FIELD ASSESSMENT OF REACTION AND YIELD OF SOME BARLEY GENOTYPES UNDER NATURAL INOCULUMS OF RHYNCHOSPORIUM COMMUNE

Kaivan Karimi¹, Mohammad S. Khaledian^2
1 Young Researchers and Elite Club, Qorveh Branch, Islamic Azad University, Qorveh, Iran
² Department of Agronomy, Agricultural and Natural Resources Research Center of Kurdistan, Sanandaj, Iran

ABSTRACT

Barley scald caused by Rhynchosporium commune is known as one of the most deleterious diseases on barley all over the world, especially in the Middle East including Iran. Barley genotypes screening against this disease is an efficient way to find the more tolerant pedigrees. For this purpose, a field experiment was designed at Ghamlou station in the Kurdistan province of Iran during 2013 and 2014, and reaction of twenty four lines and commercial cultivars were evaluated under natural inoculums of R. commune. Based on our results, the genotypes had different reactions compared with each other during both years of experiment. Disease severity rate in 2013 was higher than in 2014, while reactions of some genotypes showed a positive correlation. All genotypes in 2014 had higher yield than in 2013. It appears that different reaction of the genotypes during these both years was in association with meteorological fluctuations such as rainfall rate. Finding resistant or tolerant genotypes to scald disease and compatible to specific areas along with their extensive cultivation lead to obtain the most adapted and yielding cultivars.

Key words: Hordeum vulgaris, Scald, Disease incidence, Screening.

INTRODUCTION

Barley (Hordeum vulgaris L.) as one of the most strategic crops is globally grown on 50 million hectares and with about 15 million tones production is ranked as the fourth crop among cereals [2]. In Iran, similar to other regions where barley is widely grown, the fungal pathogen Rhynchosporium commune (formerly known as R. secalis) [23] is a major and serious pathogen on barley which causes scald or leaf blotches. Yield reduction caused by scald disease ranging from 1 to 19%, sometimes can reach up to 40% in presence of susceptible cultivars. However, in Iran yield losing is occasionally occurred around 35% on barley landraces and can reach 65% in epidemic years [4, 6, 7].

Grain quality can also be affected that leads to discounted prices for quality uses, such as malting [5]. Scald is particularly destructive where favorable environmental conditions exist and barley is continuously cultivated such as in West Asia, central and southern parts of North Africa, the highland regions of Peru, Nepal, large areas in Eritrea, Ethiopia and Middle East including Iran [1, 6]. The occurrence of scald is enhanced through continuous cultivation of barley, barley–fallow rotations and the cultivation of susceptible varieties over large areas [21]. In Iran, scald disease is currently a main constraint of barley production as a result of intensive crop cultivation and favorable environmental conditions that are basic factors to disease development [6]. Various control operations are currently applied by growers to control and manage scald disease in growing areas including crop rotation, chemical fungicides and removing of infected debris. But due to high costs of cultural practices, environmental deleterious impact of chemical fungicides and advent of new pathotypes of pathogens against them, the development of resistant or tolerant barley genotypes to scald is considered to be the most economical way for management of this disease [3]. Nowadays, there is an urgent need to improve barley varieties that are capable of adaptation to certain environments, responsiveness to fertilizer, early maturity and the possession of durable resistance [20]. All these relevant options have encouraged many studies to be carried out in relation to assay of different barley genotypes against scald disease [10, 16, 20, 24]. With regards to the above mentioned aims, our objective in present study was to evaluate and screen some cultivars and lines against scald disease and introduce suitable genotypes to environmental condition of the Kurdistan province in Iran.

METHODOLOGY

Genotypes and growing area
Barley genotypes including twenty two lines and two cultivars (Abidar and Sahand) were provided through Dryland Agricultural Research Institute (DARI) in Maragheh of Iran; which had been selected among advanced nurseries. Ghamlou station (35° 11´ N lat; 47° 29´ W long and 1910 m altitude) with suitable conditions (a hot spot for scald) in the Kurdistan province near the Gorveh city was selected to plant genotypes due to presence of R. commune natural inoculums.

Field experiment
In field, experimental plot consisted of small patches (6 m × 0.875 m) and barley seeds were sown in six lines so that each line had six m long with 17.5 cm space between them. According to genotypes numbers and three replications to each genotype; plot was divided to seventy two patches (Fig. 3 A, B). In autumn, after the first rainfall, along with sowing, nitrogen (100 kg/ha) and phosphate (40 kg/ha) fertilizers were added to experimental plots. Removing weeds was manually and chemically carried out during growing seasons. All experimental and cultural operations were repeated in both consecutive years in 2013 and 2014. Disease severity rate was visually recorded using disease index recommended by Saari and Prescott (1975) [17] (Tab. 1) and grain yield data were calculated in late of June each crop growing season. Grain yield was calculated by weighting grains [g per patch] for each patch. Meteorological data including average relative humidity [%], days below zero, rainfall [mm] and average temperature [°C] were collected for each month during both years experiment (Tab. 2).

Statistical analysis
Experiments  were  designed  as  a  completely  randomized design  (CRD)  with  three  replications and  all  analyses  were conducted  using  the  SAS  software  (SAS  institute,  Inc., 2003). The means were compared by Least Significant Difference (LSD) at P ≤ 0.05. Excel program were used to draw the charts.

RESULTS

ANOVA analysis of the results obtained from both years showed that disease severity rate of scald on genotypes were significant between genotypes in 2013 (F = 1.93; df = 23; p = 0.0279) and 2014 (F = 5.88; df = 23; p<0.01) (Tab. 3). Disease severity rate of genotypes in 2013 and 2014 exhibited that the lineUznoKazaKestan/4/4679/105//YEA132TH/3/Pamir-168 had the lowest disease severity, while the rest of genotypes did not show any significant difference in terms of disease severity (Tab. 4).

According to disease index, genotypes reaction was ranged from 4 to 7.66 in 2013 (from susceptible to moderately resistant) (Fig. 1; Tab. 4) while in 2014 was ranged from 0.33 to 4 (from immune to moderately resistant) (Fig. 1; Tab. 4). The majorities of genotypes in 2013 and 2014 were ranked as moderately susceptible and resistant respectively (Fig. 2). The most susceptible lines in 2013 and 2014 were 72565 and Schuyler//Alpha/Durra/3/Radical IRB-003-004-Omh-Omh-Omh-Omh-1Mh respectively (Tab. 4) and the most resistant line in both years was UznoKazaKestan/4/4679/105//YEA132TH/3/Pamir.

Typical symptoms of scald disease were observed during both years, but flag leaf and spike infection were only observed in 2013, so that symptoms development rate was reached up to the middle parts of the plants and appeared as foliage infection (Fig. 3 C, D, E and F).

Data analysis of grain yield revealed that there was no significant difference between genotypes in 2013 and 2014. However, grain yield rate in 2014 was higher than in 2013. The maximum grain yield was recorded to 72550 and Sahand/Radical  IRB-003-003-omH-Omh-Omh-Omh-2Mh in both years of 2013 and 2014 respectively. Contrary, the minimum grain yield was observed to Uzno-Kazakestan/3/Antares/Ky63-1294//CWB117-77-9-7 and 2550.333 lines in 2013 and 2014 respectively (Tab. 5). The comparison of correspond genotypes in both years examination revealed that the genotypes of Sahand/Radical  IRB-003-003-omH-Omh-Omh-Omh-2Mh and Uzno-Kazakestan/3/Antares/Ky63-1294//CWB117-77-9-7-ICBO3-1859-OAP-OMh-OMh-Omh-2Mh in 2014 had the most yield by 47 and 45% compared with 2013 respectively (Tab. 5).

DISCUSSION

From the viewpoint of virulence, the different strains of R. commune from various regions of world are known to be varied in many cultivated areas especially in Middle East including Iran [1, 6]. Therefore, screening genotypes against this pathogen in different regions, where barley is extensively grown, can be an efficient method for selection and isolation of potential genotypes in terms of adaptation to the region and resistance to the local pathotypes of pathogen. In the present study, some lines and cultivars were assessed against R. commune, the causal agent of scald disease in the Kurdistan province of Iran [4], in order to find suitable genotypes for introduction. In 2013, the disease severity mean was found to be high and total mean of infection severity was 6.4 based on recommended index (Fig. 1; Tab. 3). This was likely to be rainfall rate in spring season (Tab. 2), while in 2014 infection severity rate was low (2.4) (Fig. 1; Tab. 3). In both years, the genotypes were mostly categorized as moderately susceptible (MS) and moderately resistant (MR) respectively (Fig. 1, Tab. 3). Compared to 2014, scald symptoms were observed on flag leaves and spikes in 2013 (Fig. 3F) which was probably in association with favorite condition like rainfall rate (Tab. 2) which is a major factor to disease development. Grain yield analysis showed that there was no significant difference between genotypes during both years, although in 2014 all genotypes had higher yield than in 2013 (Tab. 5). Yield reduction in 2013 was probably related to high disease severity which occurred over the experimental plot. In general, it seems that in line with disease severity reduction in 2014, grain yield rate was increased, so that all genotypes had higher yield. The grain yield of both genotypes Sahand/Radical IRB-003-003 and Uzno-Kazakestan/3/Antares/Ky63-1294//CWB117-77-9-7 reached up to 47 and 45% respectively.

Although, infection severity between two consecutive years was different but reaction of some lines and cultivars against pathogen showed positive correlation based on recommended index for scald disease. For example, in our experiments in 2013, the reaction of UznoKazaKestan/4/4679/105//YEA132TH/3/Pamir-168line indexed as moderately resistant while in next year it was recorded as immune which showed more fitness compared with other genotypes in the same year. This shows real reaction of genotypes versus scald’s pathogen. Such similar results have been reported in other studies by Cromey et al. [8] and also on other crops against different pathogens such as wheat genotypes reaction to common and dwarf smut pathogens [9, 13]. However, discrepancy concerning genotypes reaction can be directly related to spatial and temporal situations. For instance, some genotypes including CDC Dolly, Ac Harper, Kasoata, Maahigan and Seebe with acceptable tolerance in a specific environment (place / year) did not show similar reaction in other environments necessarily. Also CDC Dolly cultivar, with highest cultivation in wide areas in Canada and having acceptable field resistance against scald’s pathogen, in the first year of its cultivation in Mexico showed quite susceptibility [18, 19]. Such reaction has also been noticed in other studies [1, 11, 12]. Totally, based on varied reactions of barley genotypes in different spatial and temporal patterns [10, 18, 19] and with regard to demonstration of genetic differences and lack of gene flow between some pathogen populations in different regions [15], it is necessary to note that screening processes must be limited to specific regions and genotypes reaction must also be evaluated against local populations of R. commune. However, weather condition including factors such as temperature, dew period, humidity and light density may affect on pathogen’s fitness [14].

CONCLUSION

According to the results of present study, it appears that genotypes screening versus scald’s pathogen should be examined in consecutive years in different regions. In general, because of changeability and permanent evolutionary pressure of avirulence genes among pathogen populations and possibility of the advent of corresponding resistant genes to avirulence genes [22], screening program may be an effective procedure for finding novel sources of resistance and the application of them in breeding programs.

Acknowledgments

Authors are thankful to Agriculture and Natural Resources Research Center of Kurdistan and Dryland Agricultural Research Institute (DARI) of Maragheh in Iran for providing experimental field and genotypes.

REFERENCES

Accepted for print: 9.10.2016

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.