In the years 2000–2003 under Polish climatic conditions early blight occurred at different level of incidence on over 90.6% of surveyed fields. Time of disease appearance in different regions was closely related to climatic conditions. On average, early blight appeared on potato plants 59.3 days after planting, earlier than late blight. In the years 2001–2003, efficacy of six selected fungicides in early blight control was examined in field conditions. Experiments carried out in the Department of Potato Protection and Seed Science of Plant Breedingand Acclimatization Institute. Field trials located in two sites – at Bonin and Stare Olesno revealed much slower development of early blight on these fields where chemical protection was applied as compared to untreated control. Efficacy of plant protection program carried out in Bonin over three years varied from 40% to 63.9%. Effectiveness of selected products was higher in Stare Olesno at higher infection pressure, and ranged from 49.8% to 66.6%. However, efficiency of chemical protection in early blight suppressing is not as satisfactory as in late blight control. In field experiments good control of early blight resulted in tuber yield increase. In Bonin yield increase varied from 5.5 to 24.2% and in Stare Olesno from 12.2 to 34.4%.

Early blight disease caused by Alternaria sp. is one of the most devastating diseases of

Solanaceous crops widely distributed in Sudan. The aim of this study was to determine the

genetic variation among different Alternaria isolates recovered from different Solanaceae

crops showing typical symptoms of early blight disease. Infected leaves of tomato, potato,

eggplant and pepper were collected from different geographical zones in Sudan. The recovered

fungal isolates were identified to the genus level based on cultural and morphological

characteristics. Five representative isolates were sent to the CABI Bioscience, U.K. for confirmation.

The genetic relationship among the isolates was determined using the amplified

fragments length polymorphism (AFLP) technique and the generated data were used to

create similarity matrices using the PAST 3.01 software package. Dendrograms were constructed

based on Jaccard’s similarity coefficients. A total of 70 fungal isolates was recovered

from the tested plants and all of them showed morphological characteristics typical

of Alternaria spp. The conidia appeared in multiple-branched chains with spore sizes in

the range of 2.38−13.09 μm × 12.30−43.63 μm. Therefore, the isolates were identified as

Alternaria alternata (Fr.) Keissl. The identification was then confirmed by CABI.AFLPbased

dendrogram which revealed five clusters with a significant cophenetic correlation

coefficient (r = 0.834) between the dendrogram and the original similarity matrix irrespective

of their geographical origins. Eighteen (75%) of the Alternaria isolated from tomato

leaves were clustered together in cluster I and five isolates formed two separate clusters,

viz. cluster IV (T-Kh5 and T-H1) and cluster V (T-H4 and T-Med2). The remaining isolate,

T-Am5, grouped with one of the potato isolates in cluster III. The other isolates which were

recovered from potato, pepper and eggplants were all separated from the tomato isolates

in the largest cluster.

Potato (Solanum tuberosum L.), an important food crop in the world, is susceptible to many fungal pathogens including Alternaria solani and Fusarium oxysporum causing Fusarium wilt and early blight diseases. Mycoparasitic fungi like Trichoderma encode chitinases, cell wall degrading enzymes, with high antifungal activity against a wide range of phytopathogenic fungi. In this study, a binary vector harboring endochitinase gene of ~1,000 bp was constructed and used to transform potato nodes through Agrobacterium-mediated transformation. Out of several primary transformants, two transgenic potato lines were verified for transgene insertion and integration by Southern blot. In a pot experiment for Fusarium resistance, the transgenic potato lines didn’t show any symptoms of disease, instead they remained healthy post infection. The transgenic potato lines exhibited 1.5 fold higher mRNA expression of endochitinase at 7 days as compared to 0 day post fungus inoculation. It was evident that the mRNA expression decreased over days of inoculation but was still higher than at 0 day and remained stable upto 30 days post inoculation. Similarly, for A. solani infection assay, the mRNA expression of the endochitinase gene was 3 fold higher 7 days post inoculation compared to expression at 0 day. Although the expression decreased by1.2 fold during subsequent days post infection, it remained stable for 30 days, suggesting that protection in transgenic potato plants against fungal pathogens was achieved through an increase in endochitinase transcript.

The studies conducted in two different localities revealed variable time of occurrence and severity level of potato early blight (Alternaria spp.). Each year at Stare Olesno the early blight caused considerable destruction of potato plants (90.2%-95.4%) while at Bonin the disease severity differed in particular years and ranged from 50.0% to 97.5% of destructed plants at the end of the growing season. Field trials showed good efficacy of fungicides selected for controlling the early blight compared with an untreated control. Spraying with fungicides limited development of the disease and increased tuber yield in the range from 21.9% to 60.9% for Bonin and from 13.0% to 101.9% for Stare Olesno surveys. The mixture of zoxamide with mancozeb showed the greatest efficacy.