| Soybean cyst nematode (Heterodera glycines Ichinohe1952) is an obligate parasite of soybean {Glycine max L. Merril.) and other crops. It is currently considered to be one of the most important pests of soybean causing an estimated global total yield loss of US﹩2billion.Root knot nematodes (Meloidogyne incognita)is one of the three most economically damaging genera of plant-parasitic nematodes on crops. They are cosmopolitan in distribution, ubiquitous in location, insidious in nature and are obligate parasites of the roots of more than3000different plant species and they cause about5%of global crop loss. The genus includes more than63species, with some species having several races. Four species namely; M. javanica, M. arenaria, M. incognita and M. hapla are major pests worldwide and are responsible for approximately90%of agronomical damages caused by root knot nematodes. At present, one of the most widely used methods for control of nematodes is the use of synthetic chemical nematicides. Nematicides although highly effective, they are now being re-appraised globally due to their harmful effect on the environment.The aim of this study is to search for environment friendly alternative for control of southern root knot nematodes (Meloidogyne incognita) and soybean cysts nematodes (H. glycines) against soybean.The main research achievements are as follows:1. Molecular detection of the H. glycines population from Taigu, Shanxi Province was conducted. Polymerase chain reaction (PCR) productsof rDNA were purified, coloned and sequenced.The sequences were deposited in Genebank with accession numbers; KF447768, KF745929, KF745930and KF745931.Based on the sequences, phylogenetic analysis was conducted on rDNA-ITS sequence of H. glycines from soybean. The phylogenetic tree showed some genetic variations among H. glycines and other species of the genus Heterodera.2. Results obtained in laboratory showed aqueous extracts of all four plant materials at concentrations of120μg/ml hindered H. glycines egg hatch. Percentage egg hatch inhibition after interval of96hours for Azadirachta indica, Brassica chinensis, Acacia nilotica and Ecklonia maxima was75.21%,62.90%,41.80%and26.23%respectively.Aqueousextract of A. indica at concentration of120μg/ml at an interval of84hours caused100%percentage mortality of J2, this is followed by B. chinensis, A. nilotica and E.maxima that caused J2 mortality of68.34%,43.34%and23.34%respectively. In addition, aqueous extracts of all four plant materials at concentrations of120μg/ml hindered M.incognita egg hatch. Percentage egg hatch inhibition after interval of96hours for A. indica, B. chinensis, A. nilotica and E. maxima was70.3,58.4,43.2and16.2%respectively. Similar trend, although at lower percentage inhibition was observed at low concentration of12μg/ml. SDW control treatment did not hinder egg hatch. All plant aqueous extracts caused high mortality of M.incognita J2. Aqueousextract of A. indica at concentration of120μg/ml at an interval of84hours caused100%percentage mortality of J2, this is followed by B. chinensis, A. nilotica and E. maxima that caused J2mortality of81.3,54.5and39.4%respectively. Similar mortality trend although at lower extend was observed at lower concentration of12μg/ml.3. Greenhouse experiments showed application of aqueous extracts of A. indica, B. chinensis, A. nilotica and E. maxima hindered development of H. glycines by83.12%,66.23%,50.65%and40.26%respectively.Soybean growth parameters of shoot height, root length, dry shoot and root weights at treatment concentration of120μg/ml of all four plant materials increased. However, A. indica produced the highest mean shoot height of68.7cm, followed by E. maxima, B. chinensis and A. nilotica which produced mean shoot heights of61.2cm,59.7cm and43.2cm. Other growth parameters of mean root length, dry shoot and root weight more or less follow a similar trend.4. In field experiments, results obtained showedplant material applied at the highest rate of200g,450g,1000g and2000g produced significantly (P=0.05) the lowest final H. glycines population (Pf).Nematicide, neem, brassica, acacia and seaweed caused reduction in H. glycines population by57.9%,48.3%,41.4%,34.5%and28.3%respectively. Nematicide, neem, brassica, acacia and seaweed produced increase in pods number by46.6%,58.7%,33.7%,28%and seaweed37.9%respectively.5. Based on enrichment cultures, biological, agricultural, and clinical experiments were conducted to test the toxicity of gases produced by ammonia oxidizing archaea (AOA). Experiments were conducted to determine the toxicity of AOA produced nitrous oxide (N2O), methane and other gases toxic to nematodes and mice.It wasshowed that nitrous oxide, methane and other gases produced were toxic to nematodes and mice. Biochemical analysis of blood collected from mice treated with archaea produced gasses at5and7hours periods revealed marked changes in12of the13hematology parameters.The results of this study suggest that these plant materials are potential alternative to synthetic chemical pesticides that could be utilized in a sustainable farming system to save the environment and conserve the biodiversity. Therefore, more precise research is necessary to develop an effective formulation of botanical pesticide that will optimize the quantity needed to control the pests at cost effective amount. In addition, AOA has potential using for controlling plant parasitic nematodes. |
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