الفهرس 
Wheat: Importance and ProductivityOnly 14 pages are availabe for public view
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Abstract
Leaf rust of wheat (Triticum aestivum L.) caused by Puccinia triticina is considered one of the most serious diseases in Egypt and worldwide. This disease has become a very dangerous on most of the currently used varieties because of their susceptibility to the disease. Plant Diseases are usually controlled by using resistant cultivars and application of synthetic fungicides. Owing to the breakdown of plant resistance by the new races leaf rust fungus, in addition to, the negative impacts of chemical fungicide on health and environment, alternative methods for reducing fungicides are being developed such as plant extracts. Therefore, the present study was conducted to investigate their potentiality to induce wheat resistance against leaf rust disease or their direct effect, alone or in combination with fungicide, on Puccinia triticina. The First Experiment The in vitro experiment was conducted to investigate the effect of the aqueous and methanol extracts of seven plant species (leaves of acalypha, basil, blue gum, chinaberry, henna and lantana and fruit peel of pomegranate) on the urediniospore germination of P. triticina (the causal fungus of wheat leaf rust). Results indicated that, the most effective treatments were the methanol extracts of acalypha, lantana and henna at 3500 ppm with IC50 values of 1906, 1906 and 2085 ppm, respectively. In addition, the most effective water extracts were chinaberry and lantana with IC50 values of 2205 and 2221 ppm, respectively. However, the aqueous and methanol extracts of all plant species, except for basil and blue gum, significantly reduced the urediniospore germination of P. triticina at a different extent and the inhibition percentage was dose-dependent. Thus, these extracts were used to induce wheat resistance or to control leaf rust disease in the second and the third experiments, respectively under field conditions. The Second Experiment Under field conditions, the aqueous and methanol extracts of five plant species (leaves of acalypha, chinaberry, henna and lantana and fruit peel of pomegranate) were applied as foliar spray at concentration of 1% prior inoculation with P. triticina to induce wheat resistance against leaf rust disease. Results revealed that, all foliar spray with plant extracts at 1% and fungicide at 150 mg/l significantly decreased disease severity, indicated by ACI %, and increased the concentration of total chlorophyll and total phenolics as well as the activity of antioxidant enzymes (POX and PPO) compared with non-treated control. Moreover, the exogenous treatments significantly improved growth, yield and yield-related traits over control. Lantana water extract and the acalypha methanol extract were the most effective treatments in reducing ACI by 95% over control that superimposed the effect of fungicide (94% reduction over control). Moreover, the aqueous extracts of henna and chinaberry as well as the methanol extracts of pomegranate, lantana, and henna significantly reduced ACI by 91, 89, 92, 89, and 89%, respectively over non-treated control. Similarly, the maximum increase in total chlorophyll (161 and 153%) and total phenolics (617 and 618 %) over control were obtained by foliar spray with the aqueous extract of lantana and the methanol extract of acalypha, respectively. The activity of antioxidant enzymes including peroxidase (POX) and polyphenol oxidase (PPO), in response to all treatments, were increased at the 1st day after treatments (DAT) and reached their maximum activity at the 3rd DAT, then declined to their lowest activity at 15th DAT. The activity of POX and PPO was more prominent over nontreated control owing to the application of water extracts of lantana and henna as well as methanol extracts of acalypha and pomegranate. The highest increases in plant height (31 and 32%), spike length (24 and 22%), 1000-grain weight (86 and 84%) over control were obtained by lantana water extract and acalypha methanol extract, respectively. While, the maximum increase in the number of grains per plant (22, 20 and 18%) over control was recorded by foliar spray with the methanol extracts of chinaberry, acalypha and pomegranate, respectively. Interestingly, the grain yield per plant increased by more than 100% over control in response to foliar spray with the methanol extracts of acalypha (120%), pomegranate (115%) and chinaberry (106%), as well as the aqueous extracts of lantana (109%), chinaberry (108%) and henna (100%). Moreover, the maximum increase in crude protein (33%) over control was achieved by lantana water extract followed by pomegranate water extract (23%), fungicide (22%), and the methanol extracts of lantana (17%) and acalypha (11%). It is worthy to denote that, the leaf rust disease had a high negative impacts on spike length, grain yield, plant height and grain weight. While, the number of grains per plant and grain quality indicated by the crude protein (%) were slightly affected by leaf rust disease. The Third Experiment This experiment was conducted to investigate the potential of individual application of the aqueous and methanol extracts of plant species including the leaves of acalypha, chinaberry, henna and lantana and the fruit peel of pomegranate at 5%, fungicide (Fungshou) at its recommended dose (150 mg/l), and their mixtures at the rate of 1:1 (v/v) to control leaf rust disease of wheat under field conditions. The plant extracts, fungicide and their combinations were sprayed on wheat leaves after inoculation with P. triticina. The first spray was applied after the appearance of leaf rust symptoms and the second spray was applied after 15 days from the first one. The effect of the number of sprays on disease severity (ACI %), yield, yield components and crude protein (%) of wheat grains was investigated. Results revealed that, ACI (%) was significantly decreased in wheat plants sprayed twice with all treatments compared with plants sprayed once. While, 1000-grain weight, grain yield and crude protein (%) were significantly increased in plants sprayed twice after artificial inoculation with P. triticina. While, number of grain per plant was not significantly affected by the number of sprays. Thus, the present study focused only on the effect of two sprays with plant extracts, fungicide and their mixtures on ACI (%), yield, yield components and crude protein (%) of wheat grains. The individual application of the recommended dose of fungicide attained the highest decrease in ACI (93%) over control, while the maximum decrease in ACI (74%) over control was obtained by the individual application of the water extracts of chinaberry, henna and lantana and methanol extract of acalypha. In regard to combination treatments, the maximum reduction in ACI (87% over control) was recorded by the fungicide mixture with lantana water extract, followed by 82% that was achieved by the mixtures of fungicide with water extract of henna and the methanol extracts of acalypha and pomegranate. It is worthy to denote that, these mixtures had significant effects in deceasing ACI (%) similar to that was obtained by the individual application of fungicide at 100% of its recommended dose. All foliar spray with plant extracts, fungicide and their mixtures significantly improved grain yield, number of grains per plant, 1000-grain weight and crude protein in wheat grains in comparison with control. Concerning with individual applications, the highest increase in grain yield over control was 86% that obtained by acalypha methanol extract, followed by 82% that achieved by lantana water extract. The increase in grain yield was more pronounced due to the combination treatments with maximum increase of 101% over control that was achieved by the mixtures of fungicide with acalypha methanol extract and lantana water extract. Similarly, the application of fungicide mixture with lantana water extract and acalypha methanol extract led to the maximum increase in the number of grains per plant (26%) and 1000-grain weight (60%). While, the highest increase in crude protein (36 and 33%) over control was achieved by the mixture of fungicide with the methanol and water extracts of pomegranate peels, respectively. As in the second experiment, leaf rust disease negatively affected the grain yield and grain weight slightly affected number of grains per plant and crude protein in wheat grains. HPLC analysis of the aqueous and methanol extracts of acalypha and lantana indicated that, these extracts contain a wide array of phenolic compounds and flavonoids. The flavonoid rutin was the dominant phenolic compound in the methanol extracts. The major phenolic compounds in the water extracts of acalypha and lantana were gallic and rosmarinic acids, respectively. In addition, the acalypha methanol extract was characterized by chlorogenic and p-coumaric acids, while lantana water extract was characterized by Kaempferol, ferulic and sinapic acids.