ABSTRACT
The extracts of fresh peels of lemon, orange, and grapefruit showed significant nematostatic effect against M. incognita second stage juveniles after 48 h treatment. The nemticidal activity was very low in all the extracts of fresh peels but was greatly enhanced in the extracts of stored pulpified peels with 90.8 %, 93.5 %, and 85.0 % mortality of nematodes for lemon, orange, and grapefruit,
respectively. The data indicated the possibility of essential oils from the citrus peels might have released in the extracts during storage of the pulpified peels. The egg hatch inhibition of the extracts from stored pulpified peels was 85.7 %, 91.0 %, and 78.3 % for lemon, orange, and grapefruit, respectively. The reversible tests revealed that the effect of extracts on the hatch of eggs was not permanent. The hatching partially resumed after the removal of the extracts but was still significantly lower than the control. The infection of M. incognita second-stage juveniles on mung bean roots was significantly inhibited by the extracts of the refrigerator-stored pulpified peels of lemon, orange, and grapefruit. The findings provide an alternative to chemical nematicides for organic farming and help the disposal of citrus juice processing waste as well as the fallen fruits in the orchards in the typhoon season.
CHAPTER ONE
Introduction
1.1 Nematodes
Nematodes are a diverse group of worm-like animals. They are found in virtually every environment, both as parasites and as free-living organisms. They are generally minute, but some species can reach several meters in length. This topic focuses specifically on plant parasitic nematodes, which are very small or microscopic, can cause significant damage to crops, and are extremely widespread (Agrios, 2005). Because nematodes are difficult or impossible to see in the field, and their symptoms are often non-specific, the damage they inflict is often attributed to other more visible causes. Farmers and researchers alike often underestimate their effects. A general assessment is that plant parasitic nematodes reduce agricultural production by approximately 11% globally, reducing production by millions of tones every year. The amount of damage nematodes cause depends on a wide range of factors, such as their population density, the virulence of the species or strain, and the resistance (ability of the plant to reduce the population of the nematode) or tolerance (ability of the plant to yield despite nematode attack) of the host plant (Agrios, 2005). Other factors also contribute to a lesser extent, including climate, water availability, soil conditions, soil fertility, and the presence of other pests and diseases. However, although we have some knowledge on the nematode–crop relationship and influencing factors, much remains to be learned. Damage thresholds for nematodes on various crops in various parts of the world, for example, are often unknown, and the threat nematodes pose often requires an educated guess. Plant nematodes attack all plants, they cause farmers and nurserymen millions of dollars in crop loss annually, but also can cause problems in the urban world by damaging turf grasses, ornamentals and home gardens. We are often unaware of losses caused by nematodes because much of the damage caused by them is so subtle that it goes unnoticed or is attributed to other causes (Agrios, 2005), Some scientists estimate that there are over 1 million kinds of nematodes, making them second only to the insects in numbers. However, few people are aware of nematodes or have seen any, because most nematodes are very small, even microscopic, and colorless most live hidden in soil, under water, or in the plants or animals they parasitize and relatively few have obvious direct effects on humans or their activities. Of all of the nematodes known, about 50 percent are small animals living in marine environments, and 25 percent live in the soil or fresh water and feed on bacteria, fungi, other decomposer organisms, small invertebrates or organic matter. About 15 percent are parasites of animals, ranging from small insects and other invertebrates up to domestic and wild animals and man (Benliet al.,2008). Some of the parasites of animals are the largest nematodes known: some from grasshoppers can be several inches long, and one from whales can reach lengths of more than 20 feet! Only about 10 percent of known nematodes are parasites of plants. And here in this topic I will be talking on root knot nematode. Root-knot nematodes are microscopic worms that live in soil and feed on the roots of many common garden crops, the nematode gets its name because its feeding causes galls (swellings or “knots”) to form on the roots of infected plants . Root-knot nematodes are scientifically classified in the genus Meloidogyne. There are several species of Meloidogyne, but M. incognita, also known as the southern root-knot nematode, is the most common one in gardens. Some of the crops that may be severely damaged are tomato, pepper, okra, watermelon, cantaloupe, onion, pumpkin, squash, sweet potato, sweet corn, carrot, eggplant, bean and pea. Root-knot nematodes also feed and multiply on many garden weeds, although they may not injure these plants to any extent. A female root-knot nematode can lay up to 500 eggs at a time, and root damage results from the sheer number of nematodes feeding on roots by the end of the summer (Benliet al.,2008). Root-knot nematodes tend to be more of a problem in sandy soils. Nematodes are usually confined to localized areas in the garden spreading very slowly under their own power; however, nematodes may be dispersed more rapidly by movement of infested soil through cultivation, on soil clinging to garden tools and tillers, in water, or on roots of transplants. Nematodes do not typically kill plants. They are plant stressors and act alone and in conjunction with other stress factors in vineyards to reduce growth and yields. Generally, nematode infestations occur in areas of the vineyard where vines lack vigor and have restricted growth and reduced yields (Mathai, 2000). Penetration and movement by nematodes through plant tissues results in mechanical injury to cells and subsequent cell death and necrosis. Mechanical injury interrupts the uptake and flow of water and nutrients from roots and the flow of food from leaves to roots. In addition, nematodes create openings in roots through which other microorganisms can enter, and some species are able to transmit viruses from one plant to another. All these factors increase the susceptibility of plants to environmental stress. Plant-parasitic nematodes are frequently presenting vineyards. If nematodes potentially damaging to vines are present in a field, pre plant and postplant management strategies should be developed for pathogenic species. If a vineyard or a potential planting site is not infested, a grower should implement strategies to avoid introduction of harmful specie (Benliet al., 2008).
1.2 Justification of the study
The in-vitro studies in to the efficacy of citrus peels (orange, lime, lemon and grape) helps to understand how to reduce and control root-knot nematode in the garden in to a level below economic threshold , without causing harm to plant and other useful organism.
1.3 Aims
The in vitro studies in to the efficacy of citrus peels (orange,lime,lemon and grape) control of the root-knot nematodes.
1.4 Objectives of the study
- To determine the effect of extract of pulpified citrus peel on Meloidogyne incognita invitro
- To determine the photochemical constituent of citrus peels (orange, lime, lemon and grape).
1.5 Scope and Limitations of the Study
- The scope of this project is limited to root-knot nematode collected from farm land in the university of Abuja permanent site.
