to loss of seeds, fruits, grains, vegetables and other plant products during picking, transit and storage rendering them unhealthy for human consumption even by producing mycotoxins and also reduce the total nutritive value. Tropical climate with high temperature and high relative humidity in addition to poor storage methods adversely affect the quality of cereal grains and oilseed, T Author α σ : Department of Plant Science, Modibbo Adama University of Technology, Yola. e-mail: farbinah222@gmail.com ( C ) and this can lead to the total deterioration of seed (Bhattacharya and Raha, 2002). Groundnut seed is susceptible to a wide range of pathogens and pests which cause a lot of damage to the crop, thereby reducing yield (Weiss, 2000).
Therefore, many of the seed-borne fungi were generally managed by the use of some synthetic chemicals which were also considered to be both efficient and effective (Ahmed et al., 2012). The continuous use of this fungicides unraveled its nonbiodegradability and leaving residual toxicity to cause environmental pollution (Ajobade and Amusa, 2001), hence the need for alternative safer means of control.
In resent year Much Attention has been given to the use of non-chemical systems for the treatment of the A good solvent in plant extraction should be of low toxicity, ease of evaporation at low heat, promotion of rapid physiologic absorption of the extract, preservative action and inability to cause the extract to form complex or dissociate (Hughes, 2002). Thus, the commonly used solvents for preliminary research of anti-microbial activity in plants are said to be methanol, ethanol, and water (Lourens et al., 2004;Parekh et al., 2006).
The aim of the study is to determine the inhibitory effect of aqueous and ethanol root extracts of Khaya senegalensis on post-harvest fungal pathogens of groundnut rot obtained from the seven districts of Hong Local Government Area of Adamawa state.

Materials and Method
The control with root extracts was carrived out in the Medical Laboratory of Microbiology Department, Modibbo Adama University of Technology (MAUTECH) Yola, from 18 th July 2016 to 24 th October 2016.

a) Source of Samples
Samples of groundnut seeds of two genotypes commonly found are Valencia (Kampala) and Peruvian (Kwathrumthrum) were collected from one (1) major market in each of the seven (7) districts namely Hildi, Kulinyi, Dugwaba, Uba, Gaya, Pella, and Hong. Fifty (50) of the samples of each genotype were purchased from a seller (two randomly selected sellers/ traders within the chosen market) in each district making a total of 700 collected from the various locations; the samples were carried to the laboratory in a dry clean polythene bag. Groundnut samples were labeled according to location and then photographed ( Figure    Sterilization of the laboratory environment was carried out to avoid contamination. The bench and tables used were swapped clean using 95% ethanol, and UV light switched on for 30 minutes. Petri-dishes were sterilized at 160 0 C for 1 hour in the oven, forceps and needles used for inoculation were sterilized by flaming on a Bunsen burner flame and dipping into the methylated spirit to cool.

c) Preparation of Potato Dextrose Agar (PDA)
Thirty-nine grams (39 g) of Potato Dextrose Agar (PDA) was dissolved in one (1) liter of distilled water; the PDA was then poured into two 500ml conical flask, then plugged with cotton wool and wrapped with aluminium foil before autoclaving at 121 0 C for 15 minutes at 10 lbs. Pressure, and 6 ml (0.1%) of streptomycin was added to the liter of sterilized media and swirled gently to mix appropriately, just before pouring into Petri dishes to prevent bacterial growth and allowed to cool and solidify according to the method of Suleiman and Michael (2013).

d) Collection and Preparation of Extracts
The method of Ijatoet al.  Figure III) and were allowed to air dry for seven (7) days; these were then ground using pestle and mortar. Hundred (100), sixty (60) and twenty (20) grams were dissolved in sterile distilled water and ethanol in separate conical flasks respectively. These were vigorously shaken and left to stand for 24 hours. The samples were then filtered with three layers' cheese cloth. The crude aqueous and ethanol extracts were evaporated through heating with a hot plate to complete dryness and concentrations of 100%, 60% and 20% were used.

e) Effect of Leaf Extract on the Isolates
The in-vitro test was carried out using the approach of Ijato (2011) to evaluate the growth inhibition level of the extract on fungal colony growth by creating four equal sections on the bottom of each Petri dish. The point of intersection indicates the center of the plates. This was done before dispensing the PDA mixed with the aqueous and ethanol leaf extracts into each of the Petri dish in the different concentrations of 100, 60, and 20% (pour plate method) followed by inoculation of the isolate. The control experiment was without the addition of any mahogany leaf extract. Growth inhibition was determined by ruler measurements of radial colonial expansion.
The in-vivo test was carried out by placing cotton wool onto the plates then inserting three certified seeds before inoculating mycelial/spore suspension of each of the pathogens unto the seeds and also two (2) drops of the extracts (aqueous and ethanol) with a sterile syringe. Fungal growth inhibition was determined by measuring the growth of fungus with measuring ruler (mm).

f) Statistical Analysis
All the data were analyzed using analysis of variance (ANOVA) according to Gomez and Gomez (1984). Least Significant Difference (LSD) according to Scheff (1953) was used to separate the means that were significantly different. Statistical Analysis Software (SAS) Version 9.1 was used to analyze the results.

In-vitro and in-vivo mold inhibition by mahogany root aqueous and ethanol extracts
In-vitro evaluation of aqueous and ethanol root extracts of Khaya senegalensis on mycelial growth of the pathogens proved effective. However, there was no significant difference between the two solvents. The lowest growth of the pathogens recorded in-vitro was in   (Table 3). The most effective concentration was the 100% concentration followed by 60% then 20%.  There was a significant difference between the Valencia and the Peruvian variety, however, the Peruvian showed it has more resistance than the Valencia variety (Table 4).

Discussion
Both aqueous and ethanol root extracts of mahogany are effective control agents on all the postharvest fungal pathogens of groundnuts both in vitro and in vivo, though efficacy varied with pathogens. There was, however, no variation between the aqueous and ethanol solvents. This agrees with reports (Lourens et al., 2004, Parekh et al., 2006, Rojas et al., 2006) that both water and ethanol were effective solvents for preliminary investigations against the microbial activity.
Efficacy of the extracts appreciated along with the concentration (solvent to sample ration) which conforms to an earlier report by Green (2004) observed that higher sample ratio to solvent was ideal. The best and ideal concentration of mahogany root extract is 60% since it exhibits similar efficacy.
The 'kwathrumthrum' (local genotype) exhibited higher resistance to all the eight postharvest groundnut rot fungal pathogens. Host plant resistance is considered one of the most essential disease control strategies (Hasyim et al.,2014). V.

Conclusion
The research revealed the root extract of Mahogany (aqueous and ethanol) has the potential to reduced fungal rot of groundnut seeds at different concentration. Plant extracts are cheaper, safer, affordable to the farmer and environmentally friendly, therefore, there is a need for more researches into the use of plant extracts by the pathologist. Farmers thus have hope for a cheaper and safer alternative control against deteriorating fungal agents of groundnut.