Crop production is tough and risky in the world's dry areas. Along with the stresses imposed by severe heat and drought, crops are subjected to the twin pressures of pests and disease, faced by farmers everywhere. Scientists in the countries of the Nile Valley have banded together to combat two of the most damaging crop diseases in the region, and cooperation is paying off.

he winter cereals--wheat and barley--and the cool season food legumes--faba bean, chickpea, and lentil--are among the most important food crops in Egypt, Ethiopia, Sudan, and Yemen. The food legumes are a major part of the daily diet and an important source of protein. In Ethiopia, for instance, they account for 21% of the protein consumed. Faba bean (dry broad bean) is the most important pulse, representing 80% of the pulses produced in Egypt and 36% in Ethiopia.
    In the four countries combined, food legumes are grown on 0.8 million ha. Production of these crops, however, does not meet demand from the population, which is growing at an average annual rate of 2.5%. As a result, a substantial quantity is imported annually.
    Crop yields under farmers' conditions are usually low compared to potential yields, and fluctuate considerably from season to season. This is due mainly to variability in rainfall, both within and between years, and the susceptibility of the cultivated landraces and cultivars to diseases, such as rusts, wilt, root rot, and viruses; insect pests, such as aphids; and stress from heat and drought.
     Wilt and root rot are major limiting factors in the production of faba bean, chickpea, and lentil in all the Nile Valley countries. The diseases cause up to 100% yield loss under heavy infestation, depending on relative humidity, soil moisture, and soil temperature.
      Within the framework of the Nile Valley and Red Sea Regional Program of ICARDA, a network was formed in 1995 to identify and prioritize the major soil-borne diseases of faba bean, chickpea, and lentil in Egypt, Ethiopia, and Sudan. The network includes scientists from the three countries and ICARDA. One of the main goals of the network is to pool the members' resources, such as laboratory facilities, skilled staff, and finances, to overcome the major economically important soil-borne diseases.

    Debre Zeit Agricultural Research Center of the Ethiopian Agricultural Research Organization (EARO) took the lead because it had already developed sick-plots for Fusarium oxysporum wilt in chickpea and lentil. EARO has also developed a sick-plot for F. solani, the pathogen responsible for black root rot in faba bean. In the initial phase of the project, the major activities were subdivided into four categories:

  1. Surveys to determine the distribution and importance of soil-borne diseases of the three crops (faba bean, chickpea, and lentil) in the three countries.
  2. Screening of germplasm for resistance to the major pathogens.
  3. Survey and identification of potential biocontrol agents and races of pathogens.
  4. Integrated management of diseases by use of cultural practices, resistant cultivars, and biocontrol agents and chemicals.
    All the countries carried out surveys and screening for resistance. Ethiopia was responsible for coordinating the screening. Sudan was responsible for integrated management work, while Egypt took the lead in biocontrol, chemical screening, and race identification.
    Some major achievements/findings of the network include:

  1. Chickpea wilt caused by F. oxysporum f.sp. ciceris and lentil wilt caused by F. oxysporum f.sp. lentis were found to be the common and major diseases of the three legumes in the three countries.
  2. Sclerotinia stem rot is the major disease in irrigated chickpea in the black clay soil in Egypt, while it does not occur in Ethiopia and Sudan.
  3. Dry root rot caused by Rhizoctonia bataticola was the second most important soil-borne disease in both chickpea and lentil in Ethiopia and Sudan.
  4. Black root rot caused by F. solani appears to be the major soil-borne disease of faba bean in the three countries.
While surveys were being conducted, screening for resistance to Fusarium wilt of chickpea continued at the sick-plots in Debre Zeit (Ethiopia) and Hudeiba (Sudan). Screening for other diseases in Egypt and Sudan was mainly done in pots.

Results

   Chickpea

The Ethiopian national program identified two lines of Kabuli chickpea resistant to F. oxysporum. They were both from ICARDA. These were officially released for commercial production in the midlands and highlands of Ethiopia under the names 'Shasho' and 'Arerti.' A desi chickpea line (ICC 12442) was identified for release in northwestern Ethiopia.
Similarly, ICCX 8500498-P-PBN-SH and 'Giza 88' chickpea lines proved resistant to eight isolates of Sclerotinia sclerotiorum fungus in Egypt. Their resistance needs to be confirmed before the lines are released to farmers. The Sudan national program has also identified resistant chickpea lines.

   Lentil

Although the program is in its infancy compared to chickpea program, the sick-plot of F. oxysporum at Debre Zeit Research Center has been used to screen large numbers of germplasm accessions each year. The lines identified by the Center were organized into a regional nursery in collaboration with the lentil breeding program at ICARDA. These lines have been tested in Sudan and Egypt, mainly in pots.
     Among the tested lines, 'Adaa,' a variety released in Ethiopia, and HC-972 were found to be resistant in all three countries. F 130 and SPS ILL 669 were also moderately resistant or tolerant in the three countries. The ICARDA resistant and susceptible checks were susceptible in Ethiopia, indicating the prevalence of different races. It goes without saying that the race situation should be systematically investigated to assist the breeders in designing their approach in their respective countries. Testing in Debre Zeit sick-plots is providing additional sources of resistance. Lentil lines FLIP 84-43L, 81515, and 78596013 were found resistant to F. oxysporum f.sp. lentis in Egypt.

   Faba bean

Screening for black root rot in faba bean is underway. Identified resistance could not be sustained throughout the season, due mainly to cross-pollination. However, the Ethiopian national program identified three lines that are currently being used in the breeding program.
Biocontrol
    Under greenhouse conditions in Egypt, four biocontrol agents (Trichoderma harzianum, Gliocladium virens, Pacellomyces farinasus, and Bacillus subtilis) were used successfully to control wilt/root rot diseases in food legume crops. It was found that T. harzianum was the most effective on faba bean, lentil, and lupin, as it increased the number of surviving plants and decreased the disease severity, while P. farinasus was the most effective biocontrol agent on chickpea.
    Seed coating of faba bean, lentil, and chickpea with different bioagents (T. harzianum, G. virens, P. farinasus, and B. subtilis) in combination with appropriate sowing dates resulted in an increase in plant survival and a decrease in damping-off disease.

   Pathogen variability

Variability among isolates of F. oxysporum f.sp. lentis was characterized using lentil differentials. Variability was confirmed by DNA cluster analysis using molecular marker technique RAPD-PCR.
    Isolates of F. oxysporum f.sp. ciceris were characterized using DNA bands generated by RAPD-PCR, and tested on varieties of chickpea differentials. So far, three races have been identified.

The work continues

Cooperation through networking is generating improved crop plant lines resistant to soil-borne diseases. The result is improved income and nutrition of the rural poor in the countries of the Nile Valley. The work continues.