In vitro multiplication of an industrial fiber plant: kenaf (Hibiscus cannabinus L.) ARBAOUI Sarra

a

, CAMPANELLA Bruno

b

, ROGER Paul

b

and BETTAIEB Taoufik

a

Horticultural Science laboratory, National Agronomic Institute of Tunisia 43 Charles Nicolle Street, 1082 Tunis Mahragene, Tunisia b Environmental Toxicology laboratory, Gembloux Ago Bio Tech 2, Passage de Déportés, 5030 Gembloux, Belgium

[email protected]

Introduction

Kenaf (Hibiscus cannabinus L.) is an annual fiber plant of Malvacea family. The stem produces two types of fiber, a coarser fiber in the outer layer and a finer fiber in the core. It has been cultivated for the manufactures of ropes, textiles, paper, insulation and used in many industries including automobile industry. Problems encountered in the establishment of uniform, vigorously growing kenaf result from seed germination quality. The purpose of this study was to develop a suitable protocol for micropropagation of kenaf.

Materials and Methods

Plant materials consisted of 10 cm nodal microcutting excited from shoots of plants aged 50 days.

Tests for the first culture phase (4 weeks) were conducted on basal Murashig and Skoog (1962) MS medium supplemented with 5 IBA (indolebutyric acid) concentrations (0; 0,25; 0, 5; 1; 2 mg.l

-1 ) and 5 BAP (benzyl adenine) concentrations (0; 0, 25; 0, 5; 1; 2 mg.l

-1 ). Rooting tests were conducted, during 4 weeks, on MS media supplemented with 3 IBA concentrations (0; 0,25; 0,5 mg.l-1). Growth parameters data were submitted to analysis of variance (ANOVA) using SAS program. The differences among means were analyzed by Student test at 5% significance level.

Results

•

Initiation of in vitro culture

Initiation of in vitro culture is 100% in all culture media • The highest number of nodes is obtained on the MS medium supplemented with 0.25 mg.l

-1 and 0.5 mg.l

-1 IBA BAP

Table 1: Effect of plant growth on nodes formation, shoot induction (%) and growth

Medium Plant growth regulator

0

combinations (mg/l)

MS 1 MS +0.25 BAP 2 3 MS+ 0.25 IBA MS+ 0. 5 BAP+0.25 IBA

4 MS +0.25 BAP+0.5 IBA 100

Shoot induction (%)

100 100 100 100 5 MS+ 1 BAP+ 0.25 IBA 100

Number of shoots

1.38 ab 1.22 b 1.30 ab 1.22 b

1b

1.44 a

Number of Shoot length nodes

2.22 ab

(cm)

1.67 ab 1.82 ab 1.13 b 1.15 c 1.82 ab 0.85 c 1.23 b

3.17 a 2.67 a

1.85ab

1.85 ab

Rooting (%)

66.66

44.44

40 11.11

100

28.57

Microcuttings Multiplicatio

n

6 MS+ 0.25 BAP+ 1 IBA 100 1.6 a 2.56 ab 2.66 a 70 7 8 9 MS+ 2 BAP MS+ 2 BAP+0.25 IBA MS+2 IBA 100 100 100 1.2 b 1.2 b 1.1 b 1.2 c 1.4 b 1.6 b 0.68 c 0.52 c 1.37 b 0 0 100 Rooted vitroplants Acclimatized vitroplants

-

Means of the same column followed by different letters are significantly different at P< 0.05 according to Student Test. - Conditions of the test: Photoperiod 16 hours. Light Intensity 36

µmol.m

-2

.s

-1

.

Temperature 23  1°C. Culture period: 4 weeks.

In vitro rooting Multiplication

- In vitro rooting tests led to a general rooting in shoots cultivated in different treatments.

- The highest number of formed nodes 3.8 was obtained for MS control medium.

- The highest number of roots was obtained with growth regulators free medium and - MS medium free growth regulators appeared to be the best medium for shoot induction.

- Root induction was simultaneously observed along with shoot elongation.

medium supplemented with 0.25 mg/l of IBA.

- The longest roots were obtained with medium without growth regulators.

- The exogenous supply of IBA does not improve rooting.

Number of nodes 6 5

a b a

Number of shoot

Table 2: Effect of IBA Concentration on root induction (%) and length a

Shoot length (cm)

IBA (mg.l

-1

) Rooting (%) Number of roots Root length (cm)

4 3

b b 0 100 8.67 a 1.93 a 0.25

100 8.66 a 1.46 b

2

a a a

1

0.5

100 5.50 b 1.29 b

0 0 1 Media 2 0: MS/ 1 : MS+ 0,25 BAP+ 0,5 IBA/ 2: MS+ 0,25 BAP+1 IBA (mg/l)

Acclimatization

The kenaf plants show no ex vitro adaptation problem.

The success rate of transplanted plants was 100%.

Conclusion

An efficient micropropagation method has developed to initiate shoots and regenerate plants of Hibiscus cannabinus L. in a relative short time and high multiplication rate.

The use of MS medium added with 0.25 mg.l

-1 BAP and 0.5 mg.l

-1 IBA stimulate shoot induction and nodes formation on the first in vitro culture step. During multiplication stage, MS free growth regulators was the best media for explant growth. In vitro micropropagation of kenaf does not require any additional rooting step regarding to its easy rooting aptitude. Rooted plant can growth to maturity and produce seed under open pollinated conditions.