RESEARCH ON ALTERNARIA SPECIES PRESENT ON RAPESEED (Brassica napus) IN THE SOUTH REGION OF ROMANIA

Alternaria species have a variable affinity for host although they are often found in conjunction. The aim of this study was to compare the distribution of six Alternaria species present in infected seeds samples taken directly from two districts in South Romania. Ten samples of seeds were taken directly from ten different growing fields in Teleorman and Calarasi, in June, just prior to harvest. For each of the ten samples has been performed three replicates, each of five seeds. Overall 150 seeds were placed on Petri dishes (empty set 10 cm) on PDA. A semi-permanent slides was performed from each of the colonies formed around the seeds after 10 days of incubation, at 21 degrees C. These slides were analyzed, field by field, under a microscope (x40), until 50 conidia of Alternaria species were identified. For each replicate an average of 2350 conidia (150-250 conidia/plate) were identified with certainty on 94% in vitro colonies formed by pathogens around the seeds. Alternaria brassicicola was the most frequent species identified on seeds from growing fields in Calarasi (53.91%) and Teleorman (57.12%). We found that A. brassicicola and A. brassicae were present on all infected seeds whereas A. brassicicola, A. brassicae and A. radicina were detected on 93.62% colonies formed around the seeds. The relative distribution of A. brassicae (p < 0.0001), A. brassicicola (p < 0.0001), A. radicina (p = 0.001) and A. solani (p = 0.0003) in samples from Calarasi and A. radicina (p = 0.004), A. solani (p = 0.028), A. tenuis (p = 0.0006) in samples from Teleorman were found be present statistical significant differences. Overall these results indicated that the distribution of Alternaria species can present significant variations even if samples from the same district are investigated.