B.V. Anisimov, S.N. Zebrin, Federal State Budget Scientific Institution All-Russian Research Institute of Potato named after A.G. Lorha "
International practice in the system of production, quality control and certification of seed potatoes is focused on the development and continuous improvement of the regulatory framework based on accumulated international experience in this field.
Regular updating of relevant provisions and normative indicators of commercial quality of seed potatoes allows timely and efficient reflection of the necessary changes in them related to the production and marketing of seed potatoes, the introduction of new certification methods, and especially with the evolution of pests and the changing phytosanitary situation in connection with local and global processes of climate change. Based on the summarized modern data, changes in the biological diversity of a number of pathogens and pests dangerous for potato that have occurred in recent years are particularly important, namely:
• new strains of viruses appear, causing more severe forms of damage to plants and tubers. Among them, PVY (ntn), which causes necrotic ring spotting of potato tubers (Potato Tuber Necrotic Ringspot (PTNR)), is particularly harmful;
• problems with bacterioses increase due to the emergence of new types of black-footed pathogens (Pectobacterium / dickeya spp.) And a stronger spread of ring rot (Clavibacter michiganensis) and brown bacterial rot (Ralstonia Solancearum);
• earlier dates of the appearance of late blight on plants and the formation of a more complex and more harmful population of the racial composition of this pathogen are noted;
• the spread of alternariosis is increasing, especially in varieties with increased susceptibility to this disease;
• there is a greater spread of migratory species of aphids that transmit viral infections on potatoes;
• more wireworms, scoops and other insect pests appear, causing significant damage to the commercial quality of potatoes;
• there are more nematode breeding cycles;
• The Colorado potato beetle is moving to more northern territories.
The observed changes in the biological diversity of pathogens and pests cause the need to optimize the relevant regulatory indicators and limit levels of restriction of the most dangerous phytopathogens and pests for potatoes.
A characteristic feature of recent years is also the observed effect on potatoes of elevated temperatures during the growing season, more often repeated short-term and long-term droughts in the summer, and an increase in CO2 in the atmosphere. The observed effects from the influence of these factors can also significantly reduce the indicators of the external presentation of tubers and other marketable characteristics of seed potatoes, in particular:
• there is an increase in the average tuber size and an increase in the number of large fraction tubers that do not meet the dimensional requirements for seed potatoes;
• the probability of slowing down or even stopping the growth processes during the growing season and the associated appearance of defects of the so-called "secondary growth" in the form of growth cracks in the tubers, the formation of voids in the core of the tuber and other defects are increasing;
• The development of tuber rot during storage is intensified due to dampness in the winter.
In modern international practice, the most important tool in solving the problem of regulating the commercial quality of seed potatoes is the continuous improvement of the regulatory framework based on the introduction of scientifically based norms of standards that take into account, among other things, changing climatic conditions.
From January 1, 2018, a new interstate standard GOST 33996-2016 “Seed potatoes. Technical conditions and methods for determining quality. " Employees and specialists of the Federal State Budget Scientific Institution VNIIKKH, the Union of Potato and Vegetable Market Participants (Potato Union) and the Federal State Institution Rosselkhoztsentr took part in its development.
The main goal of the development and introduction of the new standard is to optimize the normative indicators of the commercial quality of various categories of seed potatoes in the direction of their convergence with generally accepted international norms, as well as their unification with the main provisions and rules in force in the field of international trade in certified seed potatoes. To this end, when developing the new standard, all the main provisions and regulatory requirements of the UNECE international standard relating to the marketing and commercial quality control of seed potatoes were taken into account.
The structure of the standard corresponds to the main provisions of the interstate standardization system adopted in Russia and includes the following main sections:
- application area;
- Normative references;
- terms of definition and abbreviation;
- technical requirements;
- rules of acceptance and sampling;
- methods for determining quality;
- transportation and storage;
- safety requirements.
diseases on plants and tubers *
The provisions contained in the standard cover almost all basic aspects of quality control and certification of seed potatoes:
• the authenticity and purity of the variety;
• traceability of the origin of seed lots;
• quality level for various categories of seed material in relation to diseases, pests, defects;
• Tolerances regarding dimensional characteristics and appearance of tubers;
• rules for packaging, sealing and labeling.
The new standard establishes differentiated normative indicators of commercial quality for three categories of seed potatoes - original (OC), elite (ES) and reproductive (RS), which take into account the possible degree of decline in certain quality indicators with an increase in the number of generations in the process of seed potato production. The maximum tolerances for the most important quality indicators are as close as possible to the generally accepted internationally agreed regulatory requirements of the UNECE international standard (Table 1).
For batches of seed potatoes intended for planting and entering into trade, the standard also provides for rather stringent restrictions on the presence of tubers:
• not meeting the size requirements - 3%;
• affected by stem nematode - 0,5% (only for category RS);
• with glandular spotting and darkening of the pulp (if more than 1/4 of the longitudinal section of the tuber is affected) - 5%;
• with external defects and damages in the form of cracks, cuts, tears, dents of tubers tissues with a depth of more than 5 mm and a length of more than 10 mm - 5%;
• with damage by agricultural pests (wireworm - more than three moves, rodents, beetles and scoops), but without damage to the eyes - 2%.
In seed potatoes, the presence of pathogens of infectious diseases and pests of quarantine significance (potato cancer, brown bacterial rot, golden cyst-forming potato nematode, potato moth) is not allowed.
The standard establishes differentiated standards for the control of phytopathogenic viruses based on laboratory testing of leaf and tuber samples, depending on the level of propagation of the original seed material, including in vitro source material, minicubers, the first field generation of minicubers and super-super-elite.
For all classes (generations) belonging to the category of original seed material, quite strict regulatory tolerances for viruses causing severe forms of wrinkled and banded mosaic (YBK), twisting of potato leaves (VLK) and tuber spindle viroid (VVKK) have been introduced. The presence of YBK and VBLK in the in vitro source material and minitubers is not allowed.
In the first field generation of minitubers, the maximum allowable rate should not exceed 0,5%, in the super-superelite - 1%. For VVKK, zero tolerance has been established for all generations.
For batches of superelite, elite, and reproductive seed potatoes coming into circulation, the maximum allowable norms for limiting viral and / or bacterial infection according to the results of laboratory testing of tuber samples can be set in the contracts (contracts) for the supply of seed potatoes. However, for superelite and elite parties, the maximum level of YBK restriction according to the results of laboratory testing should not exceed 10%. Under the new standard, sampling standards for laboratory testing are established using the methods of PCR diagnostics, enzyme-linked immunosorbent assay (ELISA) and immunochromatographic analysis (IHA) (Table 2).
PCR diagnostics is used to determine the viroid of potato spindle tuber (VVKK), YBK and VLRV viruses, as well as pathogens of bacteriosis (black leg and ring rot) in the original material before its reproduction and at subsequent stages of reproduction. The specificity of the analysis is more than 99%, the detection limit (minimum detectable concentration) is 10 pathogen units / cm3.
Enzyme-linked immunosorbent assay (ELISA) is used to determine the infection of plants and tubers with viral (PVK, SBK, MBK, YBK, VSLK) and bacterial (black leg) infection through laboratory testing of post-harvest tuber samples taken from batches of the first field generation, super-super-elite, superelite and elite ... The detection limit (minimum detectable concentration) for viruses is 10 ng / cm3, for bacteria - 104 cells / cm3.
Post-harvest testing of tubers for the presence of a viral infection is carried out in the autumn-winter period on plants grown from indices (a peephole with an adjacent tissue). Potato testing for bacteria is carried out on segments cut from the top of the umbilical part of the tuber.
Immunochromatographic analysis (IHA) is used for the rapid diagnosis of phytopathogens on potato plants using test strips in off-laboratory conditions.
The methods for determining the quality and acceptance rules for plantings and lots of seed potatoes established by the standard include field testing of plantings, tuber analysis of seed lots, laboratory testing of post-harvest tuber samples, and soil control of variety samples for the categories of original seed coming into commercial circulation.
The standard formulates the basic requirements for packaging, labeling, transportation and storage of seed potatoes, and also provides in the annexes typical forms of working and official documents for processing the results of determining the quality of planting and commercial quality of lots of seed potatoes, describes the most dangerous infectious diseases and defects controlled tolerances of the standard.
As already noted, the main provisions of the standard in relation to regulatory tolerances and methods for determining the quality of the categories of original and elite seed potatoes are close to the level adopted in the EU countries. For example, the regulatory tolerances of the new RF standard for tuber rot are quite comparable with the requirements of the national standards of the EU countries and the UNECE international standard (Table 3).
At the same time, significant differences remain with the UNECE international standard regarding less stringent normative indicators for laboratory control of plants and tubers infected with viral infections, especially in relation to elite and reproductive (certified) seed potato categories. The introduction of stricter tolerances in the future is possible only if additional measures are taken to create special territories (zones) for the production of seed potatoes with the cleanest phytosanitary conditions that ensure the cultivation of healthy (free from pathogenic pathogens) original and elite seed potatoes with the maximum restriction of the infection load and minimizing the risks of new infections due to the effective use of natural environment-forming and environment-improving factors and spatial No isolation from possible infectious sources.
Based on modern ideas about the methods and characteristics of the transmission and spread of phytopathogenic viruses, as well as the migration of their carriers on potatoes, it is recommended to ensure the spatial distance from possible sources of infection for seed material of the primary stages of reproduction - 500 m, for subsequent field generations - 100 m (Table 4 ).
From a practical point of view, in order to create a favorable environment, especially when growing primary field generations, the most accessible and quite effective method is “micro isolation” of primary generations using protective screening crops of grain crops or grasses around the entire perimeter of the field (figure).
For enterprises specializing in potato seed growing, it is also important in the locations of original and elite seed potato nurseries to ensure constant control over crops on neighboring land plots belonging to other rightholders (citizens and organizations), within the limits of spatial isolation. As one of the possible measures, it is recommended to carry out a phased replacement of long-term reproductions on these land plots by supplying the owners of the indicated plots with seeds of original and elite seed potatoes, produced in special seed-growing territories (zones).
In conclusion, it should be noted that the mutual recognition and application of common regulatory requirements and provisions in the field of production and turnover of seed potatoes in the domestic market and the development of export-import supplies within the common market of the countries of the Eurasian Economic Union should undoubtedly contribute to the creation of a new competitive environment between suppliers seed potatoes and producers of commercial products. As a result, those producers who can offer better seed potatoes that meet the level of internationally agreed regulatory requirements will receive an obvious advantage. This, in turn, will serve as an incentive for the active introduction of modern innovative technologies, investment in the modernization of production, faster promotion of varieties that are in high demand in the domestic and international markets, the use of effective diagnostics of phytopathogens, staff training and professional development of specialists in the field of potato seed production, quality control and certification.