Studies on Genetic Diversity and Interdependence of Growth and Quality Traits in Cherry Tomato [Solanum lycopersicum (L.) var cerasiforme Mill.]

Cherry tomato [Solanum lycopersicum (L.) var. cerasiforme Mill.] having chromosome number 2n=2x=24 belongs to Solanaceae family and considered to be the ancestor of cultivated tomato. It is one of the most important warm-season fruit vegetable cultivated all over the world. It is an important crude material for different processed products such as juice, ketchup, sauce, pickles, chutneys, canned fruits, puree, paste etc. The wild cherry tomato was first found throughout tropical and subtropical America and then propagated in the tropics of Asia and Africa (Gharezi et al., 2012). The wild relatives of tomato have significant genetic diversity for important quality attributes such as color, texture, aroma and flavour (Miller and Tanksley, 1990). Thus, the presence of wide and valuable genetic diversity provides a great potential in breeding programs for selection of parental materials. Cherry tomato has various pharmaceutical properties and is advantageous for body in general. It has the potential of becoming a valuable cash crop. Its value has increased in the retail chains and is being sold at higher prices in comparison to regular tomatoes. The fundamental requirement for the incorporation of desirable characters is the knowledge of genetic variability already existing in the population with respect to those characters. Therefore, the study was aimed to evaluate different genetic parameters such as coefficients of variability, heritability, genetic gain and genetic diversity in cherry tomato for growth, yield and quality.

The field experiment was conducted under the mid hill conditions in the research farm of Regional Horticultural Research and Training Station, Bajaura, Kullu, HP, located at 1090 m above mean sea level, between 32.2^oN latitude 77^oE longitude during 2021-22. Twenty four cherry tomato genotypes namely EC2791, EC2795, EC2796, EC2798, EC7911, EC7912, EC10662, EC10664, EC521074, EC16778, EC521079, EC27251, EC139040, EC139041, EC139042, EC164650, EC164658, EC164660, EC177370,  EC521044, EC521045 , EC521076, EC531802 and EC531803 and the check variety were planted in a randomized block design with three replications. Transplanting was done at a spacing of 90 cm × 30 cm and fourteen characters of selected plants for each genotype and replication were analyzed for variance as per Panse and Sukhatme (1957). The phenotypic and genotypic coefficients of variability and heritability in the broad sense was calculated and expressed in per cent by the method given by Burton and De-Vane (1953) and Allard (1960). The method proposed by Johnson et al. (1955) was used to estimate genetic gain. The phenotypic and genotypic coefficients of correlation were calculated based on the method advocated by Al-Jibouri et al. (1958). Dewey and Lu (1959) method was used to work out the direct and indirect effects. The genetic divergence was estimated by using Mahalanobis D² statistics (1936).

The efficiency of selection depends on the nature and extent of genetic variability and degree of transmissibility of desirable characters. The genetic variability (Table 1) in general indicated that phenotypic coefficient of variation (PCV) was higher than genotypic coefficient of variation (GCV) for all the traits; however, the difference was very narrow for most of the traits suggesting the less influence of environment on expression of these traits. The phenotypic and genotypic coefficients of variation were high (>30%) for number of fruits per cluster and fruit yield per plant which suggested a higher phenotypic as well as genotypic variation among the genotypes and their acceptance for these traits for further improvement with selection. However, for number of branches per plant, days to 50% per cent flowering, number of cluster per plant, number of seeds per fruit, total soluble solids (TSS) and titratable acidity the difference between PCV and GCV was high, indicating the role of environment in controlling the expression of these characters.  These results were in consonance with Prema et al. (2011), Doddamani et al. (2017) and Renuka et al. (2017).


       
The heritability in broad sense (Table 1) was recorded from 43.49% to 97.59 % for different parameters under the study. High broad sense heritability (>80%) was observed for characters viz., number of fruits per plant, average fruit weight, fruit yield per plant, pericarp thickness, plant height and number of fruits per cluster. These high estimates of heritability indicated that these characters were least influenced by the environment. Moderate heritability (50%  -80%) was observed for characters viz., number of branches, number of clusters, fruit shape index, days to 50% flowering, TSS, number of seeds per fruit and days to first harvest. Low heritability was recorded for titratable acidity. Similar results were found in the studies conducted by Prema et al. (2011), Renuka et al. (2017) and Thakur (2020).
       
The genetic advance as per cent of mean (GAM) i.e., genetic gain (Table 1) ranged from 3.88% (days to first harvest) to 63.84% (fruits yield per plant). Higher estimates of genetic gain (more than 50 per cent) were observed for fruit yield per plant and number of fruits per cluster which explained the possibility to make a large extent of improvement. Moderate genetic gain was observed for number of fruits per plant, average fruit weight, number of seeds per fruit and number of clusters per plant. Whereas low genetic gain was reported for days to first harvest, fruit shape index, plant height, TSS, days to 50% flowering, titratable acidity, pericarp thickness and number of branches. These results were found to be in accordance with the results of Aralikatti et al. (2018), Shiksha and Sharma (2018) and Thakur (2020).
       
The results for high heritability with high genetic gain for number of fruits per cluster were in accordance with the findings of Patil (2017) and Thakur (2020) and for fruit yield per plant, Shiksha and Sharma (2018) and Mukherjee et al. (2020) found the same results. High heritability along with moderate genetic gain for number of fruits per plant and days to 50% flowering was also reported by Harogeri (2016).
       
Correlation coefficient analysis (Table 2) revealed that fruit yield per plant was positively and significantly correlated with total number of fruits per plant (0.61, 0.61), number of fruit clusters (0.72, 0.62), average fruit weight (0.62, 0.62), pericarp thickness (0.62, 0.62) and titratable acidity (0.63, 0.44) at both phenotypic and genotypic levels. Whereas negative and significant correlation of fruit yield per plant was found with days to 50% flowering (-0.51, -0.40), days to first harvest (-0.55, -0.41), fruit shape index (-0.52, -0.42) and TSS (-0.57, -0.44) at both phenotypic and genotypic levels. The results are in accordance with the findings of Harogeri (2016) and Thakur (2020).


       
The path coefficient analysis (Table 3) revealed that total number of fruits per plant (1.680) had the greatest positive direct contribution towards fruit yield per plant followed by pericarp thickness (0.649), days to 50% flowering (0.208), plant height (0.073), TSS (0.069), number of branches (0.059), titratable acidity (0.039), average fruit weight (0.037), fruit shape index (0.032) and number of seeds (0.029). Whereas negative direct contribution from number of fruits per cluster (-0.972), number of clusters (-0.623) and days to first harvest (-0.106) was observed towards fruit yield. The results were in consonance with the results of Doddamani et al. (2019), Thakur (2020) and Vijaylaxmi et al. (2021).


               
Mahalanobis D² statistics grouped 25 genotypes into four clusters (Table 4) and the (Fig 1) gives a clear picture of the cluster pattern of the cherry tomato genotypes. The maximum intra cluster (Table 5) was observed in cluster I (77.84) followed by cluster III (77.59), cluster II (22.73) and cluster IV (0). The maximum inter cluster (Table 5) was observed between cluster III and IV (621.61), followed by cluster II  and IV (541.63), I and IV (430.96), II and III (369.44), I and III (168.18) and I and II (138.27). The genotypes having broad genetic base and desirable characters are always favored in hybridization program. Therefore based on the results of inter cluster distance the genotypes from cluster III and IV can result in efficient hybridization for the improvement of various horticultural attributes.

On the ground of the mean performance of the genotypes, EC27251, EC164658, EC177370 and EC531802 along with check variety Solan Red Round performed better than other genotypes for yield and other imperative horticultural characters. The phenotypic and genotypic coefficients of variation, heritability and genetic gain were high for number of fruits per cluster and fruit yield per plant. High heritability along with moderate genetic gain was observed for total number of fruits per plant and average fruit weight which suggests the possibility of improvement through simple selection. Fruit yield per plant had significant and positive correlation with total number of fruits per plant, number of fruit clusters, average weight, pericarp thickness and titratable acidity. Positive direct effect on fruit yield per plant was highest from total number of fruits per plant followed by pericarp thickness, days to 50% flowering, plant height, TSS, number of branches, titratable acidity, average fruit weight, fruit shape index and number of seeds. Based on analysis of genetic divergence through Mahalanobis D2 statistics, the genotypes from cluster III and IV can result in efficient hybridization for the improvement of different horticultural attributes.

The authors are profoundly thankful to the Department of Vegetable Science, University of Horticulture  and Forestry-Nauni, Solan-Himachal Pradesh (India) for providing technical and financial assistance during the research programme.
 
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The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.
 
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All animal procedures for experiments were approved by the Committee of Experimental Animal care and handling techniques were approved by the University of Animal Care Committee.