Devitalisation of Cut Rose16 Ewgcutflowers 2014 June

Devitalisation of Cut Rose16_EWGCutFlowers_2014_June

Devitalisation of Cut Rose (Rosa hybrida L.) Flowers cv. ‘Bellerose’: Effects of Glyphogan® and Roundup® on Propagation Ability and Vaselife.

( Prepared by M.J. Hutchinson1, H.K. Miranyi2, C. M. Onyango1 and E. Kimani2)

1 Department of Plant Science and Crop Protection, University of Nairobi

P.O. Box 30197–00100, Nairobi, Kenya.

2 Kenya Plant Health Inspectorate Service (KEPHIS),

P.O. Box 49592–00100, Nairobi, Kenya.

Email:

ABSTRACT

The objective of this study was to establish the effectiveness of devitalisation treatment phyto-sanitary measure on propagation ability of cut rose flowers (Rosa hybrida L.) cv. ‘Bellerose’ at different dipping levels and assess the effects of the treatment on its vaselife. Harvested export quality rose cut flowers obtained from Sian Roses Flower Company, were dipped in glyphosate solutions ofRoundup® (a.i 360g/l) and Glyphogan® (a.i 480g/l) following procedures described in the Australian pre-shipment devitalisation treatment guidelines. Tap water acted as a control. To assess propagation ability, 50 cm cut roses were dipped in preparedsolutions at 15, 25, 35 or 45 cm depths. Data on percentage rooting, number of roots, root length and percentage necrotic stems was collected after 26 days in the propagation unit. For the vase life experiment, 40 cm cut roses were dipped up to 35 cm depth and thereafter held in holding solution containing 2% sucrose and 1% sodium hypochlorite solution. Changes in fresh weight, water balance, leaf abscission, chlorophyll content and vase life were determined. The results showed that devitalisation treatment inhibited rooting even at lowest dipping depth of 15 cm and triggered necrosis of the stems. The treatment further increased leaf abscission and wilting, reduced chlorophyll content and shortened vaselife of cut roses by about 2 days. Glyphosate-treated flowers also recorded a worse negative water balance and fresh weight change while the flower petals were not affected by the treatments. Considering bio-security concerns,the observed negative effects of devitalisation on the cut flower vase life cannot compromise adherence to the requirements.

Key words: Bio-security; Glyphosate; Phyto-sanitary measures; Rosa hybrida L; Vase life.

INTRODUCTION

[1]Floriculture is among the fastest growing subsectors in the Agriculture sector, with a 25% increase in total value in the year 2011 compared to 2010 (HCDA, 2012). With over 80 commercially cultivated cut flowers in Kenya, Roses take the lead in the export market share at 75.8%, Carnations (12%), Hypericum (8.3%), Arabicums (0.81%) and Easter lilies (0.79%)(HCDA, 2012). The European Union is the major destination of Kenyan cut flowers. Challenges related to over-reliance on few markets and the raging ‘carbon miles’ debate necessitates an urgent need to diversify. Some of the emerging and potential markets include Australia, Russia, Japan, U.A.E and the U.S.A(HCDA, 2011).

[2]Expansion of trade to these emerging markets, both in volume and diversity has brought with it the threat of introduction and spread of quarantine pests (IPPC, 1997). The National Plant Protection Organizations (NPPO) of member countries to the International Plant Protection Convention (IPPC) have been mandated to exercise some sovereign right to regulate imports to achieve their appropriate level of protection, while taking into account their international obligations (IPPC, 1997). Australia for example requires that propagatable cut flowers must be devitalized in accredited facilities to render them non-viable before being allowed entry and has outlined pre-shipment guidelines pertaining to this treatment (AQIS, 2011). The treatment involves immersing the cuttings in solutions of glyphosatemarketed as Roundup® (a.i 360g/l) and Zero® (a.i 170g/l) with glyphosate as the active ingredient. Despite the availability of the protocol, there have been interceptions due to non-compliance of Kenyan imports into the Australian market (Anon, 2012). Devitalized Equisetum hyemalecut flowers imported into the New Zealand from the United States of America, also failed the compliance test as reported by Large et al. (2006),raising concerns that the flowers may not have been treated as prescribed by the New Zealand Ministry of Agriculture and Forestry (MAF) Bio-security standard 152.09.05 or was not devitalized at all (MAF NZ, 2002). Effective devitalisation of floristry products entails rendering them non-propagatable while preserving its commercial use i.e. retaining its floral quality(Blanchon et al., 2012).Dipping 60 cm stems of Chamelaucium spp.to 10 cm depth in 0.1% glyphosate proved effective (Leeet al., 2003). The effect of the devitalisation treatments on the vase life and postharvest quality of cut flowers is unclear.Seaton et al. (2010) reported an improvement of flower vase life and reduced leaf vase life of varieties of geraldton wax (Chamelaucium spp)flowers.

[3]The aim of the study was to evaluate the effectiveness of devitalisation treatment at various dipping depths on propagation ability and its effects on the vase life of cut rose (Rosa hybrida L.) cv. Bellerose flowers in Kenya.

MATERIALS AND METHODS:

Plant materials

[4]Export quality standard rose cut flowers (Rosa hybrida L.) cv. Bellerose, harvested in the morning were obtained from Sian Roses, a commercial rose grower located in Karen area, 40 km South East of Kenya’s capital city, Nairobi at an altitude of 1,250 metres above sea level.

Devitalisation treatments

[5]Devitalisation was done at Sian Roses’ devitalisation facility following the AQIS devitalisation guidelines (AQIS, 2011). The treatment solutions were prepared using two glyphosate formulations: Roundup® - a.i 360g/l by Monsanto Company and Glyphogan®- a.i 480g/l by Makhteshim Agan Company. Clean tap water acted as a control.

Propagation assessment

[6]Fifteencut flowers were re-cut to 50 cm and dipped in devitalisation solutions at four levels: 15, 25, 35and 45 cm for 20 minutes.After2 hours the flowers were transferred to the Sian Rosespropagation unit with controlled environment.Cuttings of pencil-size diameter, with one leaf and a node were dipped in commercial rooting hormone, auxinbefore planting in sterile coco peat rooting media.After 26 days, the cuttings were carefully washed and data collected as percentage rooting, number of roots, root length and percentage necrotic stems (Davies, 1985).

[7]The experimental design was a Completely Randomized Design with 3 replications using 10 cuttings and repeated twice.

Vase life evaluation

[8] Forty cut flowers were re-cut to 40 cm and dipped in prepared devitalisationsolutions to 35cm depth for 20 minutes.Thereafter, the flowers were kept overnight in the cold store at 2oc and transported to the Plant Physiology laboratory at the University of Nairobi the following day. The flowers were again re-cut under distilled water and left there to rehydrate for 2 hoursbefore placingthem in flower vases containing 500mls holding solution comprising of distilled water, 1% commercial Jik® (Sodium hypochlorite) and 2% sucrose with pH adjusted to 3.5 using citric acid. Four flower vases containing the holding solution only were placed next to the replications for the purpose of correcting for direct evaporation (Ichimura et al., 2002).

[9]The data collected included water uptake and transpiration. Water balance was calculated using the differences between water uptake and transpiration. The fresh weight change, determined as the percentage of the initial weight (Van Meeteren,1989). Chlorophyll content wasdetermined using spectrophotometer absorbance readings of the extracts at 653nm(Musembi, 2008). The vase life was determined as the number of days to 50% leaf loss.

[10]The experimental design was a Completely Randomized Design with four replications using 6 stems and repeated twice.

Data analysis

[11]Data for both experiments was subjected to analysis of variance (ANOVA) by Genstat statistical software (Payne et al., 2006). Means were separated using protected LSD at P = 0.05

RESULTS

Propagation test results

1. Percent rooting

The devitalisation treatments Roundup® and Glyphogan®significantly (p<0.05) inhibited rooting on cut rose stemsfor both experiments(Figure 1A&B). In experiment 1, Roundup®recorded 10% rooting while Glyphogan®recorded 20% rootingat 15cm dipping depth only while all stems held in tap water rooted at all dipping depths in a declining trend (Figure 1A). The second experiment resulted in no roots for all the glyphosate treated stems at all the dipping depths while the control stems had roots at all dipping depths with a declining trend at 93, 90, 83 and 70% (Figure 1B).

1. Number of roots

Glyphogan® and Roundup® significantly (p<0.05) reduced the number of roots at all dipping depths in the two experiments (Figure 2). In experiment 1, both Roundup® and Glyphogan® recorded an average of 13 and 19 roots of the rooted cuttings, respectively at 15 cm dipping depth and no roots for depths 25 cm, 35 cm and 45 cm (Figure 2A). The control recorded highest number of roots in all the dipping depths ranging from 109 at 15 cm to 46.7 at 45 cm. In experiment 2, Glyphogan® and Roundup® recorded no root at all the dipping depths while the control recorded roots at all dipping depths with highest number of roots at 15 cm depth as 92.7 and lowest at 45 cm dipping depth as 58.3 (Figure 2B). There was a general decline in number of roots with increasing dipping depth.

1. Root length

The devitalisation treatments significantly (P<0.05) reduced the root length of the few roots formed on cut rose stems when compared with the controls at 15 cm dipping depth from 3.8 to less than 0.5 cm during the first experiment (Figure 3A). The cut rose stems in the control generally formed shorter roots as the dipping depth increased in both experiments (Figure 3A&B).

1. Percentage necrosis of cuttings

BothGlyphogan® and Roundup® treatments significantly (p<0.05) increased the number of stems with necrosis in both Experiments (Figure 4A&B). The necrotic effect increased with increase in dipping depth during both experiments. For the first experiment, Glyphogan® and Roundup® recorded the highest necrosis starting at 50% and 36.7% respectively at 15 cm dipping depth to end at 80% and 83.3% respectively at 45 cm depth while the controlturned necrotic only at the 45 cm dipping depth (Figure 4A). The effect of these treatments was lower for the second experiment with less stems turning necrotic (Figure 4B).

Vase life assessment results

1. Vase life and Chlorophyll loss

Application of Glyphogan® and Roundup® significantly (P<0.05) reduced the vase life by between 2 to 2.75 days in experiment 1 and 0.75 days in experiment2 (Table 9). There was no significant difference between Glyphogan® and Roundup® treated cut stems in bothexperiments and both accelerated chlorophyll loss compared to the control especially during experiment 2 (Table 9).

1. Water uptake

The uptake of water in all cut rose stems generally declined over the holding period irrespective of the devitalisation treatment from a high of around 58g/dayto less than 20g/day (Figure 5A&B). There was no clear trend during experiment 1 with Glyphogan®and Roundup® exhibiting higher water uptake up to day 3 and thereafter, significantly decreasing it below the controls (Figure 5A). In experiment 2, devitalized cut stems indicated a slightly higher water uptake than the controls over the entire holding period (Figure 5B).

1. Transpiration

Transpiration rate on cut rose stems declined over time irrespective of the devitalisation treatment from around 55 and 70g/day to around 20 g/day during experiment 1 and 2, respectively (Figure 6A&B). There was no clear difference between the treatments during both experimentswith Glyphogan®and Roundup® exhibiting higher transpiration rate up to day 3 and thereafter, significantly decreasing it below the controls during experiment 1(Figure 6A). For experiment 2, the devitalized cut stems had a higher transpiration rate than the controls till day 5 after which there was no significant difference (Figure 6B).

1. Water balance

The water balance of cut rose stems fluctuated with a general decline over the vase life period with a negative status experience after day 3 (Figure 7A&B). There was no significant (p>0.05) difference in Glyphogan® and Roundup® treatments in both experiments. The control had a more positive water balance compared to Glyphogan® and Roundup® in experiment 1 (Figure 7A). In experiment 2, the control had a slightly higher water balance up to day 5 of holding when it slumped rapidly below Glyphogan® and Roundup® till the end of the 8 days of holding (Figure 7B). The decline in water balance of control stems was more rapid in experiment 2.

1. Change in fresh weight

In both experiments, fresh weight of cut stems increased from day 1 to day 3 then started to drop for all the treatments going back to the initial by day four in the case of Roundup® and Glyphogan® and about day 5 for the control (Figure 8AB). There was no significant (p0.05) difference between the 2 devitalisation formulations in both experiments, while both were significantly different from the control. The control maintained a higher fresh weight change throughout experiment 1 compared to both Glyphogan® and Roundup®. In experiment 2, the control fresh weight was slightly above Glyphogan® and Roundup® only from day 1 to day5 recording the greatest gain in day 3 (103.8%) when it suddenly dropped below the two treatments to record the lowest weight change at 81.5%.

1. Percentage cumulative leaf loss

Regardless of the treatment, all rose cut stems started losing leaves after 3 days (Figure 9A B). The untreated cut stems started losing their leaves 1-2 days later than those devitalised. Glyphogan® and Roundup® significantly (p<0.05) enhanced leaf loss during the two experiments with no significant differences between them.

DISCUSSION

[12]The results of the present study indicate that the devitalisation process using either Roundup® or Glyphogan®was very effective in preventing rooting of cut stems at a lower dipping depth than what is recommended. The reasons for the few rudimentary roots observed at 15 cm dipping depth only in experiment 1 was not clear and the few numbers and length of less than 0.5 cm may be an indication of low vigor. Similar results were reported by Lee et al. (2003) who observed that dipping 60 cm stems of selected wax flower cultivars up to 10 cm depth in 0.1% glyphosate was effective in preventing propagation. The failure to root was linked to death and rapture of the outer cells of the cut flower stems caused by the glyphosate action (Ahmed and Zaharah, 1996). Glyphosate is said to disrupt the biosynthesis of essential amino acids such as phenylalanine that are essential for growth and ultimately root initiation (Tu et al., 2001).The same necrotic effects of glyphosate treatment were reported on Saundersoniaaurantiacaflowers (Eason et al., 2000) and on Chamelaucium spp flowers (Seatonet al., 2010). This may be attributed to the toxic nature of glyphosate to the green tissue on the stem causing death (Eason et al., 2000). The increase in necrotic stems with increase in dipping depth may be attributed to temporary oxygen stress experienced during immersion which also hinders rooting of rose cuttings (Baas et al., 1997).

[13]The results of reduced vase life and rapid chlorophyll loss of devitalisedcut rose flowers comparewith those of Large et al. (2006) who indicatedthat devitalized Equisetum hyemale stems had a shorter vase life characterized by rapid yellowing and decomposition. Glyphosate treated carnations were also unable to last through the 15 days of vase life (Ahmed and Zaharah, 1996). The contrary was reported by Seaton et al (2010) who observed that pulsing geraldton wax using 1% Roundup improved its vase life. The rapid senescence of the rose leaves that led to reduced vase life may be attributed to production of endogenous ethylene triggered by the ethylene caused stress in Kochia scoparia (Waite, 2008). The rapid reduction of chlorophyll content according to Zobiole et al. (2010) may be attributed to direct damage of the chloroplasts in the presence of glyphosate. Glyphogan® or Roundup®did not seem to affect the flower heads which remained intact (Data not shown). This is supported by Eason et al. 2000) who suggested that glyphosate was toxic to all green tissues of Sandersonia aurantiacabut not the flower. The variations between the 2 experiments may be linked to room temperature fluctuations during experimentation. Tu et al. (2001) postulated that high temperatures inhibit enzymatic synthesis of aromatic amino acids besides affecting other biochemical changes such as translocation of carbohydrates.

[14]Water uptake, transpiration and water balance are all interrelated and together constitute the water relations aspect which also affects fresh weight change in cut flowers (Halevy and Mayak, 1981). Unfortunately, literature on the effects of glyphosate treatment on water relations in cut flowersseemed unavailable. The overall declining and parallel trend of water uptake and transpiration for all the treatments in the current studymay be associated to a decline in conductivity which is a general occurrence in many aging cut flowers (Mayak et al., 1974). Air embolism which interrupts the water columns in the stem is considered one of the factors causing negative water balance (Van Doorn, 1997). The untreated stems had a more positive water balance than the Glyphogan® and Roundup® treated ones which translated to higher turgidity and better vase life. High turgidity is necessary for the continuation of normal metabolic activities of cut roses (Nair et al., 2003). The change in fresh weights of cut rose stems generally increased for all the treatments up to the third day of holding when it started to drop attaining the initial weight around day 4 for Glyphogan® and Roundup® and day 5 for the control. The effect of Roundup® and Glyphogan®on fresh weight change was similar throughout the experimental period and was generally lower than the control.Similar results were reported by Zobiole et al. (2010) who observed that glyphosate reduced water uptake and biomass production leading to reduced water use efficiency in soybeans.

CONCLUSIONS

[15]The results of the current study indicate that the devitalisation procedure, using eitherGlyphogan® and Roundup® formulations, are effective even at lower dipping depthsthan the recommended minimum 35 cm or 5 cm from the flower head. Possible incorporation of vase life enhancers to counter the negative effects of the treatment on the leaves could be a worthy compensation for the achievement of the objective of devitalisationwhich is to address bio-security concerns. To reduce possible interceptions of Kenyan flowers exported to the Australian market may need capacity building for exporters.

ACKNOWLEDGEMENTS

[16]We thank the University of Nairobi and The Sian Roses flower Company who provided their facilities for use. The Kenya Plant Health Inspectorate Service (KEPHIS) is also appreciated for allowing the student time off to undertake this study.

REFERENCES

Ahmed, S. H and Zaharah, A. R. 1998. Post Harvest treatment with Glyphosate to devitalize Rose and Carnation cut flowers. Acta Horticulturae (ISHS) 464: 541-541.