الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
A survey of plant parasitic nematodes genera associated with the rhizosphere of seven sugarbeet cvs. Athos-poly, Deprez-poly N, Farida Kawemira, Monte-bionco, Nejama and Sultan grown at five counties of Dakhlia governorate (Egypt) was carried out during the sugarbeet growing seasons 2007/2008 and 2008/2009. Nine nematode genera were recorded in the surveyed sugarbeet fields. Based on their frequency of occurrence, these genera can be arranged in descending orders as follows : Meloidogyne (J2) (22.6%) , Trichodorus (19.8%), Hirschmanniella (13.4%), Helicotylenchus (10.4%), Tylenchus (6.5%), Pratylenchus (4.7%), Dorylaimus (3.4%), Rotylenchulus (1.7%), and Tylenchorhynchus (1.3%). Soil samples of Belqas and Bany-Ebeid counties encountered eight of nematode genera i.e. Helicotylenchus, Hirschmanniella, Meloidogyne, Pratylenchus, Trichodorus, Dorylaimus, Tylenchus plus Tylenchorhynchus for Belqas but Rotylenchulus for Bany-Ebeid only. Sugarbeet plants cv. Farida encountered the nine of nematode followed by cv. Athos-poly (8), Sultan (7), Nejama (7) and Deprez-poly N (6),whereas sugarbeet cvs. Monte-bionco and Kawemira encountered the least number of nematode genera(s) each, respectively. Among the seven true nematode genera recorded, Meloidogyne and Trichodorus seemed to be the major pests of sugarbeet plantations in this work. Meanwhile , clayey soil with 413 out of 700 soil samples examined encountered the highest number of true nematode genera (7) followed by loamy (5) and clay loam (4),respectively . With regard to reaction of the seven sugarbeet varieties tested to M. incognita infection under greenhouse conditions at 30 ±5 °C, results indicated that Nejama showed the highest percentage reduction values of most plant growth parameters tested i.e. total plant fresh weight (54.1%) and shoot dry weight (48.7%) respectively, followed by Farida, Deprez-poly N, Monte-bionco and then Athos-poly respectively whereas, Kawemira and Sultan varieties accomplished the lowest percentage reduction with values of 6.8, 14.2 and 17.7 % ; and 14.2, 18.9 and 21.4 5 respectively, which were rated as resistant hosts due to their gall indices values of 2.0 each with R factor values of 0.21 and 0.27, respectively. Meanwhile, Nejama, Monte-bionco, Farida, Athos-poly and Deprez-poly N were rated as susceptible hosts to M. incognita according to their root gall indices that were 5.0 each accompanied by R factor values of 1.18, 1.03, 1.06, 1.09 and 1.13, respectivel .Concerning the impact of three levels of M. incognita eggs i.e. 1000, 2000 and 3000 eggs/ plant on plant growth parameters of sugarbeet cv. Nejama and its reproduction and development under greenhouse conditions at 17 ± 5°C, results indicated that reduction percentage of sugarbeet growth parameters were greatly affected, where the marginal effect was more pronounced on roots than shoots. Moreover, as the inoculation level increased from 1000 up to 3000 eggs of M. incognita /plant, the percentage reduction of plant growth parameters increased, where the highest values were recorded to be 48.97 and 24.18% by 3000 eggs/ plant for shoot dry and whole plant fresh weights, whereas, their lowest values of 30.93 and 4.05 % resulted by inoculation level of 1000 eggs/ plant for the same plant growth criteria, respectively. Moreover, the highest rate of nematode reproduction on sugarbeet plants cv. Nejama was recorded by the level of 2000 eggs per plant with value of 1.05 whereas the lowest ones of the same criterion resulted by the levels of 3000 or 1000 eggs per bag (plant) that were 0.85 or 0.84, respectively. M. incognita infection to sugar beet plants cv. Nejama at the three levels of egg inoculation obviously reduced N,P, K and total chlorophyll content on leave of sugarbeet plant where as the eggs inoculum levels increased from 1000 up to 3000 eggs / plant as these tested elements gradually decreased with values of 9.9% ( N), 18.5% (P), 8.8 %(K), 1.58% (chlorophyll) and 20.0%(N), 27.4% (P), 18.4%(K) and 5.9%(chlorophyll) for N,P,K, and total chlorophyll by 1000 and 3000 eggs/ plant, comparing to the unioculated plant , respectively. As for the bio-control of M. incognita on sugarbeet cv. Nejama grown within three soil textures i.e. sandy, loamy and clayey by three bio agents i.e. bio-arc, bio-zeid, nemafree and powder of sugarbeet pulp (sbp) in comparison with oxamyl at the recommended dose, under greenhouse conditions at 22±3°C results revealed that all tested treatments obviously ameliorated sugarbeet plant growth parameters and diminished nematode criteria according to the soil type textures. Moreover, bio-arc treatment significantly surpassed other bio-control applications tested in improving plant length, total plant fresh and shoot dry weights with increase percentage values of 26.4, 15.8 and 21.3%; 75.7, 68.9 and 72.2 % and 71.8, 54.1 and 70.3 % for sandy, loamy and clayey soil textures respectively, comparing to nematode alone. Meanwhile, significant difference between treatments within each soil type texture tested was clearly observed concerning sugarbeet growth parameters. Oxamyl as a nematicide at the recommended dose overwhelmed all bioagents tested in values of plant length (29.4%) in sandy soil, nemafree, and sbp powder in value of total plant fresh weight (51.1 and 43.6%) in sandy and loamy soils and nemafree in shoot dry weight (53.9%) of loamy and clayey soils, respectively. No significant difference were noticed between some treatments within each soil type and nematode alone and the untreated uninoculated plant, regarding sugarbeet shoot and root length except in some cases, especially with bio-arc or bio-zeid treatments. Moreover, all tested treatments within each soil type texture greatly reduced M. incognita reproduction, root galling and egg-masses numbers. M. incognita reproduction on sugar beet cv. Nejama was higher in sandy soil than other soil type with values of 4.21, followed by loamy (2.9), whereas the clayey soil gave the lowest rate of nematode reproduction (1.44), respectively. Bio-arc treatment achieved the highest reduction percentage of nematode population in soil and root with value of 83.9, 84.1 and 79.1 % for sandy, loamy and clayey soils, respectively, whereas oxamyl as a nematicide at the recommended dose ranked first within the tested components in suppressing the same nematode criteria values that were amounted to 86.4, 87.1 and 85.4 % for the same soil treatments, respectively, comparing to nematode alone. Once again, bio-arc treatment had the lowest rate of reproduction at all soil types i.e. sandy, loamy and clayey with values of 0.68, 0.46 and 0.30, followed by bio-zied and nemafree, while that of sugarbeet pulp (sbp) powder had the highest ones (1.74& 1.41) for sandy and loamy soil textures, except that the clayey soil with value of (1.08). In general all tested components significantly increased percentage values of leave parameters i.e. N,P and K; and total chlorophyll contents in all soil types under study except that of total chlorophyll in leaves of plant received sugarbeet pulp powder (sbp) within clay (-0.8%), loamy (-0.7%) and sandy (-1.1%) soils as well treatment of nemafree in loamy (-0.9%) and sandy (-2.31%); and bio-zeid (-1.1%) and bio-arc(-2.2%) sandy soils, comparing to nematode alone, respectively.