الفهرس 
CHAPTER IOnly 14 pages are availabe for public view
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Abstract
Barley, Hordeum vulgare L., is one of the principal cereal crops in the world. It was the fourth most important cereal crops both in terms of quantity produced and global area of cultivation. Net blotch disease caused by the ascomycete fungus Pyrenophora teres f. teres is one of the most widely distributed foliar diseases of barley as it cause yield losses due range from 10% to 40%, but in some highly susceptible cultivars losses close to 100 %. In Egypt, barley is the main crop and widely grown in the rainfed areas of the north coastal region and in the newly reclaimed lands under rainfed conditions such as the North west Coast (NWC) and a little is grown irrigated in the Nile Valley. The aim of this work was to study the pathological and biochemical indicators of barley cultivars to increase tolerance against net blotch disease that was an important factor limiting growth in NWC (Maryout) using Giza 2000, Giza 132 and foliar applications of SA, Eth, DNB, IAA, HP, PA and Si. Our results indicated that: I ) Pathological indicators : 1. Disease incidence and disease severity. The minimum mean percentage of disease incidence was achieved by SA at 200 and 400 ppm after the 1st foliar application by Giza 132, but the minimum mean percentage of disease severity was obtained at 100 and 200 ppm by the same cultivar. After the 2nd foliar application, the minimum mean percentage disease incidence and disease severity were recorded by Giza 132 at 400 ppm. Giza 132 gave lower mean values than Giza 2000 in disease incidence and disease severity after the 1st foliar application. The lowest mean percentage of disease incidence was achieved when Eth applied at 100 ppm by Giza 132 after the 1st foliar application, but after the 2nd foliar application, the lowest mean percentages of disease incidence and disease severity were obtained at rate 400 ppm by the same cultivar. Giza 132 is less than Giza 2000 in disease incidence and disease severity after the 1st foliar application. However, after the 2nd foliar application Giza 132 is less than Giza 2000 in disease severity. The minimum mean percentage of disease incidence after the 1st foliar application was achieved when DNB applied at 200 ppm by Giza 2000, but the minimum mean percentage of disease severity was achieved by Giza 132 at 100 and 200 ppm. After the 2nd foliar application, the lowest mean value of disease incidence was recorded at 400 ppm DNB by Giza 2000, while the same value of disease severity was recorded by Giza 132 at 100 and 400 ppm. Giza132 explored lower mean values than Giza 2000 in disease severity after the 1st and 2nd foliar applications. IAA at 200 ppm gave the minimum mean values of disease incidence by Giza 132 after the 1st foliar application, but the minimum mean value of disease severity was obtained at 100 and 200 ppm by the same cultivar. After the 2nd foliar application, all doses of IAA recorded the minimum mean percentage of disease incidence by Giza 132, however the minimum mean percentage of disease severity was achieved at 150 ppm by the same cultivar. Giza 132 was lower than Giza 2000 in disease incidence and disease severity after the 1st and 2nd foliar applications. The lowest mean percentage of disease incidence was achieved by Giza 132 after application by HP at all doses, but the minimum mean percentage of disease severity was obtained by Giza 2000 at 16 ppm and Giza 132 at 8 and 24 ppm after the 1st foliar application. While after the 2nd foliar application, Giza 132 gave the minimum mean percentage of disease incidence at 16 ppm, but the minimum mean percentage of disease severity was achieved at 24 ppm by Giza 2000 and at 8 ppm by Giza 132. Giza 132 is less than Giza 2000 in disease incidence after the 1st and 2nd foliar applications, while G132 was less than Giza 2000 in disease severity after the 2nd foliar application. PA showed a positive role in decreasing disease incidence and disease severity after the 1st and the 2nd foliar applications. Giza 132 is less than Giza 2000 in disease incidence, after the 1st foliar application, but after the 2nd foliar application Giza 132 took the reverse trend . Concerning the disease severity, after the 2nd foliar application, Giza132 was lower than Giza 2000. Application of Si at 400 and 600 ppm after the 1st foliar application recorded the minimum mean percentage of disease incidence by Giza 132, while the minimum mean percentage of disease severity was achieved at 600 ppm by the same cultivar After the 2nd foliar application, the minimum mean percentage of disease incidence recorded by Giza 132 at all doses of Si, but the minimum mean percentage of disease severity was achieved at 600 ppm by Giza 2000 and at 200 ppm by Giza 132. Giza 132 explored lower mean values than Giza 2000 in disease incidence and disease severity after the 1st and 2nd foliar applications. 2. Mycological parameters of (pyrenophora teres f. teres). The mycological characters that include (spore length, spore width, number of septa, length of germ tube a n d number of germ tubes) of the P. teres spores of cultivars Giza 2000 and Giza 132 have been detected. SA recorded the lowest mycological characters of the pyrenophora teres f. teres at 100 and 200 ppm for Giza 2000 and at 400 ppm for Giza 132. Application of Eth decrease the mycological characters of the pyrenophora teres f. teres at 200 and 400 ppm for Giza 2000 and at 400 ppm for Giza 132. The minimum values of mycological characters were obtained when DNB applied at 400 ppm for Giza 2000, while Giza 132 at 100 and 400 ppm recorded the same value. IAA decreased the mycological characters at 150 and 200 ppm for the two cultivars. Foliar application with HP decrease this characters, where the lowest values were obtained at 24 ppm for Giza 2000, but all doses of HP recorded positive effect on Giza 132. PA at 20 and 60 ppm achieved the lowest values for the two cultivars. The lowest mycological characters of pyrenophora teres f. teres were obtained after application by Si at 400 and 600 ppm for Giza 2000 and at 600 ppm for Giza 132. II) Growth parameters, yield and yield components: 3. Growth parameters . The highest mean values of plant height and fresh and dry weights were achieved by 400 ppm SA. The superior values of RWC was recorded by 200 ppm SA after the 1st and 2nd foliar applications. After the 1st foliar application, the highest mean value of plant height was given by Eth (400 ppm). Eth at (200 ppm) enhanced fresh and dry weights. The superior value of RWC was obtained at 100 ppm. After the 2nd foliar application, the maximum mean values of plant height and fresh weight were recorded by 100 ppm Eth. The highest mean value of dry weight was achieved by 200 ppm Eth. DNB (400 ppm) gave the highest mean value of plant height. DNB at 200 ppm gave the highest mean value of fresh weight after the 1st foliar application. After the 2nd foliar application, the highest results for plant height and fresh and dry weights were obtained at 100 ppm DNB. The maximum mean values of plant height and RWC were obtained by 100 ppm IAA. The highest mean value of dry weight was recorded by 150 ppm IAA, after the 1st foliar application. After the 2nd foliar application, IAA treatment at (100 ppm) enhanced plant height. The superior mean value of fresh weight was achieved at 150 and 200 ppm IAA. The highest mean value of dry weight was obtained at 150 ppm IAA. After the 1st and 2nd foliar applications, the highest mean values of plant height and fresh weight were recorded by HP (16 ppm). The superior values of dry weight was obtained by HP (8 ppm). The highest mean values of plant height and fresh weight were achieved by PA at 20 ppm after the 1st and 2nd foliar applications. The maximum mean values of dry weight were obtained at 20 and 60 ppm PA, respectively after the 1st and 2nd foliar applications. The superior value of RWC was recorded by 60 ppm PA, after the 1st foliar application. After the 1st and 2nd foliar applications, the superior mean value of plant height was obtained by 400 ppm Si. The highest mean values of fresh and dry weights were achieved by 200 ppm Si. The maximum mean value of RWC was recorded by Si at 200 ppm after the 1st foliar application. 4. Yield and yield components: Determination of yield and yield components are very important to study the ability of the two barley cultivars to resist net blotch disease after foliar application by some chemical inducers comparing with control plants (without foliar application). Data showed that SA at 400 ppm recorded the highest mean values of grain yield by Giza 132, but the highest mean values of plant height was achieved by Giza 2000 at 200 ppm. Data also showed that Giza 132 exceeded Giza 2000 in grain yield and plant height. Data also showed that foliar application by Eth (400 ppm) gave the highest mean values of grain yield by Giza 132, but the superior mean values of plant height and straw yield were recorded at 200 ppm by Giza 2000. Also, DNB at (100 ppm) increased grain and straw yield in Giza 132 and Giza 132 exceeded Giza 2000 in straw yield and plant height.