Efficacy of modern fungicides against tomato alternaria blotch

Goal. To determine the species composition of early blight on tomatoes and to establish the technical effectiveness of modern fungicides. Methods. The research was conducted in 2019—2020 in Cherkasy, PE «Poretsky» on tomatoes variety Zagadka. Weather conditions of the growing season favored the intensive disease development. Plot size — 10 m2 in 4 replicates, placement of plots — randomized. Agricultural techniques are common for the growing area. To determine the species composition of pathogens, during the growing season samples of plants with typical symptoms were taken. Isolation of phytopathogen in pure culture and their identification was carried out in the laboratory according to conventional methods. To determine the technical effectiveness of fungicides the following fungicides were used: Zorvek Incantia, SE (0.5 l/ ha), Orvego, KS (1.0 l/ha), Quadris 250 SC, hp (1.0 l/ha), Quadris Top 325 SC, KS (0.6 l/ha), Cabrio Duo, KE (2.5 l/ha), Signum, VG (0.3 kg/ha), Thanos 50, VG (1.0 kg/ha). Results. As a result of research, it was found that during the growing season early blight was the most common. According to our research, the disease is caused by two species of the pathogen Alternaria alternata (Fr.) Keissl. and Altrenaria solani Sorauer. We found that almost 70% of isolated and identified isolates were classified as Alternaria solani. For protecting of tomatoes against early blight following fungicides were used: Zorvek Inkantiya, CE (0,5 l/hectare), Orvego, KS (1,0 l/h), Kvadris 250 SC (1.0 l/ hectare ), Kvadris Top 325 SC (0.6 l/h), Kabrio Duo, KE (2.5 l/h), Signum, VG (0.3 kg/h), Tanos 50, VG (1.0 kg/h). Technical efficiency of them was 55.6—78.6%, and the stored harvest — 5.11—6.62 t/ha. Conclusions. As a result of researches we specified specific composition of early blight of tomatoes. It is set that disease is caused by two species: Alternaria alternata and Alternaria solani, that are different in anatomo-morphological properties. It is established that to protect tomatoes from Alternaria, it is advisable to apply the following fungicides: Kvadris 250 SC (1.0 l/h), Kvadris Top 325 SC (0.6 l/h), Kabrio Duo, KE (2.5 l/h).

Evaluation of 110 Apple Cultivars for Resistance to Alternaria Blotch Caused by Alternaria alternata Apple Pathotype

Apple blotch caused by Alternaria alternata apple pathotype is a severe disease of apple (Malus ×domestica Borkh) occurring throughout the world, especially in eastern Asia. Phenotypic and genetic information about resistance/susceptibility of apple germplasm to this disease will be extremely valuable for selecting and developing new disease resistant cultivars. In this study, 110 apple cultivars obtained from the USDA apple germplasm in Geneva, NY, were evaluated for their resistance/susceptibility to apple blotch by field surveys, and inoculation of detached leaves with a suspension of germinated conidia of A. alternata apple pathotype. Disease incidence were different among the cultivars and categorized into resistant (R), moderately resistant (MR), or susceptible (S). Two molecular markers, S428, a random amplified polymorphic DNA (RAPD) marker associated with disease resistance, and a simple sequence repeat (SSR or microsatellite) marker CH05g07, linked to susceptibility were used to correlate the phenotypes expressed in field surveys and laboratory inoculations. The detection using either the S428 marker or the CH05g07 marker in 50 common breeding cultivars was consistent with R or S traits except for ‘Bisbee’ and ‘Priscilla’. These two cultivars were MR to apple blotch through phenotyping. However, SSR markers were detected, but RAPD markers were not and therefore were considered susceptible. Combined with the record of resistance to fire blight from Germplasm Resources Information Network (GRIN), ‘Dayton’, ‘Mildew Immune Seedling’, ‘Puregold’, and ‘Pumpkin Sweet’ were highly resistant to both diseases and considered as the best choices of parents for stacking resistance to multiple diseases in breeding program.

A Simple Sequence Repeat Marker Linked to the Susceptibility of Apple to Alternaria Blotch Caused by Alternaria alternata Apple Pathotype

Alternaria alternata apple pathotype (previously A. mali) causes alternaria blotch disease of apple (Malus ×domestica), which may result in leaf spots and up to 70% premature leaf drop in serious cases. This disease is of worldwide importance but is most serious in eastern Asia (Japan, Korea, and China) and in parts of the United States. The excessive use of fungicides not only adds cost to apple growers, but also pollutes the environment. In this study, we characterized a 5-year F1 population from a cross of a resistant cultivar (Huacui) and a susceptible cultivar (Golden Delicious) consisting of 110 individuals along with 14-year-old parent trees (10 each). A field evaluation of disease severity was conducted in 2008 and 2009 under the natural conditions in Liaoning, China (lat. 40°37′ N, long. 120°44′ E). Based on the field data, 110 F1 plants were divided into five groups. Artificial inoculation was carried out both on the living trees and on the detached leaves in 2009 to ensure that A. alternata apple pathotype was the causative agent. Eighty primer pairs of simple sequence repeat (SSR) were screened against the four genomic DNA pools, respectively, from six highly susceptible F1 plants, six most resistant F1 plants, one tree of the seed parent, and the one tree of the pollen parent. One pair of primers (CH05g07) was shown to be linked to the DNA pools of susceptible F1 and the parent tree, but not to the DNA pools of resistant F1 and parent trees. This primer pair was then used to screen all individual 110 F1 progenies and two parent trees. The differentiation of 103 individuals (97.3%) with the marker matched the field disease resistance rating. This marker was further screened with 20 cultivars with known susceptibility or resistance to A. alternata apple pathotype and its linkage to susceptibility was validated. These results suggest that this marker can be used in marker-assisted selection for resistance/susceptibility to alternaria blotch disease in apple.