Protection methods

The bacterial spot , as many bacterial diseases, is very difficult to control preventively , but especially once this s disease was reported in a parcel. There are many methods of protection that are common to Bacterial Speck .

When symptoms are observed in a tomato plot during cultivation, it is unfortunately too late to intervene effectively. We do not have very effective measures to prevent the development of this bacteriosis.

Note, however, that the intensive use of copper and certain antibiotics, especially in nurseries, has led to the emergence of strains of Xanthomonas copper-tolerant in several states of the United States and in Mexico, Brazil. For example, in the latter country, resistance to this compound and to an antibiotic, streptomycin sulfate, has been detected at varying frequencies depending on the species in X. gardneri, X. axonopodis pv. vesicatoria and X. vesicatoria . Furthermore, many strains of X. euvesicatoria are believed to be copper tolerant.

As in the case of speckling, special attention should be paid to the quality of the seeds . These can be disinfected according to procedures which can be consulted in the sheet Pseudomonas syringae pv . tomato .

In addition, two sources of resistance to X. axonopodis pv. vesicatoria have been reported in the genus Lycopersicon . These resistances materialize by a hypersensitivity reaction to certain strains:
resistance to race T1 from cultivar Hawaii 7998 and conferred by 3 genes, “ Rx1 ”, “ Rx2 ” and “ Rx3 ” (let us point out in particular the recent description of the lines Ohio 9834 and Ohio 9816 partially resistant to race T1);
a second resistance obtained from Lycopersicon pimpinellifolium ( PI 128 216 and PI 126 932 ) and from L. esculentum cultivar Hawaii 7981 , effective against a second group of pathogenic T3 strains on tomato and conferred by an incompletely dominant gene, " RxvT3 ".

L accession PI 114 490 would be resistant to the three races T1, T2, T3; this resistance would be conferred by at least two loci. Resistance to race T4 would be available from accession LA 716 of Lycopersicon pennellii ; this resistance has apparently not been confirmed in the field.

Indeed, if we are interested in the virulence of strains Xanthomonas on tomato , three races (T1, T2, T3) were first described on tomato from 3 cultivars. The T1 and T2 races, described in 1990, have been reported all over the world: on the American continent, in Europe, in Australia The T3 breed has been highlighted more recently in Florida, then in Mexico, Thailand The emergence of breeds in certain production areas could be linked to the use of resistant varieties or their introduction through seeds.

Recently two new breeds have been identified in Florida from group C strains: T2 and T4 breeds. As an example, a recent survey carried out in Brazil revealed the existence of several species of Xanthomonas in the different tomato production regions: X. gardneri (group D / race T2), X. vesicatoria (group B / race T2), X. euvesicatoria (group A / race T1) and X. perforans (group C / race T3).

Finally, for information, tests were carried out with ' acidic electrolysis water , known for its germicidal activities. This would show some efficacy against X. vesicatoria , as a disinfectant on the surface of the seeds or as a contact bactericide on aerial vegetation.