EVALUATION OF TRICHODERMA HARZIANUM IN CONTROLLING LATE BLIGHT OF POTATO

Evaluation of Trichoderma harzianum in reducing mycelial growth of Phytophthora infestans as well as in controlling late blight of potato was done in Microbiology and Biocontrol laboratory and Net-house, Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh during 2019-2020, Bangladesh. The experiment was conducted using popular potato variety Diamant and native variety Challisha. T. harzianum was evaluated in net-house and in-vitro condition. Fungicide Indofil M-45 (Mancozeb) was used as positive check for comparison. In Net-house experiment, T. harzianum increased plant height, number of tubers and fresh weight of tubers over control treatment for the both of the varieties of potato. T. harzianum on late blight of potato (var. Diamant) showed a significantly better management over control treatment. In comparison to non-treated control treatment, reduced infection of late blight was found in the T.harzianum treated plants, whereas increase disease severity was calculated in control treatment. After harvesting, tuber infection in T. harzianum treated plants was not observed. Percent inhibition of tuber infection over control was 100%. Indofil M-45 suppressed Disease severity but comparatively less effective than T. harzianum in the long run. In case of variety Challisha similar trend of results were observed. In dual culture assay, T. harzianum showed highest inhibitory effect in suppressing mycelial growth of P. infestans. T. harzianum showed 86.67% inhibition of mycelial growth of P. infestans over control. Thus, it can be concluded that T. harzianum is effective to control late blight of potato and sometimes comparable to chemical fungicide in net-house condition.

Pectobacterium brasiliense 1692 Chemotactic Responses and the Role of Methyl-Accepting Chemotactic Proteins in Ecological Fitness

To adapt to changing environmental niches, bacteria require taxis, a movement toward or away from a stimulus (ligand). Chemotaxis has been studied in some members of the Soft Rot Pectobacteriaceae (SRP), particularly members of the genus Dickeya. On the contrary, there are fewer studies on this topic for the other genus in the SRP group, namely Pectobacterium. This study evaluated chemotactic responses in Pectobacterium brasiliense (Pb 1692) to various ligands. A total of 34 methyl-accepting chemotactic proteins (MCPs) were identified in the Pb 1692 genome and the domain architectures of these MCPs were determined. Four Pb 1692 MCPs previously shown to be differentially expressed during potato tuber infection were selected for further functional characterization. Toward this end, Pb 1692 mutant strains each lacking either AED-0001492, AED-0003671, AED-0000304, or AED-0000744 were generated. Two of these mutants (AED-0001492 and AED-0003671), were attenuated in their ability to grow and respond to citrate and are thus referred to as MCPcit2 and MCPcit1, respectively, while the other two, AED-0000304 (MCPxyl) and AED-0000744 (MCPasp), were affected in their ability to respond to xylose and aspartate, respectively. Trans-complementation of the mutant strains restored swimming motility in the presence of respective ligands. The four MCP mutants were not affected in virulence but were significantly attenuated in their ability to attach to potato leaves suggesting that ecological fitness is an important contribution of these MCPs toward Pb 1692 biology.

Sclerotinia sclerotiorum Causes Decay and Forms Sclerotia in Potato Tubers in Idaho

Potato tubers (cultivar ‘Austrian Crescent’) displaying a dry rot decay symptom and internal sclerotia were received for diagnosis. Isolations were attempted from symptomatic material, and Sclerotinia sclerotiorum was frequently recovered. Pathogenicity tests for S. sclerotiorum in potato tubers were completed using agar plugs with S. sclerotiorum placed over tuber wounds and through injecting stolon end with a S. sclerotiorum hyphal suspension. Both inoculation methods induced decay symptoms, although these were observed less frequently with the agar plug inoculation (37.5%) compared with hyphal injection (100%). S. sclerotiorum was consistently reisolated from inoculated symptomatic tubers. This symptom is rare, but potato growers should be aware that tuber infection is possible when white mold is present.

Methods of inoculation of potato tubers when assessing resistance to Phoma exigua

The results of studies on methods of inoculation of potato tubers when assessing resistance to Phoma exigua. For this is suitable both ways tuber infection, making inokulumu (agar blocks) in the hole and sinking bubbles in the suspension of mycelium fungus.

The Effect of Potato Ridge Height and Harvest Date on Tuber Injuries

A potato experiment was conducted from 2004 to 2006 at the Zawady Experimental Farm. The farm is part of the University of Natural Sciences and Humanities in Siedlce, Poland. Tuber infection and injury by diseases and pathogens of three potato cultivars were assessed according to the potato ridge height and harvest date. The weight of mechanically injured tubers was also determined depending on the potato ridge height and harvest date. The weight of potato tubers infected by fungal and bacterial diseases was influenced by the cultivar, growing season, harvest date, and ridge height. Potatoes grown to their standard height and height ridges, were significantly less infected by diseases at the first harvest date. The weight of tubers in which the tubers were injured by soil pests, was affected by the cultivar and ridge height. Potatoes cultivated in a ridge which was 20 cm high, had tubers with significantly less mechanical injuries compared with a low (16 cm) ridge and high (24 cm) ridge.