W. Abu-Gharbieh
Introduction
Nematology in Jordan
Nematological problems
Control measures
Infrastructure and training
Support for nematology
Conclusions and recommendations
Bibliography
Jordan is located between 29° and 33° north and 36° and 39° east. The area of Jordan is about 90 000 km2, with a cultivated area of about 215 284 ha (Table 12).
The cultivated land in Jordan may be subdivided into four main regions:
· Ghor area (GA), Jordan Rift Valley, characterized by a subtropical climate with hot, dry summers and mild humid winters with low rainfall. The main crops are irrigated vegetables, cereals and fruit-trees comprising about 63, 14 and 23 percent of the planted area, respectively. Citrus and banana are the two major fruit crops.· Eastern rainfed uplands (ERU), located on the eastern mountains and characterized by a Mediterranean climate with mild dry summers and cold rainy winters.
· Side wadis (SW), valleys which include cultivated lands located along the main tributaries descending from the mountains to the Jordan Rift Valley area. The climate is subtropical in the lower valley, but Mediterranean in the upper valley. Vegetables and fruit-trees are grown mainly under irrigation.
· Eastern irrigated uplands (EIU), comprising certain irrigated areas alongside the desert periphery which are characterized by low rainfall (200 mm or less annually) and a continental desert climate. Jordan imports nearly two-thirds of its food requirements. In 1988, the percentage of agricultural labour decreased to 10 percent of the labour force, while the agricultural sector contributed only 10 percent of the gross national income. Several agricultural and socio-economic plans have been developed in
TABLE 12
The area and production of each of the main groups of crops grown in Jordan
|
Crops |
Area (ha) |
Production (tonnes) |
|
Vegetables |
28969 |
695168 |
|
Field crops |
131 405 |
119616 |
|
Fruit-trees |
54910 |
284 484 |
|
Total |
215284 |
1 099 268 |
Source: Statistical yearbook, 1991. the past 20 years. These plans have had a considerable impact in terms of placing large additional areas under irrigation, which increased crop production and ultimately helped reduce the food deficit in Jordan.
There are two nematology laboratories in Jordan. The first is located in the central Jordan Valley and administered by the Ministry of Agriculture. It is moderately equipped and supervised by an M.Sc. degree holder in nematology, assisted by two laboratory technicians. The main duties of this laboratory include examination of soil and plant samples received from farmers and identification of nematodes in order to make recommendations for their control; sometimes staff work on certain aspects of nematode research in the field. The second laboratory is located in the Faculty of Agriculture, University of Jordan, in Amman. This laboratory is involved in teaching and research functions. It is currently supervised by a professor in nematology who holds a doctorate degree, assisted by a research assistant and laboratory technicians.
The first report on plant-parasitic nematodes in Jordan was made by the author in 1963. In subsequent years several surveys were made that demonstrated the presence of a large number of nematode genera and species affecting crops planted in the various areas, especially under irrigation. The impact of several genera of nematodes, e.g. Meloidogyne, Pratylenchus, Helicotylenchus, Ditylenchus and others, is substantial.
However, the root-knot nematode has received the greatest attention on the part of farmers and technical personnel alike.
Almost all nematological work in Jordan in areas of research and education is currently carried out at the Faculty of Agriculture, University of Jordan. Research involves nematode surveys and investigations on the biology, ecology, host-parasite relationships and control of several plant-parasitic nematodes, especially species of Meloidogyne.
In the area of teaching, official courses in plant nematology are given only at the Faculty of Agriculture, University of Jordan. One obligatory course, Plant nematology (three credit hours), is given to all B.Sc. senior students in the Department of Plant Protection. Another two advanced courses which include Identification of phytonematodes (two credit hours) and Economic nematology (three credit hours) are given to all graduate students in plant nematology. Also, in the Plant Protection Department there is a graduate programme in nematology, from which 15 students have so far graduated with master's degrees, and the programme is still ongoing. The nematology group at the University of Jordan also offers services to farmers, receiving samples, giving recommendations, carrying out demonstrations and giving lectures in extension centres and providing nematology information through various information media.
In comparison with other disciplines in plant protection, nematology is receiving much less attention than that given to entomology or plant diseases caused by fungi. However, it stands on an equal footing with plant virology or acarology. Actual nematology work at the Ministry of Agriculture is receiving minimal attention. This is probably due to a lack of senior nematologists among technical staff.
Nematode problems in Jordan result from the occurrence of certain nematode species, particularly those related to the root-knot, lesion, spiral, stem and bulb, citrus, dagger and needle nematodes. The root-knot nematodes are very familiar to the farmer, while other nematodes are unknown as they do not produce such obvious and clear-cut symptoms. Meloidogyne spp. have received the greatest attention because they appear to cause considerable damage to various crops. The author estimated that yield losses to irrigated vegetables are in the neighbourhood of 15 percent in the Jordan Valley as a result of root-knot nematode infection; for this reason, Meloidogyne has received intensive research attention.
Pratylenchus species are encountered in the rhizosphere of many crops. Of particular importance is the occurrence of P. thornei on the roots of wheat and barley in the uplands under rain-fed conditions. Under such adverse conditions, it is believed that the nematode causes significant yield reduction. The spiral nematodes, Helicotylenchus and Rotylenchus, are widespread and usually occur in large populations around the roots of plants. Helicotylenchus multicinctus causes considerable damage to roots of banana plants grown in the Jordan Valley. The stem and bulb nematode, Ditylenchus dipsaci is devastating to broad beans in the side wadis and irrigated uplands. In years of heavy rains in the spring, the nematode may cause complete failure of the broad bean crop.
Recent investigation on the occurrence and distribution of the citrus nematode, Tylenchulus semipenetrans, revealed that this nematode is widespread in almost all groves where citrus is grown in Jordan. The nematode is also believed to cause considerable damage.
Species of Xiphinema and Longidorus are widespread and occur in large numbers particularly on irrigated fruit-trees. These nematodes also occur on fruit-trees grown under rain-fed conditions, and are expected to cause heavy damage to the roots. Several species of cyst nematodes, Heterodera spp., have been encountered in Jordan. Of significance is H. schachtii which was found in large populations in cabbage fields in the Jerash area (EIU). This nematode is believed to cause great losses to cruciferous crops. Anguina tritici has been frequently reported to occur in the northern areas of the country, particularly in years of heavy rainfall in the spring.
The impact of phytonematodes on crop production, and the economic losses incurred, have not yet been experimentally determined. General ideas were gathered from results of experiments where nematicides were used. Such treatments revealed significant yield increase in soils heavily infested with root-knot nematodes. Nematode problems are pronounced in the Jordan Rift Valley, resulting from the prevalence of a favourable subtropical climate with a long growing season and irrigated conditions. Nematode problems are also of great significance in horticultural crops grown in plastic tunnel-houses, which is a widespread practice in Jordan.
TABLE 13
The most common phytonematodes in Jordan
|
Nematode |
Host(s) |
Region(s) |
|
Anguina tritici |
Wheat |
GA, ERU |
|
Aphelenchoides sp. |
Alfalfa |
EIU |
|
Criconemoides sp. |
Red beet, cabbage, carrot |
EIU |
|
Ditylenchus dipsaci |
Broad bean |
GA, SW |
|
Helicotylenchus sp. |
Many crops |
Widespread |
|
Heterodera sp. |
Red beet |
EIU |
|
Longidorus sp. |
Fruit-trees and certain vegetables |
Widespread |
|
Meloidogyne javanica |
Most cultivated crops |
Widespread |
|
Meloidogyne incognita |
Most cultivated crops |
Widespread |
|
Pratylenchus sp. |
Many crops |
Widespread |
|
Tylenchorhynchus sp. |
Many crops |
Widespread |
|
Tylenchulus semipenetrans |
Citrus |
Widespread |
|
Xiphinema sp. |
Mainly fruit-trees |
Widespread |
´Note: GA: Ghor area; ERU: eastern rain-fed uplands; EIU: eastern irrigated uplands; SW: side wadis.
In order to combat the ill-effects of phytonematodes in Jordan, the following is a summary of the measures employed.
Legislative
In the plant quarantine section of the Jordan agricultural law, prevention of the introduction of certain plant-parasitic nematodes is specifically mentioned. Among these nematodes Globodera rostochiensis, Heterodera schachtii, Meloidogyne spp. and Ditylenchus dipsaci are included. However, at the points of entry there are no reliable laboratories to test plant shipments for nematode presence. Inspectors only look for galling, caused by root-knot nematodes, on the roots of imported plants.
Cultural
Abu-Gharbieh and Hammou (1977) concluded that susceptible tomato cultivars may escape root-knot nematode infection in the central Jordan Valley by planting during November through December. Earlier plantings must be supplemented by soil fumigation or the use of resistant varieties. Abu-Gharbieh (1982b) showed that neither hoeing nor removal of infested refuse of the previous crops gave significant nematode control in heavily infested soils.
Cultural practices also include the use of crop rotation in which susceptible, resistant and non-host varieties and cultivars are planted in a certain sequence, so that nematode counts remain at non-damaging levels. In this respect, a large number of varieties, cultivars and lines of vegetable crops have been tested in Jordan for their relative susceptibility or resistance to the root-knot nematodes M. javanica and M. incognita.
Biological
Addition of Fusarium oxysporum, Aspergillus flavus and Preussia sp., grown on wheat grains, reduced postharvest cyst populations on sugar beet by 81.9, 74.5 and 62.4 percent, respectively. Abu-Laban and Saleh (1992) showed that Paecilomyces lilacinus, F. solani and F. oxysporum formulated on chicken layer manure significantly reduced root-knot nematode galling on tomato roots by 58, 59 and 53 percent, respectively. Naturally occurring fungi that parasitize cyst and root-knot nematodes in Jordanian soils were investigated; the most important fungi found included Verticillium chlamydosporium, Aspergillus flavus, Fusarium oxysporum and Fusarium solani.
Chemical
Khatoom (1981) showed that preparasitic, second-stage juveniles of Meloidogyne javanica were not detected at the end of the growing season of cucumber in a soil treated with methyl bromide. Abu-Gharbieh (1982b) reported that 75 days of preplanting soil fumigation treatment with DBCP (Nemagon) gave a marked reduction in population densities of the nematode M. javanica and increased tomato yield. However, a 15-day preplanting treatment showed significant nematode control but without significant yield increase, which may suggest a phytotoxic effect on tomato. Investigations also indicate the effectiveness of liquid oxamyl, Di-Trapex and Basamid treatments.
Physical methods
One of the most recent methods for control of nematodes and other soil-borne pathogens is soil solarization. In this method solar energy is used to heat up the moist soil to lethal or sublethal levels. The treated soil is adequately prepared and tarped with a tight transparent plastic sheet for six to eight weeks. A team of researchers, headed by the author, and a number of graduate students launched an extensive programme on the testing and development of soil solarization. This method proved highly effective, cheap and safe as compared with chemical treatment. Significant increases in tomato, eggplant, cucumber and musk melon yields were demonstrated. The Jordanian research group also demonstrated the effectiveness of a low-cost method of soil solarization, by simply using a non-perforated black plastic mulch (instead of transparent). At the end of the solarization period, the black plastic is perforated for transplanting.
Farmers in Jordan solve their nematode problems by using nematode-free transplants. In plastic houses and intensive agriculture they fumigate their soils largely with methyl bromide, as a biocide. In other minor cases soils are fumigated with Nemacur or Di-Trapex. The liquid formulation of Vydate is also used and generally applied through drip irrigation systems. More recently, farmers have begun to adopt soil solarization to control soil-borne pathogens both in plastic houses and in the open fields.
Both the laboratories at the Ministry of Agriculture and the Faculty of Agriculture are equipped with isolation and identification facilities. Other necessary equipment, usually found in general laboratories, is also present.
In the university laboratory there is a modest permanent slide collection used for identification purposes. There is also a greenhouse and a growth room used for conducting research on the university campus. Greenhouse, plastic house and open field facilities are also available at the university farm located in the central Jordan Valley.
Personnel involved in research, education and extension, currently at the University of Jordan include. Professor Walid Abu-Gharbieh, who supervises the nematology programme. He is assisted by Zakaria Musallam (M.Sc. in nematology) and two M.Sc. students in nematology. Dr H. Saleh worked in this laboratory for four years before he left for Germany two years ago. Luma Al-Banna (B.Sc.) worked for nearly ten years as a research assistant. She is currently working for her Ph.D. degree at the University of California, Davis, and will join this laboratory after graduation. Z. Hashem (M.Sc. in nematology) also worked for several years there, but left for the United Kingdom in 1979. Personnel in the Ministry of Agriculture laboratory include R. Khalaileh (M.Sc. in nematology) and two other laboratory assistants.
Cooperation between the two institutions in which the nematology laboratories are located is satisfactory. More cooperation is expected in the near future, as more defined administrative cooperation between the two institutions is currently being worked out. Cooperation with institutions outside Jordan includes: full participation in, and membership of the International Meloidogyne Project, which was managed by North Carolina State University and sponsored by USAID; and the author officially investigating nematode problems in all emirates of the United Arab Emirates and in Yemen, and unofficially in Saudi Arabia and Lebanon.
Training in nematology is carried out only at the University of Jordan where there has been an M.Sc. programme since 1979. Fifteen M.Sc. students have so far graduated and two of them completed their studies for the Ph.D. degree abroad. Training has also involved groups of trainees from Jordan and several other Arab countries. Regular courses in nematology are given to students at the undergraduate and graduate levels.
In order to improve and develop nematology in Jordan, it is imperative to make available advanced infrastructure and more advanced and precise equipment, such as microtomes, advanced microscopes, advanced equipment for isolation of nematodes and possibly SEM facilities. Also it is important to make available up-to-date and more extensive literature in nematology.
Establishment of the nematology' laboratory at the University of Jordan was done from university sources. Research and extension activities were supported by several sources.
Local support. This included a Deanship of Research at the University of Jordan; Higher Council of Science and Technology/Jordan; and Ministry of Agriculture, Agricultural Development Fund (ADF) sponsored by USAID. As a result of this support many achievements were made, particularly those involving the adoption of soil solarization by many farmers in the Jordan Valley.
Foreign aid. Foreign aid was often limited, but worth while, and was also secured from participation in the International Meloidogyne Project. Seventy-five countries, including Jordan, have participated in this programme since 1975. The major achievements of the programme include the proper identification of the root-knot nematode species in Jordan, and being part of a worldwide study on ecological factors determining the occurrence and distribution of Meloidogyne species.
Because of the limited number of specialists in the field of nematology, research findings are limited and emphasis has only been given to the root-knot nematode problem. Much work is needed in all aspects of nematology, but emphasis should be directed towards the following areas:
· surveys should be undertaken to elucidate the identity and impact of nematode species on certain important crops;· determination of the population dynamics and economic losses caused by certain nematodes on their primary crops;
· determination of the economic thresholds for root-knot nematodes and other important nematode species on various economic crops;
· emphasis should also be given to the control of nematodes by biological means and the use of resistant cultivars.
In order to perform the above tasks, it is imperative that additional nematologists, research assistants and technicians be employed. Also laboratory facilities, equipment and financial support, as illustrated earlier, are needed.
Abu-Gharbieh, W.I. 1978. The root-knot nematode, Meloidogyne in Jordan. Proc. First Res. and Planning Conference on Root-Knot Nematodes, Meloidogyne spp., p. 16-18. Cairo, Egypt, 29 January to 2 February.
Abu-Gharbieh, W.I. 1979. The root-knot nematodes, Meloidogyne in Jordan. Proc. Second Res. and Planning Conference on Root-Knot Nematodes, Meloidogyne spp., p. 24-29. Athens, Greece, 26-30 November.
Abu-Gharbieh, W.I. 1982a. Reaction of locally grown eggplant, hot and bell pepper cultivars to Meloidogyne javanica. Dirasat, 9:205-206.
Abu-Gharbieh, W.I. 1982b. Dates, rates and methods of DBCP application for the control of Meloidogyne javanica on tomato. Dirasat, 9:33-39.
Abu-Gharbieh, W.I. 1982c. Identification of Meloidogyne species in the major irrigated areas of the East Bank of Jordan. Dirasat, 9:43-49.
Abu-Gharbieh, W.I. 1982d. Distribution of Meloidogyne javanica and Meloidogyne incognita in Jordan. Nematologica, 28:34-38.
Abu-Gharbieh. W.I. 1982e. Effect of cultural vs. chemical treatments for the control of Meloidogyne javanica on tomato. Dirasat, 9:155-162.
Abu-Gharbieh, W.I. 1982f. The root-knot nematodes, Meloidogyne species in Jordan. Proc. Third Res. and Planning Conference on Root-Knot Nematodes, p. 39-58. Coimbra, Portugal, 13-17 September.
Abu-Gharbieh, W.I. 1987. Plant-parasitic nematodes associated with cereal and forage crops in Jordan. Proc. workshop on Nematodes Parasitic to Cereals and Legumes in Temperate Semi-Arid Regions, p. 106-168. Larnaka, Cyprus, 1-5 March.
Abu-Gharbieh, W.I. & Hammou, A. 1977. Population effect of Meloidogyne incognita on the different plantings of tomato in the central Jordan Valley. Nematol. Medit., 5: 227-232.
Abu-Gharbieh, W.I., Kasrawi, M.A. & Al-Banna, L. 1989. Screening tomatoes against two species of root-knot nematodes. Tomato Genetics Cooperative, 39: 5.
Abu-Gharbieh, W.I., Makouk, K.M. & Saghir, A. 1978. Response of different tomato cultivars to the root-knot nematode, tomato yellow leaf curl virus and Orbanche in Jordan. Plant Disease Reporter, 62: 263-266.
Abu-Gharbieh, W.L, Saleh, H. & Al-Banna, L. 1991. Application of solar-heated water for soil solarization. In FAO Plant Production and Protection Paper No. 109. Soil Solarization. Proc. First Int. Conf. on Soil Solarization. Amman, Jordan, p. 69-77. 19-25 February 1990.
Abu-Gharbieh, W.I., Saleh, H. & Abu-Blan, H. 1991. Use of black plastic for soil solarization and postplant mulches. In FAO Plant Production and Protection Paper No. 109. Soil Solarization. Proc. First Int. Conf. on Soil Solarization, p. 229-242. Amman, Jordan, 19-25 February 1990.
Abu-Gharbieh, W.I. & Tamimi, S.A. 1982. Reaction of wheat and triticale cultivars to the wheat gall nematode and covered smut in Jordan. Dirasat, 9: 91-96.
Abu-Laban, A.Z. & Saleh, H. 1992. Evaluation of animal manures for mass production, storage and application of some nematode egg-parasitic fungi. Nematologica, 38: 237-244.
Al-As'ad, M.A. & Abu-Gharbieh, W.I. 1990. Use of black plastic tarping for soil solarization. Int. Nematol. Network Newsl., 7(2): 33-34.
Hattar, B.I, Abu-Gharbieh, W.I. & Al-Banna, L. 1988. Effect of elemental sulphur and sulphuric acid amendments on root-knot nematodes and tomato growth in calcarious soils. Damascus Univ. Journal, 15: 35-56.
Muhammad, A.G., Suwwan, M.A. & Abu-Gharbieh, W.I. 1991. Silver thiosulphate effects on yield and growth of plastic house tomato in root-knot nematode infested soil. Emr. J. Agric. Sci., 3: 41-65.
Saleh, H. & Qadri, A. 1989. Fungal association with Heterodera schachtii in Jordan. II. Identification and incidence. Nematol. Medit., 17: 109-112.
Saleh, H., Abu-Gharbieh, W.I. & Al-Banna, L. 1989. Augmentation of soil solarization effects by application of solar-heated water. Nematol. Medit., 17: 127-129.
M.Sc. theses in nematology
Abdulhadi, N.K. 1989. Effect of organic amendments, soil solarization, and their interaction on soil-borne plant pathogens. Faculty of Agriculture, University of Jordan. 93 pp.
Abu-Laban, A.Z. 1991. Evaluation of three nematophagus fungi in controlling root-knot nematode using animal manure and wheat grain as carrier substrates. Faculty of Agriculture, University of Jordan. 78 pp.
Al-As'ad, M.A. 1983. Effect of solarization on soilborne fungi and nematodes in the central Jordan Valley. Faculty of Agriculture, University of Jordan. 74 pp.
Atieh, S.A. 1986. Pathogenicity and histopathology of Meloidogyne javanica and Meloidogyne incognita on olive and tomato. Faculty of Agriculture, University of Jordan. 145 pp.
Barakat, R. 1987. Comparative effect of different colors of polyethylene tarping on soil-borne pathogens. Faculty of Agriculture, University of Jordan. 82 pp.
Khalaielah, R. 1988. Effect of soil solarization using different thicknesses of transparent polyethylene on cucumber grown in plastic houses in the Jordan Valley. Faculty of Agriculture, University of Jordan. 119 pp.
Khatoom, M. 1981. Effect of methyl bromide soil fumigation and black plastic mulching on cucumber grown under plastic tunnels. Faculty of Agriculture, University of Jordan. 74 pp.
Musallam, Z.A. 1992. Effect of soil solarization and methyl bromide fumigation on production of three muskmelon cultivars in the Jordan Valley. Faculty of Agriculture, University of Jordan. 77 pp.
Qasim, M. 1992. Occurrence and distribution of the phytonematode Tylenchulus semipenetrans in citrus groves in Jordan. Faculty of Agriculture, University of Jordan. 96 pp.
Saleh, H.M. 1979. Biology of Meloidogyne javanica (Treub) Chitwood on tomato in the central Jordan Valley. Faculty of Agriculture, University of Jordan. 60 pp.
Sharawi, S.A. 1982. Control of the root-knot nematodes on olive transplants with oxamyl. Faculty of Agriculture, University of Jordan. 128 pp.
