Evaluation of Stevia rebaudiana genotypes

Introduction Materials and Methods Results and Discussion -Performance of the genotypes under open field conditions -Impact of foil houses on the performance of the genotypes Conclusions

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Introduction Results from previous studies (presented at EUSTAS Symposium, 2008):

¾Stevia is cultivable under European temperate zone conditions (51 °N) as an annual crop ¾Selection of ‘Gawi‘ •Adapted to local site conditions •Vigorously growing •Sweetener quality unsatisfactory

Field trials

Studies 2009 & 2010 ¾Evaluation of six Stevia genotypes as compared to ‘Gawi‘ •Vegetative performance •Yield of rebaudioside A ¾Testing of two types of foil material ‘Gawi‘

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Materials and Methods Genotype

Type of material provided

‘Gawi‘ (Standard)

Complete plants

A, B

Seeds

C, E, F

In vitro cultures

D

Complete plants Mother plants

Greenhouse conditions •Day/night = 16/8 h •Temperature: 24/18 °C Cuttings

Propagation of experimental plants by rooting soft cuttings in Jiffy pots in the greenhouse

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Materials and Methods Experimental procedure •cultivation in 10 l containers from mid May (2009) and mid April (2010), resp., until mid October •under outdoor conditions and in foil tunnels, resp., (FEP-foil: PAR 94%, UV-A 90%, UV-B 82%; PE-foil: PAR 82%, UV-A 55%, UV-B 2,1%) •randomised block design (8 plants per genotype)

PE: polyethylene

FEP: perfluoro (ethylenepropylene) copolymer

Experimental plots and foil houses

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Materials and Methods

Measurements, calculations and analyses •shoot length, number of nodes and branches; stem and leaf weight (fresh and dry matter); specific leaf weight (SLW) •Leaf-to-stem-ratio, yield of rebaudioside A (= leaf dry weight x rebaudioside A content) •HPLC-analyses of stevioside and rebaudioside A (according to Wölwer-Rieck et al., 2010) •Means compared by ANOVA (α ≤ 0.05)

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Results and Discussion Leaf dry weight

Content of Rebaudioside A a

a

a

b ab bc

bc c

c

de

c e

cd

e

Yield of Rebaudioside A

Comparison of six Stevia rebaudiana genotypes cultivated in the open field in 2009 (n = 8); different letters indicate significant differences according to Tukey´s multiple range test (α ≤ 0.05) and means ± SD (standard deviation) are given, resp.

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Results and Discussion Profiles of six genotypes of Stevia rebaudiana compared to ‘Gawi’, cultivated in the open field in 2009

Ranking: C > F (> D)

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Results and Discussion Stevioside-to-rebaudioside A ratio of the genotypes evaluated in the open field and in two different foil houses in 2009 and 2010 open

FEP

PE

genotype

2009

2010

2009

2010

2009

2010

Gawi

2.10

2.06

2.08

2.17

2.16

2.21

A

2.56

1.65

4.73

B

4.01

2.10

3.34

C

0.17

0.37

0.23

0.29

0.23

0.30

D

0.90

0.97

0.80

1.02

0.79

1.12

E

1.12

F

0.34

1.18 0.51

0.32

1.07 0.69

0.32

Christa Lankes and U. Mora Zabala

0.58

Evaluation of Stevia rebaudiana genotypes

Results and Discussion

Leaf Dry Weight

Content of Rebaudioside A

Yield of Rebaudioside A

Comparison of three Stevia rebaudiana genotypes cultivated in the open field in 2010 (n = 8); means ± SD (standard deviation)

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Results and Discussion

Profiles of three genotypes of Stevia rebaudiana compared to ‘Gawi’, cultivated in the open field in 2010

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Results and Discussion

Reduced global solar radiation (May and Aug.) and lower temperatures (May – Oct.) in 2010 compared to 2009 Global solar radiation (Wh/m²)_sum

Mean daily temperature (°C)

Month

2009

2010

difference 2010 - 2009

Month

April

124776

127735

2959

April

May

152832

122059

-30773

May

21.9

12.5

-9.4

June

158468

176517

18049

June

21.0

19.9

-1.1

July

159734

165219

5485

July

25.1

23.3

-1.8

Aug.

149756

119384

-30372

Aug.

25.2

18.6

-6.6

Sep.

92369

94041

1672

Sep.

20.5

14.6

-5.9

Oct.

51593

59554

7961

Oct.

13.1

11.7

-1.4

2009

2010

difference 2010 - 2009

17.1

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Results and Discussion Impact of two foil houses (FEP and PE) on four Stevia rebaudiana genotypes; means ± SD (standard deviation) Leaf Dry Weight

Leaf Dry Weight

open FEP PE

open FEP PE

open FEP PE

open FEP PE

Christa Lankes and U. Mora Zabala

open FEP PE

open FEP PE

Content of Rebaudioside A

open FEP PE

open FEP PE

open FEP PE

open FEP PE

open FEP PE

Content of Rebaudioside A

2010

open FEP PE

open FEP PE

open FEP PE

open FEP PE

open FEP PE

2009

Evaluation of Stevia rebaudiana genotypes

Results and Discussion Impact of two foil houses (FEP and PE) on four Stevia rebaudiana genotypes; means ± SD (standard deviation) Yield of Rebaudioside A

Yield of Rebaudioside A

Response to foil houses Genotype

2009

2010

Gawi

positive

positive

C

negative

positive

D

positive

positive

F

indifferent

indifferent

Christa Lankes and U. Mora Zabala

FEP PE

open

FEP

PE

open

FEP

PE

open

PE

FEP

open

2010

FEP PE

open

FEP PE

open

open FEP PE

FEP PE

open

2009

Evaluation of Stevia rebaudiana genotypes

Conclusion Performance of the genotypes under open field conditions ¾ Genotype 'Gawi' proved to be well adapted to European temperate zone conditions ¾ Genotypes C and F were superior in sweetener quality and yield ¾ Profiles and ranking of the genotypes was modified by weather conditions Impact of foil houses on the performance of the genotypes ¾ Effect was specific to the genotype ¾ Response type was modified by weather conditions ¾ Transparency for PAR and UV-radiation was of minor importance

Christa Lankes and U. Mora Zabala

Evaluation of Stevia rebaudiana genotypes

Acknowledgements

The authors gratefully acknowledge •The generous donations of five genotypes of Stevia rebaudiana by EUSTAS members and one provided by the University of Monteria, Colombia •The funding of U. Mora Zabala´s research stay by the German Academic Exchange Service (DAAD) • Helpful advice for HPLC-analyses by Ursula Wölwer-Rieck and Benno Zimmermann • Manifold support provided by the technicians of INRES – Gartenbauwissenschaft, Bonn

Christa Lankes and U. Mora Zabala