Pathogenic and morphological variability among the isolates of Fusarium udum (Butler) causing wilt of pigeonpea (Cajanus cajan)

Wilt is the most serious disease causing irreversible losses and lethal damage to the crop in Bihar, Jharkhand, Orissa and the West Bengal states of Eastern India. Because of the existence of high pathogen variability, management of the disease using resistant cultivars will be a challenging task. For breeding resistant varieties, knowledge of pathogen variability in the particular crop area is essential. In present study, fifteen isolates viz., Fu-9, Fu-10, Fu-27,Fu-32, Fu-42, Fu-49, Fu-63, Fu-72, Fu-73, Fu-74,Fu-75,Fu-84, Fu-86, Fu-87, Fu-97of Fusarium udum obtained from wilt infected pigeonpea plants of Bihar, Jharkhand, Orissa and West Bengal of Eastern India were assessed for the phenotypic variation. The isolates exhibited considerable variations in cultural and morphological characters viz., radial growth, mycelial color, sporulation, size and shape of macroconidia. Pathogenic variability on soil inoculated pot grown plants of pigeonpea resulted in 12.0 to 57.1 percent wilt incidence. The isolates also exhibited significant variations in symptoms like drooping of shoots, latent period, timing of fungal invasion, vascular clogging, drooping of shoots, and wilt establishment etc. Based on the wilt incidence, the fifteen isolates were distinguished into pathogenic groups. Fu- 10, Fu-27, Fu-32 and Fu-49 were found highly pathogenic and predominantly causing the typical wilt symptoms of more than one 31% wilt incidence. The present study indicates the existence of variability among isolates of vascular wilt pathogen collected from Eastern region of India.

Comparative transcriptomic profiling of susceptible and resistant cultivars of pigeonpea demonstrates early molecular responses during Fusarium udum infection

Vascular wilt caused by Fusarium udum Butler is the most important disease of pigeonpea throughout the world. F. udum isolate MTCC 2204 (M1) inoculated pigeonpea plants of susceptible (ICP 2376) and resistant (ICP 8863) cultivars were taken at invasion stage of pathogenesis process for transcriptomic profiling to understand defense signaling reactions that interplay at early stage of this plant–pathogen encounter. Differential transcriptomic profiles were generated through cDNA-AFLP from M1 inoculated resistant and susceptible pigeonpea root tissues. Twenty five percent of transcript derived fragments (TDFs) were found to be pathogen induced. Among them 73 TDFs were re-amplified and sequenced. Homology search of the TDFs in available databases and thorough study of scientific literature identified several pathways, which could play crucial role in defense responses of the F. udum inoculated resistant plants. Some of the defense responsive pathways identified to be active during this interaction are, jasmonic acid and salicylic acid mediated defense responses, cell wall remodeling, vascular development and pattering, abscisic acid mediated responses, effector triggered immunity, and reactive oxygen species mediated signaling. This study identified important wilt responsive regulatory pathways in pigeonpea which will be helpful for further exploration of these resistant components for pigeonpea improvement.

Evaluation of Some New Generation Fungicides against Pigeonpea (Cajanus cajan (L.) Millsp.) Wilt Causal agent Fusarium udum under in vitro Conditions

Pigeonpea wilt disease caused by Fusarium udum is one of the most devastating soil borne disease. The objective of this investigation was to determine the antifungal activities of fungicides which can be used to control wilt disease of pigeonpea. Among all the fungicides Azoxystrobin+Tebuconazole, Carbendazim, Tebuconazole+Trifloxystrobin, Hexaconazole, Tebuconazole exhibited 100% inhibition at all the concentrations, followed by Azoxystrobin+ Difenconazole which exhibited 92.22%, 94.4%, 94.4% and 100% inhibition at 250 ppm, 500 ppm, 750 ppm and 1000 ppm respectively.

Biosynthesis of silver nanoparticles from Pseudomonas fluorescens and their antifungal activity against Aspergillus niger and Fusarium udum

In recent years, emerging plant diseases have posed a significant danger to global economies. Fungicide resistance and climate change are the two primary sources of pathogen outbreaks. The silver nanoparticles have been demonstrated to restrain pathogenic bacteria, fungi, and viruses with minimal risk of developing resistance and phytotoxicity. The synthesis of silver nanoparticles via chemical and physical methods raises concerns about environmental safety and production costs. The microbial bio-fabrication of silver nanoparticles is simple, cost-effective, and ready-to-use technology. In the current investigation, we used Pseudomonas fluorescens cell filtrates for the synthesis of silver nanoparticles. The silver nanoparticles were characterized using Dynamic Light Scattering (DLS), zeta potential (ζ), UV-Vis spectroscopy, SPR analysis, Transmission Electron Microscopy. Both silver nanoparticles and AgNO3 were tested for their ability to inhibit two phytopathogenic fungi, i.e., Fusarium udum and Aspergillus niger. Potent inhibition of mycelial growth was observed when silver nanoparticles were used at a concentration of 150 ppm. However, further research is needed to assess the toxicity of AgNPs before they are mass-produced and used in agricultural applications.

The Evaluation of Trichoderma consortia against Fusarium udum causing wilt of Pigeonpea

Pigeonpea is one of the important pulse crop of Madhya Pradesh, a State of India. The plant gets infected by the pathogen Fusarium udum causing wilt disease, which is one of the major constraints in the production and productivity of pigeonpea. The present study aimed to carry out in vitro condition to assess the possible use of biocontrol consortia in field conditions. Six Trichoderma consortia viz., T1- T. viride + T. harzianum (JC-I), T2- T. viride + T. virens (JC-2), T3:- T. harzianum +T. virens (JC-3), T4- T. hamatum +T. viride (JC-4), T5- T. hamatum + T. harzianum (JC-5), T6- T. hamatum + T. virens (JC-6) and T0- Control were evaluated for their antagonistic activity against F. udumunder in vitro conditions. The consortia of T4- T. hamatum +T. viride (JC-4) was found most effective(58.82 %) in inhibiting the radial growth of Fusarium udum. The volatile compound from consortium of T5-T. hamatum + T. harzianum (JC-5) exhibited maximum growth inhibition (81.84%) and sporulation of Fusarium udum followed by T1-T. viride + T. harzianum (JC-I) (55.49% inhibition) . The culture filtrate of consortia of T4- T. hamatum +T. viride (JC-4) showed 100% inhibition of test pathogen followed by T5-T. hamatum + T. harzianum (JC-5) (82.89%) at 5 % concentration. It was also observed that with an increase in the concentration of culture filtrates of all the Trichoderma species, the radial mycelial growth of the test pathogen was proportionally decreased. The Trichodema consortium viz., T4- T. hamatum +T. viride (JC-4) may be tried in the field to manage wilt of pigeonpea because they worked synergistically and gave the high impact of their use.

Biosynthesis of Silver Nanoparticles and Their Biocontrol Potentials Against Aspergillus Niger and Fusarium Udum

Silver nanoparticles can be biosynthesized from bacteria, fungi, and plant extracts but due to their ability to synthesize nanoparticles in varying sizes and shapes at ease, bacterial has drawn interest. Bacterial based biosynthesis is effective, inexpensive, and simple thus, Pseudomonas fluorescence cell filtrates were used to synthesize silver nanoparticles in the present study. The chromatic shifts (yellow to brown) in the media after overnight incubation and the absorption of UV-Vis spectra at 420 nm confirmed the biosynthesis of AgNP’s. Besides that, the SPR analysis of AgNP’s showed a 400–500 nm band width, supporting the formation of silver nanoparticles and their small size with a uniform shape. AgNP’s transmission electron microscopy (TEM) images confirmed their shape as quasi spherical, mean size as 30 nm and anisotropy. From the Zeta potential analysis (-42.7 mV at pH = 7 with a single peak), highly repulsive nature of nanoparticles was confirmed. On the other hand, bio-fabricated silver nanoparticles were tested for antifungal activity against Fusarium udum and Aspergillus niger under in vitro conditions. At 150 ppm concentration of AgNP’s, Fusarium udum and Aspergillus niger were inhibited up to 100 and 80.50 %, respectively. In conclusion, synthesis of nanoparticle with aqueous Pseudomonas fluorescence extract is simple and environmentally benign.