Wheat is cultivated in most regions of Iran. This crop is affected by various diseases such as fungal disease each year. Stripe rust, caused by the obligate parasite Puccinia striiformis f.sp. tritici, is one of the most important diseases of wheat (Triticum aestivum L.) in Iran [1-5]. This forma specials infects numerous wheat cultivars, as well as a few barley cultivars and certain grass species [6,7]. This disease, in comparison with the leaf rust (P. triticina) and stem rust (P. graminis f.sp. tritici) pathogens of wheat, the global distribution of P. striiformis f.sp. tritici is more restricted [8]. Stripe rust can severely damage wheat production worldwide [6] and cause yield losses from 10% to 70% and reducing the quality of grain and forage [1,9]. Stripe rust was the dominant wheat disease in Central Asian countries in the late 1990s and early 2000s, accounting for yield losses of 20%-40% in 1999 and 2000 [10]. Stripe rust epidemics in most of the wheat growing-areas of Iran caused over 30% crop loss and estimated grain losses were 1.5 million tons and 1.0 million ton in 1993 and 1995, respectively [1]. On susceptible cultivars, stripe rust can cause 100% yield loss if infection occurs very early [4,7]. Controlling of Stripe rust is done by fungicides or resistant cultivars [6,9,10]. Although fungicides cause a considerably effect in controlling of yellow rust disease, it can’t be used as the only controlling strategy of this disease because of environmental contaminations and high cost in long term [10]. Resistance to fungicides is also another main disadvantage in using the fungicides for controlling this disease [9]. Using the resistant cultivars is the most important controlling approach in increasing the wheat yield [6,11-13]. However, growing resistant cultivars is the most efficient, economical, and environmentally friendly approach to control the disease [6,12]. Two types of resistance have been identified in several cereal-rust pathosystems: Hypersensitive or qualitative (race-specific) and quantitative (race nonspecific) resistance. This type of resistance [3,14] with evaluating the reaction of 415 genotypes to 3 races of yellow rust at seedling and adult plant stage, indicated that most of genotypes are susceptible to all three races at seedling stage, the contrary, most of genotypes had considered resistance to all three races at adult plant stage. Umirov et al. [15] at Uzbekistan with evaluating reaction of 4500 wheat genotypes to yellow rust indicated that 66 genotypes were Immune, 118 genotypes were resistant, and 278 genotypes were moderately susceptible. Foroutan and Ahmadian moghaddam [2] with studying 137 lines of selected resistant wheat from experiments of some areas at 1996- 1997 and 1997- 1998 and further evaluating of them at 1998-1999 at in Mazandaran, Iran. Compound analysis of variance concludes that 33 lines of experiments of 1997- 1998 were resistant to yellow rust in most of examined areas. Torabi et al. [1] with assessing the resistance of wheat advanced lines to some races of yellow rust at seedling stage and by cluster analysis, classified wheat cultivars into three groups. 1; lines which had infection type of 7-9 2; lines which had infection type of 0-3 and 3; lines which had infection type of 4-6. Nazari [5] with assessing wheat lines resistance to three races of yellow rust by measuring relative mean area under disease progress curve (rAUDPC), obtained field resistance to race of 134E134A+ that positive and significant correlation was observed between seedling infection type and rAUDPC to mentioned race. Coefficient of infection is obtained from multiplication of infection percentage (0% to 100%) and host respond to pathogen (I=0,R=0.2, MR=0.4, M=0.6, MS=0.8 and S=1) that were Immune; Resistant; moderately resistant; intermediate resistant; moderately susceptible and susceptible respectively. rAUDPC will be calculable when disease severity is recorded during disease development in several times. Iran is one of the major wheat growing countries in the world [1]. In Ardabil province of Iran where different wheat varieties are grown, table wheat are major productions and play very important role in the provincial agriculture. Due to the importance of yellow rust in the Ardabil and Moghan fields, this study was conducted and completed between 2009 and 2010 to evaluate resistance of different wheat genotypes to strip rust (Puccinia striiformis f.sp. tritici) in order to identify the resistant and moderately resistant genotypes for recommendations to the national and international wheat research centers.

Reaction of 100 wheat genotypes to race 134E134A+ of wheat yellow rust was evaluated in two regions of Ardabil and Moghan for two years (2009 and 2010) in field conditions (Table 1). Field tests were conducted at two locations (Ardabil and Moghan regions) in a Randomized Complete Block Design (RCBD) with 3 replications. Wheat entries were planted in November 2009 (first year) and 2010 (second year) at the rate of 10 g-15 g of seed on two 1 m long rows and spaced 30 cm apart. In this experiment, a susceptible cultivar (cv. Bolani) was planted in a margin and between of each 10 genotypes for spreading disease. Experiment was carried out under field condition and mist irrigation. Besides, artificial inoculation of the nurseries was done by mixing spores with talcum powder using a duster and before of flag leaf emergence. At the flag leaf stage, infection type (IT): R (resistant), MR (moderately resistant), MS (moderately susceptible) and S (susceptible), of each entry was evaluated based on Roelfs et al. [16] method, when disease developed well on susceptible check. The percentage leaf area affected (0-100, disease severity) also scored using the modified Cobb,s scale at the same time. The infection type and disease severity scored each time were used to calculated coefficient of infection (CI) and finally Area Under Disease Progress Curve (AUDPC). For statistical analyzing and mean comparison, MSTATC software was used and for ranking and clustering genotypes, SPSS software was used.

Table 1: Parentage and pedigree of different wheat genotypes under study in Ardabil province during 2009-2010.

In the field assessment, genotypes with disease severity of 0 were placed in Immune group, 0%-5% in resistant group, 5%-10% in moderately resistant group, 10%-30% in moderately susceptible group and genotypes with disease severity of more than 30 were placed in highly susceptible group. According to infection type in Ardabil region, genotypes Alborz/4/k6290914/4036, Azd//top, Gk.zombor/attila, Azd// inia, Bav92, M-70-4//kayson/glen4056, Fin/acc, Munia, Gen/kauz, 40- 71-23//kayson/glenson4044, 40-71-23//kayson/glenson4042, Alborz/4/ k6290914/4039, M-70-4/5/alborz/4/k4051 and Kalyansona/glenson4276 placed in susceptible group. Genotypes Ias58/kal/bow20, Ias58/kal/ bow24, Tajan, Milan159, Ias58/kal/bow25, Pri/bagula/milan, Maya/ falat4210, Sw89.3060/kauz, Oasis/kauz4/113, Ias58/kal/bow17, Maya/ falat4208, Na160/bagula, up/falat, Oasis/kauz4/114, Star2/99, Oasis/ star/3, Pri/bagula, Pri/bagula, Jup/maya4196, Jup/trifon4202, Ias58/kal/ bow18 and 4777//fkn/gb/vf620 placed in resistant group. Other examined genotypes were placed in moderately susceptible group. In Moghan, genotypes 4//kayson/glen4056, M-70-4/5/alborz/4/k4051, R37/gh1, Chil/2/star and Azd//inia were placed in susceptible group. Genotypes Ures/bow4205, Alborz/4/k6290914/4036, Vee”s”/nac// kasyon/genaro.81, Kalyansona/glenson4279, Imbabura, Ias58/kal/ bow25, Chil”s”/cham4, Maya/ures, Shi//4414/vee4224, Chum18, 4777// fkn/gb/angas4087, Shi//4414/hd2169, Pri/bagula, 4777//fkn/gb/ angas4089, Ias58/kal/bow18, Ias58/kal/bow19, Tajan, Pri/bagula, Ias58/ kal/bow24, Pri/bagula/milan, Ias58/kal/bow20, Karawan1/ yamama4108, ald”s”/snb”s”/5/alborz4031, Ures/bow4203 and Ns732.her//darab were placed in resistant group. Genotypes M-70-4//kayson/ glen4056, Kalyansona/glenson4276, Bav92, Munia, Chil/2/star, Batanf96 and Bekele.100 showed susceptibility to yellow rust in both regions. Genotypes Ias58/kal/bow18, Ias58/kal/bow20, Ias58/kal/ bow24, Pri/bagula, Pri/bagula/milan, Sw89.3060/kauz and Pri/bagula showed resistance to stripe rust disease about infection type in both regions. In Ardabil and Moghan regions, Genotypes Alborz/4/ k6290914/4039, 40-71-23//kayson/glenson4042, R37/gh1, Bekele.100, 40-71-23//kayson/glenson4044, Gk.zombor/attila, M-70-4/5/alborz/4/ k4051, M-70-4//kayson/glen4056, Azd//inia, Azd//top, Batanf96, Kalyansona/glenson4276, Bav92, Munia, Chil/2/star and Fin/acc with having coefficient of infection more than 15 belong to susceptible genotypes to yellow rust and it will be excluded from commercial production and using them in improvement programs. Experiments results indicated that in Ardabil and Moghan areas some of genotypes had significant differences in rating resistance. This subject indicates pathogenicity difference of used races and climate difference of Ardabil and Moghan. It shows Moghan with having warm climate can’t be a suitable region for assessing resistance and selection of resistant sources. Genotypes Pri/bagula, 4777//fkn/gb/vf620, Ias58/kal/bow25, Ias58/kal/bow20, Ias58/kal/bow24, Pri/bagula/milan, Ias58/kal/bow18, Sw89.3060/kauz, Chum18, Oasis/kauz4/114, Ias58/kal/bow17, Pri/ bagula, Tajan and Ng8319 had coefficient of infection less than 15 in both Ardabil and Moghan regions so above genotypes will inter to commercial production and will be used in future improvement program (they have better coefficient of infection than control). Similarly, Torabi et al. [1], Foroutan et al. [2], Malihipour et al. [3], Nazari [5], Youssef et al. [17], Ali et al. [18] and Shahin et al. [19] also carried out field assessment of resistance to yellow rust for ranking of genotypes. According to the resistance level based on disease severity along with other resistance parameters, they found that resistance level ranged from very low to very high among the tested genotypes. There wasn’t possibility of comparison one genotype in Ardabil and Moghan regions due to qualitative recording factor in the field. With calculating the average coefficient of infection, that is determined through applying constant for each type of infection at adult plant stage, a genotype reaction can be compared quantitatively in different regions (Ardabil and Moghan areas). In this method for infection type of S, MS, MR, R, and O were considered 1, 0.8, 0.4, 0.2 and 0 respectively. So, for reactions of 50S and 40MS were considered coefficient of infection 50 and 32 (50 × 1 and 40 × 0.8). Although environmental conditions and racial diversity in Ardabil and Moghan regions can affect reaction of examined genotypes, genotypes with coefficient of infection less than 15 will be introduced as suitable genotypes for using in improvement programs for resistance to yellow rust. Results of our study and the differences in the reaction of genotypes to yellow rust disease are in agreement with those of previous studies (McIntosh, [20]; Bariana and McIntosh, [21]; Torabi et al. [1]; Malihipour et al. [3]; Foroutan and Ahmadian-Moghaddam, [2]; Afshari, [4]; Youssef et al. [17]; Wellings and Park, [22]; Herrera-Fossel et al. [23]; Bux et al. [13]; Shahin and Abu El-Naga, [19]). Different researchers studied the reaction of different wheat varieties to stripe rust disease in different countries [11,12,18,24]. Like in our study, the results of their study also showed that different varieties showed variable reactions to the disease and they ranked from immune to highly susceptible. The overall results of this study show that it may be possible to introduce some moderately resistant and resistant domestic wheat varieties to yellow rust disease. These varieties may be used as a genetic source in the development and production of resistant wheat varieties both on national and international scales. Compound analysis of variance indicated that region effect was significant at the 5% level of probability. There is basic and general difference between regions in disease severity. Since yellow rust mainly develops under colder climate with higher altitude, in north latitude and colder years, condition for development and spread yellow rust disease in Moghan is unsuitable than Ardabil. So, genotypes 4777//fkn/gb/angas4089, Shi//4414/vee4223, Chum18, Sw89.3060/ kauz, Karawan1/yamama4108, 4777//fkn/gb/angas4087, Ns732.her// darab, Maya/ures, Imbabura, Chil”s”/cham4, Pri/bagula, Ias58/kal/ bow24, Pri/bagula/milan, Ias58/kal/bow25, Ias58/kal/bow20, Ias58/kal/ bow19, Ias58/kal/bow18, Ures/bow4203, Shi//4414/hd2169, Shi//4414/ vee4224 and Pri/bagula in Moghan region were as Immune but these same genotypes in Ardabil indicated different reaction from sensitivity to resistance. Results of our study and the differences in the reaction of genotypes to Puccinia striiformis f.sp. tritici are in agreement with those of previous studies [1,4,17,18]. Compound analysis of variance indicated effects of cultivar is so significant at the 5% level of probability. There is a significant difference between mean genotypes in Ardabil and mean genotypes in Moghan. Compound analysis of variance indicated interaction of genotype × region is completely significant. It shows that reaction of genotypes in Ardabil and Moghan regions to yellow rust wasn’t equal. It means there is an interaction between genotype and region. Each genotype in both regions had a different reaction to yellow rust. Genotypes Pri/bagula/milan, Star2/99, Oasis/ kauz4/114, Ias58/kal/bow18, Ias58/kal/bow17, Ias58/kal/bow20, Pri/ bagula, Sw89.3060/kauz and Pri/bagula in both regions indicated resistance to Puccinia striiformis f.sp. tritici. Other examined genotypes in both regions showed different reaction to yellow rust. With decreasing of interaction between genotypes and environment, we can distinguish resistant genotypes to yellow rust in both regions. Similarly, Youssef et al. [17] and Shahin et al. [19] also the results obtained demonstrated the superiority of Yr8 at both seedling and adult stages. Susceptible genotypes have higher mean and variance in AUDPC than resistant genotypes. According to Figure 1 in Ardabil, between genotypes, Bolani has the most AUDPC and genotypes Thb”s”ton, Pr1/ bau”s”4191 and Jup/falat have the least one. Genotypes Azd//inia, 40- 71-23//kayson/glenson4044, M-70-4//kayson/glen4056 and Ures/ bow4204 with having moderate resistance can be used to create more stable resistance than other genotypes. Based on Figure 2 in Moghan, between genotypes, Bolani, Azd//inia and M-70-4//kayson/glen4056 have the most AUDPC and genotypes Pr1/bau”s”4191, up/falat, Ures/ bow4204 and Thb”s”ton have the least AUDPC (Table 2). Genotype 40- 71-23//kayson/glenson4044 with having moderate resistance can be used in creating more stable resistance than the others. Comparison of two figures shows genotypes M-70-4//kayson/glen4056 and Azd//inia in Ardabil have middle AUDPC but the same genotypes in Moghan have the most AUDPC. Genotype 40-71-23//kayson/glenson4044 in both regions, according to figures has middle AUDPC. Infection rating of all genotypes was less than Bolani during 2009-2010. Similarly, Wellings [22], Ali et al. [18] and Umirov et al. [15] and the present study demonstrated that infection rate seemed an unreliable estimate of resistance when compared with disease severity, coefficient of infection and AUDPC, because it did not mark some genotypes as having different level of resistance with regard to other parameters. This group comprised genotypes with varying degrees of resistance which has been advocated to be more durable [5,14]. Moreover, lines with acceptable levels of partial resistance restrict the evolution of new virulent races of the pathogen because multiple point mutations are extremely rare in nature [18,19]. Since stripe rust disease caused by Puccinia striiformis f.sp. tritici is a serious disease of wheat around the world, results of such studies may be promising and could be used in the formulation of integrated control strategies for the management of this destructive disease around the world. The results of this study may have practical applications in formulation of disease management strategies for controlling yellow rust in a safe environment. The use of resistant and moderately resistant genotypes to manage different plant diseases including wheat yellow rust can potentially replace or minimize the application of harmful chemical fungicides and could be used as an important component of integrated pest management (IPM) which is a promising approach to a sustainable agriculture.

Figure 1: AUDPC in flag leaf for 8 wheat genotypes to yellow rust in field conditions using Cluster analysis in Ardabil region.

Figure 2: AUDPC in flag leaf for 8 wheat genotypes to yellow rust in field conditions using Cluster analysis in Moghan region.

Table 2: Field reaction and AUDPC different wheat genotypes to yellow rust disease in Ardabil province during 2009-2010.

In general, results of our study and the differences in the reaction of genotypes to yellow rust disease are in agreement with those of previous studies. Results of this study were promising and some immune, resistant, and moderately resistant genotypes to Puccinia striiformis f.sp. tritici were identified and they may be used as a resistance genetic source for management of the disease in national and international programs. In Ardabil, genotypes Oasis/star/3, Ias58/kal/ bow25, Pri/bagula, Ias58/kal/bow20, Pri/bagula, Star2/99, Ias58/kal/ bow24, Pri/bagula/milan, Sw89.3060/kauz, Jup/maya4196, up/falat, Milan159, Ias58/kal/bow17, Jup/trifon4202, Oasis/kauz4/113, Tajan, Maya/falat4210, Na160/bagula, Oasis/kauz4/114 and Ias58/kal/bow18 were placed in resistant group. Genotypes M-70-4//kayson/glen4056, Azd//inia, Munia, Alborz/4/k6290914/4036, N-75-16, Alborz/4/ k6290914/4039, Fin/acc, Gen/kauz, M-70-4/5/alborz/4/k4051, Azd// top, Kalyansona/glenson4276, Gk.zombor/attila, Bav92, 40-71-23// kayson/glenson4042, 40-71-23//kayson/glenson4044 and Ures/bow4204 were placed in susceptible group. The others were placed in moderately susceptible to yellow rust disease. In Moghan, genotypes Vee”s”/nac// kasyon/genaro.81, Shi//4414/vee4224, Sw89.3060/kauz, Shi//4414/ hd2169, Tajan, Chil”s”/cham4, Pri/bagula, Ns732.her//darab, Ias58/kal/bow20, Ias58/kal/bow19, Ias58/kal/bow18, Ias58/kal/bow24, Shi//4414/vee4223, Ias58/kal/bow25, 4777//fkn/gb/angas4087, 4777// fkn/gb/angas4089, Karawan1/yamama4108, Kalyansona/glenson4279 and Chum18 were placed in Immune group. Genotypes Pri/bagula/ milan,Thb”s”ton, ald”s”/snb”s”/5/alborz4030, Imbabura, Gen/kauz, Tajan, ald”s”/snb”s”/5/alborz4031, M-70-4/5/alborz/4/k4048, Bow/nkt, Unknown4067, 4777//fkn/gb/vf620, Oasis/kauz4/114, pvn”s”/cii//nac, Jup/trifon4200, Bualbek/bagula, Maya/falat4211, Maya/bau4215, Pr1/ bau”s”4190 and Ias58/kal/bow17 placed in resistant group. Genotype Azd//inia was placed in susceptible group. The other genotypes were placed in moderately susceptible groups. Wheat yellow rust in Iran has caused significant crop loss and resulted in unprecedented costs in chemical control expenditure in epidemic seasons. It can be anticipated that control measures will be largely based on the development and release of resistant cultivars, although chemical control may have a place in high input/high yield situations in irrigation areas and high rainfall zones. Breeding for resistance will continue to be based on current awareness of variability in Puccinia striiformis f.sp. tritici, the search for and commercial development of new and effective resistance combinations, and the resolve of industry to adopt best management practices that minimize disease risk.