Wheat Seed-Borne Mycoflora, Pathogenicity of Fusarium moniliforme Isolates and their Molecular Characterization

Abstract

Nine samples of wheat grains cv. Sakha 69, were screened for the associated fungi, 15 fungal species belonging to eight genera were isolated from wheat seeds. The isolated fungi were Aspergillus flavus, Aspergillus niger, Aspergillus ochraceous, Aspergillus parasiticus, Alternaria alternata, Stemphylium sp., Cladosporium sp., Drechslera sp. Fusarium solani, Fusarium moniliforme, Fusarium semitectum, Fusarium nivale, Fusarium oxysporum, Penicillium spp., Trichoderma sp. The genus Aspergillus gave the highest percentage of seed colonization of the isolated fungi followed by Fusarium spp. Pathogenicity test for nine isolates of F. moniliforme was conducted under greenhouse conditions to investigate the levels of infection against wheat cv. Sakah 69 and the percentage of infection was used as a criteria to evaluate the pathogenicity of F. moniliforme isolates against wheat seedlings. Cluster analysis was a reliable method to differentiate between nine isolates belonging to the genus Fusarium. Three different primers were used in the following study to differentiate among F. moniliforme isolates and the third primer proved to be the best in grouping F. moniliforme isolates into numerous distinct groups. Key Words: Wheat (Triticum aestivum L.), seed-borne mycoflora, RAPD technique, pathogenicity of F. moniliforme. I. Introduction Numerous injuries and stresses, affect on wheat plants at all stages of growth, which interfere with their normal functioning and development. Each year wheat losses are increased due to seed infection and contamination [1] and [2].Therefore a seed health technique usually plays an important role for successful cultivation and yield exploitation of a crop species. From various factors that affect seed health, the most important are the seed borne fungi that lower seed germination and reduce seed vigor resulting in low yield and quality [3]. Earlier investigations reported that seed plays an important role not only for successful cultivation but also for increasing yield of crop. Numerous seed-borne pathogens of grain crops are responsible to cause variation in plant morphology and also reducing yield [4] and [5]. Fusarium sp. is one of the most important genera of plant pathogenic fungi, with a record of devastating infections in many different kinds of economically important plants [6]. Numerous crops all over the world are attacked by Fusarium spp. which are responsible for wilt blights, root rots and cankers. In recent years the use of various nucleic acid-based techniques for the detection and identification of microorganisms has dramatically increased and may provide high specific tools for molecular studies [7] and [8]. Restriction fragment length polymorphisms (RFLPS), which are costly and time consuming, can be used; however, the random amplified polymorphic DNA (RAPD) is also a suitable technique to evaluate taxonomic identity. The application of (RAPD) to produce isolate-specific DNA-finger prints is especially promising [8] and [9]. This technique has the advantage of that no DNA base sequence information of the organism is needed. The technical simplicity and speed of RAPD methodology is a principal advantage over other techniques [7]. The aim of the present study was to survey wheat seed-borne fungi, test the pathogenicity of some isolates against wheat cv. Sakha 69 and to compare the molecular characterization for these isolates by using RAPD technique.