Results and Discussion

FRUITS

Diyan GEORGIEV¹*, Teodora MIHOVA¹, Maria GEORGIEVA¹, Petya IVANOVA², Georgi POPSKI¹, Galya NAYDENOVA³, Dimitar MITEV¹

1Research Institute of Mountain Stockbreeding and Agriculture - Troyan, 281 Vasil Levsky Str., 5600 Troyan, Bulgaria

2Food Research and Development Institute, 154 Vasil Aprilov Str., 4000 Plovdiv, Bulgaria

3Experimental Station on Soybean, 61 Ruski Str., 5200 Pavlikeni, Bulgaria

*Corresponding author: [email protected]

Abstract

Blackberry is one of the main berry crops. It is not particularly demanding on soil and climate conditions. Foothill regions are suitable area for its cultivation, where plants develop to a large extent their biological and economic potential. The experiment was conducted during the period 2014-2016 in a plantation of the Research Institute of Mountain Stockbreeding and Agriculture (Bulgaria) at altitude of 400 m on grey forest soils. The experimental setting consists of interrow grass cover with common bird's-foot-trefoil, bird's-foot-trefoil of Aegean region and vetch.The influence of grass cover on some indicators of the biochemical composition and flowering characteristics of fruits was studied of 'Black Satin' blackberry cultivars. Higher values were registered in the content of anthocyanins and pectin. The grass cover with bird's-foot-trefoil and vetch had no influence on the colour characteristics of fruits.

There were no significant differences in relation to the average weight of different fruit variants.

Keywords: blackberries, cultivars, chemical composition, fruit weight Introduction

Blackberry is one of the traditional crops with proven economic and social efficiency in the foothill and mountain regions of Bulgaria. Most of the plantations are located on slopes, which require anti-erosion systems for maintaining of soil surface. The soils in the mountain and hilly areas are among the most infertile in Bulgaria – with poor drainage, overdamping surface, low in organic matter, digestible forms of phosphorus and poorly supplied with mobile forms of nitrogen. These regions are catchment areas, where the use of pesticides is not desirable. What has been pointed so far requires the study of artificial grass cover as an adequate and effective practice for maintaining of soil surface in plantations of small-sized fruit species in the region of Troyan (Petkov, Petrov, 1998; Gergov et al., 2004). It is also necessary for the development and approval of environmentally friendly technologies for organic production of blackberries. Blackberry fruits are distinguished by a specific taste, aroma and rich biochemical composition (Boycheva et al., 1999). The very good balance of sugars and acids makes them attractive both for fresh consumption and for processing into various derivatives/products. Nowadays the interest to small-sized fruit species has been increased and especially to introduced varieties (Stoyanova et al., 2015). The aim of study was to follow the influence of some legumes on the biochemical composition and colour characteristics of fruits of 'Black Satin' blackberry cultivar.

Material and Methods

The experiment was conducted in the period 2014 – 2016 in the collection plantation of Research Institute of Mountain Stockbreeding and Agriculture – in Troyan.

The object of the present paper is 'Black Satin' blackberry cultivar. 'Black Satin' is American cultivar that was introduced in Bulgaria in 1984. The bush has a moderate growth, with average number of shoot, thornless. It is relatively resistant to high temperatures and drought, but it is susceptible to winter frosts. Fruits are globose-conical to oblong, with intensive black colour, with a glance (Velchev § Boycheva, 1983; Hristov et al., 1988; Ivanov, 2003).

The following variants of grass cover for soil surface were studied: control, common bird's-foot-trefoil, bird's-foot-trefoil of Aegean region and vetch.

Biochemical composition of fruits of the studied cultivar was conducted in the chemical laboratory in the institute, as the following indicators were observed: dry matter weight (%), refractometric determination of dry matter, total sugars % (total, inverted and sucrose) according to the method of Schoorl and Regenbogen; acids % (malic acid); ascorbic acid according to method of Fialkov; tanning according to Levental method; anthocyanins according to method of Fuleki and Francis; pectin according to Melitz method. Analyses were conducted in the chemical laboratory of RIMSA.

The fruit colour was determined according to Gardener in the Food Research and Development Institute – Plovdiv.

The colour was determined according to Gardner – using the laboratory apparatus 'GOLORGRAD2000' of BYK-GARDNER INC. USA. The blackberry samples were grounded in laboratory apparatus MPIЯ–2М with 4 mm diameter of grid holes. The sample was deaerated in a vacuum chamber at vacuum of 0.85 kPa for 10 min.

The indicators were given according to the system CIE Lab. Chromaticity coordinates L, and b were taken for the measurement: L - colour brightness; + a - red; -a green; +b - yellow, -b - blue.

Precipitation amount in the period from April – September were significantly higher than the annual average for that area.

In 2014 were reported 820.4 l, for 2015 – 594.2 l and for 2016 484.8 l, as for a ten-year period there were 528.51 l.

Results and Discussion

Data from biochemical composition of fruits are presented in Table 1. The analysis of results shows varying in the values of the individual indicators of the biochemical composition of fruits throughout the period, probably due to different agro-meteorological conditions.

The highest average dry matter weight was recorded in the variants with common bird's-foot-trefoil - 16.06% and bird's-foot-bird's-foot-trefoil of Aegean region - 15.93% (Table 2). As in 2015, its amount reached up to 18.16% in the control fruits, and it was the least in the vetch variant – 11.28% in 2014.

There were no large differences in the average refractometric dry matter of different experimental settings that were in the range from 9.33% (variant with vetch) to 10.40%

(control). There was no significant variation in that indicator amount either during the years of study.

In 2015, a higher content of total sugars was found in control fruits and the variants with bird's-foot-trefoil, which were in the range from 6.35 % to 7.85 %. In the variant with vetch, the values were almost identical for s three-year period. There were no significant differences in the amounts of total sugars among the variants average for the period.

Values were almost identical also in the case of inverted sugar. They were higher in the

control (7.20%) and the common bird's-foot-trefoil (7.85 %) in 2015. There were no significant differences for the other two variants. They were the least average for the period in the variant with bird's-foot-trefoil of Aegean region - 5.40%

There was no sucrose in the control and variant with vetch. For the other variants, there were minimum amounts only in one of the years.

Organic acids were in close values among variants in the experiment. The average amounts were in the range 0.5 %-0.6 %.The content of ascorbic acid varied over the years in all variants. On the average, this indicator was higher for the common bird's-foot-trefoil – 20.53 mg/% and bird's-foot-trefoil of Aegean region – 22.88 mg/%. Similar results were reported by Skrovankova et al. (2015). Tanning substances were recorded in different values for each year of the variants. The highest amounts were determined for bird's-foot-trefoil of Aegean region – 0.333 % (2016) and vetch – 0.333 % (2015). They were the most for the above mentioned variants average for the period. Over the years the values of anthocyanins reached 129.35 mg /% (bird's-foot-trefoil of Aegean region) and 97.58 mg /% (common bird's-foot-trefoil) in 2015 and the lowest were reported in variants with vetch - 40.16 mg /% in 2014. Average for the period, they were the most in the variant with bird's-foot-trefoil of Aegean region – 98.92 mg /% (Figure 1). There was a significant variation of pectin in the study period. Its values increased twice and even more in different years.

The highest amounts were reported in the variants with vetch – 2.320% and with common bird's-foot-trefoil – 1.400% in 2016. The highest average value of the indicator was also obtained for these variants for the period.

The parameters of the fruit color characteristics are presented in Table 3.

In terms of fruit brightness, there were no significant differences for all variants. There were higher values in the control and common bird's-foot-trefoil variant. Red colour shade was higher in the control and for vetch variant. Yellow colour had the highest values for the same two variants.

Table 1. Biochemical composition of 'Black Satin' cultivar for different variants of grass cover for the period 2014-2016.

Table 2. Biochemical composition of 'Black satin' cultivar for different variants of grass Table 3. Colour characteristics of fruits for grass cover variants

Grass cover variants

Indicators

L a b

Control 14.98 31.74 8.67

Common bird's-foot-trefoil 14.83 29.33 7.39

Trefoil of Aegean region 13.27 30.30 7.87

Vetch with barley 14.02 31.04 8.16

The highest average fruit weight was recorded for the variant with bird's-foot-trefoil of Aegean region – 3.30 g and the control – 2.85 g, and it was the lowest for the vetch variant – 2.50 g. Variation of that indicator is great for all variants.

Table 4. Fruit weight (g) of 'Black satin' cultivar for different variants of grass cover

Grass cover variants Year Min Мах Average STDEV VC

An analysis was conducted of the influence of interrow grass cover with some legumes over the biochemical composition and colour parameters of 'Black Satin' blackberry fruits.

Higher anthocyanin values were recorded for grass cover with bird's-foot-trefoil of Aegean region, and pectin in the three variants in comparison with control.

The grass cover with bird's-foot-trefoil of Aegean region had a positive influence over the fruit size of 'Black Satin' cultivar.

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COMPARATIVE INVESTIGATION OF THREE CHERRY CULTIVARS WITH