Role of some Factors Affecting Crown Gall Disease Development

Document Type : Original Article

Authors

1 Department of Plant Pathology, Faculty of Agriculture, Cairo University, Giza, Egypt.

2 Plant Pathology Research Institute, Agricultural Research Center, 12619, Giza, Egypt

Abstract

The wounds, its depth and the time of inoculationof Agrobacterium tumefaciens on castor bean )Ricinus communis( plants affecting on the development of apricot crown gall disease whereas, the increase of wound depth and adding the pathogen after directly wounding plants increased the disease severity and gall formation. Where, the highest infection and gall formation resulted from inoculation of A. tumefaciens after directly wounding plants (zero time) at 3mm depth followed by 5mm depth, while the lowest gall formation and disease severity showed when adding A. tumefaciens suspension after 48 hrs. from wounding at one mm depth.
On apricot plants (Prunus armeniaca), The plant hormones indole acetic acid (IAA) and cytokinin (CK) were decreased in the first stage of gall formation, while they were increased in the other stages of gall formation. Gibberellic acid (GA) was decreased in the first stage and then increased but it decreased again in the last stage.
On the other hand, abscisic acid (ABA) inactivation plant hormone showed an opposite result whereas, ABA was increased in the first stage of gall formation and then it was decreased in the other stages of disease. Also, A. tumefaciens isolates obtained from different hosts having different gall index (different in virulence) produced different rates of plant hormones IAA, GA, ABA and CK. But the rate of CK was found to be correlated with virulence. Also, crown gall disease development dependent on the production amount of the three plant hormones (IAA, GA3 and CK) and the ratio between them.
Fertilizers with (NPK) and compost resulted in decrease the severity of crown gall disease on apricot plants whereas; they reduced the number and weight of galls and root gall index in the treated plants compared with control. The best one treatment was (NPK) then (NP) and (NPK plus compost). Fertilizers with (NPK plus compost) due to increase the foliage of plants and in all fertilizer treatments increased the roots of plants compared with control except that treated with (NP). Also, no variation considered in the height of plants in all treatments, but the highest height recorded from (NPK plus compost) treatment. On the other hand, the uptake of (N) was increased in all fertilizers when used (N) alone or in combination with (P or K), also, (P) up take increased when used (P) alone or with (N or K). But (K) up take was increased only when used it with (N) or (P) and in combination with (NPK)

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