Bacterial-fungal interaction in stimulation of growth and amelioration of physiological condition of citrus (Citrus spp.)

An experiment was conducted to find out the effect of arbuscular mycorrhizal fungi (Glomus intraradices) and mycorrhizal helper bacteria (phosphorus-solubilising bacteria, i.e. PSB containing mixture of Bacilus subtilis and B. megatherium, Azospirillum brasilence and Providencia sp. on growth and physiological status of two citrus rootstocks, Troyer citrange (Citrus sinensix × Poncirus trifoliata) and Cleopatra mandarin (Citrus reshni). The inoculation was done in soil during transplantation of seedlings in plastic containers. Troyer citrange co-inoculated with G. intraradices and PSB and Cleopatra mandarin co-inoculated with G. intraradices and A. brasilence significantly recorded highest root colonization 30, 60 and 120 days after inoculation (DAI). The inoculation of G. intraradices along with PSB or A. brasilence exhibited highest growth performance in terms of plant height, stem diameter, number of leaves and leaf area in both the rootstocks. The co-inoculation of G. intraradices and PSB recorded maximum relative water content, leaf chlorophyll and total carotenoids content in both the rootstocks at all the growth stages. The significantly more content of total phenols and proline were recorded in leaves of both the rootstocks co-inoculated with G. intraradices and A. brasilence and G. intraradices and PSB at all the growth stages, respectively. The soil application of G. intraradices along with PSB, A. brasilence or Providencia sp. recorded maximum total soluble sugars in leaves. Maximum photosynthesis, stomatal conductance and minimum leaf respiration were noticed in both the rootstocks co-inoculated with G. intraradices and PSB.