Seed-borne mycoflora of alfalfa (Medicago sativa L.) in the Riyadh Region of Saudi Arabia

Fifteen seed samples of local alfalfa (Medicago sativa L.) cultivar (Hegazy) collected from fields at different governorates of the Riyadh region in Saudi Arabia were screened for their seed-borne mycoflora. Standard moist blotter and deep-freezing blotter methods recommended by the International Seed Testing Association, in addition to an innovative alkaline seed-bed method were applied. A total of 24 genera and 35 species of fungi were isolated using the above-mentioned techniques. Alternaria alternata, Cladosporium sp., Aspergillus sp., Stemphylium sp. and Penicillium sp. were the genera most commonly isolated. Among the various techniques adopted for detection, the alkaline NaOH method was found to be effective and yielded the maximum number of pathogenic fungi. Syndromes of seed discoloration were also investigated. The alkaline seed-bed method using NaOH was used to detect saprophytic and pathogenic seed-borne fungi associated with discolored seeds. A total of 15 genera and 26 species of fungi were isolated. Cladosporium sp., Alternaria alternata and Aspergillus species were the saprophytic species detected most, while Stemphylium botryosum and Fusarium incarnatum were common pathogenic fungi found on discolored seeds. The average of incidence and occurrence percentages of most detected fungi were higher in discolored seeds than in normal seeds. Seed germination was also affected significantly by discoloration. The data also indicate that seed discoloration decreases seed germination significantly (by 26.3–60%).