To artificial inoculation of sunflower plants with modern pathotypes of rust for breeding on immunity

Under global warming of the last decade, there is observed an intensive spread of rust in sunflower fields in the Russian Federation, due to the emergence of new races of the pathogen. It is obvious that there is a need to breed sunflower for resistance to new pathotypes and to correct the technique of artificial inoculation of plants in relation to them. Sunflower breeding for rust resistance has not been carried out since the 1980s. Objective of the study is determining the optimal temperature range for artificial inoculation of sunflower leaves with modern pathotypes (300 and 700) of the rust pathogen. The work was performed in the laboratory of immunity of the V.S. Pustovoit All-Russian Research Institute of Oil Crops in 2020–2021 using monopustular isolates of Puccinia helianthi with virulence codes 300 and 700. The germination of mature urediniospores, the duration of the incubation period and the degree of damage to sunflower plants at different temperatures were studied. The incubation period of pathotypes 300 and 700 of P. helianthi at a temperature of 26–28 °C is reduced by 2–3 days, which is essential both for the rapid identification of the racial identity of the pathogen isolates and for shortening the period for assessing sunflower genotypes when breeding for immunity. To speed up this work, the infection of sunflower plants should be carried out in the phase of the first pair of true leaves at a temperature of 22 °C, followed by a 24-hour stay in a humid chamber at 20 °C and a further increase in the growing temperature to 26–28 °C.

Evaluation of fungicide efficacy on sunflower rust (Puccinia helianthi) on oilseed and confection sunflower

Sunflower rust, caused by Puccinia helianthi, is an economically and globally important disease of sunflower. Two types of sunflowers are produced in the US Northern Great Plains; the oilseed type and the confection type. Although approximately 80% of the acreage in this region is planted as the oilseed type sunflower, fungicide efficacy and timing studies have been conducted primarily on the more rust-susceptible confection type. A total of ten sunflower rust efficacy field experiments were conducted on oilseed type and confectionary type hybrid trials from 2016-2018. Eleven fungicides from three FRAC groups were evaluated for efficacy and protection of yield. Severity differences among fungicide treatments were identified in both confection and oilseed type sunflower trials. A combined analysis of all confection field trials (five) indicated that rust severity was lower in all fungicide treatments as compared to the non-treated control. Despite rust severity levels below the fungicide action threshold for confection sunflower, seven of the eleven fungicide treatments had yield higher than the non-treated control. In oilseed trials, rust severity was lower in all fungicide treatments as compared to the non-treated control, similar to the findings of the confection type. Rust severity was too low to detect yield differences in oilseed trials. Additional work is needed to elucidate yield-loss potential on oilseed type sunflower and refine the fungicide action threshold on confection type sunflower.

New races of rust pathogen on sunflower in Russia

Over the past two decades, there was observed a widespread of rust on sunflower in some regions of Russia. The identification of the racial structure of Puccinia helianthi populations in Russia has not been done since the early 80s of the last century. At that time, races 100 and 300 were identified. In our recent study, in addition to these races, new biotypes: 700, 710, 722, 772 were identified for the first time. The purpose of this study is to determine the racial identity of 160 P. helianthi isolates collected from 2018 to 2020 in the Rostov, Saratov, and Krasnodar regions. We used eight standard differentiating lines of sunflower: SM-90, SM 29, R-386, HАR-1, HАR-2, HAR-3, HAR-4, HAR-5. Sunflower variety VNIIMK 8883 was used as a differentiator susceptible to all races of the pathogen. In addition to the six races mentioned above, we identified 11 more new races for the first time: 304, 351, 352, 364, 704, 736, 740, 741, 745, 760, 762. Race 700 prevailed among the isolates collected in the Rostov region in 2020; we also identified single specimens of races 760, 762. Thus, 17 races of P. helianthi were found on sunflower in three regions of the Russian Federation. Other races may be also present here, so further research is required.

Sunflower rust (Puccinia helianthi Schwein) (literature review)

Diseases caused by fungi, bacteria and viruses are a serious obstacle to high yields of sunflower seeds. One of the most harmful fungi is the rust pathogen (Puccinia helianthi Schw.). Based on the analysis of domestic and foreign scientific literature, there has been presented the information on the history of the study of sunflower rust, the biology of the pathogen, the racial composition of its populations, the pathogenesis of the disease and selection for resistance to this disease in the Russian Federation and in other countries of the world. There has been considered the contribution of G.V. Pustovoit and her students in the development of breeding sunflower material with rust resistance based on interspecific hybridization of cultivated sunflower with wild species. There has been shown the contribution of the researchers W.E Sackston, T.J. Gulay, S. Masirevic and others, who proposed methods for assessing breeding material for resistance to a pathogen, methods of artificial infection of plants in a greenhouse and a field, who developed differentiator lines of the rust races. Currently, when calculating the virulence and race code of Puccinia helianthi, there is used a nomenclature adopted by a special international committee. Recently, there have been reports from different countries of the emergence of new, more aggressive races of the causative agent of sunflower rust. In Russia, the work on the study of this pathogen has also expanded. The scientists have monitored the rust races and revealed the racial composition of the fungus populations on sunflower in the regions with a strong manifestation of the disease (Tambov, Saratov and Lipetsk regions, Krasnodar Area). Based on the studied literature data, there has been made a conclusion that it is necessary to expand and accelerate work on monitoring the racial composition of populations of the rust pathogen in agrocenoses and developing breeding material that is resistant to the identified races.

Monitoring of diseases in crops of sunflower varieties bred at VNIIMK

We observed the diseases in crops of oil and confectionary sunflower in the environments of the central zone of the Krasnodar region in 2018–2020. There are prevailed in crops: bacterial diseases (Xanhomonas, Pseudomonas, Pectobacterium, Rhizobium), dry rot (Rhizopus Ehrenb.), rust (Puccinia helianthi Schw.) and Alternaria blight (Alternaria Nees.). The strongest bacterial blight was observed on confectionary sunflower varieties (up to 72.5%) in 2020. Frequency of dry rot varied depending on the weather conditions of a year: on oil sunflower varieties from 10.0 to 64.0%, on confectionary varieties – from 4.5 to 55%. In recent years rust infection is increased significantly. Frequency of this disease varied from 10 to 64.8% on confectionary sunflower varieties. Rust prevalence on oil sunflower varieties is from 0 to 17.5%. Alternaria blight infection was more on confectionary varieties Karavan (40%) and Conditer (42.5%). Prevalence of the dangerous quarantine disease phomopsis (Phomopsis helianthi Munt.-Cvet.) was insufficient in the years of the research and varied from 0 to 3.7% at the level of infection intensiveness of sunflower plants 0–4 scores due to 4-score scale.

Mycoses as causes of biotic stress in sunflower production

Osjetljivost suncokreta na biotski stres uvelike određuje vrijednosti agronomskih svojstava. Uzročnici biotskog stresa mogu biti različiti, a u svijetu pa tako i u Hrvatskoj se po svome utjecaju izdvajaju bolesti. Uslijed pojave različitih biljnih bolesti, u pojedinim godinama prinosi zrna i ulja suncokreta mogu biti reducirani i preko 50%. Najčešći uzročnici bolesti suncokreta su gljive, a prema stupnju štete koje prave ističu se Sclerotinia sclerotiorum, Diaporthe/Phomopsis helianthi i Plasmopara halstedii te u nešto manjoj mjeri Alternaria helianthi, Phoma macdonaldii, Puccinia helianthi, Verticillium spp., Botrytis cinerea, Macrophomina phaseolina i Erysiphe cichoracearum. Kreiranje otpornih/tolerantnih linija iz divljih formi suncokreta, a zatim transfer poželjnih gena u komercijalne linije i hibride je najčešći oblik povećanja otpornosti/tolerantnosti linija i hibrida suncokreta na biotski stres. U ovom postupku značajnu ulogu ima primjena molekularnih markera. Pored toga važan je stalni monitoring, ali i pravovremena primjena agrotehničkih, kemijskih i bioloških mjera.

Phenotypic and genotypic variation of Puccinia helianthi in South Africa

Sunflower (Helianthus annuus L.) is the third largest grain crop by area planted in South Africa (SA). The annual yield is negatively affected by sunflower rust caused by Puccinia helianthi Schw. (Phe). Four Phe races were described in SA in the middle 1990’s, but since then, no new race descriptions have been conducted. This has resulted in an information gap on the current Phe population, making it difficult to explain increased disease incidence and loss of resistance in previously resistant hybrids. To address this, 114 Phe field isolates along with 23 historic isolates were phenotyped using the international set of eleven sunflower differentials containing the R1, R2/R10, R3, R4a, R4b, R4c, R4d, R5, Pu6 and Radv resistance genes. Three new Phe races were identified, bringing the total number of South African races recorded to seven. No avirulence was detected to the R1 gene, with the R4d and Radv genes remaining effective. Four main genetic lineages were detected with no obvious correlation between phenotype and genotype. The detection of three genetic lineages consisting exclusively of field isolates collected post-2006, suggested the possible recent entry of exotic introductions into SA. This, combined with the fact that one lineage consisted exclusively of the most virulent race Phe7721, confirmed a clear shift in the Phe population that could explain the increased virulence and occurrence of the disease in SA.