Volume 21(2), 103- 111, 2017 JOURNAL of Horticulture, Forestry and Biotechnology

www.journal-hfb.usab-tm.ro

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The dynamics accumulation of biochemical components in sweet potato tubers depending on the variety in the conditions sandy soils of southern Oltenia Croitoru Mihaela 1, Diaconu Aurelia 1, Drăghici Reta 1, Dima Milica 1

1Centrul de Cercetare Dezvoltare pentru Cultura Plantelor pe Nisipuri Dăbuleni

*Corresponding author. Email: mhlcroitoru@yahoo.com Abstract Alongside production, the nutritional quality of sweet potato highlights the importance of this crop in human nutrition, still little known to consumers in Romania.

In order to determine the various biochemical components content in tubers of sweet potato in sandy soil the conditions the Dăbuleni were studied different varieties cultivated in culture with transparent mulch and the mulch smoky. Sweet potato varieties studied behaved differently from the point of view of quality and production tubers, in function of the vegetation period of the variety, as well and depending on the method of culture.

The greatest amount of total dry matter was determined in tubers obtained from the culture with mulch transparent, 39.41%, the average varieties, and depending on the variety, Hayanmi presented the highest content (45.43%). The maximum starch content was determined at 120 days after planting, regardless of the mulch used, with an average of varieties of, 14.75% in the culture smoky mulch and 14.14% in the culture of the transparent mulch. The higher starch content was determined to the varieties Juhwangmi (15.35%) and Yulmi (15.94%). The data obtained are similar to those in specialty literature, the differences being due to genotypes studied and climatic conditions from area of culture. As for the content of vitamin C, it presented the highest values in all varieties, to 100 days after planting after which begins to diminish.

Regardless of the color mulch used to planting and harvesting epoch, from the point of view of production, sweet potato varieties experimented were statistically differentiated. The varieties Juhwangmi and Yulmi have passed production control variety (KSC 1), but the largest difference ( 15067.5 to 37502.5 kg / ha), as a very significant statistically, there have been variety Juhwangmi.

Key words sweet potato, variety, sandy soils, Starch, C vitamin

Sweet potato is native to Central America and

northwestern South America and is cultivated on large

areas in China, India, Japan, Africa, USA ,

Mediterranean areas of Europe (Srisuwan, Saranya et

al. 2006).

Besides production, the nutritional quality of

sweet potato highlights the importance of this crop in

human nutrition, still little known to consumers in

Romania.

Sweet potato is an important food in a healthy

nutrition. It is rich in nutrients and fiber (of which 40%

soluble fiber, which helps lower blood sugar and

cholesterol), sweet potato is the ideal food for

diabetics, children and pregnant women [2, 3].

Through qualities, sweet potato varieties with

yellow and orange pulp constitutes a valuable source of

A vitamin , B6 vitamin, C vitamin and D vitamin

essential in the formation, the bones for good digestion,

wound healing and strengthening the immune system.

Orange and yellow varieties have a high

content of beta-carotene, A vitamin precursor [12].

Various studies have highlighted information

about the dry matter content, water, C vitamin,

carbohydrates, etc. of sweet potatoes grown in different

areas of the world [2,6,12,13,17, 20, 25].

Sweet potato plants grow best at an average

temperature of 24 °C, with abundant sunshine and

warm nights. Annual rainfall of 750-1000 mm are

considered most appropriate, with a minimum of 500

mm in the growing season. The culture is sensitive to

drought in the initiation developed during of the

vegetation period in air at an average temperature of

22.3 0C, by accumulating in the air, 2266.3

0C,

biologically active [8].

104

In order to determine various biochemical

components content in tubers of sweet potato under the

conditions, of sandy soils from the Dăbuleni were

studied different varieties, grown in culture with

transparent mulch and the mulch smoky.

Material and Method

During 2015-2016 the CCDCPN Dăbuleni

were included in the study following varieties of sweet

potato: Yulmi, Juhwangmi, Hayanmi, KSP 1 and KSC

1. The culture was mulched with polyethylene film

transparent white and smoky.

Determinations were performed with regard to the

biochemical composition of sweet potato tubers in,

dynamic 90-100 - 110-120 days after planting, for the

purpose of determining the period when the

accumulation of assimilates is at a maximum. In the

laboratory of biochemistry were performed following

determinations:

• the water and the total dry matter (%) - gravimetric

method;

• simple soluble carbohydrates (%) - Soxhlet Fehling

method;

• C vitamin (mg / 100g fresh substance) - iodometric

method;

• starch (%) - colorimetric method;

• tuber production (t / ha).

Results and Discussions

The studied varieties behaved differently from

point of view of quality tubers, depending for the

vegetation period of the variety, of culture conditions

and of climatic conditions.

The results on the dynamics of total dry matter

accumulation in tubers of sweet potato varieties studied

are shown in Table 1. In smoky mulch culture, the

majority of the total dry matter accumulation variety

presents a maximum at 100 days after planting (30.

93% for the variety Juhwangmi and 40.39% for the

variety Yulmi), with the average variety of 36.56%.

The only variety to the total dry substance

accumulates continuously up to 120 days after planting

is Hayanmi with 42.39%.

In the case transparent mulch culture the total

dry substance in the tubers of sweet potato reaches a

maximum at 110 days after planting (33.34% to variety

Juhwangmi and 45.43% for the variety Hayanmi) with

an average variety of 39.41%. Although the mulch

smoky ensures in the first stage of growth and

development of plants more heat in the soil and

accumulating assimilates in tubers is more intense, the

rate of accumulation is higher in the culture with

transparent mulch.

Table 1

Dynamics of total dry matter accumulation in tubers of sweet potato depending on the variety and growing

method (2015-2016)

Variety

Smoky mulch Transparent mulch

90

days

100

days

110

days

120

days

90

days

100

days

110

days

120

days

Yulmi 34.91 40.39 38.84 37.59 35.50 42.85 40.93 37.76

Juhwangmi 28.25 30.93 30.18 31.13 30.14 30.08 33.34 34.70

Hayanmi 31.53 36.73 37.76 42.39 34.00 39.45 45.43 38.85

KSP 1 37.55 38.37 37.07 31.83 37.66 42.40 41.11 32.68

KSC 1 36.67 36,38 35.96 32.75 38.11 37.70 39.34 38.90

The average

varieties 33.80 36.56 35.96 35.14 35.08 38.50 39.41 36.58

Between harvesting period and total dry

matter accumulation in sweet potato tubers on the two

types of mulch, were established correlations data of

polynomial equations with insignificant factor (r =

0.94) in the case of mulch smoky and significantly (r =

0.99 **) to transparent mulch (Figure 1).

105

Fig. 1 - The correlation between the total dry matter accumulation in tubers of sweet potato, in dynamics and used type

of mulch

The literature indicates a total dry matter

content in tubers of sweet potato between 19.69% and

39% depending the variety, the climatic conditions and

cultivation technology [12, 13, 25]. Rumbaoa et al.,

2009, [18] have determined to a few autochthonous

varieties in Taiwan a total dry matter content of

between 26.9% and 35.4% results, which are similar to

those grown in other regions.

Sanoussi et al., 2016, [19] in the Republic of

Benin were determined in 10 varieties selected a total

dry matter content which varied between 25.09% -

46.12%. These values are similar to those reported by

Ellong et al., 2014, [9] in Martinique (29.56% -

39.32%), but higher than those reported by Laurie et

al., 2012, [14] in South Africa (18.5% -30.5 %).

In sandy soil conditions from the Dăbuleni,

depending on the variety studied and climate

conditions, of total dry matter content may reach up to

45%.

The results on the dynamics of accumulation

in tubers of sweet potato starch to varieties studied are

presented in Table 2. The maximum starch content was

determined at 120 days after planting, regardless of the

mulch used, with an average variety of 14.75%, in the

culture of with smoky mulch and 14.14% in the culture

of with transparent mulch. The higher starch content

was determined to the varieties Juhwangmi (15.35%)

and Yulmi (15.94%).

Table 2

Dynamics of starch accumulation in tubers of sweet potato depending on the variety

and growing method (2015-2016)

Variety

Smoky mulch Transparent mulch

90 days 100 days 110 days 120 days 90 days 100 days 110 days 120 days

Yulmi 11.57 13.43 14.27 15.94 11.66 13.00 12.40 14.51

Juhwangmi 12.88 13.10 13.96 15.09 13.31 13.09 13.03 15.35

Hayanmi 11.91 11.27 13.01 13.93 12.41 12.54 12.86 13.17

KSP 1 12.78 13.50 14.02 13.84 12.50 14.18 13.63 13.80

KSC 1 12.18 13.82 14.35 14.96 12.24 14.70 13.24 13.87

The average

varieties 12.26 13.00 13.92 14.75 12.42 13.42 13.78 14.14

Thao and Noomhorm, 2011, [23] determined

a starch content in sweet potatoes between 12.38% and

17.52%.

Surendra Babu and Parimalavalli, 2014, [21]

bought sweet potatoes on local market in Salem, Tamil

Nadu, India and have determined a starch content of

between 14.11% and 17.76%, similar to results

obtained by Tsakama et al., 2010, and Suraji et al.,

2013, [22] in weather conditions from Sri Lanka were

found in sweet potatoes 14.2 to 17.2% starch.

In spite of the high content of carbohydrates,

sweet potato has a low glycemic index due to the low

digestibility of the starch making it suitable to

diabetes [9, 10, 11, 15].

Between harvesting period and srarch

accumulation in sweet potato tubers on the two types

106

of mulch, were established correlations data of

polynomial equations with significantly factor

(r=0,99**) regardless of the mulch used (Figure 2).

Fig. 2 - The correlation between the starch accumulation in tubers of sweet potato, in dynamics and used type of mulch

The results concerning to the dynamic

accumulation simple soluble carbohydrates in tubers by

sweet potatoes to varieties studied are presented in

Table 3. The maximum amount of soluble simple

carbohydrates was determined at 100 days after

planting, on both types of mulch, but the accumulation

of carbohydrates were more intense to tubers obtained

in culture with mulch transparent. The highest amount

of carbohydrate was determined to varieties Yulmi

(10.23%) and KSC 1 (10%).

Adu- Kwarteng Evelyn et al., 2014, [1] in a

study conducted in a few varieties of sweet potato to

Crops Research Institute of Ghana, have shown that the

harvest maturity to significantly affected the total

content of soluble sugar and the activity of the enzyme

amylase.

Table 3

Dynamics of simple soluble carbohydrates accumulation in tubers of sweet potato depending on the variety and

growing method (2015-2016)

Variety

Smoky mulch Transparent mulch

90 days 100 days 110 days 120 days 90 days 100 days 110 days 120 days

Yulmi 7.44 9.05 7.38 7.98 7.80 10.23 8.60 7.50

Juhwangmi 6.06 8.08 6.95 7.98 7.38 8.57 7.98 7.53

Hayanmi 6.30 7.60 8.61 8.60 7.10 9.20 8.69 8.81

KSP 1 6.93 7.45 8.50 7.50 7.76 9.45 9.05 7.71

KSC 1 7.80 8.38 8.15 7.95 8.23 10.00 9.73 7.40

The average

varieties 6.80 8.10 7.92 8.00 6.96 9.48 8.81 7.79

Wang et al., 2006, [26] showed that, in sweet

potato starch and sucrose content increase with

increasing period from the planting to harvesting and

the glucose and fructose decrease.

Yung-Chang Lai et al., 2013, [15] have

determined in sweet potatoes grown to Agricultural

Experiment Station Chia-Yi Branch in Taiwan, a

simple soluble carbohydrate content of between 4.50%

and 8.41% .

Between epoch harvesting and accumulation

carbohydrate in sweet potato tubers the two types of

mulch were established correlations data polynomial

equations with insignificant factor (r = 0.93) in the case

of smoky mulch and significantly (r = 0.95 **) in the

case of transparent mulch (Figure 3).

107

Fig. 3 - The correlation between the simple soluble carbohydrates accumulation in tubers of sweet potato, in

dynamics and used type of mulch

Between the amount of starch and soluble

carbohydrates simple in tubers of sweet potato on the

two types of mulch were established correlations given

to polynomial equations with insignificant factor (r =

0.91) in the case of smoke mulch and significantly (r =

0.99 **) the transparent mulch (Figure 4, a and b). The

amount of soluble simple carbohydrates increases with

increasing starch to values of 13.5 to 14% after which

begins to decline.

a b Fig. 4 - Correlations between the amount of soluble starch and the amount of simple carbohydrate in the tubers

of sweet potato, in dynamic and depending on the type of mulch used

The C vitamin content of sweet potato tubers

were influenced by cultivar studied and culture

method. The maximum amount was determined at 100

days of harvested plants at all varieties the studied,

then decreases with the prolongation of the period of

harvest (Table 4). On the two types of mulch C vitamin

content presented values close, 11.06mg / 100g fresh

substance, the average varieties in the variant with

smoke mulch and 10.93mg / 100g fresh substance in

the case of transparent mulch. The highest content of C

vitamin was determined at variety Juhwangmi

(11.45mg) and at variety KSP1 (11.66mg).

Barbara Krochmal-Marczak et al., 2014,[13]

have determined to a few sweet potato varieties grown

in Poland, a C vitamin content of between 20mg and

24mg / 100g fresh substance and Otieno et al. 2008,

[17] showed an contained of 16.13-23.42mg. Collins

and Walter, 1982, [6] have determined to a number of

45 sweet potato genotypes from North Carolina a

content of C vitamin between 1.7 mg and 17.4 mg /

100 g fresh substance. Also, Aywa et al., 2013, [2] in

Kenya, showed a content of C vitamin of between

4.85mg and 5.73 mg / 100g fresh substance.

108

Table 4

The dynamics C vitamin accumulation in tubers of sweet potato depending on the variety

and growing method (2015-2016)

Variety

Smoky mulch Transparent mulch

90 days 100 days 110 days 120 days 90 days 100 days 110 days 120 days

Yulmi 6.82 11.44 11.00 7.04 6.60 10.56 10.55 8.01

Juhwangmi 8.36 11.45 10.34 6.59 7.70 11.22 10.56 10.12

Hayanmi 6.16 10.12 9.68 6.82 8.36 10.07 10.12 7.48

KSP 1 7.26 10.78 7.56 8.46 7.48 11.13 8.35 8.58

KSC 1 7.75 11.50 10.12 6.81 7.04 11.66 10.56 6.95

The average

varieties 7.27 11.06 9.74 7.14 7.44 10.93 10.03 8.23

Ukom et al., 2009, [25] have shown that C

vitamin is mainly altered by the genetic characteristics

of varieties, and in the opinion of Barbara Sawicka,

2000, [20] differences in chemical composition of the

tubers are conditioned tubers phenotypic variability

and change in climatic conditions.

From epoch harvesting and C Vitamin

accumulation in tubers of sweet potato on the two

types of mulches vwere established correlations

polynomial equations given by the significant

correlation factors (r = 0.97 *) in the case of smoky

mulch and (r = 0.96 *) to the transparent mulch (Figure

5).

Fig. 5 - Correlation of C vitamin accumulation in tubers of sweet potato in dynamic and used type of mulch

Regardless of the color mulch used for

planting and harvesting epoch, from the point of view

of production, sweet potato varieties tested were

statistically differentiated. The varieties Juhwangmi

and Yulmi have passed production control variety

(KSC 1), but the largest difference (from 15067.5 to

37502.5 kg / ha), as a very significant statistically,

were recorded for the variety Juhwangmi (Table 5).

Between on varieties production average, on

two types of mulch and harvest epoch correlations have

been established by given polynomial equations with

factors significant correlation (r = 0.99 **). The

differences between the two types of mulches are very

low (Figure 6).

109

Table 5

Dynamics of production of sweet potato depending on the variety, epoch of harvesting and used type of mulch

Variety

The production of commercial tubers (Kg/ha)

Transparent mulch Smoky mulch

90 days 100 days 110 days 120 days 90 days 100 days 110 days 120 days Yulmi 13650*** 24867.5*** 26827.5* 33250* 18725*** 29977.5*** 26600 39550***

Juhwangmi 24202.5*** 43312.5*** 60427.5*** 44152.5*** 28875*** 42450*** 53900*** 47215***

Hayanmi 10955* 15505 1783000 23581.500 9975 152250 17080000 25491.5

KSP 1 8697.5 12530 21525 30004 8400 12425000 21997.5 31109*

KSC 1

(Witness) 7315 13475 22925 29085 8505 10902.5 23552.5 26915

DL 5%= 3397.905 kg/ha Dl 1%= 4530.54 kg/ha DL 0.1%= 5899.845 kg/ha

Between on varieties production average, on

two types of mulch and harvest epoch correlations have

been established by given polynomial equations with

factors significant correlation (r = 0.99 **). The

differences between the two types of mulches are very

low (Figure 6).

Fig. 6 - The correlation between the production of sweet potato tubers,

in dynamic and the type of mulch used

Between the average production on varieties

and quantity of total dry matter from sweet potato

tubers, on the two types of mulch correlations have

been established by given polynomial equations with

factors significant correlation (r = 0.99 **) regardless

of the mulch type (Figure 7, a and b). The amount of

total dry matter increase with increasing production up

to values of 24000kg / ha in the case of smoke mulch

and values of up to 30000kg / ha to mulch transparent,

after which it begins to decrease.

a b

Fig. 7 – The correlations between the amount of the total dry matter of sweet potato tubers and the production

of tubers, in dynamic and used type of mulch

110

Conclusions

1. The varieties of sweet potato studied in conditions

sandy soil of southern Oltenia, they behave differently

from the point of view of quality and production

tubers, in function of the vegetation period of the

variety and culture method.

2. The higher amount of total dry matter from sweet

potato tubers was determined with the mulch

transparent variant, 39.41% average varieties, and

depending on the variety, Hayanmi presented the

highest content (45.43%).

3. The maximum content of starch was determined at

120 days after planting, regardless of the type of mulch

used, with an average variety of 14.75% in the culture

smoke mulch and 14.14% in the culture of the

transparent mulch. The higher starch content was

determined to the varieties Juhwangmi (15.35%) and

Yulmi (15.94%). Obtained dates are similar to those in

specialty literature, the differences being due to

genotypes the studied and climatic conditions in the

area of culture.

4. As regards the content of vitamin C, it presented the

highest values, in all varieties to 100 days after

planting after which begins to diminish.

5. Regardless of the color mulch used for planting and

harvesting epoch, from the point of view of production,

sweet potato varieties tested were statistically

differentiated. The varieties Juhwangmi and Yulmi

have passed production control variety (KSC 1), but

the largest difference (from 15067.5 to 37502.5 kg /

ha), as a very significant statistically, were recorded

for the variety Juhwangmi.

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