الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
Wheat (Triticum aestivum L.) has been considered the first strategic food crop for more than 7000 years in Egypt. It has maintained its position during that time as the basic stable food in urban areas and mixed with maize in rural areas for bread making. Wheat loose smut caused by Ustilago tritici ranked the second serious disease following rusts. The losses of wheat yield were ranged between trace to 5% on the local and Indian cultivars.
The pathological studies concerned with chemical, varietal and genetic control of wheat loose smut were carried out at Gemmeiza Research Station during 1998/99 and 1999/2000 growing seasons. The items of the present study included evaluation of certain systemic fungicides on spore germination, its phytotoxicity on root and shoot system of wheat seedlings and the effect of these fungicides on seed germination, disease incidence as well as grain yield. Fifteen of old and new released Egyptian wheat cultivars were evaluated to artificial inoculation to identify those that posses any forms of resistance using embryo test technique, relation between disease incidence and grain protein, total content, field expression and effect of loose smut on some agronomic traits. Genetic study deals with inheritance of wheat loose smut using 4 susceptible Egyptian wheat cultivars and 2 leaf and stem monogenic lines showed resistant reaction .The obtained results could be summarized as follows:
1-All the tested fungicides showed significant inhibition to loose smut teleutospores comparing with the control except with 5 ppm. The fungicide Diniconazole- 2FL gave 100%inhibition at 100 ppm while, Thiophanate-methyl, Benalaxyl and Propineb showed complete inhibition at 750 ppm. 2-Concerning phytotoxicity of the tested fungicides, the obtained data gave evidence that the fungicides Vitavax-200, Thiophanate-methyl, Benalaxyl and Propineb showed the highest values of IC50 and could be used safety at relatively high concentrations. On the contrary, Diniconazole- 2FL, Diniconazole- 5EC and Triticonazole showed the lowest IC50 values and must be used at lower
concentrations.
3-The obtained data revealed that all the tested fungicides at the recommended dose had no effect on seed germination which percent of germination ranged from 98.57% to 100 % comparing with the control.
4- The results clear that the fungicides Diniconazole- 2FL, Triticonazole, Diniconazole- SEC and Vincit—P respectively were the best in increasing grain yield/row. While Thiophanate-methyl, Flutviafdol-thiabemdazole, Diniconazole- 5EC and Diniconazole- 2FL respectively gave the highest values of 1000-grain weight.
5-Embryo test technique enabled us to detect the dormant mycelium of Ustilago tritici before sowing and this procedure has an important role for saving time and efforts. a-The obtained results indicated that all the tested cultivars showed susceptible reaction ranged from 16- 58 % and 18-70 % in 1998 / 99 and 1999 /2000 respectively.
b-The cvs Sakha-61, Gemmeiza-3, Sakha-92, Giza-164 and Sakha- 69 showed the highest percentage of infected embryos. While the cultivar Sakha-8 was moderately susceptible since showed 16-18 % during the two seasons.
c-The cultivar Giza-155 is considered to be resistant under artificial inoculation (4-6 %).6-The results concerning with the effect of loose smut infection on grain protein and total carbohydrate content showed adverse response as follow:
a-Protein content of the inoculated grains of all the tested cultivars increased (Av. = 12.05 and 12.01 %) during the two years over the healthy grains (Av. =10.68 and 10.71%). b-The percentage of protein increase in the inoculated grains was varied according to the cultivar and disease incidence. c-The total carbohydrate in the inoculated grains of the tested cultivars was decreased (Av. = 82.37 and 82.23%) in 1998/99 and 1999 /2000 respectively, comparing with the healthy grains (Av. = 84.34 and 84.27%). The highest reduction was noticed in the cultivars Gemmeiza-3, Sakha-61 and Sakha-92.
d-Values of 1000-grain weight showed significant difference between the inoculated and healthy grains of the tested cultivars. The percentage of reduction in the inoculated grains ranged from 20.66 to 51.60% in 1998/99 and 16.97 to 51.37 % in 1999/2000.
7-The obtained results clear that all the tested fungicides decreased percentage of disease incidence. The fungicides Sumi—eight 2FL, Premis, Vincit—P and Sumi—eight SEC respectively, are considered the most effective in controlling loose smut during the two growing seasons as compared with the other ones.
8-The obtained results gave evidence that the situation of the tested cultivars under artificial inoculation as follow: a-The cultivar Giza-155 was immune and considered a good source of resistance to loose smut under the Egyptian conditions.
b-The cultivars Sakha-8, Giza-162, 165, 168 and Gemmeiza-1 are considered moderately resistant.c-The cultivars, Sakha-61, Gemmeiza-3, Sakha-92, 69, Giza 164, Gemmeiza-5, Giza-163, 167 and 160 were susceptible to loose smut.
9-The agronomic traits of the tested cultivars were affected by loose smut infection since showed a reduction as compared with those of the healthy plants i.e., number of tillers/plant, plant height and grain yield/row.
10-The obtained results revealed a high relation between spike length distance between spikelts and loose smut infection. The cultivars with compact spikes were the most resistant and vice versa.
11-The results showed that highly significant differences for loose smut incidence among the studied parents .
12-The GCA /SCA ratio revealed the importance of additive gene action in the inheritance of loose smut resistance .
13-The best general combining for loose smut resistance were Lr 19 , sakha 61 and sakha 69.
14-The cross L.r.19 x Giza 163 was the best among the tested crosses for resistance to loose smut .