Management of wilt of linseed caused by Fusarium oxysporum f.sp. lini by using fungicides and bioagents

Introduction

The linseed (Linum usitatissimum L.) is an important rabi oilseed crop which belongs to family Linaceae and genus Linum. The oil percent in seed varies from 37.8 to 43% and contain a high level of protein 20.00 to 24.8% and flaxseed oil contains more than 50% linolenic acid, about 80 per cent of the oil produced goes to industries, used as drying oil for the manufacture of many products, including paints, varnishes, linoleum, oilcloth, printer's ink, patent and imitation leather products and many others. Flax fibers are amongst the oldest fiber crops in the world after silk (Narayan, 1987). Linseed oil containing a mixture of rich fatty acids, is rich in two essential fatty acids, alpha-linolenic acid (ALA) and linoleic acid (LA) and is used on food applications where stability is essential (Green et al. 1981). In the 2023-24, linseed cultivation covered approximately 2.39 lakh hectares, yielding about 1.67 lakh tonnes, with an average productivity of 698 kg/ha. Madhya Pradesh, Jharkhand and Uttar Pradesh were the leading states in both area and output, jointly contributing nearly 80% to national production. Notably, Rajasthan recorded the highest productivity, followed by Bihar and Nagaland. Among the fungal diseases of linseed, wilt is a major constraint responsible for low production and productivity along with rust and powdery mildew (Kishore et al. 2011). The crop losses due to wilt in the range of 80-100% have been reported by (Sattar and Hafiz 1952). To date, various strategies have been developed for the management of plant diseases. Among these, the use of biological control agents has emerged as an effective and eco-friendly approach for managing diseases in a wide range of crops. Among the various bioagents Trichoderma spp. have been recognized as highly effective biological control agents that successfully suppress numerous plant pathogens (Jain et al., 2017;Kharte et al., 2022). Fungicides are commonly used as seed treatments for the management of seed-borne diseases because they effectively eradicate seed-borne inoculum, thereby reducing the primary source of infection and improving seed germination and seedling establishment. The purpose of this study was to determine the most efficient biocontrol and fungicides that are widely utilized in disease control.

Materials and Methods

This experiment was conducted at field of AICRP on linseed and Mustard, College of Agriculture, Nagpur during rabi season 2024-25 and laboratory of Plant Pathology Section, College of Agriculture, Nagpur.

In-vivo management of linseed wilt under sick field conditions: Eight treatments comprising of different bioagents and fungicides were evaluated against Fusarium oxysporum f.sp. lini under natural field condition. Untreated seeds were used as control. Susceptible linseed variety PKV NL-260 was used in the experiment. Each treatment was plotted in plot size 5 x 4 m 2 with four replications in Randomized Block Design (RBD). At each treatment, observations on total number of linseed plants and total wilted plants in 1m 2 area were recorded to calculate per cent disease incidence of wilt by using formula as detailed below.

The observations were recorded regarding the per cent disease incidence at 30, 45, 60 DAS, per cent disease reduction over control, yield/plot and percent yield increase over control. Treatment details are as follows. In-vitro evaluation of bio agents against Fusarium oxysporum f.sp. lini by dual culture technique Four bioagents Trichoderma viride, Trichoderma harzianum, Pseudomonas fluorescens, and Bacillus subtilis were evaluated against Fusarium oxysporum f.sp. lini by dual culture technique. In case of Trichoderma spp. 5 mm discs of actively growing culture of pathogen and antagonists were placed at opposite sides on PDA media at distance of 5 cm. In case of Psueudomonas fluorescens and Bacillus subtilis 5 mm diameter mycelial disc from one week old test fungus was cut aseptically with the help of cork borer and placed in centre of petri plates containing a mixture of sterilized PDA and NA medium and bioagents Pseudomonas fluorescens and Bacillus subtilis were streaked in a square shape around the centrally placed pathogen. The plates containing PDA medium inoculated with pathogen alone served as control. All plates were incubated at 28 ± 2 0 C for seven days and all treatments were replicates four times. After the incubation period, the radial growth of the fungal mycelium on each plate was measured.

The percent inhibition of radial growth of the pathogen by bio agents in comparison to the control was calculated using the formula described by Vincent (1927).

Where;  C = Growth of fungal mycelium in control.  T = Growth of fungal mycelium in treatment In-vitro evaluation of fungicides against Fusarium oxysporum f.sp. lini by poison food technique Seven fungicides were evaluated in-vitro against Fusarium oxysporum f.sp. lini by poison food technique. The requisite quantity of each fungicide was added aseptically to the molten PDA to obtain the desired concentration. About 20 ml of the poisoned medium was poured into each sterilized petri plate and each petri plate was inoculated aseptically at the centre with a 5 mm diameter mycelial disc cut from the actively growing margin of a seven day old culture of Fusarium oxysporum f. sp. lini. Control plates containing PDA medium without any fungicide were similarly inoculated with the pathogen. All plates were incubated at 28 ± 2 0 C for seven days and all treatments were replicated thrice.

Results and Discussions

In-vivo evaluation of fungicides and bio agents against Fusarium oxysporum f.sp. lini under natural field conditions The data presented in (Table 4, Fig. 1, Plate 1, 2, 3) showed that among all eight treatments minimum mean percent disease incidence (30, 60 and 60 DAS) was recorded in treatment (T5) seed treatment with Trichoderma and soil application of Trichoderma through FYM (14.59%) with highest percent disease reduction over control (59.82%) followed by treatment (T2) seed treatment with Thiophanate methyl 45% + Pyraclostrobin 5% FS (14.93%) with percent disease reduction over control (58.89%) and both the treatments were significantly superior over control.

Maximum mean per cent disease incidence was recorded in untreated control (T8) (36.32%).

Effect of fungicides and bioagents on yield of linseed

Conclusion

In in-vivo evaluation of bio agents and fungicides under sick field condition, seed treatment with Trichoderma and soil application of Trichoderma found most effective and could be suggested for farmers. In-vitro evaluation of bio agents and fungicides, Trichoderma harzianum found most efficient and fungicides which showed 100 percent mycelial growth inhibition were Propiconazole 25% EC, Thiophanate methyl 45% + Pyraclostrobin 5% FS and Captan 70% + Hexaconazole 5% WP.

Acknowledgement

AcknowledgementI extend my sincere thanks to my guide and Head of Plant Pathology Section, College of Agriculture, Nagpur for supporting my research work.

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