Morphological and Biochemical Characterization of Tomato Accessions and Their Screening Against Major Viral Diseases Under Controlled Environment

Abstract

A set of fourty tomato accessions having diverse origin were tested at two locations viz., Swabi and Haripur Districts, Khyber Pakhtunkhawa, Pakistan, to assess morphological and biochemical attributes viz-a-viz resistance level for major viral diseases. The experiments were carried out in Randomized Complete Block Design (RCBD), with three replications. Data was recorded on morphological traits across two locations, during 2013-14. Biochemical analysis was carried out during 2013-14 in central laboratory, University of Haripur. Screening against Tomato Mosaic Virus (ToMV) and Tomato Yellow Leaf Curl Virus (TYLCV) were carried out at the Department of Agro-ecology Flakebjerg Research Institute of Aarhus University, Denmark. DAS-ELISA test and TAS-ELISA test (at different leaf stages) were performed in the laboratory for screening the samples against ToMV and TYLCV, respectively. However, disease symptoms were recorded in glass house under controlled environment on inoculated plants. Highly significant differences were oserved between locations except fruits weight plant-1, which manifested non-significant differences. Similarly, accessions (G) and G × E interaction for majority of the traits revealed highly significant differences except plant stem diameter, plant stem girth, fruit width, locules fruit-1, corolla color, fruit shoulder shape, plant growth type and predominant fruit shape. For all the biochemical attributes except fats, accessions revealed significant differences. Oveall accessions showed best performance in the environmental conditions of Haripur than Swabi for yield and yield attributing traits. The accessions in question exhibited extraordinary performance for biochemical traits as well. Regarding genotypic coefficient of variation (GCV), high estimates (21.79 to 86.38) were recorded for majority of the traits. Furthermore, phenotypic coefficients of variation (PCV) values were moderate to high (13.00 to 90.66) for all the traits except days to first flowering in both locations. Similarly, all biochemical traits revealed moderate to high GCV and PCV except moisture content, pH, oxidation reduction potential and percent protein. High broad sense heritability estimates were observed for majority of the morphological traits in Swabi (0.62 to 0.99) and Haripur (0.61 to 0.99). High heritability ranges were 0.69 to 0.98 for all biochemical traits except moderate heritability for protein (0.39%). In Swabi, high selection response was observed for fruits plant-1 (99.37) and plant height (50.38 cm). However, yield plot-1 revealed moderate selection response (10.09). Similarly, high genetic advance was observed for fruits plant-1 (79.53) and moderate for clusters plant-1 (9.67) and plant height (16.78 cm) in Haripur. Furthermore, moderate selection response was observed for potassium (11.8042 mg/100g) and oxidation reduction potential (15.12 mV). Yield components revealed highly significant positive correlation with yield hectare-1 and yield plot-1. Calcium revealed significant positive correlation with potassium, oxidation reduction potential and fiber content. Sodium exhibited highly significant positive correlation with potassium. Total sugars manifested highly significant correlation with reducing xi sugars and non-reducing sugar. Total soluble solids indicated highly significant positive correlation with pH, reducing sugars and total sugars. Highly significant positive association was observed for firmness with total sugars and total soluble solids. Vitamin-C showed highly significant positive correlation with moisture content. Principal component analysis was carried out based on 27 morphological traits. It was found that 5 out of 27 principal components with an Eigen value above than 1.0 considered for 74.10% of the total variation. Five principle components viz., PC-1 (37.12%), PC-2 (15.79%), PC-3 (8.17%), PC-4 (9.94%) and PC-5 (6.07%) were more contributing to total variation. In PC-1 accessions (Acc-10572, Acc-17867, Acc-17872, Acc-17889 and CLN-362) and accession STM-2 in PC-6 showed greater genetic variability. Principal component analysis for 18 biochemical attributes of tomato accessions revealed that Eigen value for 5 out of 18 principal components ranged between 1.00 to 59.99%. Five principal components viz., PC-1 (17.23%), PC-2 (31.20%), PC-3 (52.07%), PC-4 (42.16%) and PC-5 (59.99%) were found more participatory in the total variation. First and second principal components showed that the accessions were dispersed in all quarters, which revealed high extent of genetic variability. It was observed in the PC-1 accessions AVR-201, CLN-282 and in PC-2 Acc-17890 showed greater genetic variability. On the basis of morphological and biochemical traits all the accessions were divided into four and five cluters, respectively. These clusters were further divided into subclusters. DAS-ELISA test against Tomatoes Mosaic Virus (ToMV) revealed significant differences in overall mean values. Among all the accessions, the accession Acc-17878 was found resistant to Tomato Mosaic Virus. However, on the basis of TAS-ELISA test and disease symptoms severity scale for TYLCV, accessions Acc-17890, AVR-261, CLN-312, AVR-321, EUR-333, CLN-352 and CLN-362 revealed negative sign with no symptoms. Based on morphological and biochemical characterization, heritability, selection response and G × E interaction, the attributes viz., earliness, fruits plant-1, yield plot-1, clusters plant-1, fruits cluster-1, potassium, lycopene, oxidation reduction potential, firmness and fiber content the accessios CLN-312, Acc-17889, AVR-241, Acc-17878, CLN-352, AVR-211, CLN-282, EUR-303, Acc-10587 showed best performance. High estimates of heritability and selection response suggest that genetic variance could play an important role in the inheritance and selection for improvement of these attributes. Therefore, these tomato genotypes could further be explored in future breeding program for varietal development. For disease resistance viz., tomato mosaic virus, the accession Acc-17878 and for yellow leaf curl virus, the genotypes Acc-17890, AVR-261, CLN-312, AVR-321, EUR-333, CLN-352 and CLN-362 confirmed resistance. It is therefore, recommended that in future tomato breeding programes the disease resistance characters may be incorporated into high yielding and quality attributed accessions through back crossing.