Identification and evaluation propagation techniques of Hypoestes forskaolii (Grbia) as bee fodder for smallholder farmers

Haftom Gebremedhn and Yaynishet Tesfay

Department of Apiculture and sericulture, Mekelle Agricultural Research Center, Tigray Agricultural Research Institute,
P.O. Box 492, Mekelle, Tigray, Ethiopia
haftush@yahoo.com
* Mekelle Universities, Faculty of dry land agriculture and natural resource,
P.O. Box 231, Mekelle, Tigray, Ethiopia

Abstract

Hypoestes forskaolii is one of the most important honeybee floras of Northern Ethiopia. However the plant is currently threatened due to population pressure and farmland expansion. Moreover, for rapid propagation of the plant its propagation techniques were not identified. Thus the study was designed to identify and evaluate different propagation techniques of the plant. The study was conducted in Mekelle Agricultural Research Center, Mekelle. Data were statistically analyzed using one way ANOVA analysis of variance.

 

Least significant difference /LSD were calculated to identify significant difference among the treatments using Genstat 13^th version statistical software. Six successful propagation techniques of the plant were identified. These were direct cutting, cuttings using pot, transplanting seedlings, splitting or dividing the main branch of the mother plant, air layering and ground layering. There was significant difference among the means of techniques on canopy cover,  flowering period, height, number  of flowers and branches,  and seed yield per plant (p<0.05). Splitting had the highest flower numbers (2029); while air layering had the smallest numbers of flowers (703). The number of flowers had positive correlation with the number of branches, height and flowering period of the plant. Finally, it is recommended to use splitting as best propagation technique of H. forskaolii under its natural growing areas or under in-situ.

Key words: flowers, honeybee, planting method

Introduction

Plants are the food source of honeybees. Honeybee visit flowers to collect pollen and nectar (Jones and Yates 1991). They obtain protein from pollen and carbohydrate from nectar source plants (Bista and Shivakoti 2001). Honeybee plants are best suited for honey production as well as colony maintenance. Globally there are millions of plant species. However, not all plants are important for honeybee and those plants that supply both nectar and pollen abundantly when in bloom and these are often called honeybee plants (Akratanakul 1990). 

Ethiopia is gifted with diverse and unique flowering plants of 6000 to 7000 species. Thus making it highly suitable for large number of colonies (Admasu 1996, Fitchel and Admasu 1994;  Gezahegn 2007, Gidey and Mekonen 2010). Hypoestes forskaolii (Vahl) is one of the most important honeybee plants of Ethiopia and has abundant pollen and nectar. It is described as perennial herb or sub shrub that belongs to the family Acanthaceae (November et al 2002; Haftom et al 2011; Fitchel and Admasu 1994; Kamundi 2006;  Alemtsehay, 2011). The plant is a very important honey source and honeybees forage it for the abundant pollen and nectar. It is locally known as Grbia (Tigrigna) ( Haftom et al 2011; Alemtsehay 2011).  Honeybees produce large quantities of light and pure white honey which has high demand and price in the market, and generate high income for the beekeepers (Haftom et al 2011). 

Tigrian white honey of the nation comes from localities including Hawzien, Atsby Wonberta,Woukro and Adigrat districts (Taddele and Nejedan 2008) which are the potential  H. forskaolii growing areas (Haftom et al 2011;  Alemtsehay 2011) . Honey from the region is very popular and the demand for it is very high in the export markets (UNIDO 2009).  Since the plant has high number of flowers, giving white honey, long flowering period and high honeybees’ preference;  farmers, bee experts, bee technicians and other NGOs involved on beekeeping state that the H. forskaolii is the best honeybee flora in the region. Hence, beekeepers ranked the plant second in Atsby Wonberta, third in Hawzen and fourth in Kolatemben districts among the existing honeybee floras of the areas (Haftom et al 2011; Alemtsehay 2011). 

The plant is growing in open woodland, disturbed mountain forest, grassland and is common along roadsides. The species spans over altitude ranges more frequently between 500 and 2700 m a.s.l. (Fitchel and Admasu 1994). However, H. forskaolii is currently threatened due to population pressure and the associated farmland expansion. Hence, natural regeneration of the plant from seed becomes very difficult due to widespread human interference. Moreover there is shortage of bee forage and honeybee colonies abscond to areas where resources are available for their survival (Gidey and Kibrom 2010). Moreover, for rapid propagation of the regionally important species, its propagation techniques were not identified and were not well researched. To this end, propagation technology on regionally important species has increased within the past decade.  

Hence this study was designed to identify and evaluate different propagation methods of H. forskaolii and select the best method/s for the fast production of the plant biomass. This would have a great contribution on minimizing the shortage of bee forage in the region.  

Methodology

Description of study area 

The study was conducted at Mekelle agricultural research center, Illala site. Illala is geographically located in the North east of Mekelle city at elevation of 1970 m.a.s.l at 25⁰ 51N latitude and 39⁰ 61 longitude. The site was selected based on the availability of the plant, access to transport and to conduct the study under its in-situ. The type of soil in the study is dominantly vertisol.  

Experimental management 

Prior to the experiment mature seeds and a total of 80 mother plants which had the same provenance were collected from the beginning of June to December (2010) from Illala site to be used as source of planting materials for conducting the study. Seeds were collected from 60 plants by selecting mature fruits. Immediately after collection, seeds were packed in perforated Polyethylene bags and allowed to dry for one month at room temperature. The packages were maintained at room temperature until date of sowing on May and used for propagating the plant in plastic pots. To avoid moisture stress and to establish easily, the mother plants were collected at the beginning of rainy season /June, 2010/ and transplanted within the same day. 

After collecting the planting materials, preliminary observation trial was done to identify propagation method/s of the plant. Throughout the observation trial six successful propagation techniques of H. forskaolii were identified. These were direct cutting, cutting using pot, plant splitting, air layering, ground layering and transplanting seedlings. Then, the study was continued to evaluate the identified propagation techniques of the plant under the experimental plot.   

To evaluate the propagation techniques of the plant  60 number of plastic sleeves (diameter, 8cm; length, 15cm) were prepared by filling them with a soil mixture of silt, sand and manure at the ratio of 20: 2: 5, respectively for raising seedlings through transplanted seedling and cutting propagation techniques. The seeds were covered with a thin layer of the same soil mixture and watered by sprinkling irrigation to avoid erosion. The sleeves were then arranged on the ground in open air. Dried grass stalks were used to cover the mouth of the arranged sleeves for conserving moisture, but the grass cover was removed as the seeds germinated and germinant emerged to the surface of the soil. While germination of the seeds /65 %/ started at 27^th day, transplantation of the seedlings to the experimental plot was done at 52^th days on July/2010/ to have matured roots.  

For evaluating cutting using pot, 60 cuttings with a height of 15cm were collected early in the morning from 25 mother plants. Each cutting had green leaves (5-10) to maintain photosynthesis. To compare germination responses of the cuttings planted in plastic sleeves with those in the open field, 60 cuttings were planted directly in rows on a plot of land / 15cm soil depth/ prepared with soil mixture indicated above. Finally, transplantation of the seedlings to the experimental plot was done at 52 ^th day for cuttings using pot and 45^th day for direct cuttings. 

For air layering to form roots on the aerial part of a plant, the stem was not girdled or slit with sharp knife below a node. Hence it has very thin stem. The stem was enclosed via a moist rooting medium soil /with the above soil mixture/ at the point of its node. Then plastic wrap and proper sealing was done to keep the layer from drying out and to retain the moisture around the node area for weeks/months. Finally simple cutting of the branch was done closely to the new plant. Before removing the plastic cutting of the new plant was done just below the roots. The seedlings were transplanted at 28^th day directly after cutting the newly emerged seedlings from their mother plants. During transplanting the new plants to the experimental plot there was plenty of soil around the roots.

Ground layering was done by bending 60 selected branches. The middle portion of the selected branches were put in the ground (i.e., shoot tip comes back up above ground) under the existing soil. The branches had enough length / 15 to 25 cm/ from the tip so a few inches of leaves were left on the tip. The stem bend to the ground was covered part of it with the above soil mixture and the rest were leaved, exposed. For ground layering even the branches started root initiating at 14^th day, cutting of the newly emerged seedling from their mother plant was done at 21^th days to have well developed roots.  Cutting of the stem was done just below the rooted zone. Lastly, the seedlings were transplanted to experimental plot at 15^th day after cutting the branches from their mother plants or after 36 days from the time of covering the branches with the above soil mixture. 

For splitting 10 mother plants which had more number of young main branches were selected from the established mother plants. Until transplantation of the seedlings there was supplementary irrigation for the selected mother plants from the begging of May once a week. This was done to develop the branches more green leaf, split the braches easily from their mother plants and avoid root injury. After treating the mother plants in this manner transplanting and splitting/ dividing of the main branches from their mother plants was done after 40 days on July first.  

For all treatments to avoid moisture stress the newly emerged seedlings were transplanted early on the morning and planted on the same day. All the young plants or seedlings deriving from the different propagation techniques were planted in pits of 10cm in diameter and depth. After transplanting the seedlings to the experimental plot, the plants were supplemented with irrigation once a week when there was no rain falls.  

Experimental design  

The study was conducted in six treatments to evaluate the propagation techniques of the plant. These were seedling, direct cutting, splitting, ground layering, air layering and cutting using plastic pot.  Each propagation techniques were considered as treatment. The numbers or types of treatments were selected based on the preliminary study of the observation trial. Each treatment was replicated three times in three blocks.  50cm between plants, 60cm between rows, 70cm between plots and 1m between blocks distances were used to plant the plants in the experimental plots.  

Data collection and analysis  

To collect the data four plants were taken randomly per plot and a total of twelve plants per each treatment. The data were collected on the following parameters.

Canopy cover was calculated by  

C.C = (D₁ +D₂)/2 

Where D₁ is diameter of the plant toward the larger canopy coverage, D₂ is diameter of the plant towards the small canopy coverage and C.C represents canopy cover of the plant in cm.

And then the canopy cover of the plant was expressed in terms of the average diameter in cm.  

The total numbers of flowers per plant were calculated by counting the total head flower per plant and number of flowers per head flower. The total number of flowers per plant was calculated by  

T.F = H.F *N.F.H 

Where, H.F is the number of head flowers per plant, N.F.H is the number of flowers per head flowers and T.F represents the total number of flowers per plant. To know the number of flowers per head flower a sample of 10 head flowers per plant were taken randomly.   

The height of the plant was measured from ground level to the tip of the largest branch with the help of a measuring tape. The flowering period of the plant was determined by recording the flowering starting and ending date of the randomly selected plants. Actual number of branches and seeds per plant were determined by counting and data were recorded. 

The collected data were statistically analyzed using one way ANOVA analysis of variance and least significant difference / LSD was calculated to identify significant difference among the treatments using Genstat 13^th version statistical software. Correlation analysis was applied for specific variables using SPSS version 16.

Results and Discussion

Propagation methods of H. forskaolii 

Throughout the study six successful propagation techniques of H. forskaolii were identified. These were direct cuttings, cutting using pot, plant splitting, air and ground layering from asexual or vegetative propagation and transplanting seedlings from sexual. Among the techniques, the vegetative propagation needs mother plants for multiplying the plant. However, the new seedlings produced through air layering can be transplanted to introduce to new areas. Unlike splitting and taking cuttings, ground layering and air layering had an advantage in that they multiplied the plant without damaging the mother plants.  

Height, canopy cover and number of branches  

The study noted a significant difference on the height of the plant among the means of the techniques (P < 0.05, Table 1). Plants propagated through splitting had the highest height (34.92cm), while Plants propagated by air layering had the shortest height (27.75 cm). In this study the plant had a maximum of 48cm height, which is similar with the natural (30–60cm) height of the plant (Kamundi 2006). Height of the plant had none significant weak positive correlation with number of branches per plant (r= +0.25, Table 2, P > 0.05), seed yield (r=+ 0.06, P>0.05) and flowering period (r = + 0.01, P>0.05). This might be due to growth habit of the plant. Stems of the plant developed from a single original stem that branched repeatedly at the soil level. These branches orient horizontally than growing up ward.  

Regarding the number of branches there was significant difference (P< 0.001) between the means of the treatments. Splitting had the greatest number of branches (7.8) and canopy cover per plant (41.3 cm), while air layering had the smallest number of branches (4.9) and canopy cover (33.5cm). The highest number of branches for splitting might be due to splitting way of propagation rejuvenate or make younger the new splinted branches. Moreover during dividing the branches from their mother plants each seedling had matured stem and roots. This might help them to stay the plants longer vegtatively and develop more number of branches.  John et al (1987) also revealed that the more vegetative growth of a plant develops to more flowers and seeds.Number of branches per plant had positive correlation with canopy cover (r= +0.39, P< 0.05). 

Number of flowers, flowering period and seed potential 

Concerning the number of flowers per plant, there was highly significant difference among the means of the treatments (p< 0.01). The plants propagated through splitting showed the highest number of flowers (2029), whereas air layering had the smallest number of flowers (703). The flowering pattern and flowering performance of a plant are considered to be the sum of all the genetic, physiological and morphological traits of a species variety (Rajesh 2010). The variation on the number of flowers per plant among the techniques might be due to differences on the number of branches per plant. The number of flowers had significant positive correlation with the number of branches (r = +0.56, P<0.001). Rajesh (2010) also reported a significant positive correlation of flower number per plant with primary branch number and secondary branch number in Linum usitatissimum L.

 

  

Plants propagated from splitting had long flowering period (65.6 days), whereas plants propagated through ground layering had the shortest flowering period (55.5 days). Since the plants raised through splitting had matured root and stem during transplantation compare to other techniques, this might help them to stay longer vegetatively. Because flowering period showed significant positive correlation with number of branches (r =+ 0.26, P<0.05). The flowering period had significant positive correlation with number of flowers (r =+ 0.26, P<0.05). Arthur and Kossler (2004) also observed, flowering time was correlated positively with flower production in Brassica rapa. 

There was also high significant difference in seed production potential between the means of the techniques (P< 0.001). Plants propagated from splitting had the greatest number of seeds per plant (581), while cutting using pot had the smallest number of seeds per plant (407). This might be due to difference on the number of flowers and branches among the techniques. And as described by John et al (1987) plants that grow longer vegetatively before flowering are typically bigger and able to support more reproductive growth. Beside to this seed yield per plant showed significant positive correlation (r=+ 0.40, P<0.001) with number of branches and flowers (r =+ 0.56, P<0.01).