Effect of plant extracts on radial growth of Helminthosporium oryzae causative of Brown spot disease of rice under in-vitro

Abstract

Brown spot disease, caused by Helminthosporium oryzae, is worldwide problem capable of causing considerable damage to paddy in the nursery, field or grain yield. The disease is seed borne, and thus can be transmitted through infected seeds and crop residues, alternate hosts and contaminated irrigation water. The objective of this study was to evaluate the effect of plant extracts on radial growth of Helminthosporium oryzae on rice plants. An in-vitro experiment was conducted at the Plant Pathology Laboratory of National Root Crop Research Institute, Umudike, Abia State, in Nigeria. Treatments included water and alcohol extracts of Azardiractha indica (Neem leaves), Piper guinensis (seeds), Garcinia cola (Bitter cola seeds), Ocimum gratissimum (leaf) and Vernonia amygdalina (leaf); and synthetic fungicide (Benomyl) at a concentrations of 10, 25 and 30% of the extract applied to H. oryzae in culture. The test materials were administered on Helminthosporium oryzae, sourced from rice seeds and infected shoot system of rice. Alcohol extract of Piper guineensis had the highest radial growth inhibition (89.89%) by the fifth day, but was not significantly different from Azardiractha indica, which had an inhibition value of 81.02%. The least effective plant extract was Ocimum gratssimum with radial inhibition of 11.50%, which occurred also on the fifth day. Plant extracts were as effective as the synthetic fungicide in inhibiting growth of the test fungus. Therefore, the effective extracts, all of which are readily available to the farmers, should be promoted instead of the synthetic fungicides, which are in limited supply and invariably expensive for rice farmers in Nigeria.

Effects of Variety and Fungicides on Germination Percentage and Seedling Vigor of Rice (Oryza sativa L.) Seeds

“…Both the plant extract and synthetic fungicide where effective in protecting the rice seeds. This is in agreement with [29], who reported that the crude aqeous extract of Azadiractha indica gave the second highest mycelial growth inhibition of Helminthosporium oryzae after extract of Piper guineesis with inhibition in an in-vitro experiment. The plant extracts were as effective as the synthetic fungicides in inhibiting the radial growth of the test fungi.…”

“…Plant metabolites and plant-based pesticides appear to be one of the better alternatives as they are known to have minimal environmental impact and danger to consumers in contrast to the synthetic pesticides [17]. Plant materials fresh leaves of Azadirachta indica (neem), clove of Allium sativum (garlic) and rhizome of Zingiber officinale (ginger) have been effectively in controlling fungal pathogens of rice [7] and [18]. In this work, attention will be given to the use of Aidan fruit (Tetrapleura tetraptera) crude extract.…”

Comprehensive Phenotypic Assessment of Rice Diseases in Cultivated Farms within Okpuitumo Community, Ikwo Local Government Area, Ebonyi State: Implications for Sustainable Rice Crop Management

“…Ikwo Local Government Area of Ebonyi State is well known for rice production in Nigeria, but pest and disease infestation have been progressively affecting rice production potential of the area. Rice blast disease caused by Fungus [5][6][7][8][9][10], Stem nematode disease caused by Nematodes (Ditylenchus dipsaci), Rice Yellow Mottle Virus (RYMV) disease caused by Virus (Sobemovirus) and Maize Streak Virus (MSV) disease caused by viruses as well as brown spot disease caused by the fungus (Bipolaris oryzae) have been identified as major constraints to rice production in Nigeria, causing low grain quality and significant yield loss [11][12][13][14][15][16]. Rice farmers in the study area are really suffering serious yield loss which is discouraging young persons from engaging in rice production business for a leaving.…”