Evaluation of Tomato (Lycopericon Esculentum Mill.) Germplasm (26-Cultivars) Using Morpho-Molecular And Biochemical Techniques

Abstract

Twenty-six genotypes of tomato were characterized on the basis of morphological, biochemical and molecular characters for their drought tolerance level and yield potential. Drought is one of the most important limiting factors for agricultural crops and vegetable production. To assess the effect of drought stress on the growth and yield of tomato a pot experiment was conducted in green house conditions at Garri Dopatta, Azad Kashmir, Pakistan. Twenty-six genotypes of tomato were evaluated for morphological characters. They were subjected to drought stress during vegetative growth by using Poly ethylene glycol (PEG-6000) at different concentrations ranging from, 0 percent (control), 5 percent, 7.5 percent, 10 percent and 12.5 percents. The Morphological parameters compared were number of branches, number of leaves, Plant height, internodal distance, number of flowers, number of trusses, number of fruits, root length, root diameter. Polyethylene glycol showed significant effect on the production of number of branches. The maximum number of branches were recorded at control leading to minimum were at highest level of the drought. Maximum number of branches (10.667) at control and 2 at 12.5 percent PEG were found in genotype G19289. Plant height data also indicated that drought stress adversely affect the plant height. The maximum plant height 184 cm was recorded in genotype 19289 at control and 70 cm at 12.5 percent PEG. Similar trends in number of leaves and number of flowers were recorded. The number of fruits were also recorded and showed the similar pattern. The internodal distance decreased with the decreasing plant height. The number of trusses, the root length and root diameter also indicated the similar trend. However root length was better in genotype 19219 and its diameter was xi higher in genotype 88572. Genotype 19289 proved to be the best performing under drought stress compared with other genotypes. Different biochemical tests were also applied to assess the drought tolerance level of the tomato genotypes which includes antioxidant activities, proline contents, total phenolics and flavonoids. The reducing and non-reducing sugar contents were also determined in different tomato genotypes. Biotic and abiotic stresses make changes in natural physiological performance and capabilities of the plants and cause serious damages. Drought is an important stress which inhibits full use of genetic potentials in agricultural crops and reduces the yield. Antioxidants are important constituents of the plants that protect the organisms from injuries during oxidative stress. The DPPH free radical is commonly used to evaluate the antioxidant activity of antioxidants produced during oxidative stress. A pot experiment in green house conditions was conducted to evaluate the effect of PEG induced drought on the antioxidant activity of different genotypes of tomato. The maximum antioxidant activity 53.046 percent is shown by the G-21-006234 at 25 μl sample and with the increase in the sample concentration to 500 μl the antioxidant activity is also increased up to 71.54 percent. By increasing the PEG concentration the antioxidant activity shows decline. The genotype G-21-00643 showed 21.189 percent at maximum level of drought induced by the PEG. The genotype G- 31- 19289 was found to be the best for producing the antioxidant activity. This genotype showed 52.424 at 25 μl sample with control PEG concentration and 39.210 percent at 12.5 percent PEG concentration. The 39.210 percent is the highest among the other genotypes at same xii concentration of the PEG 12.5 percent. The genotype G- 31- 19289 was found to be the best among the studied genotype showing highest antioxidant activity. The leaf extract was used to quantify the proline contents. The proline contents in all the genotypes of tomato are increased by increasing the drought stress induced by application of PEG. The maximum proline contents was observed by G 45 19212 which is 54.5 mg/g and minimum was observed in the 32.9 mg/g at 12 percent PEG. The maximum proline contents 20. 7 mg/g at control was observed in G 31 00623 and minimum 16. 5 mg/g was observed in the G 8 19219. The proline contents showed regular increasing behavior with increasing the concentration of PEG. All the genotypes showed an increase but the increase with in genotypes was different when compared to control. In the present study the phenolic contents decreased as by increasing the concentration of PEG. The maximum phenolic contents 60 μg / g were observed in the genotype G 19896 and minimum 5 μg / g were recorded in the G 19219 at control (without PEG). All the genotypes with the exception of G10593 and G 19289 show continuous decline in phenolic contents as by increasing the PEG concentration. The maximum phenolic contents were produced by G 08527 at highest level of PEG 12.5 percent and minimum were recorded in G19219. The results indicated that flavonoid contents decreased by increasing the concentration of polyethylene glycol. The maximum flavonoid contents 12μg /g were observed in the genotype G 19896 and minimum 4 μg /g by G 10593 at control (without PEG). By increasing the PEG concentration the flavonoid contents were decreased. All the genotypes show the same behavior of decreasing the flavonoid contents as xiii increasing the PEG concentration. G 19289 showed a constant flavonoid contents as by increasing the PEG concentration. The reducing sugars showed the non significant behavior in different tomato genotypes. The non-reducing sugars showed different results in different genotypes. Twenty-six genotypes of Tomato (Lycopersicon esculentum Mill.) fingerprinted with 30 SSR markers by using PCR. Nei’s genetic distances for SSR markers, data was calculated and relation matrix between genotypes shown graphically in the form of a dendrogram. All 26 tomato genotypes showed genetic distances of 1.0-2.20 between them. A smallest genetic distance was recorded 0.2 between genotypes G 17909, G 17904 and G 21 006234, G12 0852, G7 88572 G32 19233, G28 17903, G12 17806 indicating closer relationship between the genotypes. The most distant accessions were G7 1059 and G45 19212. The marker (SSR) based fingerprints will assist for their future potential in crop improvement.