This study was conducted to determine the effect of H. avenae initial population densities (Pi) on the yield of wheat (two growing seasons) and barley (one season) and on nematode reproduction, under Saudi field conditions. At increasing Pi, H. avenae suppressed (P lessequal 0.05) the number of spikes, weight of spikes, weight of 1000 kernels, grain yield and straw yield of wheat and barley. Grain yields were reduced by 40 to 92% for wheat (during the two seasons) and 17 to 77% for barley. Straw yields were also reduced, by 50 to 85 for wheat and 30 to 77% for barley. As Pi increased, final populations of H. avenae increased (P lessequal 0.05) on both hosts, but the nematode reproduction factor (Rf) decreased. Significant negative linear regressions were obtained between H. avenae Pi and grain yield of wheat and barley. Final populations (Pf) were positively correlated with Pi on wheat and on barley. Rf was negatively correlated with Pi on wheat and barley. Schadigungspotential und Vermehrung von Heterodera avenae an Weizen und Gerste unter Freilandbedingungen in Saudiarabien - Die vorliegende Untersuchung wurde durchgefuhrt, um die Wirkung unterschiedlicher Ausgangspopulationen (Pi) von Heterodera avenae auf den Ertrag von Weizen (zwei Vegetationsperioden) und Gerste (eine Vegetationsperiode) sowie auf die Vermehrung der Nematoden unter saudiarabishen Freilandbedingungen zu ermitteln. Bei steigender Pi verminderte (P lessequal 0.05) H. avenae die Anzahl der Ahren, das Ahrengewicht, das Tausendkorngewicht, den Korn- und den Strohertrag von Weizen und Gerste. Die Kornertrage wurden bei Weizen (zwei Vegetationsperioden) um 40-92% vermindert, bei Gerste um 17-77%. Auch die Strohertrage gingen zuruck, bei Weizen um 50-85% und bei Gerste um 30-77%. Mit zunehmender Pi stiegen die Endpopulationsdichten von H. avenae bei beiden Wirtspflanzen an (P lessequal 0.05), doch nahm der Vermehrungsfaktor (Rf) der Nematoden ab. Zwischen Pi von H. avenae und dem Kornertrag von Weizen und Gerste wurden signifikante negative Regressionen erhalten. Die Endpopulationen (Pf) waren an Weizen und Gerste positiv korreliert mit Pi. Rf war an Weizen und Gerste negativ korreliert mit Pi.

A greenhouse study was conducted to compare the relative efficacy of different approaches to managing on green bean. These approaches included chemical (fumigant, non-fumigant, seed dressing, and seed dip), biological (the egg-parasitic fungus, and the mycorrhizal fungus sp.), physical (soil solarization), and cultural (chicken litter and urea) methods. Accordingly, nine different control materials and application methods plus nematode-infected and non-infected controls were compared. Two important parameters were considered: plant response (plant growth and root galling) and nematode reproduction (production of eggs and the reproduction factor Rf). The results showed that the use of chicken litter as an organic fertilizer severely affected the growth and survival of the plants. Therefore, this treatment was removed from the evaluation test. All of the other eight treatments were found to be effective against nematode reproduction, but with different levels of efficacy. The eight treatments decreased (38.9-99.8%) root galling, increased plant growth and suppressed nematode reproduction. Based on three important criteria, namely, gall index (GI), egg mass index (EMI), and nematode reproduction factor (RF), the tested materials and methods were categorized into three groups according to their relative control efficacy under the applied test conditions. The three groups were as follows: (1) the relatively high effective group (GI = 1.0-1.4, Rf = 0.07-0.01), which included the fumigant dazomet, the non-fumigant fenamiphos, soil solarization, and seed dip with fenamiphos; (2) the relatively moderate effective group (GI = 3.4-4.0, Rf = 0.24-0.60), which included seed dressing with fenamiphos and urea; and (3) the relatively less effective group (GI = 5.0, Rf = 32.2-37.2), which included and sp.

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Two field experiments were carried out to study the efficacy of different biological control agents in controlling certain plant-parasitic nematode species including Meloidogyne javanica, Tylenchorhynchus mediterraneus, Hoplolaimus seinhorsti, Longidorus latocephalus, and Xiphinema elongatum on guava and fig trees under the tropical field conditions of Jazan region, south-west Saudi Arabia during two successive seasons from Feb. 15, 2016 to Jan. 15, 2017. The evaluated bioagents were used in different integrated management combinations of certain fungal species (Trichoderma harzianum, Verticillium chlamydosporium, and Purpureocillium lilacinum), the bacterium Pasteuria penetrans, some organic amendments (cow manure, compost, and chicken manure), urea 46% as a nitrogenous fertilizer, and the nematicide carbofuran 10G for comparison. Results showed that all the tested treatments gradually decreased (P ≤ 0.05) the population densities of plant-parasitic nematodes on guava and fig trees over the study period. The highest reduction of nematode densities occurred at the end of the experiment. Carbofuran 10G was the most effective treatment in suppressing the nematode densities on guava and fig trees. The most effective management combinations, next to carbofuran 10G, in suppressing the nematode densities in the rhizosphere of guava trees were P. lilacinum + P. penetrans + urea 46%, P. lilacinum + P. penetrans + chicken manure, and T. harzianum + P. penetrans + chicken manure (66.54-69.22% nematode reductions). Correspondent combinations in the rhizosphere of fig trees were P. lilacinum + P. penetrans + cow manure, T. harzianum + P. penetrans + cow manure, P. lilacinum + P. penetrans + urea 46%, and V. chlamydosporium + P. penetrans + urea 46% (54.68-57.17% nematode reductions). On the other hand, nematode population densities continued to increase (P ≤ 0.05) in the rhizosphere of guava and fig trees in the absence of nematode management combinations. All the tested treatments significantly increased (P ≤ 0.05) the number of fruits/tree on guava and fig trees. Treatments which included the combinations of fungal and bacterial parasites along with chicken manure gave the highest numbers of fruits/tree, followed by the treatment with the nematicide carbofuran 10G. Regression analysis showed a significant negative linear relationship between the number of nematodes/kg soil and the number of guava and fig fruits/tree.

The physiological response of mungbean (Vigna radiata (L.) R. Wilczek) to drought stress and root-knot nematode infection was studied under greenhouse conditions at King Saud University, Saudi Arabia. A randomized complete block Design (RCBD) with factorial arrangement having three replications was used. Treatments included three water deficit (80%, 40% and 20% of field capacity), two mungbean genotypes (Kawmay-1 and VC2010) and two root-knot nematodem, Meloidogyne javanica (Treub) Chitwood, infection levels (noninfected and infected @ 15000 egg/pot). Results showed that water deficit stress and M. javanica infection significantly hampered most of the studied parameters, except shoot water content (SWC). There were highly significant differences in stomatal conductance, shoot dry weight and leaf area among the tested mungbean genotypes. A significant positive correlation among chlorophyll (a and b) contents, stomatal conductance (SC), leaf area (LA) and shoot dry weight (SDW) was recorded. The outcome of the study also revealed that maximum water deficit stress has adversely affected all parameters except SWC, regardless of the genotype or nematode infection status. Similarly M. javanica infection adversely affected the growth and physiological processes of mungbean plants. Moreover, drought and M. javanica infection had synergistic adverse effects on the growth and physiology of mungbean plants. Results also showed that VC 2010 genotype surpassed kawmay-1 in most of the studied characteristics which

Stomata conductance (g s ), Shoot water content (SWC), chlorophyll pigments (chl a,b) and enzymes involved in anti-oxidant photo-protection were determined in two mungbean genotypes (Kawmay-1 and VC2010) under greenhouse conditions. The two genotypes were subjected to water deficit stress (20, 40 and 80% of field capacity) and two root-knot nematode (Meloidogyne javanica) infection levels (noninfected and infected at 15000 juveniles per pot). Both water deficit and nematode infection resulted to a fast decline in the chlorophyll pigments, g s and SWC in both genotypes; however, VC2010 was recorded as being comparatively resistant. Increase in antioxidant enzymes activity was detected for superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and polyphenol oxidase (PPO) in both stresses, but this activity was more pronounced in water deficit stress than nematode infection, especially at 40% field capacity. APX and PPO production peaks recorded at 20% of irrigation in VC2010 were highest. This revealed that VC2010 genotype was tolerant to environmental stresses compared to Kawmay-1. It was conceived from the present study that water deficit stress significantly hampered the physiological representatives of plant health, while on the other hand enzymatic alterations to cope with the biotic and abiotic stresses in plants could be used for better tolerability and plant health. The results indicated that oxidative damage (ROS) produced under environmental stress can be minimized by increasing the antioxidant enzymatic activities in mungbean.

Root-knot/charcoal root rot disease complex caused by the interaction of Meloidogyne javanica and Macrophomina phaseolina is a serious disease complex attacking bean crop either in the field or greenhouses. In two different greenhouse tests, the influence of soil texture and moisture on the severity of the root-knot/charcoal root rot disease complex on green beans, Phaseolus vulgaris were examined. Results of the soil texture test indicated that the disease severity (suppression of plant growth and rootknot/charcoal root rot disease index), the nematode reproduction and the fungus growth in soil increased with the increase of sand content in the soil. Results of the soil moisture test showed that the greatest plant damage occurred at the soil of moisture level of 30% of field capacity, and disease severity decreased gradually as the moisture level was increased.

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