Determination of phenotypic stability of quantitative morphological features and economic value characteristics of sweet potato tubers (Ipomoea batatas L.)

Purpose. To justify the use of the Lewis phenotypic stabi­lity factor (SF) to determine the stability of the manifestation of quantitative and economic value characteristics of national varieties of sweet potato (Ipomoea batatas L.). Methods. Field research on the comprehensive assessment of new sweet potato varieties was carried out in 2021–2022 at the Institute of Vegetable and Melon of the NAAS (Kharkiv Region). Phenological observations and biometric measurements of plants were carried out, as well as recording of meteorological data during the growing season, in particular during interphase periods of the culture. The stability of the studied traits was determined by finding the limit values of their manifestation (Xmax and Xmin) and further calculating the Levis phenotypic stability factor (SF). Results. The use of the Levis phenotypic stability factor (SF) made it possible to determine the stability of the manifestation of morphological features of sweet potato varieties (I. batatas), in particular, the quantitative characteristics of tubers: their number under the bush for the variety ‘Admiral’ is 5.3 pcs., for ‘Slobozhanskyi rubin’ – 3.7 pcs.; the average weight of the tuber is 254 and 283 g, respectively. The trait “sweet potato tuber shape index” ensured stability with a coefficient of 0.98 (‘Admiral’) and 1.03 (‘Slobozhanskyi rubin’). The stability of the manifestation of morphological features of sweet potato tubers was established for the varieties ‘Admiral’ and ‘Slobozhanskyi rubin’, which are common in Ukraine. They represent two maturity groups, and therefore differ in the duration of the tuber formation period. Thus, the early-ripening ‘Admiral’ has a vegetation period of 100–110 days; medium-ripening ‘Slobozhanskyi rubin’ – 110–120 days. Conclusions. The quantitative trait of sweet potato tubers of the ‘Admiral’ variety was more stable in terms of width; ‘Slobozhanskyi rubin’ variety – in terms length. Tuber length values varied within cultivars. The shape index of sweet potato tubers as an identification feature of varieties turned out to be variably unstable; the calculated Lewis phenotypic stability factor was lower than unity for both studied varieties.

Mulching Effect on Quantitative and Qualitative Characteristics of Yield in Sweet Potatoes

Sweet potatoes have multiple uses as food, feed, and in industrial production. They are characterized by their need for high temperatures for optimal development. This study aimed to analyze the quantitative and qualitative aspects of growing sweet potato cultivars in southwest Romania using mulching and non-mulching systems. The effects of mulching on the production of tuberous roots and the contents of total soluble substance, vitamin C, starch, total polyphenols, and antioxidant activity (DPPH) were evaluated in three cultivars with white pulp (the ‘Pumpkin’ and ‘Chestnut’ cultivars) and with orange pulp (the ‘Italian’ cultivar). It was found that mulching with polyethylene film improved the production of sweet potatoes, amounting to 41.42 t/ha in the case of the ‘Italian’ cultivar. Moreover, the effect of mulch induced increases in total soluble substance (16.40%) and starch (16.01%) in the ‘Chestnut’ cultivar, in vitamin C (9.23 mg/100 g d.w.) in the ‘Pumpkin’ cultivar, and in antioxidant activity in the ‘Pumpkin’ (2716.55 µmol AsA/g d.w.) and ‘Chestnut’ cultivars (1131.31 µmol AsA/g d.w.), while the polyphenols in the ‘Italian’ cultivar decreased.

Study of the efficiency of sweet potato growing in the Forest-Steppe of Ukraine by different methods of soil mulching

Sweet potato (Ipomoea batatas L.) is a new crop for soil and climatic conditions of Ukraine, the active implementation of which is hindered by the lack of recommendations on technological aspects of cultivation. One of the important technological measures for growing sweet potatoes is the use of soil mulching, which improves the water regime and regulates the thermal regime of the soil; prevention of weed growth and growth of sweet potato shoots to the soil. Thus, the aim of the research is to determine the efficiency of growing sweet potatoes in the Forest-Steppe of Ukraine by different methods of soil mulching. Field research was carried out on typical low-humus light loamy chernozem on loess loam. It was noted, that when growing sweet potatoes on ridges, the introduction of mulching the soil with black polyethylene film provides more active growth of the vegetative mass throughout the growing season (5.33 shoots/plant with a total length of 252.1 cm), while growing without ridges has a positive effect on plants growth due to the general absence of mulch (2.53 shoots/plant with a total length of 107.8 cm). The use of ridges and mulching the soil with black polyethylene film causes the yield of sweet potato tubers at 34.8 t/ha, while the mulching of the soil with straw, the yield was 18.3–21.9 t/ha, without mulching – 13.0–17, 1 t/ha. Mulching with black polyethylene film ensures the accumulation of vitamin C and starch in sweet potato tubers. When growing the culture on ridges by this method of mulching, the maximum level of vitamin C according to the experiment (4.78 mg/100 g) and starch (11.73 %) was noted. The introduction of mulching and ridge formation involves additional material and labor costs, but helps to reduce weed control and tuber digging costs. When growing sweet potatoes on ridges with mulching with black polyethylene film, the minimum additional labor costs for the formation of a unit of yield (1.95 man-minutes/kg of tubers) were noted, while without mulching and without ridges this figure was 6.76 man-minute/kg

The evaluation of selected qualitative parameters of sweet potato (Ipomoea batatas L.) in dependence on its cultivar

The sweet potato (Ipomoea batatas L.) is relatively known vegetable species, but it is grown only on small area in the Middle European region. Its cultivars are characterized by different colour of tuber flesh which can be white, beige, yellow, orange and purple. The aim of this study was to determine and compare selected qualitative parameters of tubers (total carotenoids, vitamin C and total soluble solids) among orange, white and purple sweet potato cultivars. The field experiments were established at Slovak University of Agriculture in Nitra in 2016 and 2017. Sweet potatoes were grown by hillock system with using of black non-woven textile for soil mulching. The tuber harvest was realised on the 6th October 2016 and 13rd September 2017. The highest content of total carotenoids was found in orange sweet potato cultivars (78.47 - 122.89 mg.kg-1 fresh weight) and its values were multiple-fold higher in comparison with purple (4.22 mg.kg-1 f. w.) and white (10.71 mg.kg-1 f. w.) cultivars. Orange cultivars were also richer source of vitamin C (246.31 - 325.99 mg.kg-1 f. w.) compared to white (179.66 mg.kg-1 f. w.) and purple (187.75 mg.kg-1 f. w.) cultivars of sweet potatoes. The total soluble solids, expressing mainly sugar content, was higher in purple (10.13 °BRIX) cultivar of sweet potatoes, followed by cultivars with orange (8.52 - 9.72 °BRIX) and white (5.57 °BRIX) tuber flesh. Obtained results showed the significant effect of cultivar, characterized by different tuber flesh colour, on the composition and contribution of sweet potatoes for human health.