Response of different tomato varieties to the replacement of chemical toxins controlling tomato fruit borer (Helicoverpa armigera Hubner) by some endogenous plant compounds

Pests and their controlling pesticides are among the most serious threats to the health of agricultural products. The present study was aimed to investigate the effect of genotype and the possibility of replacing chemical pesticides controlling fruit borer by some compounds of natural origin for plant traits improvement and damage reduction of tomato fruit borer. Factorial experiment was done in the template of randomized complete block design with three repetitions.

Factors include 9 levels of pest control compounds and 5 varieties. Compounds involves Salicylic acid (5 and 15 mM), Jasmonic acid (50 and 100 μM), Abamactin (750 and 1500 mg/L), chlorpyrifos (1250 and 2500 mg/L) and control. Measured traits involve morphological traits (fruit yield, fruit weigh, numbers of fruit per cluster, plant height, chlorophyll index), phonological traits (days to flowering and days to physiological maturation), phytochemical traits (TA, TSS, and Vitamin C) and relative properties to evaluating resistance to fruit borer (the percentage of leaf and fruit damage).

Results of analysis of variance and mean comparison test present significant variation between varieties. The maximum fruit yield per plant was related to PA-136 variety with applications of two-levels of Chloropyrus and Jasonic acid, PA-162 variety with application of first level of Abamactin, second level of Salicylic acid and PA-135 and PA-688 varieties with the second level of Chloropyrus. Reducing pest damage on leaf and fruit in applying Salicylic acid, Jasonic acid is suitable and evaluated the same level of chemical control use. The highest significant positive correlation with yield related to single fruit weight (r=0.48**) and the highest significant negative correlation was related to days to flowering (r= -0.52**).

In stepwise regression analysis of single plant yield as a dependent variable, three traits including days to flowering, single fruit weight, and a percentage of pest damage on leaf as an most important traits introduced in the model that totally explained 49% of variation. Path analysis results indicated that the highest positive direct effect(0.42) was related to single fruit weight, and the highest indirect effects(-0.047) was also related to this trait via days to flowering. Four first components were chosen in principal component analysis which verifying totally 62.5% of phenotypes variation. The results can be used in the design of breeding programs for plant trait improvement and integrated pest management of tomato fruit borer.