MSc

Mycorrhizae are mutualistic symbiotic associations based on bidirectional nutrient transfer between soil fungi and the roots of vascular plants. Over 80% of terrestrial plants can form symbiotic relationship with AMF in the natural environment. AMF being an obligate symbiont, it is completely dependent on the host plant for their life cycle and their relationship always been linked with improved plant performance. Colonisation of plant roots with mycorrhizal fungi greatly increases the root surface area which helps in water and nutrient uptake by plants. The mycorrhizal fungi not only provides the host plant with nutrients, such as phosphate and nitrogen, but also contributes to abiotic (drought, salinity, heavy metals) and biotic (root pathogens) stress tolerance of the host.
The present study was undertaken to assess the effect of native arbuscular mycorrhizal fungi for the growth promotion and management of rhizome rot in ginger (Zingiber officinale). The rhizospheric soil samples were collected from ten different ginger growing areas of Wayanad district namely Kalpetta (KAL), Pachilakkad (PAC), Edakkal (EDA), Varadoor (VAR), Anappara (ANA), Vaduvanchal (VAD), Ambalavayal (AMB), Malavayal (MAL), Nenmeni (NEN), and Poomala (POO).
Isolation of AMF spores, identification through morphological character and mass multiplication of selected spores were carried out at the Department of Agricultural Microbiology, College of Agriculture, Vellanikkara. Totally 74 types of AMF spores were isolated from the ten samples and tentatively identified at genus level based on morphological characters like colour, size, shape, nature of hyphae, bulbous suspensor, number of spore walls, surface ornamentation. Among 74 isolates,
47 isolates showed characteristics similar to Glomus, 15 to Scutellospora, 9 to
Gigaspora, and 3 to Acaulospora.

From among these isolates, five most predominant AMF species were selected based on abundance. They included brown spore from PAC AMF 2 sample (28 spores
/100 g of soil), dark brown spores from EDA AMF 1 sample (30 spores /100 g of soil), black spore from ANA AMF 5 sample (35 spores /100 g of soil), yellow spores from NEN AMF 2 sample (32 spores /100 g of soil), and brownish orange spores from POO AMF 3 sample (27 spores/100 g of soil).


Mass multiplication of selected spores were carried out with maize as host plant in vermiculite – perlite medium. Percent root colonization of maize roots ranged between 80 % to 100 % and spore count of the inoculum ranged from 10 spores / 10 g of inoculum to 22 spores / 10 g of inoculum. Glomus sp. (Black spore) selected from ANA AMF 5 sample showed highest root colonization and maximum number of spores in mass multiplied inoculum.
The pot culture experiment was conducted in a completely randomized block design (CRD) with two experiments with eight treatment and five replication at Regional Agricultural Research Station, Ambalavayal of Wayanad district. First experiment was conducted to assess the effect of AMF on the growth and yield promotion of ginger and the treatment consisted of T1 (PAC AMF 2), T2 (EDA AMF 1), T3 (ANA AMF 5), T4 (NEN AMF 2), T5 (POO AMF 3), T6 (POP of KAU, 2016),
T7 (Organic POP of KAU, 2015), T8 (Absolute control). The second experiment was conducted to assess the efficacy of AMF in the management of soft rot of ginger. For this, the above treatments were repeated along with the challenge inoculation with Pythium myriotylum, the causal organism of rhizome rot.
In the experiment for growth and yield promotion of ginger, T5 (POO AMF 3 - Glomus sp.) significantly higher in ginger yield (T5 on par with T1) and performed better in growth parameters like number of tillers and leaf area (T5 followed by T1) and T1 performed better in growth parameters like plant height, number of leaves. In second experiment (rhizome rot management), T1 performed better in plant height, number of tillers, leaf area and yield of ginger. T1 also recorded lesser disease incidence of soft rot. Final spore count and per cent root colonization was also recorded highest in the T1. Finally T1 (Glomus sp. selected from PAC GRS - AMF 1) was identified as the best AMF isolate which performed better in growth promotion as well as in disease suppression. However, extensive field studies are needed under different season and agro ecological zone, in order to develop an efficient AMF isolate for ginger in high range zones of Wayanad district