Aspergillus species groundnut seed invasion as influenced by soil solarization and time of planting

KT Mawcha , DA Assefa2

Author address: 

1Department of Plant Pathology, Aksum University, Shire, Ethiopia 2Department of Plant Sciences, Mekelle University, Mekelle, Ethiopia

Abstract: 

Purpose: A wide range of abiotic and biotic stresses negatively impact groundnut production in the field and generally contributes to the reduced quality of marketed peanut in Ethiopia and Africa. Groundnut is economically important oil and food crop and is one of the most susceptible crops to aflatoxin contamination yet it is a major staple, widely cultivated and consumed in Africa. However, owing to lack of appropriate management practices, Aspergillus fungi and subsequent aflatoxin contamination can be an extremely serious health problem. Soil solarisation could increase the soil temperature and could minimize fungal inoculum in the soil. Use of different planting times could help overcome conditions of drought stress and elevated soil temperature which are known to favour pre-harvest aflatoxin contamination.

Methods: Laboratory and field experiments were conducted in northern Ethiopia, at two locations to determine the effect of soil solarization on Aspergillus spp. inocculum in the soil and to evaluate the effect of soil solarization and time of planting on A.flavus seed invasion. Soil temperature has measured three times per day using digital thermo meter. Eighty soil samples were taken in three rounds and analyzed for aflatoxigenic population. Seed samples (80) of the three varieties were plated on Czapek-Dox Agar medium. Individual and total cfu g-1of soil was determined before, after solarization and at harvest. different species of Aspergillus were isolated form seed and soil samples and identified morphologically.

Results: Soil solarization reduced fungal inoculums. Aspergillus flavus, A. parasiticus, A. niger and A. terreus were identified. Aspergillus flavus and A. parasiticus were found reduced by 53.8 and 45% cfu g-1 in Ramma and 36.4 and 44% cfu g-1 at 5 and 10cm soil depths at Mayweyni, respectively, after soil solarization in the solarized plots than the nonsolarized plots.Aspergillus niger was found the most dominant species (0.6 x 103 and 1.6 x103cfu g-1soil) at 5cm soil depths in Mayweyni and in Ramma, respectively. At harvest, Fusarium spp., A. flavus and A. terreus were detected from soils. Three Aspergillus species namely, A. flavus (32.8%), A. niger (22.5%), and A. parasiticus (15.51%) were isolated from seed samples and early planting of the varieties showed the lowest level of seed invasion by A. flavus (32.8%).

Conclusion: Improved production in the field, storage, adequate soil solarization, with adequate soil moisture can increase groundnut yield and quality and minimize aflatoxin contamination. Hence, pre-harvest seed invasion of groundnuts could be minimized by using soil solarisation and appropriate agronomic practices, i.e. using appropriate planting times and planting suitable varieties.

2018

Full conference title: 

The 8th Advances Against Aspergillus, Lisbon Conference Center, Lisbon, Portugal
    • AAA 8th (2018)