ABSTRACT

Studies were carried out at the Department of Crop science, University of Nigeria Nsukka (UNN) to evaluate botanicals control of diseases associated with growth and germination of Moringa seeds. Five accessions of Moringa seeds collected from Imo, Enugu, Kogi, Plateau and Kaduna states of Nigeria were used. The following experiments were carried out: seed viability test, isolation of fungal pathogens, determination of phytochemicals, in vitro control of the pathogens with six botanicals, phytoxicity test of the botanicals on M. oleifera seeds and early growth study of the treated and untreated seeds. The viability test revealed significant (p < 0.05) differences in some of the germination traits of the five accessions of moringa seeds. Kaduna accession gave the highest number of days to first germination (approx. 6 days) followed by Jos and Imo with same value (approx. 4 days) and the lowest was Nsukka (approx. 3 days). The following organisms were isolated from the seed coats; namely, Aspergillius niger, A. flavus, A. glaucus, Fusarium oxysporium, Mucor spp, Cunnighamella spp, Penicillium digitatum. Only A. flavus was isolated from the cotyledon (seed without coat). The percentage disease incidence was highest in Kaduna (99.90%) on seed with coat and (89.75%) on seed without coat. Enugu accession had the lowest percentage disease incidence (10%) and (0%) for seed with coat and those without coat respectively. Aspergillius flavus had the highest percentage frequency of occurrence (16.31%) while the value for Fusaruim oxysporium and Mucor spp were lowest and statistically the same (0.27%). At both 50 and 70 grams/liter levels of concentration, Aspilia africana leaf extract showed the highest percentage growth inhibition for 14 days while the lowest was obtained in Cassia alata. Phytotoxicity test revealed that at 50 grams/liter O. gratissemum leaf extract significantly ( p < 0.05) gave the highest number of days to first germination (approx. 6 days) while A. africana leaf extracts gave the lowest (approx. 4 days). The main effects of Aspilia africana leaf extract treatment on plant height, stem girth, number of leaves, number of buds and number of nodes were significant (p , 0.05). The seedlings treated with Aspilia africana leaf extracts at 12 weeks after planting had higher plant height, stem girth, number of leaves, number of buds and number of nodes than the untreated. (Treated: 59.61, 3.21, 17.90, 4.51 and 18.18 cm) while the untreated gave lower values (untreated: 54.58, 3.19, 16.60, 4.27 and 15.89 cm) respectively. The duration of storage significantly (p < 0.05) affected the incidence of diseases on the fresh and stored Moringa oleifera leaf products. Two months of storage gave the highest percentage disease incidence (19.66%) which differed significantly (p < 0.05) from others. Zero storage (at harvest) gave the lowest value (0.92%). The result of the study shows that all the leaf extracts inhibited the growth of the fungal isolates but Aspilia africana leaf extract was more effective because it gave relatively less adverse effect to germination and growth of the Moringa oleifera seeds tested.

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INTRODUCTION

Moringa oleifera Lamarck belongs to the family of Moringaceae which consists of 13 species of deciduous trees (Keay, 1989; Price, 1985). Other species of Moringa in the family are M. arborea, M. berzian, M. concanensis, M. drouhaddi, M. hildebrandtii, M. longituba, M. ovalifolia, M. peregrina, M. pygmaea, M. rivae, M. ruspoliana and Moringa stenopetala. Moringa oleifera is the most cultivated among all the species in the family Moringaceae. It is a native of India but is widely distributed in many tropical and pacific regions, in West Africa as well as Central America and the Caribbean (Freiberger et al., 1998; Locket et al., 2000; Ramachandran et al., 1980 and Aregheore, 2002).

The common name of Moringa oleifera is Moringo in Malabar (a region in southern India) and it is believed to be the origin of the generic name (Jackson, 1990). It appears to have more names than any plant ever studied. It is known as Rawag in Arabic, Kelorin in Indonesian, Horse- radish tree, Drumstick tree in English (Hutchinson and Dalziel 1966), Ewe igbale (Ewe ile) in Yoruba, Zogallagandi (Zogalle) in Hausa, Okwe oyibo in Igbo (Gbile, 1984). The common names are Miracle tree, Life saver, Never die, etc. (Ofor et al., 2011). Every part of Moringa plant is useful; the root, seed, leaf, etc. (Fahey, 2005) and may be consumed raw, roasted, cooked, and processed domestically or industrially. The products of this tree have been reported to be useful to nutritionists, animal scientists, pathologists, entomologist, environmentalists, practitioners of natural medicine, etc. (Ofor et al., 2011).

Ogwo and Ogbonnaya (2010) presented Moringa oleifera as one of the few plants that have the capacity to meet the millennium goals in Nigeria in terms of food security. This is in response to the prediction of the Food and Agriculture Organization (FAO) that the world population may rise to about 10 billion in 2050. By 2008 statistics, almost 40% of the world population lived within the tropical zone and by 2060, 60% of the human population will be in the tropics due to high birth rates and migrations (Wikipedia, the free Encyclopedia, 2012). There is a need to increase production of useful plants like Moringa to ensure food security in the tropics. Though Moringa tree is widespread throughout the tropics, around farms and compounds and often used as fence especially in northern Nigeria, not much has been done to enhance its large scale production to ensure sustained availability (Ofor et al., 2011). One of the major challenges of large scale production is how to handle the pests and diseases of the plant. Farmers generally suffer great loss through pests and diseases especially through fungal infections which may not only inhibit the production of foliages, fruits and stems, but lower the overall quality

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and quantity of the cultivated crops. The known pests are caterpillars, budworms, borers and fruit flies. Most of the reported diseases of Moringa oleifera are fungal. They are

•                     The root rot (Diplodia spp)

•                     The papaya powders mildew (Levellula taurica (Lev) Arn)

•                     Pod rot disease (Drechslera haraiiensis)

Fungi are significant destroyers of foodstuffs, vegetables and grains during storage rendering them unfit for human consumption by retarding their nutritive value and often by producing mycotoxins (Janardhana et al., 1998; Marin et al., 1999). A significant portion of the agricultural produce in some countries and the world over become contaminated by fungus infected grains (Janardhana et al., 1998). The main toxic effect of fungi is genetoxicity, hapatoxicity, nephrotocity, carcinogencity, terratogencity, reproductive disorder and immune suppression (Hacey, 1988). More than 25% of the world cereals are contaminated with known mycotoxin and more than 300 fungi metabolites are reported to be toxic to man and animals (Galvano et al., 2001). A sizeable portion of the world population living below poverty line in the developing and under developed countries of Asia and Africa are suffering from health problems associated with consumption of contaminated grain and cereals (Majunder et al., 1977).

Plant disease invasion started when man began to devastate the ecosystem and then broke the food chain in ecology and that led to food shortage and famine across the world (Walker, 1969). The increase in demand for moringa and its products has undoubtedly increased the rate at which the plant is moved from one locality to another and this may contribute to more imbalances in ecosystem and may also mean exposition of these localities to new diseases. India had been enjoying disease free farming of Moringa except mild attacks of Diplodia spp. which occurs mainly in water logged conditions but recently, the threats of Drechslera haraiiensis and its rot ravages is described as a new disease in India. Its symptoms are observed all over the surface of the pods, more conspicuously at the stigmatic end. On the green pod, elliptical or elongated sunken spots with reddish brown raised margins can be observed. Diseased pods are shrunken to thinner dimensions at their stigmatic ends than healthy ones. In advanced stages of the disease development, the pods are rotten and dried up prematurely leaving uneven raised spots over them.

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Plant is the major source of world food. However, it competes with about 80,000 to 100,000 plant diseases caused by pathogenic organisms such as viruses, bacteria, mycoplasma-like organisms, rickettsia, fungi, algae and parasitic seed plants. About 3,000 species of nematodes attack plants and over 800, 000 species of insects of which about 10,000 species are more devastating and can cause various economic losses in crop production worldwide (George, 1978). Losses caused by pests and diseases in the field have been estimated by the Food and Agriculture Organization (FAO) to be about 20 to 40% in the developed countries and may be higher in the developing countries (FAO, 1981). The issues of providing efficient and effective control of these diseases are a great challenge to the farmers. Though, the seed born fungi could be controlled efficiently with pesticides but it is at the consumers risks because some pesticides are toxic to man and animals. It is reported that the world health organization (WHO) banned many agricultural fungicides due to their wide range of toxicity on non-target organisms including humans and are known to contribute to environmental pollution (Bernard et al., 1997). Alternatively, it is also known that plants extract exhibit anti-bacterial, antifungal and insecticidal properties (Satish et al., 1999). These plant extracts could be preferred to the conventional fungicides and pesticides because they are mild in nature, friendly to man, livestock and plants and at the same time effective control for fungal diseases.

Generally, it is observed that some Moringa seeds when the coats are removed, contain kernels that look brown with signs of decay, some are eaten up. It may be dangerous for those that eat it raw with the seed coat. That means that whether infected or infested it is still dangerous. These abnormalities can be as a result of pathogen attack in the field or in the store due to poor storage or poor handling from the farmers to the consumers. Therefore, in response to these challenges, the objectives of this study are to:

•                     isolate and identify some of the disease organisms associated with the seed to ensure good health and boost the crop yield;

•                     determine the phytochemical contents of six botanicals for the control of the disease organisms;

•                     determine the efficacy of the six plant extracts in the management of the disease organism;

•                     determine the effect of the botanicals in the growth of Moringa oleifera seedlings in the nursery and

•                      determine the persistence of the organism on the Moringa oleifera leaf product.

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LITERATURE REVIEW Propagation of Moringa oleifera

It is propagated by seeds, vegetatively by cutting and by roots. Mature pods contain 15 - 35 seeds on the average per pod (Foidl et al., 2001). There are variations in seed colour, weight and flowering phenology among varieties across locations. The trigonous seeds are dark brown to black with semi- permeable seed hulls and whitish papery wings to dispersal. The average weight per seed is 0.3kg and the kernel to hull ratio is 3: 5 (Marker and Becker, 1997). Flowering occurs 4 – 12 months after planting (Ritu et al., 2011). M. oleifera seeds germinate 5 – 12 days after planting in the soil (Palada and Changi, 2003). Cracking or soaking seeds overnight in water may speed up germination (Price, 2000). M. oleifera prefers a neutral to slightly acidic soil wit PH of 5.0 – 7.0 but can tolerate PH up to 9.0 (Palada and Changi, 2003). It does best in sandy loam soil and areas with temperature of 25 – 400c, an annual rainfall of at least 500mm and elevation of 600 – 1000 meters above sea level (Rajandam et al., 2001). Quality seedling obtained from the nursery influences subsequent productivity (Bayeri, 2006). Seeds remain viable for extended periods if kept under conditions of low temperature and moisture content (Agbo and Obi, 2006). Generally, seeds deteriorate during storage, M. oleifera seeds lose their vigour as from three months of storage (Anonymous, 2002), from 7 -12 months viability is reduced to 0% (Bosh, 2010). Known pest and diseases of M.oleifera are Caterpillars, bud worms, aphids, borers and fruit fles (Bosh 2004; Ramachandran et al., 1980). Most of the reported diseases of M. oleifera are the root rot caused by Diplodia spp, the Papaya powdery mildew caused by Levellula taurica and pod rot disease caused by Dreshlera haraiinsis (Rajangam et al., 2001).

PROPERTIES OF THE BOTANICALS USED

Medicinal Properties of Moringa oleifera Lam.

In many cultures throughout the tropics, differentiation between food and medicinal uses of plants (e.g. bark, fruit, leaves, nuts, seeds, tubers, roots, flowers), is very difficult since plant uses span both categories and this is deeply ingrained in the gradation and the fabric of the community (Lockett et al., 2000). An examination of the phytochemicals of Moringa reveals a range of fairly unique compounds. The family of Moringaceae is rich in compound containing

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the simple sugar, rhamnose, and it is rich in a fairly unique group of compound called glucosinolates and isothicyanates (Benneth et al., 2003). Some specific components of Moringa have been reported to have anti bactieral, anti cancer, hypertensive activity include 4-(4-0-acetyl-a-l.rhamnophyranosydloxy) benzyl isothiocyanate) Niazimicin (Akhtar and Ahmad, 1995), Pterygospermin (Anderson et al., 1986), benzyl isothiocyanate (Anwar and Bhanger, 2003), and 4- (a-l- rhamnopyranosyloxy) benzyl glucosinolate (Asres, 1995). These compounds are relatively unique to Moringa family. The family is also rich in a number of vitamins and minerals as well as other more commonly recognized phytochemicals such as the carotenoids (including b-carotene or pro-vitamins A).The compound found in the leaf extracts are alkaloids, glycosides, saponins, tannins, pterygosperm and neomycin which have been found to have a broad spectrum of action against gram positive and negative bacteria (Duke, 1983). Leaf extracts is believed to reduce glucose levels in cases of diabetes. It is also used to treat typhoid fever, urinary tract infection, staplylococus infection, dysentery, diarrhea, etc in folk medicine (Fahey, 2005).The leaves are exceptionally good source of vitamins, minerals and Amino acids. Moringa fruit pods are believed to be anti helmintic, anti-inflammatory and helpful to the spleen and liver (Ezeamuzle et al., 1996). The seeds are used at homes as a natural flocculent because of the presence of Aluminum sulphate (alum) in purifying turbid water (Fuglie, 1999).

Medicinal properties of Aspilia africana (pers) Adams

Aspilia africana is one of the many indigenous plants used by tradomedical practitioners in Nigeria to cure certain illness. It is known as organgila in Ibo, Tazalian in Hausa, Yungung in Yoruba and Edemedong in Efik (Single, 1965). Aspilia africana is a common weed of field crops in West Africa found in fallow land, especially in the forest zone. It is a scrambling perennial herb varying in height from 60 cm to about 1.5 m depending on rainfall (Agyakwa and Akobundu, 1987). The flowers are showy yellow florets and the fruits are bristly and minutely hairy with 4 angled schemes about 5 mm long. There are several indigenous uses of the leaves and flowers of this plant. The most notable is using it to stop bleeding and fast healing of wounds. They are used in the treatment of rheumatic pain (Oliver, 1960) as well as bee and scorpion stings (Single, 1965). The plant is used to treat different diseases in different ecological zones due to varying chemical composition as a result of various ecological conditions of different places. In Kenya, they are used to kill intestinal worms in Uganda, it is used to treat

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gonorrhea (Page et al., 1992). The methanol extract of the leaves are reported to cure malaria and respiratory problems (Musyimi et al., 2007). A concussion of the leaves are used to cure eye problem and as a lotion for the face to relieve frabrile headache. They are also used to cure ringworm and dysentery.

Medicinal properties of Chromolaena odorata (L) King and Robinson (Eupatorium odorata) Chromolaena odorata was introduced to Ivory Coast in 1952 because of it allelopathic nature to control Imperata grasses (Pierre, 1977). However, Chromolaena odorata contains carcinogenic pyrrolizidine alkaloids which is toxic to cattle (Fu, 2002). It can also cause allergic reactions. C. odorata is considered an invasive weed of field crops and natural environments in its introduced range. It has been reported to be the most problematic invasive species within protected rainforests in Africa. In Western Africa it prevents regeneration of tree species in areas of shifting cultivation. It affects species diversity in southern Africa. The plants flammability affects forest edges. In Sri Lanka it is a major weed in disturbed areas and coconut plantations (Lalith, 2009)