KALPANA SHARMA, MARIA RENATE FINCKH
University of Kassel, Department of Ecological Plant Protection, Germany
Resistance induction is a commonly observed phenomenon in many plants and usually occurs in reaction to exposure to avirulent pathogens or certain chemicals (e.g. BABA). Induction can be achieved via the leaves and there is evidence that some plant strengthening products can induce resistance via the root. Currently we are working on the possibility to use induced resistance in tomato against Phytophthora infestans, causal agent of late blight by selecting more inducible varieties and the compounds that can be best used to induce resistance in practice with an emphasis on products that are easy to be applied preferably via the soil.
A total of 32 tomato varieties with various levels of susceptibility to late blight were grown in standard soil with mineral fertilisers. Detached leaves of 1 month old plants were screened for inducibility of resistance using BABA (DL-3-amino butyric acid) seven days before challenge inoculation. Control plants were sprayed with distilled water in a similar way. Leaves directly treated with BABA (old) and newly grown leaves (young) were included in the test. Resistance induction was usually higher on leaves newly grown after treatment than on old leaves that had been directly treated by BABA. The degree of induction varied among varieties based on the absolute (measured in cm2 diseased leaf area) and relative disease reduction achieved through the use of BABA with several varieties showing no induction at all and others more than 90% disease reduction.
Based on the initial screening, various varieties were tested for their inducibility under greenhouse conditions using field soil, comparing the effects of different organic fertilisers and plant strengtheners on young and adult plants. Soil application of the plant strengthener Quality (Bio-Feed Product), an aqueous extract of herb reduced plant susceptibility in all combinations with fertilisers, soil and plant age between 20% (adult plants) and 46% (young plants). Other strengtheners such as PEN, alfalfa extract, and meat extract usually also enhanced resistance but not as strongly.
Keywords: BABA, late blight, plant strengtheners, resistance induction