Obtaining tomato form with higher lycopene content in fruits after seed treatment with diagnostic imaging element Тс-99m

 

S. Grozeva, V. Rodeva, G. Pevicharova

Maritsa Vegetable Crops Research Institute, 4003 Plovdiv, Bulgaria

stanislava.grozeva@abv.bg; velirod@evrocom.net; gpevicharova@abv.bg;

 

Introduction

For induction of genetic variability in many crops including tomato, specialists often combine the mutagenesis with in vitro techniques (Jain, 1998; Emmanuel and Levy, 2002). Results obtained by utilization of chemical and physical mutagens in tomato include changed growth habit (sp), inflorescence (s) and other characters, with positive effects on plant productivity, higher pigment content in the fruits, disease resistance, etc. (Nabisan et al., 1992; Rodeva, 2003; Mukandama et al., 2003). Some of these changed forms are successfully included in tomato breeding programs.

The radionuclides are still not widely used in mutation breeding. Nell and Onasch (1989) have observed cytological changes in somatic cells and intercellular spaces as well as structural disturbances of cell membranes in young soybean plants after treatment with Tc-99m. We didn’t find data in the literature about the mutagenic effect of the diagnostic imaging elements of Тс-99m in tomato.

The goal of this experiment was to study some of the altered characteristics in plants of two seed generations of tomato obtained after seed treatment with Тс-99m.

 

Material and methods

The experiments were carried out in 2003-2005. The plants of M₂ /200/ and M₃ /50/ generations of tomato form N1276-13, were obtained as a result of a 24-hour treatment of seeds from line N120 with Тс-99m (as Na⁺TcO⁴ with average specific concentration 35 МBq/ml) and in vitro germination, then grown in the field. Control plants were grown after treating the seeds of the same line in modified Krebs solution /C1/ and non-treated seeds germinated in vitro /C2/. Thirty plants were in each of the controls. Data recorded included: productivity/plant, fruit weight and index. In 20% of the plants in each of the studied generations and also in the controls, dry matter content (⁰brix), total pigments and lycopene were analyzed in the fruits (Manuelyan, in Kalloo, 1991) .

 

Results and discussion

In year 2003, tomato plant N1276-13 was selected with higher pigment content in the fruits compared to all other studied plants obtained after seed treatment with Тс-99m. The data in Table 1 proves that the plants in M₂ and M₃ generation of N1276-13 are distinguished by some characteristic compared with control plants of the original line N120. The observed differences in the plants are significant especially regarding total pigments and lycopene content which was confirmed by the statistical analysis. The values of these characteristics are higher in the plants of the experimental tomato compared to the control plants. The recorded lower values in year 2005 probably are due to unfavorable weather conditions – wide temperature fluctuations and high humidity because of daily rain. Although the pigment content in the fruits of plants N1276-13 (M₃) was lower than in the previous year, it was again two times higher than that of the control plants. The statistical analysis shows lower coefficients of variability for these two characteristics in year 2005, probably due to the selection process in M₂.

There were no statistically significant differences established for any other studied characteristics in tomato plants with the exception of fruit index. The fruit index showed that the fruit shape in tomato plants of N1276-13 is more elongated (1,23 and 1,24 respectively) compared to the oval fruit shape of the control plants (from 1,10 to 1,16).

As a result of this experiment and treating the seeds with radionuclide Тс-99m it was possible to obtain a change in tomato form with a characteristic of interest for breeders. We suppose that Тс-99m influences the mechanism that controls carotenoid biosynthesis in tomato fruits. Much of what has been learned about the carotenoid pathway in the last decade has come from the selection and analysis of mutants, primarily of Arabidopsis and tomato (Francis and Cunningham, 2002). High resolution mapping of QTLs in such forms is important for finding the differences in carotenoid content and may lead to the identification of gene(s) that influence carotenoid accumulation.

 

Table 1. Comparison of morphological and biochemical characteristics of tomato plants of N1276-13 and control plants

Genotype	Productivity per plant g	Fruit index	Fruit weight g	Dry matter content %	Total pigments mg%			Lycopene mg%
					mean	sd	CV%	mean	sd	CV%
2004
M2	3500ns	1,23az	65,3b	5,7ns	13,41a	2,77	20,63	11,27a	3,14	27,86
C1	3700ns	1,10b	76,0a	5,5ns	6,19b	0,25	3,96	4,84b	0,48	9,91
C2	3600ns	1,11b	78,7a	5,3ns	6,94b	0,22	3,22	5,10b	0,58	11,24
2005
M3	3300ns	1,24a	76,3ns	5,0ns	9,00a	0,87	9,62	5,59a	0,79	14,20
C1	3400ns	1,16b	75,0ns	5,0ns	4,57b	0,13	3,07	3,27b	0,31	9,67
C2	3250ns	1,11b	73,5ns	5,2ms	4,25b	0,08	1,97	2,91b	0,19	6,87

^z Means in column for each year not followed by same letter are significantly different byDuncan’s Multiple Range Test at P<0.05.; ns – not significant

 

Literature cited:

Emmanuel E., A. Levy, 2002. Tomato mutants as tools for functional genomics. Plant Biol., 5:112-117.

Francis X., Jr. Cunningham, 2002. Regulation of carotenoid synthesis and accumulation in plants. Pure Appl. Chem., vol. 74, No. 8, pp. 1409–1417, 2002.

Jain S. M., 1998. Induction of somaclonal variation and mutation in developing new improved cultivars. MIIT Pune J., pp. 23-31.

Manuelyan H., 1991. Express methods for assessing the carotenoid composition of tomato fruits. In: G. Kalloo, Genetic improvement of tomato, Springer-Verlag, 193-195.

Mukandama J. P., M. C. Gonzalez, L. Suares, Y, Alvarez, 2003. Increasing the high productive potential of tomato (Lycopersicon esculentum Мill.) by ⁶⁰Co gamma radiation in condition of agricultural drought. Alimentaria, 40: 95-98.

Nambisan P., V. L. Chopra, T. Mohapatra, 1990. DNA polymorphism in cab locus of tomato induced by tissue culture. Indian J. Experimental Biology, 30: 178-180.

Neel J. W., M. A. Onasch, 1989. Cytological effects of Tc on young soybean plants. Health Physics., 57(2): 289-298.

Rodeva V., 2003. Tomato mutant form obtained after irradiation with γ-rays ⁶⁰Co. National Conf.“Breeding and seed production in agriculture” – 18 June, Sofia, 77-81.