Inhibition of seed germination and development of tomato plants in soil infested with Pseudomonas tomato

Infestation of sterilised or natural soil with Pseudomonas tomato at inoculum concentrations of 10² to 10⁹ propagules/ml inhibited germination of seeds and caused damping-off of tomato cv. VF-198, susceptible to bacterial speck. Infestation with saprophytic P. fluorescens at an inoculum concentration of 10⁹ propagules/ml did not cause any damage. Germination of seeds of tomato cv. Rehovot-13, resistant to P. tomato, was not affected in P. tomato-infested natural soil, but was inhibited when tested in P. tomato-infested, sterilised soil. Tomato plants which were symptomless from sowing to the flowering stage when growing in infested soil had 20–30% less foliage than plants growing in uninfested soil.     

Genetics of resistance to bacterial speck of tomato caused by Pseudomonas syringae pv. tomato

Two tomato cultivars, Ontario 7710 and Rehovot 13, and their F₁, F₂, F₃ and backcross progenies were screened for resistance to bacterial speck (Pseudomonas syringae pv. tomato) of tomato. The results support the hypothesis that the resistance factors contained in the two parents are non-allelic and controlled by two different genes.     

Morphology of Leaf Surfaces of Tomato Cultivars in Relation to Possible Invasion into the Leaf by Pseudomonas syringae pv. tomato

The role of morphological characteristics of tomato leaves inthe infection process of the pathogen Pseudomonas syringae pv.tomato was studied in 15 cultivars of varying susceptibility.Natural openings such as stomata, broken trichomes and cuticularcracks were counted. It was found that susceptibility increasedin proportion to the number of these potential penetration sites.However, their role is probably limited because even in thehighly resistant cultivars there are enough natural openingsto enable successful bacterial penetration. Bacterial speck of tomato, Lycopersicon esculentum, phytopathogenic bacteria, plant morphology, Pseudomonas syringae pv. tomato, tomato     

Inheritance and sources of resistance to bacterial speck of tomato caused by Pseudomonas syringae pv. tomato

Inheritance of resistance to bacterial speck of tomato was determined by analysing F₁ F₂ and backcross progenies of crosses involving a susceptible (VF-198) and a resistant cultivar (Rehovot-13). The results fit the hypothesis that resistance is controlled by a single dominant gene in interaction with minor genes. Cultivar susceptibility to Pseudomonas syringae pv. tomato was tested under greenhouse conditions under high inoculum pressure using infested tomato seeds together with infested soils and spray-inoculated wounded plants. Of 21 species, cultivars and lines, Rehovot-13, Ontario 7710 and Lycopersiconpimpinellifolium P.I. 126927 were found to be resistant to the pathogen. VF-198 and Tropic-VF were the most susceptible. Extra Marmande, Saladette, Acc.339944–3 and the wild type Lycopersicon esculentum var. cerasiforme were moderately resistant.     

A Note on the Detection of Phytopathogenic Bacteria within the Leaf by a Differential Staining Procedure

A simple differential staining procedure for demonstrating infection within the leaf tissue by Pseudomonas tomato, Ps. lachrymans and Xanthomonas vesicatoria has been developed. It is based on (1) clearing of plant tissue with a mixture of glycerol, lactic acid, phenol and water; (2) treating the leaf tissue with boiling KOH; and (3) staining with aniline blue-chloralhydrate. When observed under a light microscope, the bacteria appear dark blue, whereas the leaf tissue appears transparent and colourless.