Quantitative Trait Loci for Resistance to Potato Dry Rot Caused by Fusarium sambucinum

Tuber dry rot is an important disease of potato caused by soil and seed-borne pathogens of the Fusarium genus leading to losses that may reach 60% of the yield. The goal of this work was to study the inheritance of the dry rot resistance in two diploid potato hybrid populations (11-36 and 12-3) with complex pedigrees, including several wild Solanum spp. We used an aggressive isolate of F. sambucinum for phenotyping both progenies, parents, and standard potato cultivars in laboratory tuber tests, in three subsequent years. The QTL for dry rot resistance were mapped by interval mapping on existing genetic maps of both mapping populations. The most important and reproducible QTL for this trait was mapped on chromosome I and additional year- and population-specific QTL were mapped on chromosomes II, VII, IX, XI, and XII, confirming polygenic control of this resistance. This is the first study mapping the loci affecting tuber dry rot resistance in potato genome that can contribute to better understanding of potato-F. sambucinum interaction and to more efficient breeding of resistant potato cultivars.

Sunflower diseases control by biological fungicides

The demand for organic food has grown rapidly over the last 25 years in many countries of the world. Organic farming standards require the application of biological products of disease control. The article presents the material on studying the effectiveness of fungicides based on microbiological antagonists against sunflower diseases. We carried out the study in 2020-2021 at V.S. Pustovoit All-Russian Research Institute of Oil Crops (VNIIMK) (Krasnodar). We established that the fungicides Geostim Fit type E, WS based on microbiological antagonists did not reduce the germination of sunflower seeds and actively suppressed seed infection. Their effectiveness against Alternaria spp. reached 50-74 %, against Rhizopus spp. – 74–100 %, against bacteria – 76–80 %. Double treatment of sunflower plants with BFTIM, WS (different strains) reduced the frequency of bacterial blight to 37 %, of dry rot – to 60 %, of Alternaria blight – to 39 %, of Phoma rot – to 41 %, and of Fusarium blight – to 75 %. The application scheme of Geostim Fit E (G), WS; BFTIM (E), WS; BFTIM (Zh), WS showed the best economic effectiveness with a seed yield of 3.56 t/ha, net income of 122 910 rubles, and profitability of 311 %.

EVALUATION OF POTATO VARIETY CHARACTERISTICS DURING STORAGE

The potato (Solánum tuberósum) is one of the main food crops of the Siberian region. The research goal was the selection of potato varieties of different maturity periods suitable for storage. We analyzed the yielding capacity and storage of potatoes in the Kemerovo Region from 2016 through 2020. Over 5 years of research, the range of yield variation of early maturing varieties averaged 11.9%. The fluctuations over the years were from 6.2% to 18.9%. It was found that the decrease dynamics of potato gross har-vest was similar to the decrease dynamics of the sown areas and yields. Potato storability studies were carried out on the farm of KFKh Tumanov A.A. The farm is located in the steppe zone of the Kuznetskaya Depression. The soil type is the leached heavy loamy chernozem with the hu-mus layer of 20-25 cm and pHof 5.6-5.8. The preceding crop was wheat. The research targets were potato tubers of medium early and early maturity varieties. The following was determined: potato tuber quality, starch weight per-centage, ascorbic acid content according to L.E. Gunar, and dry solids according to GOST (Russian National Standard). Mathematical processing was carried out ac-cording to B.A. Dospekhov. It was found that the quality of potatoes placed for storage depended on the cultivation conditions and varietal characteristics. All varieties lost some dry solids, vitamin C and starch during storage. The maximum losses were found regarding the number of pota-to tubers affected by dry rot. It was found that after 4 months of storage, the natural tuber weight loss aver-aged 1.8% for early-maturing varieties; it decreased to 6.6% over 9 months of storage; the weight loss averaged 2.0% for medium-early varieties (after 4 months); 5.4% -after 9 months; that was by 4.8% and 3.4% more, respec-tively.

Fungi Associated with Postharvest Diseases of Sweet Potato Storage Roots and In Vitro Antagonistic Assay of Trichoderma harzianum against the Diseases

Sweet potato is the 11th most important food crop in the world and an excellent source of nutrition. Postharvest diseases were monitored in sweet potato storage roots collected from the local markets in Korea during 2021. Several diseases including Fusarium surface and root rot, charcoal rot, dry rot, and soft rot were observed in the postharvest sweet potatoes. A total of 68 fungal isolates were obtained from the diseased samples, and the isolates were grouped into 8 different fungal colony types. Based on multilocus phylogeny and morphological analysis of 17 representative isolates, the isolates were identified as Fusarium oxysporum, F. ipomoeae, F. solani, Penicillium citrinum, P. rotoruae, Aspergillus wentii, Mucor variicolumellatus (Mu. circinelloides species complex), and Macrophomina phaseolina. F. oxysporum was the predominant pathogen as this is the most common pathogen of sweet potato storage roots causing the surface rot disease, and M. phaseolina caused the most severe disease among the pathogens. Dual culture antagonistic assays were evaluated using Trichoderma harzianum strains CMML20–26 and CMML20–27. The results revealed that the two strains showed strong antifungal activity in different ranges against all tested pathogens. This study provides an understanding of diverse postharvest diseases in sweet potatoes and suggests potential biocontrol agents to manage the diseases. In addition, this is the first report of sweet potato storage root rot diseases caused by A. wentii, and P. rotoruae worldwide.

Draft genome sequence of Diaporthe batatatis causing dry rot disease in sweetpotato

Dry rot caused by Diaporthe batatatis leads to the serious decay of sweetpotato storage roots during postharvest storage, which can result in considerable economic loss. Genomic research of the pathogen could provide a basis for study and prevention of sweetpotato dry rot. Herein, we report a high-quality draft genome sequence of D.batatatis CRI 302-4 isolated from infected sweetpotato storage roots in Taizhou City, Zhejiang Province, China. The size of the genome was 54.38Mb and consisted of 36 scaffolds with a G+C content of 50.56% and an N50 of 2,950,914 bp. The information provided in this genome sequence will be an invaluable resource for molecular genetic research and disease control in sweetpotato production.