| In this thesis, the causes of grapevine chlorotic disease were investigated in Lanzhou eara measures for controlling chorosis and indexes of screening for iron-efficient genotype were studied .The investigation results indicated that chlorotic diseases of grapevine cultivars in Lanzhou region were very severe. Difference in tolerating iron deficiency stress was significant in grapevine cultivars.V.vinifera L have strong tolerating iron deficiency stress, while V.Labrasca.l is low. Different cultivars in the same species groupe have difference in the Fe-deficiency stress response. The degree of chlorosis of the same cultivar is different in the different fertilization soil.Chlorosis causes baurgeon wither of grapevine plants, poor growth and lower or no yield, bad quality of fruit. Grapevine plants that developed severe chlorosis appeared gradually light-mild-severe-more severe chlorosis leaves. Compared with normal leaves, the chlorophyll content and photosynthesis of chlorotic leaves significantly decreased. The stomatal conductance of chlorotic leaves did not obviously correlate to the degree of chlorosis. A large number of florescence of severe chlorotic Zizhenxiang and Fujiminori plants dropped and fruit set ratio decreased.The studies showed some factors that effected on grapevine chlorosis.Soil pH value: the pH value was over 7.5 in the grapevine fields, so soil was the alkaline or calcareous soil. The rhizosphere grapevine plants had reducing capacity, the more the chlorotic rate increased, and the more the rhizosphere pH value decreased.The type of iron of soil: The soil total iron content was 6790mg/kg, the active iron content was only 6.81mg/kg,it cannot satisfy the iron need of plants. The essential cause of iron nutrition deficiency lie in that soil soluble iron cannot satisfy the need of plants.Vultivars and chlorosis: The active and total iron content of different grapevine cultivars gradually increased from young leaves to old leaves, especially young leaves of severe chlorotic plants, the active iron content was remarkably lower than that of normal plants, while the total iron content of all plants had not obvious regularity, so it neither react to degree of chlorosis nor be a index of chlorosis. The active iron content of leaves positively correlate to degree of chlorosis and chlorophyll content, it can be a reference index to screen Fe-efficient grapevine genotype.Graft and chlorosis: Many seedlings of branch grafting and all seedlings of hard twig cutting did not appear chlorotic disease at the initial growth stage. Seedlings of green grafting that winegrapevine cultivars grafted on 520A disapeared chlorosis, when Zizhenxiang and Rizamat mutually grafted, leaves of scion appeared mild chlorosis. Several Fe-efficiency cultivars respectively grafted on Benizuiho, with growth of scion, twigs appeared different degree of chlorosis. These related to absorption of iron of different cultivars and rootstocks and transportation of iron and other nutrition substance at healing site. To control chlorosis, Fe-efficiency rootstocks are screened and used in production.Experiments were conducted to correct chlorosis by spraying iron fertilization on leaves and drenching iron fertilization into root. Results showed that the effect of foliar spraying simple FeSO4 was not obvious, the effect of spraying compound iron fertilizer on leaves was better, chlorotic leaves recovered green rapidly, but they appeared chlorosis again. The best effect was obtained by combining spraying with soaking root. Based on above results, proper use of organic matter to decrease soil pH value are important measures to improve and remain Fe availability in soil. After correcting chlorosis, the chlorophyll content and active and total iron content of all slight and severe chlorotic leaves increased, especially those of young leaves of chlorotic plants significantly increased.Cutting root soaked in the red iron fertilizer liquid. Iron was actively uptaked by cutting root through transpiration in plant.
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