Crack-entry invasion of wheat roots by Azospirillumbrasilensevia chemical-enzyme treatment: a way facilitating para-nodule formation and forced association for proper crop yield

The induction of nodule-like structures referred to para-nodules was assessed due to 2,4-D, IAA and the enzyme mixture of cellulase and pectolyase in presence of PEG treatment of wheat cultivars inoculated with Azospirillumbrasilense. In gnotobiotic model experiment; 9-18 and 6-19 para-nodule plant-1 were produced due to 2,4 D and IAA treatments respectively. Less than 7 para-nodules plant-1were attributed to Azospirllum alone, numbers increased to 26 when the diazotroph was introduced in combination with p-nodule-inducing agents. The cell wall-degrading enzyme mixture with PEG facilitated the crack-entry invasion of the diazotroph in population of > 5x105cfu g-1 root. High rates of C2H2 reductions of > 200 nmoles C2H4 g-1 root hr-1 were estimated for the enzyme mixture-PEG treated plants. The average glutamine synthetase activities of plant leaves were the highest (57.1-86.3 µ mol g-1Fw hr-1) for IAA-Azospirillum treatment. Wheat plants successfully paranodulated in pot experiment when pre-treated with IAA and enzyme mixture and inoculated with Azospirillum in presence of 50 % of recommended N, plant biomass and N yields increased as well. The highest levels of chlorophyll a (2.10 µg g-1Dw), chlorophyll b (2.28) and carotenoids (1.59) were estimated for inoculated plants pre-treated with IAA plus enzyme mixture. In the field trial, as high as > 2.0 kg plot-1 total biological yield was produced by plants initially primed by soaking in water. The superior grain yields of 441.7-571.4 g plot-1 were attributed to Azospirillum inoculation together with IAA and enzyme mixture for 50 % N-supplied plants. Seed priming somewhat raised the grain yield.