World production of potato is second to cereals. One of the most efficient key factors of increasing potato production is the quality of seed potato as planting material. In order to control the varieties production, it is necessary the use of a high biological value material, with no viral diseases. The present study revealed that the ELISA method is applicable for the determination of the viral infection degree with effect on the yield of potato seeding material from superior biological categories. Also, the elimination of virus-infected plants using the ELISA method has resulted in a higher yield of potato seeding material from superior biological categories (SE and E basis).

Keywords: planting material, varieties, biologic potential

Of late years, as a consequence of the decay of fossils resources and of the increase of agricultural yield, the role of the biological resources has grown. Therefore, it has become common the use of superior genetic structures which are materialized through high quality seeds, forming a variety or a hybrid.^1-4 The viruses control represents one of the most complicated issues of plants’ protection.^5-7 The losses from agriculture caused by plants infection with viruses can be enormous.^8-10 The aim of this study was to evaluate the effect of planting area, variety, planting time, vegetation interruption time, biological category and virus infection on the yield of potato seeding material.

Materials

Considering the variety as a technological factor for realizing high production yields at performing agriculture level, the creation of new potato varieties solves two major problems: offers the agricultural producers the varieties which are consonant with the ecological conditions and with the zone specific technology; and succeeds in applying the specific technology for the morphological attributes of the created varieties in the existent pedoclimate conditions. The selected planting areas (Figure 1) were from Suceava County, Romania: the Experimental Center in Lucina locality (altitude of 1400 m) and the Station for Agriculture Research and Development in Suceava – SARD (altitude of approx. 400 m). The studied potato varieties (Figure 2), created and certified at the Station for Agriculture Research and Development in Suceava, with the year of their entering in the system of seed material production and reproduction are presented in Table 1. 

Figure 1 Planting areas under study

                                                                 a) Rapsodia Variety                     b) Astral Variety

Figure 2 Potato varieties under study

Methods

The experiments were conducted according to „latin square subdivided plots” method, on type 2×2×2×2, in four replications,¹¹ taking into consideration the following factors;

1. The planting area
2. The variety
3. The planting time
4. The vegetation interruption time
5. And the biological category

The factors’ classes are presented in Table 2. The complex effect of all studied factors was studied and interpreted in all experimental years, going to clone D (prebasis) taking in the study the seeding material yield for both varieties. Fertilization of the potato plots with N:P:K, 100:100:100kg s.a/ha, in a balanced rapport, was accomplished. The tubers were planted semi-mechanically at a distance of 21.5cm between tubers and 70cm between rows, using the fraction of 30-45mm. In order to destroy of the potato herbage the first treatment was made mechanically, at warning–after 70 days from the plant sprouting. The second treatment was made with Diquat (Reglone forte) 5 l/ha. After three weeks from the vegetation interruption, the harvesting of the tubers was accomplished. The ELISA (Enzyme-Linked-Immuno-Sorbent-Assay) technique was used for the study of diseases produced by the virus of crop plants and also to detect low concentration of viruses in the studied potato cultures. It permits a simple and accurate detection of viruses in stems and in other vegetative organs of plants. Its principle is based on the interaction antigen–antibody. The applied method was DAS–ELISA (double antibody sandwich - ELISA). The tested viruses were: PLRV (potato leaf roll virus), PVA (potato virus A), PVM (potato virus M), PVS (potato virus S), PVX (potato virus X), PVY (monoclonal and polyclonal potato virus Y). There were used the following reagents: IgG (immuno-conjugate), conjugate, positive control, negative control, extraction buffer, coating buffer, conjugate buffer, washing buffer, substrate, micro plates, substrate (pNPP tablets). Due to the test’s high sensibility, viruses could be detected before symptoms manifestation.

As it can be seen in Table 3, the seeding material yield was mostly dependent on the planting time. The yield was diminished with 32% (56.5 q/ha) when planting the potatoes 30 days later. A significant decreasing was also observed for the vegetation interruption factor, the yield at 20 days after warning being smaller with 17% (26.7 q/ha) comparing with the culture with vegetation interruption at warning. Considering the biological category factor, the SE class basis culture presented a potato seed yield with 11% (17.8 q/ha) above the yield of the certified A culture. The yield of Rapsodia variety culture surpassed the Astral variety culture’s yield with 13% (17.5 q/ha). Also, in comparison with Suceava culture, at Lucina it was registered an increase in potato seeding material yield with 9% (13.3 q/ha), as it can be observed in Figure 3. From Table 4 it can be observed effect of planting time and vegetation interruption time on the cultures’ yield (q/ha) and Table 5 show the influence of variety on the cultures’ yield (q/ha) at different planting times and different vegetation interruption times. The relative yield decrease due to the vegetation interruption time was depended to a certain extent by the planting time. The data in the table reveal that the best results were obtained when the planting was realized earlier and the vegetation interruption was made at warning, for both planting areas and varieties. Quantitatively, when the crop establishment is accomplished earlier, the vegetation interruption at warning is more important than the later planting. The later planting generated the same quantitative decreasing at both varieties, independent of the planting area (Suceava or Lucina).

Figure 3 The influence of the technological factors on the potato seeding material relative yields

 *DL - limit difference; *83, 100 – the values of relative yield (%) of potato according to vegetation interruption; 68, 100 – the values of relative yield (%) of potato according to planting time; 113, 100 – the values of relative yield (%) of potato according to variety; 89, 96, 100 – the values of relative yield (%) of potato according to biological category; 68, 100 – the values of relative yield (%) of potato according to planting time; 111, 100 – the values of relative yield (%) of potato according to locality.

The ELISA technique is indicated on a wide scale for the tests of events on the field, in the study of the diseases produced by the viruses which result from plants of culture. The sensibility of this method in the direct detection of viruses in the plants’ extracts, can drive us to the study on the field of these viruses for which we have not found available adequate practical methods. Among the measures which had a major negative impact on potato seeding material yield, the later planting is the first, followed by later vegetation interruption. The yield diminishing as a consequence of later vegetation interruption was significantly amplified when the planting was conducted later, for both planting areas (Suceava and Lucina) and varieties (Astral and Rapsodia).

None.

The authors declared there is no conflicts of interest.

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