Garlic White Rot (Sclerotium cepivorum Berk.) in Shewa: Significance, Variability and management options.

morphological studies indicated that colony diameter, days to production of sclerotia, number of sclerotia, and size of sclerotia were significantly different among the isolates of pathogen.greater number of sclerotia (648.50/Cm2) was recorded from isolates colleted from Angolela and Asagirt district.Larger sized (612.60µm) sclerotia were measured for isolates of Lalo maama Mider. Using the random amplified polymorphic DNA (RAPD) method iwth M13 primers, genetic diversity was identified among the isolates.At species level, Nei's gene diversity (b)was 0.3474 and Shannon's index of fdiversity (I) was 0.5184. At population level, the percentage of polymorphic bands (PPB), the average number of alleles (na), and the number of effective alleles (ne) of the populations were different.The unweighted pair-group mean analysis (UPGMA) cluster analysis showed that the isolates form different district were grouped in different clusters.The coesfficient of gene differentation (Gst) in the total population was 0.1128, indicating that the genetic variation among popilations was 11.28%. Garlic yield of both Tseday (G-493) and local garilic cultivars were improved by fungicide application.On average marketable yield increased 27-44.1% at Debre Zeit and 33-70% at Bakelo over the control plots.Treatment of garlic cloves with tebuconazole at the rate of 2.1ml kg and spray at 0.25 1ha at stem bases resulted in a significatnt reduction in initial and final white rot incidence, progress rate, and severity on bulbs. Captan at the rate of 4.17gkg and benomyl at 5.2gkg gave significant reduction in final disease incidence and the disease reduced by 16% and 24%, respectively over control at Bakelo. At Debre Zeit these fungicides decreased final disease incidence by 40-44%. Highest marketable yield was obtained from tebuconazole (43-73%), captan (48-77%) and benomyl (42-64%) over the control. Amendments of infested soil with brassica carinata seed meal, green manure and dried plant residue reduced the incidence of white rot and increased bulb weight.Incorporation of seed meal at 10,20 and 25gkg of soil singificantly decreased white rot incidence (0%) and increased bulb weight by 43-51% as compared with unamended soil.Green manure amendments with B. carinata lines having high glucosinolates reduced disease incidence up to 2-20.7% and Brassica line with medium glucosinolates up from 5 to 24.5%. Dried crop residue,on average, reduced the disease incidence from 0-35%.