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Mominur Rahman Scientific Officer Soil Microbiology Laboratory Bangladesh Agricultural Research Institute Joydebpur, Gazipur-1701

BIOCONTROL OF FOOT AND ROOT ROT DISEASE OF GRASSPEA (Lathyrus sativus) BY DUAL INOCULATION WITH RHIZOBIUM AND ARBUSCULAR MYCORRHIZA

INTRODUCTION Foot and root rot is considered as an important and destructive disease of pulses in almost all legume-growing countries of the world. Though this disease can be controlled by using chemical pesticide but it causes environmental pollution, health hazards, affects non target organisms and also is not economical. Hence, biological control agents can be used for green, safe and sustainable agriculture. Arbuscular Mycorrhizal Fungi (AMF) are the major component of the rhizosphere of most of the plants and play a very important role as biocontrol agent and help in decreasing plant disease incidence (Akthar and Siddiqui, 2008).

OBJECTIVES To investigate the potential of AM fungi alone and in combination with bioinoculants i.e. Rhizobium to find out the best combination on plant growth, and their biocontrol against grasspea foot and root rot caused by Sclerotium rolfsii.

MATERIALS AND METHODS Table 1. Initial fertility status of the soil samples Soil Properties Texture pH OM (%) Ca Mg K meq 100 g-1 Result Sandy clay loam 7.6 0.32 6.6 2.3 0.09 Crit. level - 2.0 0.5 0.12 Soil Properties Total N (%) P S B Cu Fe Mn Zn µg g-1 Result 0.017 12 25 0.10 1.0 14 1.3 0.85 Crit. level - 10 0.20 0.2 4.0 0.60

Design : RCBD Replication : 4 (Four) Treatments : 8 (Eight) Variety : BARI Khesari-1 Seed : 15 seeds/pot Fertilizer dose : As per STB Pathogen : Sclerotium rolfsii Rhizobium strain : BARI RLs-10 AM inoculum : Soil based AM inoculum containing approximate 252 spores pot-1 Spore morphology, size, shape and peridium of spore, sporocarps colour, wall ornamentation, subtending hyphae and mode of attachment are considered for identification of spore.

Glomus fugianum Glomus macrocarpum Glomus warcuppi Acaulospora foveata Acaulospora denticulate Gigaspora albida

Gigaspora rosea Gigaspora spp Glomus spp Not identified Not identified Not identified Fig. Different spore of Arbuscular mycorrhizal fungi used for the experiment

TREATMENTS The eight treatments were: T1: Arbuscular mycorrhiza (AM) T2: Rhizobium (R) T3: AM+Rhizobium T4: Sclerotium rolfsii T5: Sclerotium rolfsii + AM T6: Sclerotium rolfsii + Rhizobium T7: Sclerotium rolfsii + AM + Rhizobium T8: Control

RESULTS

Fig. Effect of inoculation of AMF, Rhizobium and Sclerotium rolfsii on germination (%) after 23 DAS of grasspea during 2014-2015 and 2015-2016

Foot and root rot affected by Sclerotium rolfsii AM+Rhizobium inoculated seedlings showed better performance

Photo: Effect of inoculation of AMF and Rhizobium at the time of flowering stage of grasspea

Fig. : Effect of inoculation of AMF, Rhizobium and Sclerotium rolfsii on seed yield of grasspea during 2014-2015 and 2015-2016

Fig. : Effect of inoculation of AMF, Rhizobium and Sclerotium rolfsii on stover yield of grasspea during 2014-2015 and 2015-2016

Photo: Effect of inoculation of AM and Rhizobium on nodule number in rhizosphere soils of grasspea

Fig.: Effect of dual inoculation of AMF and Rhizobium on root infection of grasspea during 2014-2015 and 2015-2016

Fresh root Mycelium Mycelium Mycelium Fig. : Different mycorrhizal structure in the root cortex of Lathyrus sativus

Fig.: Effect of dual inoculation of AMF and Rhizobium on pre+post emergence foot and root rot disease% in grasspea during 2014-2015 and 2015-2016

SUMMARY AND CONCLUSION Dual inoculation increased germination (20% in 2014-2015 and 23% in 2015-2016), seed yield (52% in 2014-2015 and 42% in 2015-2016) and stover yield (13% in 2014-2015 and 29% in 2015-2016) compared to control. It reduced foot and root rot disease (48% in 2014-2015 and 44% in 2015-2016) compared to control. On the contrary, Sclerotium rolfsii + Rhizobium, Sclerotium rolfsii + AM, and Sclerotium rolfsii + AM + Rhizobium reduced 12-17%, 16-17% and 28-31% foot and root rot disease, respectively compared to only Sclerotium rolfsii trearment.   Therefore, use of these bio-control agents could be promoted as an active component of bio-intensive Integrated Disease Management Program (IDMP) under organic mode.

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Figure : Phosphate uptake pathways : Phosphate (Pi) uptake by mycorrhizal plants and non-mycorrhizal plants

Fig. The benefits of plant-fungal symbiosis are stabilized by the constant of mutual nutrient supply Back

Mycorrhizal association, showing the interactions between fungus, plant and soil Diagrammatic representation showing role of Mycorrhizae as biocontrol and biofertilizers

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