Induction of resistance against Brevicoryne brassicae by Pseudomonas putida and salicylic acid in canola.

The cabbage aphid, Brevicoryne brassicae L. (Hem: Aphididae), is one of the most serious pests of canola worldwide. In this research, the effects of Pseudomonas putida, salicylic acid (SA), and integrated application of both inducers were studied on the resistance of canola to B. brassicae. In free-choice situation, the number of B. brassicae attracted on canola plants under treatments containing P. putida and SA was significantly lower compared to control plants. In the life table study, pre-adult survival, longevity, reproductive period, and fecundity of this aphid were lowest on plants treated with P. putida + SA. The net reproductive rate (R0), intrinsic rate of population increase (r), and finite rate of increase (λ) of B. brassicae decreased significantly in the following order: control (47.19 offspring, 0.293 and 1.340 day-1), P. putida (16.7 offspring, 0.238 and 1.269 day-1), SA (6.37 offspring, 0.163 and 1.178 day-1), and P. putida + SA (3.24 offspring, 0.112 and 1.119 day-1). Moreover, the beneficial effect of the integrated application of P. putida and SA on plant growth parameters was significantly evident in our study. The highest values of glucosinolates, total phenol, and flavonoids were recorded in P. putida + SA treatment. We concluded that canola plants treated with P. putida + SA are more resistant to the cabbage aphid. These findings demonstrated that SA integrated with P. putida on canola plants act effectively for reducing the population of B. brassicae and can be used in integrated management programs of this pest.

Effects of humic acid and plant growth-promoting rhizobacteria (PGPR) on induced resistance of canola to Brevicoryne brassicae L.

The cabbage aphid, Brevicoryne brassicae L. (Hem: Aphididae), is an important pest of canola that can considerably limit profitable crop production either through direct feeding or via transmission of plant pathogenic viruses. One of the most effective approaches of pest control is the use of biostimulants. In this study, the effects of humic acid, plant growth-promoting rhizobacteria (PGPR), and integrated application of both compounds were investigated on life table parameters of B. brassicae, and the tolerance of canola to this pest. B. brassicae reared on plants treated with these compounds had the lower longevity, fecundity, and reproductive period compared with control treatment. The intrinsic rate of natural increase (r) and finite rate of increase (λ) were lowest on PGPR treatment (0.181 ± 0.004 day-1 and 1.198 ± 0.004 day-1, respectively) and highest on control (0.202 ± 0.005 day-1 and 1.224 ± 0.006 day-1, respectively). The net reproductive rate (R0) under treatments of humic acid, PGPR and humic acid + PGPR was lower than control. There was no significant difference in generation time (T) of B. brassicae among the tested treatments. In the tolerance test, plants treated with PGPR alone or in integrated with humic acid had the highest tolerance against B. brassicae. The highest values of total phenol, flavonoids, and glucosinolates were observed in treatments of PGPR and humic acid + PGPR. Basing on the antibiosis and tolerance analyses in this study, we concluded that canola plants treated with PGPR are more resistant to B. brassicae. These findings could be useful for integrated pest management of B. brassicae in canola fields.