| | Introduction | Disease evaluation | Collaboration with advanced research institutes and national research institutes | Breeding strategies | Results obtained | Conclusions | References
Introduction
The International Center for Agricultural Research in the Dry Areas (ICARDA), with the headquarters in Aleppo, Syria, is one of 15 centers strategically located all over the world and supported by the Consultative Group on International Agricultural Research (CGIAR). With its main research station and offices based in Aleppo, Syria, ICARDA works through a network of partnerships with national, regional and international institutions, universities, non-governmental organizations and ministries in the developing world; and with advanced research institutes in industrialized countries. ICARDA serves the entire developing world for the improvement of barley, lentil, and faba bean; and dry-area developing countries for the on-farm management of water, improvement of nutrition and productivity of small ruminants (sheep and goats), and rehabilitation and management of rangelands. The Global Barley Enhancement Program has its headquarters in Syria, while the sub-program based in Latin America, targets the developing countries in that region. The development of germplasm with resistance to the main biotic and abiotic stresses has always had the highest priority in the program. Genetic resistance still is the most environmentally-friendly and durable method of control of crop stresses, as well as the only affordable method for low income farmers at different regions worldwide.
Disease Evaluation
To reach our objectives it is very important to have screening environments where it is possible to maximize the response to selection for a determined trait. This many times implies the need to decrease the environmental variation, giving the optimal conditions for disease development (misting, inoculation) or stress expression (drought). This is possible in the environments that the program uses regularly in different parts of the world. In Syria, selection is carried out at key environments where the main diseases in the region can be reproduced. Selection for scald, loose smut, covered smut, barley stripe, powdery mildew, net blotch and root rot are carried out at the headquarters at Tel-Hadya, Aleppo. In Lattakia, selection is also performed for net blotch and powdery mildew, while in Terbol (Lebanon), scald resistance is selected during the winter and powdery mildew and leaf rust resistances during summer. In Haymana (Turkey), scald, net blotch and powdery mildew resistances are selected.
In Mexico, key experimental stations have also allowed the accumulation of resistance to different important diseases in an efficient manner. Toluca and El Batán, during summer time, are key selection hot spots for several diseases. At Toluca, stripe rust, scald, Fusarium head blight and BYDV can be selected with highest confidence. Heritabilities for Stripe Rust are usually higher than 95% at Toluca (Vales et al., 2005). The inoculation of all the program segregant material with scald and the natural infection with stripe rust as well as the artificial inoculation of the advanced material with this disease, practically makes all germplasm coming out from the program resistant to these diseases. At Ciudad Obregón during winter season, ideal conditions for leaf rust allow us to confidently select for resistance to this disease in all the inoculated segregant material. Again, most of the germplasm deployed is expected to be resistant to this disease also.
Collaboration with Advanced Research Institutes and National Research Institutes
The close collaboration with centers of excellence or “Advanced Research Institutes” (ARIs) is fundamental to develop the superior germplasm needed in the target areas, as well as the close contact with the “National Research Institutes” (NARs) is essential to receive input about research priorities. The ICARDA/CIMMYT program for Latin America has had long term collaboration with several programs worldwide. Among the longest and most productive has been the collaboration with the barley program of Alberta Agriculture, Food and Rural Development, headed by Dr. James Helm. For many years, the synergistic interaction which included germplasm exchange, screening and expertise, helped developing superior barleys with resistance to 5-7 important diseases. No less important has been the interaction with the barley program at Oregon State University, mainly regarding stripe rust research. That program under the leadership of Dr. Patrick Hayes, made it possible to map several populations, while carrying out the phenotyping at Toluca. These studies have helped to understand the genetics of the diseases and generated germplasm with pyramided genes for resistance available to all the programs in the region and worldwide. The participation in the now discontinued North American Stripe Rust Nursery, coordinated by Drs. Bill Brown and Vidal Velasco, allowed for the determination of the level of resistance to Stripe Rust present at the different programs in North America, and to use the resistance for germplasm enhancement. The screening of the Australian programs through the PBI of the University of Sydney, under the leadership of Dr. Colin Wellings, also reaches the same objectives with that country. More recently, the collaboration with Bush Agricultural Resources Inc. (BARI) through Dr. Leslie Wright and Linnea Skoglund allowed us to incorporate malting quality in our multiple disease resistant gemplasm. Using their malting barley varieties as templates, in one cycle of breeding it was possible to obtain attractive lines that combined resistance levels to the main diseases at higher level than the parents. In following cycles additional gains in the agronomic and quality traits are expected.
Undoubtedly one of the greatest challenges that the barley programs in the region and worldwide has faced in the last decade has been the epidemic outbreaks of Fusarium head blight (FHB). As several of us know, FHB has always been present in the barley cultivated area, but never in the proportions and frequency reached lately. The epidemic patterns appear to repeat in several countries worldwide. After the outbreak in the Midwestern US in 1993, outbreaks of different intensities have occurred in Uruguay, Brazil, Peru, Ecuador, etc. This supports the need to continue intensively working with this destructive disease. Our program has, in several opportunities, linked the NARs and the ARIs in order to facilitate research exchange. Our collaboration within the US Wheat and Barley Scab Initiative has been essential to support our research as well as to keep scientists updated with the latest research advances. Probably as with no other disease has the interaction among colleagues and the synergistic relationships been so important, from the collaborative germplasm screening networks to the brainstorming sessions carried out when working together, from China to the Midwest or Mexico.
Breeding Strategies
ICARDA/CIMMYT - México
Since the early 1980s, several programs have been involved in breeding for disease resistance. The program in Mexico took advantage of collaboration and experience to build the foundation of resistances to the different diseases. Webster et al. (1980) screened 18,000 accessions from the world barley collection for scald resistance. They found 273 entries that showed no symptoms. Resistant entries were introduced and screened for virulence in Central Mexico. From the 273, 13% showed susceptibility under those conditions and were discarded.
The national research program at Colombia screened 8,650 accessions for race 24 of Puccinia striiformis f. sp. hordei (Anonymous, 1984). In Mexico, 285 entries were found to be resistant out of 11,087 accessions screened at CIANO experiment station in Obregón for races 8, 19 and 30 of P. hordei . Vivar (1986) in México and Takeda and Heta (1989) in Japan screened 5,000 accessions and found 23 lines with resistance to FHB. The germplasm identified above was used as the starting point for disease resistance in the program.
Resistant germplasm was evaluated against the virulence of the most aggressive pathogens collected and introduced into the US and Europe from hot spots around the world. Work on leaf rust by Sharp and Reinhold (1982) in Montana and Parlevliet in Holland (1977) helped the program identify parents to use in the crossing program. To accomplish the goal of introgressing the resistance of all those diseases into high yielding germplasm, “templates” were developed, first for scald and leaf rust, followed by templates to which stripe rust and other diseases resistances were added. Over a period of 25 years (two growing seasons per year) different diseases were pyramided. Varieties produced appeared to be commonly resistant to scald, leaf rust, stripe rust and stem rust, BYDV, net blotch and spot blotch and since several cases also to FHB. Besides the resistance, the agronomic type made the germplasm attractive enough to be extensively used as cultivars or as source of resistance by our colleagues.
ICARDA – Syria
To target the poor, the breeding philosophy of the project, which evolved during the last 14 years, is based on exploiting specific adaptation through direct selection in the target environments using locally adapted germplasm and sustainable levels of external inputs.
The two major implications of this philosophy were that (1) many varieties were generated by national programs, each adapted to specific conditions, and (2) the superior performance of the varieties developed for low-input and less-favored lands are not dependent on agronomic practices that require large amount of inputs. A breeding program based on this philosophy does not endanger biodiversity, and is environmentally benign.
A fundamental question the barley program has addressed in the last 14 years is why plant breeding has been beneficial to those farmers who either enjoy favorable environments or could profitably modify their environment to suit new cultivars, and it has not been equally beneficial to those farmers who could not afford to modify their environment through the application of additional inputs. Farmers in favorable environments, using high quantities of inputs, are now concerned with the adverse environmental effects and the loss of genetic diversity. Poor farmers in less-favored environments continue to suffer from chronically low yields, crop failures and, in the worse situations, malnutrition and famine. Because of its past successes, conventional plant breeding has tried to solve the problems of poor farmers living in unfavorable environments by simply extending the same methodologies and philosophies applied earlier to favorable, high potential environments. We have now concluded that difficult environments and resource-poor farmers require a different type of breeding.
Using contrasting sites in NW Syria we found repeatable genotype x environment (GE) interactions of crossover type between the main experiment station and experiment sites managed according to farmers' practices. GE interactions of crossover type are common in the literature, in different crops and in different types of stress environments. We then concluded that selection in high input experimental stations is very effective in generating varieties for favorable environments, but does not allow the identification of the best genotypes for less-favored lands, and promotes genotypes which are in fact inferior in stressful conditions.
Formal breeding has taken a negative attitude towards GE interactions of crossover type, in the sense that only breeding lines with low GE interaction (good average grain yield, across locations and years) are selected, while lines with good performance at some site and poor performance at others are discarded. Because lines with good performance in unfavorable sites and poor response to favorable conditions have a low average grain yield, they are systematically discarded. Yet they would be the ideal lines for farmers in unfavorable locations. Therefore, having recognized the importance of GE interactions of the crossover type, a major conclusion has been that breeding for difficult environments must be based on the exploitation of specific adaptation, and this in turn can only be done by selecting directly in the target environments.
While the application of this philosophy started being successful in Syria with the adoption of three varieties in stress environments, the next question was: how to reconcile the mandate of an international breeding program with the importance of specific adaptation?
The response to this question has been the decentralization of the breeding work. The term decentralization has been used often to describe two fundamentally different processes, namely decentralized selection and decentralized testing.
Decentralized selection is a term first used by Simmonds (1984) and defined as selection in the target environment(s). Decentralized selection has been also termed in-situ or on-site selection. In the case of self-pollinated crops it consists in selection of early segregating populations (such as F2) in a number of locations representing the target environment(s) (climate, soil, farming system and management) the breeding program aims to serve. Decentralized selection becomes selection for specific adaptation when the selection criterion is the performance in specific environments rather than the mean performance across environments.
Decentralized selection is different from decentralized testing, which is a common feature of breeding programs and takes place, usually in the form of multi-location trials and on-farm trials, after a number of cycles of selection in one or few environments (usually with high levels of inputs).
Addressing the issue of resistance to biotic stresses, it is acknowledged that barley is affected by several foliar and root diseases, several insects, nematodes, and viruses. The organisms which can potentially damage a barley crop can be divided in two broad categories, namely those which are specific (either as organism or as a physiological race) to a given country or area, and those which are widespread to several countries.
The overall strategy, once the priority biotic stresses have been identified together with NARs, is to decentralize the work on biotic stresses of the first type to NARs following the development of the necessary expertise, and to concentrate at the headquarters on the second type of biotic stresses. The latter is an ideal ground for collaboration with ARIs.
Within this broad strategy, the work on biotic stresses is integrated in the more general, decentralized approach to plant breeding followed by the project.
In the case of foliar diseases, insects and viruses, the screening of large amount of breeding material, which has represented 90% of the activities in the past, has been gradually reduced to about 10% of the total work on biotic stresses. Eventually, screening was entirely transferred to NARs. Specific pests are tested at hot spots, and information circulated to all collaborators. Sources of resistance are being characterized at the headquarters which focus on the transfer of genes for resistance into the breeding material developed by the decentralized program for specific countries and/or regions. In these cases the national programs receive F4 families homozygous for the resistance gene(s), but variable for everything else. This is done at the headquarters in the case of genes with non-specific resistance (for example, the genes for resistance to RWA and BYDV), and within five years it will be done routinely with the aid of molecular markers. These first molecular markers assisted selection programs will also be used to train national program scientists.
In the case of foliar diseases, where a large variability exists for physiological races, the responsibility of the headquarter pathologist is the identification of genes which are effective against the virulences of target countries/regions. Sources of resistance for these genes are used in the targeted crosses at the headquarters, but the selection of the segregating populations are done in the target environments. Marker assisted selection will be made available to NARs to increase the efficiency of selection.
Two areas which need expansion are a) scab, root diseases and nematodes, and b) durable resistance and population improvement.
The entire area of durable resistance, and of the consequent changes in the breeding strategies which are needed, are addressed by the barley project, and at least one case-study is being developed to address one of the most variable foliar diseases (powdery mildew) with two alternative strategies, one based on deployment of major genes and one based on the increase of horizontal resistance through population improvement.
Results Obtained
In decentralized selection, the barley project at ICARDA continues to generate genetic variation by maintaining a large crossing program, but selection is carried out by the breeders in the National Programs. At this moment, decentralization of barley breeding is fully implemented in North Africa, Iraq and Ethiopia, and it is gradually being implemented in the Mediterranean highlands in the framework of the ICARDA/Iran Project, and in other countries (Table 1).
Table 1. Countries and regions where decentralized barley breeding has been initiated.
| Country/Region | Countries/Area | Status |
| North Africa | Egypt, Libya, Tunisia, Algeria, Morocco | Fully implemented |
| Iraq (Baghdad) | Central Iraq | Fully implemented |
| Iraq (Mosul) | Northern Iraq | Fully implemented |
| East Africa/Red Sea | Yemen, Eritrea, Tigray | First crosses made in 1998 |
| Ethiopia | Ethiopia (except Tigray) | Use of local landraces fully implemented, first crosses in 1998. |
| Central Asia |  | First special nursery in 1997 |
| Turkey | | First nursery planned for 1999 |
| Cyprus | Cyprus | First special nursery in 1995, first crosses in 1998 |
| Far East | India, Thailand, Vietnam, China | First special nursery in 1996, first crosses in 1997 |
| Pakistan | Pakistan | First special nursery in 1997 |
| Gulf Countries | S. Arabia, Qatar, Oman | First crosses made in 1992 |
| Ecuador | Ecuador | First nursery planned for 2006 |
The project in Latin America has been successful in developing useful germplasm adopted by the programs in the main target area, as well as in some other regions worldwide. In Ecuador, all the commercial varieties are directly released from material received from Mexico, or were derived from crosses made with that germplasm, and selected in the country. In Uruguay, Brazil and México, germplasm has been intensively used as a source of disease resistance as well as to improve agronomic types. The same situation occurred with several of the most planted varieties released in Peru in the last 25 years. According to information received from China (Dr. Zhonghu He, CIMMYT representative in China, personal communication), the area planted to barley in 2000 with germplasm developed by the program (either direct introduction or varieties derived from past introductions) account for 40% of the one million hectares cultivated to barley in the country. The key traits for a successful variety in that region is the resistance to FHB, tolerance to barley yellow mosaic virus (BYMV) and consistent high yield potential.
The strategy used to incorporate leaf rust resistance into Shyri, a variety released in Ecuador, may explain the durability of the resistance obtained. The virulence present in that country is capable of overcoming all major resistance genes (Brodny and Rivadeneira, 1996). Shyri was released in 1989 with low symptoms for leaf rust. After two years a race was able to overcome the major gene located on chromosome 1 of the variety (Toojinda et al., 2000), however it produced reasonable yield despite the presence of symptoms on leaves late in the season. In 1991 Ochoa concluded that Shyri had partial resistance that delays disease development.
In Stripe rust, the collaboration with Oregon State University has been fundamental to understand the genetics of resistance and create germplasm which pyramids resistance genes from different sources. Using resistance sources as Shyri, Calicuchima (a variety also released in Ecuador) and CI10587, mapping studies determined that resistance QTLs were present in the chromosome 1H in Shyri, 4H and 5H in Calicuchima and a major gene was present at the 7H in CI10587 (Figure 1). The importance of this type of study was evident when new resistance patterns were observed in Peru and Ecuador after the year 2000. After more than 15 years of no observed changes, several well known resistant lines appeared as susceptible in that region. The pyramided germplasm allowed us to determine that the resistance QTLs and major gene present at chromosomes 4H, 5H and 7H were susceptible to that putative new race of the disease, while the QTL at Chromosome 1H (from Shyri) was still holding resistance. All the germplasm developed by OSU was planted in those countries, and are expected to collaborate in the development of varieties that still are resistant in the region. Although in North America the old sources still appear as resistant, it is expected that, like has occurred in the past, the possible new race would come to the region and change the resistance patterns of the varieties present there also.
Figure 1.
Pedigree developed by Patrick Hayes, Oregon State University.
Another example of progress in the fight against disease losses has been the case of FHB. When FHB epidemics occurred in the Midwestern US after 1993, the barley program at México had already been working in that disease for several years. That allowed the main source of resistance to become available to the US programs that were re-starting their work with FHB. Several well-known resistance sources like Atahualpa, Shyri, Gobernadora, etc. were rapidly introgressed into the programs. At present, the collaboration is in a more formal fashion, through the USWBSI. This has allowed the testing of high numbers of genotypes every year and participation in the testing network at different locations allows confirmation and sharing of the resistance observed. In the Table 2 we can see some lines developed through the agreement with BARI that have had their resistance confirmed at several locations.
In recent studies of the resistance sources for scald used in the program, slow-scalding resistance (S-SR) appeared to be present in the core material released by the program. Little was known about the inheritance of S-SR. Studies carried out by B. Sorkhilalehloo et al. (2001, 2004) showed indications of incomplete dominance for that trait and additive variance was the major portion of total genetic variance for S-SR. The estimates of narrow-sense heritability of S-SR were quite high (0.80-0.98). Such resistance genes with additive effects and high heritabilities, should support successful phenotypic selections for S-SR in early generations, and are promising for pyramiding resistance genes for achieving stable resistance against barley scald using back-crossing methodology. The results also showed that none of the barley genotypes were immune against all the isolates used in the study. However, the cluster of “highly resistant” genotypes contained barleys resistant to the majority of the pathotypes among which there was some malting, hulless, slow-scalding, and differential lines as promising potential sources of stable resistance to scald.
The more than 20-year collaboration with the FCDC in Alberta, focusing on scald resistance and other diseases, has allowed both programs to develop germplasm resistant to all the regionally important diseases. New combinations of resistance genes have been found, with some lines containing resistance to 5 and 6 diseases. Helm et al. (2004) determined that these gene combinations for scald resistance should give durable resistance in Canada and México. The classification of breeding lines according to resistance genes combinations is currently under pedigree analysis to determine the relationship for sources of resistance genes. Some of the lines from the collaborative program also showed high level of resistance to FHB in Mexico, Canada, USA and China.
Table 2. Sample of 6-row barley lines with mating quality parents and higher levels of resistance to FHB and other diseases and desirable agronomic traits.
| Entry | Cross | FHB | | P.hordei | | Protein | | Yield | | PS* |
| | (%) | (%) | (%) | (%) | (1-5) | (0-5) | | (Cobbs) | | (%) | | (t/ha) | | (1-5) |
| | | Type I | Type II | Type I | | | | | | | | | | |
| | Hangzhou | Toluca | Toluca | Toluca | ND | Brandon | | Obregón | | Obregón | | Obregón | | Mean |
| | | 2004 | 2004 | 2004 | 2003 | 2004 | 2004 | | 2004 | | 2004 | | 2004 | | |
| 254 | 6B89.2027/CHAMICO | 5.9 | 3.0 | 2.5 | 0.15 | | | | R | | 13.7 | | 5.4 | | 4.25 |
| 77 | LEGACY//PENCO/CHEVRON-BAR | | 2.3 | 4.4 | 1.52 | 3 | 2.5 | | 60S | | 11.0 | | 8.1 | | 1.75 |
| 148 | LEGACY/3/SVANHALS-BAR/MSEL//AZAF/GOB24DH | 8.2 | 2.0 | 10.3 | 0.64 | | | | R | | 14.6 | | 3.9 | | 2.50 |
| 147 | LEGACY/3/SVANHALS-BAR/MSEL//AZAF/GOB24DH | 11.1 | 1.4 | 4.1 | 1.32 | | | | R | | 14.3 | | 4.3 | | 3.00 |
| 55 | LEGACY/4/TOCTE//GOB/HUMAI10/3/ATAH92/ALELI | 6.3 | 1.7 | 4.0 | 0.38 | 1 | 1.5 | | R | | 11.4 | | 6.8 | | 2.25 |
| 53 | LEGACY/4/TOCTE//GOB/HUMAI10/3/ATAH92/ALELI | 5.3 | 1.4 | 3.9 | 0.13 | 2 | 4 | | R | | 11.3 | | 6.4 | | 3.00 |
| 54 | LEGACY/4/TOCTE//GOB/HUMAI10/3/ATAH92/ALELI | | 1.1 | 4.1 | 1.09 | 1 | 2 | | R | | 12.7 | | 6.0 | | 2.75 |
| 60 | LEGACY/4/TOCTE//GOB/HUMAI10/3/ATAH92/ALELI | | 1.0 | 13.3 | 1.71 | 1 | 2.5 | | R | | 11.7 | | 5.8 | | 4.50 |
| 65 | LEGACY/4/TOCTE//GOB/HUMAI10/3/ATAH92/ALELI | | 2.3 | 6.0 | 2.14 | 1 | 3 | | R | | 12.0 | | 6.5 | | 3.25 |
| 73 | LEGACY/4/TOCTE//GOB/HUMAI10/3/ATAH92/ALELI | | 0.8 | 4.0 | 1.80 | 1 | 3 | | R | | 10.9 | | 6.0 | | 3.00 |
| | | | | | | | | | | | | | | |
| CHEVRON | 3.4 | | | | 1 | 1.5 | | | | | | | | |
| STANDER | 9.6 | 5.15 | 13.94 | | 3 | 3 | | 80S | | 13.0 | | 4.6 | | 3.0 |
| | LEGACY | 13.2 | | 6.32 | | | | | 60S | | 13.0 | | 5.5 | | 3.0 |
PS = Phenotypic Score 1 = Best; 5 = Worst
Conclusions
Giving support to research programs and producers in developing countries raises challenges that sometimes are not only technical. Despite historical fluctuations in resources available for research, the system implemented has been successful in deploying germplasm and products highly demanded by the customers – either NARs in developing countries or producers in those areas. Successful strategies have to be flexible and adapted to the different and highly variable target areas, and academic recipes most often cannot be directly applied.
The results obtained would have been impossible to reach without the close collaboration with the NARs as well as the ARIs worldwide. Sometimes the roles of our international research programs were to serve as catalysts and facilitators for cooperation among these groups. The unique situation created by the links and networks has allowed the confirmation of the results found in one location and around the world, an approach that is now being validated with other working groups from developed countries (e.g. USWBSI). In addition to the developing areas of the world, the products obtained have also been beneficial to the ARIs and programs present in developed countries.
References
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Flavio Capettini (1), Stefania Grando (2), Salvatore Ceccarelli (2), Amor Yahyaoui (2)
(1) ICARDA/CIMMYT Mexico
(2) ICARDA Syria
Presented at the 18th North American Barley Researchers Workshop, July 17-20, 2005. |
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