Beáta JURIAN, Marin ARDELEAN, Lehel LUKÁCS, Rodica POP, Monica BODEA, Mihai JURIAN, Mirela CORDEA

Department of genetics and plant breeding, Faculty of Horticulture, University of Agricultural Science and Veterinary Medicine Cluj-Napoca, str.Mănăştur, nr.3-5, Cluj-Napoca, România (contact e-mail: bjurian@yahoo.com)

Introduction

In view of obtaining in vitro mutagenesis treatments with the lettuce, it is necessary to work out an in vitro multiplication protocol for this species, allowing for getting an as high number of neoplantlets as possible within the shortest lapse of time.

From the previous experiments carried out for such a purpose, there resulted that the fittest culture medium for a high rate of multiplication of the lettuce is Kartha III, with a hormone balance slightly altered (AIA 1.0 mg/l, BAP 1.5 mg/l) (Ardelean et al., 2003).

Material and methods

The scope of our experiment was that of finding out the most suitable varieties and types of explant, in view of obtaining high rates of multiplication in vitro. Thus, there has been studied the behavior-in vitro conditions-of three varieties, i.e., Attraction, Maykönig and Greatlakes Osena.

The in vitro culture with the three varieties has been initiated with seeds. At two months after the initiation of the culture, the resulted neoplantlets were fashioned in minilayers and were passed on to fresh cultivation medium. The culture medium utilised both for seed- and minilayer inoculation was Kartha III (KARTHA, 1982), made up of macro-and microelements in the same quantities as with Murashige & Skoog, the difference being represented in the proportion of the vitamins and in that of phytohormones (AIA-1.0 mg/l, BAP - 1.5 mg/l).

Results and discussion

Observations on multiplication rate were statistically processed in view of finding out the impact of variety and type of explant.

Table 1 displays the results on the impact of variety on multiplication rate in seed-initiated culture:

Table 1: Impact of variety on multiplication rate in vitro with lettuce (explant type: seed), Cluj-Napoca, 2003

DS 5% - for three mean variety = 1.2

- the difference between two values followed by the same letter or groups of letters is not significant

Data in table 1 reveals the fact that varieties have responded differently to in vitro cultivation started with seeds.

The highest multiplication rate has been obtained with Greatlakes Osena producing, on average, 11.2 shoots from one single explant, and the difference being significant, as to the other two varieties. The poorest rate of multiplication is noticeable with Attraction (4.2 ofshoots/explant), Maykönig taking an intermediary position between the two above mentioned varieties, and a multiplication rate of 7.1 ofshoots/cultivar.

With the cultures started with minilayers the results obtained are introduced by table 2.

Table 2: Impact of variety on multiplication rate in vitro with lettuce (explant type: :minilayers), Cluj-Napoca, 2003

DS 5% - for three mean variety = 1.1 - 1.2

- the difference between two varieties followed by the same letter or group of letters is not significant

One can see that in with this case too, when initiation has been carried out by means of minilayers obtained in vitro, varieties displayed differing rates of multiplication. The highest multiplication rate - with this case too - has been obtained with Greatlakes Osena, being followed by Maykönig. Thus Attraction is lagging behind with a mere 4.3 offshoot/cultivar.

Based on data in tables 1 and 2, one can draw the conclusion that regardless the type of cultivar, and the list of varieties rests unchanged, i.e., 1st Greatlakes Osena; 2nd Maykönig ; 3rd Attraction, thus suggesting the idea that rate of proliferation is influenced to a higher degree by the regenerating ability of variety on Kartha III than by the explant type utilised to initiate cultivation.

Table 3 introduces both variety impact and explant type on in vitro proliferation rate in the lettuce.

Table 3: Impact of variety and explant type on proliferation rate of the lettuce in vitro ,Cluj-Napoca, 2003

DS 5% for three mean variety = 0.63-0.66
DS 5% for two mean explant = 0.5
DS 5% for two interaction mean = 0.88 - 0.92 - 0.94 - 0.96 - 0.97

- difference between two values followed by the same letter or group of letters is insignificant

As we have already seen, varieties have reacted differently in in vitro conditions, by having displayed differing rates of proliferation. However, proliferation rates varied also by the explant used to start the culture.

The highest proliferation rate has been obtained when the culture is initiated with minilayers obtained from Greatlakes Osena (13.0 neoplantlets/explant), followed by cultures started with Greatlakes Osena seeds (11.2).

Maykönig reacted similarly, by producing 8.4 ofshoot/explant as average, with variants started with minilayers, as to 7.1 ofshoot/explant on using seeds to inoculate on Kartha III medium. The most wanting proliferation rates were recorded with Attraction, no matter the explant type involved (4.2 - seeds; 4.3 - minilayers).

Conclusion

Of the three varieties submitted to trial, the highest proliferation rate on Kartha III medium has been recorded with Greatlakes Osena followed by Maykönig and Attraction.

By analysing the impact of explant type on proliferation rate we can come to the conclusion that with cultures started with minilayers obtained in vitro , there is generally granted a substantially higher proliferation rate.

The identical rating of the varieties - regardless the type of explant utilised - suggests that variety has a substantial impact upon the rate of proliferation, i.e., to a larger extent than the type of explant.

For the programmes meant for improving the quality of lettuce by in vitro mutagenesis , most recommendable variety of those tested is Greatlakes Osena-followed by Maykönig -which besides outstanding qualities, also provides for a high rate in multiplication, thus speeding up the process of improvement.

References

1. Ardelean, M., Jurian Beata, Rodica Pop, Monica Bodea, Mirela Cordea, Effect of Differing Culture media Upon in vitro Multiplication Rate in Two Cultivars of Lettuce, in: Hintum, Th. J.L., A.Lebeda, D.A. Pink, J.W. Schut (eds), Eucarpia Leafy Vegetables 2003, Proceedings of the Eucarpia Meeting on Leafy Vegetables Genetics and Breeding, Noordwijkerhont; 19-21 March, 2003. Centre for Genetic Resources, The Netherlands (CGN), Wageningen, The Netherlands.

2. Kartha K.K., 1982, Meristem Culture, 19-24, in : Wetter and Constabel (eds), 1982 (q.V.)