Volume 22(4), 20- 26, 2018 JOURNAL of Horticulture, Forestry and Biotechnology www.journal-hfb.usab-tm.ro

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Effects of the treatment with fungicides on the physiological processes in Pyrus communis L. attacked by Venturia pyrina aderh. Nicolae I.1*, Bușe-Dragomir Luminița1, Camen D.2 1University of Craiova,

2Banat University of Agriculture Sciences and Veterinary Medicine Timisoara

*Corresponding author. Email: ionnicolaebio@yahoo.com

Abstract Researches regarding the effects of treatment on the physiological processes with fungicides were effectuated on pear tree (Pyrus communis L.) cultivated in the climatic conditions in Oltenia region.

The physiological researches were performed on July 12th 2017, both

for leaves of the pear trees treated with Dithane M 45 (0.2%), in five phases at 10 days interval (May 15

th 2017, May 25

th 2017, June 4

th 2017, June 14

th

2017 and June 24th 2017) and also in case of pear tree leaves affected by

Venturia pyrina (Aderh.) DC. in which treatments have not been performed (not treated with fungicide).

Regarding pear tree leaves where fungicide treatments have been performed it is observed that the photosynthesis and transpiration is higher in comparison with leaves in case of pear tree affected by Venturia pyrina (Aderh.) DC. Leaves analysed after performing treatments with fungicide present a higher clorophyll content and water content, compared to leaves attacked by the pathogen were the deterioration of the chlorophyll and the decrease of the cellular turgescent already took place.

Key words fungicide, leaves of the pear tree, pathogen, physiological processes, Venturia pyrina

Pyrus communis L. known as the European

pear or common pear is a species of pear native to

central and Eastern Europe and Southwest Asia.

Venturia pyrina is a species of fungus in the

Venturiaceae family. A plant pathogen, it causes scab

or black spot of pear. It has a widespread distribution

in temperate and subtropical regions wherever pears

are grown [9].

The pear production, especially in the

integrated and organic production systems, is

constrained by diseases, which reduce the viability of

plants, fruit development and quality. European pear

scab (Venturia pyrina Aderh.) is common and

economically important disease in commercial

orchards in most of the pear (Pyrus communis L.)

growing areas worldwide [10].

The major losses caused by Venturia pyrina

are due to scabbed fruits, which are not marketable.

Because of the loss of commercial value, frequent use

of fungicides is required [2].

In case of physiological photosynthesis

intensity research, Pyrus communis L. indicates

values of 11.2 μmol CO2 / m2 / s [4].

Photosynthesis proportionally increases with

intensity of transpiration and is also depending on

solar radiation intensity [1].

Transpiration and photosynthesis intensity

during daytime, depends on the leaf temperature and

the photosynthetic active radiations received by leaves,

which depend on the leaves position on the plants. [7].

Interception of surface solar radiation is correlated

with the intensity of transpiration and with the quantity

of heat retained by the leaves [3].

The growth of the photosynthesis and

transpiration correlate with the increase of the

photosynthetic active radiations, but the values in the

attacked leaves are different as a result of numerous

structural modifications appeared in the host plants

under the action of the pathogen, in comparison with

the leaves plant at one month after treatments with

fungicide [6]. In case of plants attacked by the pathogen it

can be noticed that the diurnal dynamics of the

photosynthesis and of transpiration present a minimum

in the morning and toward the evening, a maximum

after lunch, with specific variations in the plants

affected [5].

Material and Method

Researches were performed regarding pear

trees (Pyrus communis L.) in specific climatic

conditions of Oltenia region.

The pear tree has a pyramidally shaped crown

and can reach a height of 4-5m.The leaves of the pear

are summer green, ovoid. The leaf margin is serrated.

The pear bloomins before the leaves shoot.

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The flowers have white petals which are

arranged in a corymb inflorescens and appear before or

with the leaves. The branches are gray shiny and the

buds are brown, slightly hairy and protruding.

Treatments with Dithane M 45 (0.2%)

fungicide were applied on the leaves of the pear during

vegetation period, in five phases at 10 days interval

(May 15th

2017, May 25th

2017, June 4th

2017, June

14th

2017 and June 24th

2017) and the physiological

researches were performed on July 12th

2017, both for

leaves of the pear trees treated with fungicide and also

for the affected leaves which were not treated with

fungicide.

Dithane M 45 is a contact fungicide with a

wide action spectrum. It has a good persisting effect

remaining on the treated area from 7 to 10 days,

depending on local conditions. For very good results in

the application of fungicides, we need to consider

growth phenophases and climatic conditions.

Calculation formulae elaborated by Săvescu

& Rafailă was able to estimate the attack (the

frequency, intensity and degree of the attack) [8].

Both transpiration and photosynthesis

intensity were determined with the ultra compact

photosynthesis measurement system (LCi) and results

obtained were graphically represented.

Using the gravimetric method, dry substance

content and total water content were determined and

also the chlorophyll content was estimated using

Minolta SPAD 502 chlorophyllmeter.

Results

Pear scab produced by Venturia pyrina Aderh.

appears on the leaves in the form of circular spots, of

greenish-brown colour in the first stage, then grey-

brown, with a velvety appearance. Over time, the

tissues corresponding to spots are necrotizing (Fig. 1

and Fig. 2).

Deep cracks appear on branches in all

directions and cause the branches to dry out.

Deformation and cracking of fruits is caused

by joining together of the attacked spots, in time.

Venturia pyrina Aderh develops mycelium

under cuticle, it is septal, branched, it has a brownish-

olive color, and forms brown stroma that appear on

conidia and conidiophores. Conidiophores are short,

brown, unicellular, cylindrical, and show on each end a

brown conidia. (Fig. 3).

Leaves tha fall in autumn form antheridium

and ascogonium, and then form the asca with

ascospores.

Venturia pyrina develops sexual stage in leaf

litter, where it overwinters as a saprotroph during the

dormant season, and asexual (conidial spores) state is

formed on infected plants during the season [11].

Fig. 2. Leaf belonging to the

pear tree affected by Venturia

pyrina Aderh. - advanced attack

(Original).

Fig. 3. Venturia pyrina

Aderh.- brown conidia

(oc. 10 x ob. 20)

- Original.

Fig. 1. The leaves that belong to

the pear tree affected by

Venturia pyrina Aderh. - the

beginning of the attack

(Original).

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The physiological researches were performed

on July 12th

2017, both for leaves of the pear trees

treated with Dithane M 45 (0.2 %) fungicide and also

for the attacked leaves of the pear trees in which

treatments have not been performed (not treated with

fungicide).

Estimation of the attack (intensity, frequency

and degree of attack) caused by Venturia pyrina Aderh.

at the leaves pear trees is showed in Fig. 4.

Transpiration intensity and the photosynthesis,

during the day, is low in the attacked leaves of the pear

trees by the pathogen, compared to the leaves

belonging to the pear trees treated with Dithane M 45

(0.2 %), as a result of the reduction of the assimilation

surface due to the formation of rounded spots, grey-

brown color, with a velvety appearance which in time

necrotizes (Fig. 5 and Fig. 6).

Intensity of transpiration and photosynthesis

are correlated with the physiological parameters (leaf

temperature, stomatal conductance and photosynthetic

active radiation), but present different values in the

leaves of the pear tree in which treatments have been

performed, in comparison with the leaves that belong

to pear trees attacked by the pathogen, a strong

association being established between these.

Leaf temperature, stomatal conductance and

photosynthetic active radiation in leaves, show an

increase from the morning until after noon and then a

gradual decrease towards the evening (Table. 1).

Fig. 6. The transpiration intensity regarding pear

tree leaves (Pyrus communis L.).

Fig. 5. The photosynthesis intensity regarding

pear tree leaves (Pyrus communis L.).

Fig. 4. The estimation of the attack produced by Venturia pyrina Aderh.

in Pyrus communis L.

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Table 1

The physiological parameters registered in the leaves of the pear tree

Linear regression made between the

photosynthesis intensity and photosynthetic active

radiations present on the surface of the leaves displays

a positive correlation between these, the coefficient of

determination (R2) was 0.92 for treated leaves and

0.90 for the untreated attacked leaves. Linear

regression made between the transpiration intensity and

photosynthetic active radiations dispalys a good

positive correlation, the coefficient of determination R2

was 0.94 for the treated leaves and 0.95 for the leaves

not treated with fungicide. - Fig. 7 and Fig. 8.

Linear regression made between

photosynthesis intensity and leaf temperature displays

a good positive correlation, the coefficient of

determination (R2) was 0.98 for the leaves of the pear

tree in which treatments have been performed and 0.97

for the attacked leaves by the pathogen (not treated

with fungicide). Linear regression made between the

transpiration intensity and leaf temperature displays a

good positive correlation, the coefficient of

determination R2 was 0.99 for the leaves that belong to

the pear tree treated and 0.98 for the attacked leaves

(not treated with fungicide) - Fig. 9 and Fig. 10.

The physiological

parameters

The leaves of the analyzed plants The hours of the analysis performing

and the recorded values (July 12th

2017)

900

1100

1300

1500

1700

The photosynthetic

active radiation

(μmol / m2 / s)

The leaves of the plants after treatments

with fungicide 1154 1282 1474 1430 1360

The leaves of the plants attacked by pathogen

(not treatments with fungicide) 1132 1250 1458 1418 1347

The leaf

temperature

(oC)

The leaves of the plants after treatments

with fungicide 27.6 32.5 35.9 35.7 34.5

The leaves of the plants attacked by pathogen

(not treatments with fungicide) 27.5 31.9 35.6 35.3 34.5

The stomatal

conductance

( mol / m2 / s)

The leaves of the plants after treatments

with fungicide 0.06 0.09 0.13 0.11 0.09

The leaves of the plants attacked by pathogen

(not treatments with fungicide) 0.04 0.08 0.11 0.09 0.07

Fig. 7. Correlation between the intensity of

photosynthesis and the photosynthetic active radiation

in case of pear trees (Pyrus communis L.).

.

Fig. 8. Correlation between intensity of transpiration

and photosynthetic active radiation regarding pear

trees (Pyrus communis L.).

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Linear regression made between

photosynthesis intensity and stomatal conductance

displays a positive correlation, the coefficient of

determination (R2) was 0.85 for the treated leaves and

0.82 for the attacked leaves by the pathogen (not

treated with fungicide). Linear regression made

between the transpiration intensity and stomatal

conductance shows a positive correlation, the

coefficient of determination R2 was 0.85 for treated

leaves and 0.82 for the attacked leaves (not treated with

fungicide) - Fig. 11 and Fig. 12.

Leaves analysed after performing treatments

with fungicide show a lower dry substance content and

a higher water content compared with the attacked

leaves by the pathogen (not treated with fungicide) -

Fig. 13.

In the leaves analysed after performing

treatments with fungicide it registers a higher

chlorophyll content, compared with the leaves

attacked by Venturia pyrina Aderh. where the

deterioration of the chlorophyll already took place (Fig.

14).

Fig. 9. Correlation between intensity of

photosynthesis and leaf temperature

(Pyrus communis L.).

Fig. 10. Correlation between intensity of

transpiration and leaf temperature

(Pyrus communis L.).

Fig. 11. Correlation between intensity of

photosynthesis and stomatal conductance

(Pyrus communis L.).

Fig. 12. Correlation between intensity of

transpiration and stomatal conductance

(Pyrus communis L.).

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At the analysed plants it can be observed that

between the clorophyll content and the photosynthesis

intensity is a positive correlation.

Conclusions

Regarding the pear tree (Pyrus communis L.),

transpiration and photosynthesis intensity), during the

day, is low in the leaves attacked by the pathogen,

compared with the leaves treated with Dithane M 45

(0,2 %), as a result of reduction of the assimilation

surface due to round spots formation , grey-brown

color, with a velvety appearance which in time gets

necrotized.

The intensity of the transpiration and

photosynthesis intensity are correlated with the

physiological parameters, but present different values

in the leaves that belong to the pear tree at which

treatments have been performed, in comparison with

the leaves attacked by the pathogen (not treated with

fungicide), a strong association between these being

established.

In leaves attacked by the pathogen (untreated

with fungicide) one can observe a decrease of water

content and chlorophyll content, which is manifested

by the deterioration of the chlorophyll, decrease of the

cellular turgescent and gradual drying of the leaves

affecting quantity and quality of fruits.

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