ISSN 2394-966X International Journal of Novel Research in Life Sciences Vol. 7, Issue 2, pp: (23-34), Month: March - April 2020, Available at: www.noveltyjournals.com Evaluation of Commercial Bread Wheat Cultivars and Monogenic Lines for Their Adult Plant Resistance to Stem Rust WorkuAbebe Ethiopian Institute of Agricultural Research, Holleta Agricultural Research Center (HARC), P.O. Box 2003, Holeta, Ethiopia E-mail: [email protected]: +251913317619 Abstract: Wheat is one of the most important food crops in the world and is a major cereal crop cultivated world- wide and contributes substantially to human daily calories and food security. Ethiopia is among the top three wheat producers in Africa, with wheat accounting for 20% of the nation’s total cereal production. However, it is highly vulnerable to many diseases, of which stem rust is significantly causing yield loss. In Ethiopia stem rust disease causes yield loss up to 100% when susceptible cultivars planted and the environment is conducive. To elevate the threat of stem rust it is important to identify resistant genes in different sources. Thus, this study was designed to evaluate 21 commercial bread wheat cultivars and 40 monogenic lines against wheat stem rust disease in fields under natural condition. The wheat genotypes were planted in un-replicated plots of 1m long with two rows and 20 cm spacing between rows at research stations of Kulumsa and Melkasa Agricultural Research Centers in four districts of Arsi zones. In this study, cultivars Enkoy, paven 76 and monogenic lines that contain Sr24, Sr26, Sr22 and Sr32 have been found resistant against the prevailing wheat stem rust pathogen population in the study area. Hence, those wheat genotypes that showed adequate level of adult plant resistance can be used in wheat breeding program for stem rust resistance at national or regional levels. Keywords: Evaluation, Cultivars, Monogenic Lines, Wheat, Stem rust, Adult plant, Resistance, Trap nursery. 1. INTRODUCTION Wheat is the most widely grown cereal crop (Curtis and Halford, 2014) in more than 122 countries (FAOSTAT 2015). It accounts for over 35% of the world food sources and provides 20% of proteins and calories to humans (Braun et al. 2010; Hawkesfordet al. 2013). Bread wheat and durum wheat are the two main commercial types of wheat and are grown on approximately 215 million hectares annually, with an estimated production of 700 million metric tons (Singh et al. 2011). It is used as a major ingredient in food products, a major market commodity which is internationally traded as a cash crop. Wheat is also used for livestock and poultry feed as a by-product of the flour milling industry. It is grown on about 17% of global crop acreage which is about 215 million hectares producing about 630 million tons of grain annually(Singh et al., 2011). Wheat also provides 16% of total dietary calories in the developing countries and about 4.5 billion people in 94 developing countries depend on wheat (Dixon et al., 2009) Though wheat is a very important cereal crop, its production is threatened by biotic and abiotic factors. Of biotic factors wheat rusts are the major ones. Stem rust is the most damaging disease of the three wheat rusts (Roelfs et al., 1992). Currently stem rust is known for causing severe devastations in all wheat- growing countries of the world and it remains the most important disease of wheat worldwide (Watkins, 2005). Historically, several wheat stem rust epidemics have been reported from Africa (eastern, southern and north Africa), Asia, Europe, North and South America (Canada, United Page | 23 Novelty Journals ISSN 2394-966X International Journal of Novel Research in Life Sciences Vol. 7, Issue 2, pp: (23-34), Month: March - April 2020, Available at: www.noveltyjournals.com States, Mexico, Paraguay, Argentina, Brazil, Bolivia, Uruguay and Chile), and Australia and New Zealand (CIMMYT, 2005). Stem rust epidemics was effectively controlled for the last several decades in most wheat growing regions of the world because of the worldwide deployment of effective stem rust resistance genes in wheat varieties (Singh et al., 2006; Jin et al., 2006). However, stem rust has again become a major threat to the world wheat production with a new race of stem rust pathogen, Ug99 (Pretorius et al., 2000). Ug99 pathotypes defeat most of the race-specific resistance genes currently deployed worldwide and are considered to be the most virulent strain of stem rust to emerge in the last 50 years(Stokstad, 2007).At present, among the 58 catalogued resistant genes against stem rust, only less than half of them are effective to Ug99 (McIntosh et al., 2014). Worldwide virulence, for many of these genes is now common; making them useless for crop protection. This is also true in Ethiopia where most of the wheat varieties used by Ethiopian farmers are susceptible to the new race of stem rust pathogen, Ug99 and its derivatives (CIMMYT, 2005) In Ethiopia, the importance of wheat stem rust was recognized as early as 1930 (Mengistuet al., 1991). Currently, most of bread wheat varieties grown in the country are susceptible to either the previously identified races of stem rust pathogen or the newly evolved race Ug99 and its derivatives.Therefore, replacement of the currently popular susceptible varieties with high yielding resistant varieties is very important and should be the best strategy to protect wheat production in the country. Deployment of resistant varieties is the most effective and environmentally sound method to control this disease. However, an effective deployment of resistance genes for the management of stem rust in wheat production requires knowledge about the resistance status and the diversity of resistance genes in varieties under consideration (Belaynehet al., 2008). Moreover, knowledge on the current status of wheat varieties under cultivation against the prevailing wheat stem races is crucial; as the pathogen is known to evolve its virulence frequently (Jin et al., 2009). Therefore, achievement of durable resistance against wheat stem rust requires constant characterization of the pathogen; and identification and deployment of resistance genes that overcome the prevailing virulent races (Belaynehet al., 2008). Thus, evaluation of the current status of available genotypes for their adult plant resistance is important. Hence, this study was initiated with the objective to evaluate commercial bread what cultivars and monogenic lines for their adult plant resistance to wheat stem rust disease. 2. MATERIALS AND METHODS 2.1 Description of the Study Area The study was conducted in four districts of Arsi and west Arsi zones: Gedeb Asasa, Arsi Negele, Arsi Robe and Tiyo districts. The four districts of the study area were selected for their wheat stem rust hot spot areas in Arsi zones. Gedeb Asasa and Arsi Negele districts are found in West Arsi zone whereas Tiyo and Arsi Robe are found in Arsi zone. Gedeb Asasa is located at 7012‟ N and 390 20‟ E, with an elevation of 2300 masl. The mean annual rainfall of the area is 650 mm while the mean minimum and maximum air temperature is 5.6 and 23.60C, respectively. The geographic location of Arsi Negelie is 70 33‟ N, and 380 66‟ E, at an altitude of 1950 masl. The district has mean annual rainfall of 985 mm. with a mean minimum and maximum air temperature of 15 and 25.40C, respectively. Arsi Robe is located at 70 80‟ N, and 39o 70‟ E, with an elevation of 2400 masl. and a mean annual rain fall of 900 mm. Its mean minimum and maximum air temperature is 9.2 and 22.50C, respectively. Tiyo is the district in which Kulumsa Agricultural Research Center (KARC) is located. It is located at 80 N and 390 12‟E, at an altitude of 2200 masl. It has a mean annual rainfall of 820 mm and its minimum and maximum air temperature is 10.1 and 22.70 C, respectively. 2.2 Experimental Design The experiment was arranged in an augmented design 2.3 Experimental Materials and their Sources In this study 21comercial bread wheat cultivars and 40 monogenic lines (Table 1) together with two check varieties, morocco & PBW343 were used and all of them were obtained from Kulumsa Agricultural Research Centre (KARC), Ethiopia. Kulumsa Agricultural Research Center is located at 169 Km South-east of Addis Ababa at 080 01‟10‟‟N latitude and 390 09‟11‟‟ E longitudes and at elevation of 2200masl. Kulumsa Agricultural Research Center is a center of excellence for wheat production research in the country. Page | 24 Novelty Journals ISSN 2394-966X International Journal of Novel Research in Life Sciences Vol. 7, Issue 2, pp: (23-34), Month: March - April 2020, Available at: www.noveltyjournals.com wheat stem rust trap nurseries consisting of 21 commercial cultivars, 40 monogenic lines and universally susceptible wheat variety, “Morocco” as a check and PBW343 as standard check for Ug99 were established at four environmentally different districts (Arsi Robe, Tiyo, Gedeb Asasa and Arsi Negele) in Arsi and West Arsi zones in South East Ethiopia (Table 1). Arsi Robe and Tiyo districts are found in Arsi zone while Gedeb Asasa and Arsi Negele are found in West Arsi zone. These four districts were selected as testing location because they are known hot spot areas for stem rust disease in Arsi zones ( Admassu and Fekadu, 2005; Admassu et al., 2009; Worku et al., 2016) Arsi Robe testing location is internationally known stem rust testing site and is used for large-scale wheat screening for resistance to stem rust in wheat (Worku et al., 2016). Not only Arsi Robe district, but also most Arsi zones in Ethiopia are known hotspot for the development of stem rust epidemics and many stem rust race analysis by researches have been indicated the presence of diversified/varied races with wider virulence spectrum (Admassu and Fekadu, 2005; Admassu et al., 2009; Worku et al., 2016) The two nursery sites in Arsi Robe and Gedeb Asasa districts were established at Kulumsa Agricultural Research Center stations whereas the nursery site in Arsi Negele district was established at Melkasa Agricultural Research Center station and the fourth nursery site in Tiyo district was established at Kulumsa agricultural Research Center main station.