Development of the cereal cyst nematode on wheat and barley under field conditions in central Saudi Arabia

The development of the cereal cyst nematode (CCN), Heterodera avenae, on wheat cv. Yecora Rojo and barley cv. Justo was studied in the field in central Saudi Arabia. Second-stage juveniles (J,) were observed. .in the roots of both hosts within the first week of sowing. However, presence of J, in wheat roots continued for about two months after sowing, whereas in barley roots were only for 20 days. Subsequent development of CCN (J3, h adult females & white cysts) was faster on barley than on wheat by 5-14 days. TIle nematode life cycle was completed within 74 and 64 days after sowing on wheat and barley roots, respectively. Keywords: Cereal cyst nematode, Heterodera avenae, life cycle, field study, Saudi Arabia

COMPARATIVE EFFECTS OF SOME APPROACHES TO CONTROL MELOIDOGYNE INCOGNITA ON GREEN BEANS

Different approaches to control M. incognita race 2 on the green bean. Phaseolus vulgaris. Cv. “Contender” were comparatively evaluated. In this respect, nine control measures were compared in a greenhouses pot experiment (25 ± 2˚C). Control measured included dazomet (soil fumigant). Fenamiphos (soil treatment), fenamipohse (seed treatment), fenamiphos (seed dipping), Paecilomyces lilacinus (egg-parasitic fungus), urea (46%), chicken manure, Golmus Sp. (mycorhizal fungus), and soil solarization, in addition to; M. incognita-infected and non-infected (free) checks. All tested control measures, except chicken manure, were effective in controlling M. incognita race 2 on the green bean. P. vulgaris, cv. “Contender”. The tested materials decreased (P ≤ 0.05), numbers of root galls and nematode eggs/root system by 38.9-99.8% and 40.6-99.9% respectively, compared to the nematode-infected check. Thus, nematode reproduction factor (Rf) has accordingly decreased (P ≤ 0.05), and reached the minimum (0.009) in the treatment of soil fumigation with dazomet. However, the reduction in the number of galls and nematode eggs/root system resulted in a better growth of infected plants, and increased (P ≤ 0.05) plant fresh weight (except in the treatments of urea and the mycorrhizal fungus. Glomus sp.) by 43.3-68.2%, compared to the nematode-infected check. Based on gall index (GI), egg mass index (EI) and nematode reproduction factor (Rf), the tested control measures were categorized in three groups according to their relative efficacy: 1) relatively high effective group (dazomet, soil solarization, fenamiphos as soil treatment and fenamiphos as seed did treatment), 2) relatively moderate effective grop (fenamiphos as seed treatment and urea), 3) relatively low effective group (P. lilacinus and Glomus sp.)

Interacting effects of soil texture and inoculum levels on reproduction and pathogenicity of meloidogyne javanica on potato

A 2-year study was conducted in the greenhouse to determine the effects of three soil types (sand , sandy loam and loam) and four inoculum levels (0t 1000, 2000 and 4000 nematode eggs / 500 env* soil) of Mehidogyne Javanica on nematode reproduction and pathogenicity on potato cv. Spunta. Nematode reproduction and host damage were both affected by the soil texture and the initial inoculum level. Number of egg masses, eggs and galls across all soil types increased (P = 0.05) as the inoculum level increased. The least (P = 0.05) nematode reproduction and host damage occurred in the loam soil. The sandy and sandy loam soils showed higher nematode reproduction and damage with no significant differences. Regression analyses of the independents Pi-sand-clay vs. number-of eggs and gaits gave values of 0.45 and 0.56 , respectively. The R^ for Pi alone vs. eggs was 0.39 and vs. galls 0.52. Soil affected tuber Yield with the least fresh tuber weights occurring in the loam soil. The for Pi-sand-day vs. yield was 0.13.King Abdul-Aziz City for Science and technology, grant $ AR-10-81.Corresponding Author: Dr. Ahmad Sa'ad Fahad Al-Hazmi, Professor of Plant Pathology (Nematology), Plant Protection Department, College of Food and Agricultural Sciences, P.O. Box 2460, Riyadh 11451, Saudi Arabia. Email: [email protected]

Distribution, frequency and population density of nematodes associated with potato in Saudi Arabia

Department of Plant Protection,King Saud University.In a survey of nematodes associated with potato conducted in six major potaro- producing regions of Saudi Arabia from 1989 to 1991, following genera in descending order of frequency were found: Aphelenchus (40%) Okyiencht-(28%). Tylenchorhynchus(20%),Mebittogynt (19%).Aphebnthoidet lyttnchuisi. (10%),Subanguina (6%), Tnchodarus (5%). fratylcnchus and Heltcntfenehzx (2%), MacMpasihohia (0.7%) and ParaiylcHchus and Cocoptmrvs if (1%). Distribution ircrjuency and population density of these genera varied among the six regions - Hail and Tsthyk wcie ihe lowest Wiih respect IO diversity and density, Gassim and Riyadh were moderate ami Hofuf and Najran were itac highest. Prominence- values of the jssoriatcd ncrnstixles indicated that Mclaidagyne $pp (mainly Mjavanica) were, by far the must prominent plant-parasitic nematodes in Saudi potato fields, followed by 7>tenckorhynchus spp., and then by Ditytenchus spp (mainly D. destructor)

Nematicidal properties of rhazya stricta and juniperus polycarpos on meloidogyne javanica in Saudi Arabia

Plant Protection Department, College of Agriculture, King Saud University P.O. Box 2460, Riyadh 11451, Saudi ArabiaFour alkaloidal extracts from Rhazxa stricta and a phenolic extract from Juniperus polycapos were found to possess nematictdal activity against Metoidayvne ,a\anica. At 100ppm concentration, the tested extracts suppressed egg hatching by 4 17-68.92%. The alkaloidal extracts were mare effective than the phenolic extract. Mortality of J2 increased as the extract concentrations increased (LC$o values ranged from 370 to 620ppm). Results were compared with those of the nematicide fenamiphos. Because of the high alkaloidal content °ffL stricta. it could be considered as a promising nematictdal plan

Comparative effect of root-knot nematode on severity of Verticillium and Fusarium wilt in cotton

The effect of root-knot nematode (RKN) (Meloidogyne incognita) on Verticillium dahliae and Fusarium oxysporum f.sp. vasinfectum in cotton (Gossypium hirsutum) was investigated. Two different inoculation methods were used, one in which inoculum was added to the soil, so that nematode and fungal inoculum were in close proximity; the other, inoculation into the stem, whereby the two inocula were spatially separated. Invasion of the roots by RKN enhanced disease severity, as measured by the height of vascular browning in the stem, following inoculation with either wilt pathogen. The effect of RKN on Fusarium wilt was more pronounced than that on Verticillium wilt. Nematode-enhanced infection by F. oxysporum is a well known effect but there are few reports of enhanced infection by Verticillium due to RKN. Relative resistance of a number of cotton cultivars to both wilt diseases, as measured by height of vascular browning, was similar to the known field performance of the cultivars. The use of vascular browning as an estimate of disease severity was therefore validated