Morphological variability
The results obtained from the present investigation on growth parameters exhibited significant difference by the genotypes in both climatic zones of Meerut (India and Doha (Qatar) (Table 1). The mean performance of different genotypes for different phenotypic traits are tabulated in Table 1.
In Indian agro-climatic conditions, the maximum plant height was recorded in genotype EC620534 and the lowest in EC620380. Plant height of remaining genotypes was below one meter. The maximum number of fruits per cluster was observed in EC620534 and minimum in EC620380. Significant differences were observed among the entries with respect to days to 50% flowering. The value ranged from 30.36 to 34.31 days. It was lowest in EC620534 and highest in EC 620380. However, in Qatar agro-climatic conditions, the variation among phenotypic traits was observed. The maximum plant height was recorded in genotype EC620534 and the lowest in EC 620380. Plant height of remaining genotypes was below one meter. The maximum number of fruits per cluster was observed in EC-620534 and minimum in EC 620380. Significant differences were observed among the entries with respect to days to 50% flowering, the lowest in EC620380 and highest in EC 620534, respectively. A wide variation was found among the germplasm genotypes for the number of fruits per plant, which significantly varied from 9.5 to 15.67 among the genotypes.
Eshteshabul et al., (2010) also concluded that the mean number of fruits per plant range between 4.46 and 38.30 which is closely similar to our findings in this study. In Indian conditions, EC 620380 showed the lowest number of fruits per plant and EC620534 the highest number of fruits per plant, whereas, in Qatar conditions, EC620380 being the lowest and EC620378 highest. The average fruit weight ranged from 36.67g to 77.81g. The minimum fruit weight was recorded by the genotype EC620378 and maximum by EC620534 in both climatic conditions. Our findings accord with several other authors
(Sushma et al., 2021; Mounika et al., 2020; Kumar and Rana, 2018;
Turhan et al., 2011 and
Abrar et al., 2011). The minimum numbers of fruits per cluster were recorded by the genotype EC620380 and maximum by the genotype EC620534 in both agro-climatic conditions. Besides EC620534, the genotype EC 6205383 showed a good number of fruits per cluster. The minimum number of locules was registered with genotype EC 620380, while maximum with genotype EC620534, in both Indian and Qatar agro-climatic conditions. Similar results were shown by other researchers
(Kumar and Rana, 2018;
Nalla et al., 2016; Ahmed et al., 2007 and
Sankari, 2000). The line EC 620534 was shown to be better general combiner for number of branches per plant, number of fruits per truss and total number of fruits per plant
(Vilas et al., 2015). The wide variation in growth parameters of all the genotype might be due to their genetic makeup, which indirectly governs the morphology of the plant that has a direct impact on the formation of floral buds since all the genotype were grown under the same climatic condition.
The fruit yield per plant of tomato evaluated varied significantly among the genotypes, ranging from 0.47 to 1.21 Kg. In both growing conditions, the minimum fruit yield per plant was recorded with genotype EC 620380, while maximum with genotype EC620534. Other genotype exhibiting promising fruit yield was EC620383. Similar results were obtained by other workers
(Anuradha et al., 2021; Das et al., 2012; Mehta and Asati, 2008). Also, genotype EC620383 showed to be earliest to marketable maturity while the most delayed one being EC620534. Significant difference among genotypes for the total soluble solid content of fruit at the marketable stage was noticed. TSS of fruit ranged from 2.77 to 3.90 (oBrix). The highest TSS content of fruit was recorded with the genotype EC 620378 (India) and EC620534 (Qatar). These results are in conformity with the finding of
Swaroop and Suryanarayana (2005) and
Ahmed et al., (2007). The ascorbic acid content of fruit at marketable stage ranged from 16.60 to 27.58, the highest being EC620380 in both agroclimatic conditions. However, the content was found to be low in Qatar conditions which may be due to the humidity percentage. Similar type of results is reported by other researchers
(Sushma et al., 2021, Anuradha et al., 2021; Kumar and Rana, 2008;
Shashikanth et al., 2010; Manna and Paul, 2012).
Genetic variability
All the studied agro-metrical characters showed significant differences (P<0.05) among genotypes (Table 2), indicating that the tomato genotypes were genetically divergent. Thus, there is a huge scope for selection of promising lines with different agro-metrical traits from the present gene pool.
Wide range of variability among genotypes might be due to diverse sources of the materials, as well as environmental influence affecting the phenotypes. The coefficient of variation (%CV) compares the relative amount of variability between plant traits in a particular crop
(Sharma, 1988). The value of coefficient of variation (CV%) ranges from 0.61 to 20.61 in Indian zone, while, 0.26 to 6.64 in Qatar zone (Table 3). In Indian zone, the highest being recorded plant height followed by fruit shape index and number of locules per fruit. Similarly, in Qatar zone, highest being recorded by yield per plant followed by fruit shape index and number of locules per fruit. These results imply that the plant height, number of locules per plant and fruit shape index, in that order, had higher amounts of exploitable genetic variability among the studied tomato characteristic traits. It implies that there is greater potential for favorable advance in selecting these attributes compared to others. Further, the lowest CV% was recorded for fruit weight and days to marketable maturity for both zones, which exhibits low exploitable genetic variability and, thus, has less potential for favorable advance in selecting when compared to other traits.
The estimated values of Phenotypic variance (PV), Genotypic variance (GV), genotypic (GCV) and phenotypic (PCV) coefficient of variation, broad sense heritability (h2bs) and genetic advance mean (GAM%) of genotypes for yield and yield attributing traits of tomato are presented in Table 3. In general, the phenotypic coefficient of variation (PCV %) was higher than its genotypic counterpart (GCV %) for all the characters studied (Table 3). The higher PCV and GCV for all traits showed that there were environmental influences on the phenotypic expression of all the genotypes. Among all the traits, yield per plant showed highest, plant height and fruit weight showed the moderate and days to marketable maturity showed lowest PCV and GCV values respectively. So the selection on the phenotypic value can be effective for the improvement. Similar conclusions were drawn earlier by researchers
(Mohamed et al., 2012; Kaushik et al., 2011; Das and Sharma, 2011). The low difference between phenotypic and genotypic coefficient of variations indicated a slight environmental influence on the expression of this character. High PCV and GCV indicate the existence of a greater scope of selection for the trait being considered, which depends on the amount of variability present
(Khan et al., 2009). Thus, a greater potential is expected in selecting for the yield per plant, plant height and fruit weight among the studied tomato genotypes. Strikingly, in Qatar agro-climatic zone, a greater difference between PCV and GCV estimates for yield per plant and fruit shape index indicates a greater degree of environmental control for these traits. The environmental coefficient of variation (ECV %) is also high in both these traits in Qatar zone.
Heritability estimates
The heritability along with GA gives an insight into the array of genetic control for phenotypic expression and phenotypic reliability in predicting its breeding value and higher index indicates less environment influence in observed variation.
Burton (1952) suggested that the genetic coefficient of variation together with heritability estimates gave a better picture of the extent of heritable variation. Broad sense heritability (h2bs) and genetic advance mean (GAM%) estimates were interpreted as low, medium and high as per the classification of
Johnson et al., (1955). In Indian zone, broad sense heritability ranged from 99.97% for fruits per cluster and fruits per plant to 73.49% for days to 50% flowering, whereas in Qatar zone, the value ranged from 99.99% for fruit weight and plant height to 83% for fruit shape index. This indicates presence of considerable genetic variation and thus, these traits may be given special emphasis during tomato improvement programs. In this analysis, although high h2bs estimates were recorded for most of the traits in both agro-climatic zones, they were associated with low genetic advance (Table 3) indicating non-additive gene action and environmental influence, especially in days to marketable maturity, days to 50% flowering and fruit shape index (in Qatar zone).
The findings of present investigation reveal that high heritability accompanied by estimates of GAM% for most of the traits measured, that indicates the selection of genotype based on phenotypic levels would be useful for the improvement of these traits. High heritability with low GA and GA% of various yield-contributing traits has been reported by other researchers in tomato.
Mehta and Asati (2008) reported that the highest GCV and PCV with high heritability and genetic advance for plant height.
Meena and Bahadur (2014b) also obtained high heritability for plant height which also supports our findings. These findings were in agreement with
Dar and Sharma (2011) and
Golani et al. (2007).
Mohanty (2002) also found that days to 50% flowering has low heritability and low GA%, which is in support of the present results.
Meitei et al. (2014). reported high heritability and high GA% in fruit cluster per plant, number of fruit per plant, fruit weight which are similar to our experiment results.
Pujari et al. (1995) obtained high heritability, high GA% with low genetic gain for fruit yield per plant. Similar resutls were also found by other researchers as well
(Ghosh et al., 1995; Vinod et al., 2003). Therefore traits with high heritability with low GA can be improved by hybridization followed by progeny selection.
Principal component analysis
In the present findings, all the selected traits are considered for principal component analysis, by which two main components were found that explained 98% of total variance in both zones (Table 4). In the Indian zone, the first component (PC1) described 92.56% of the total variation and was positively and highly associated with days to marketable maturity, plant height and fruit weight, whereas, negatively associated with yield per plant, fruit shape index and fruits per cluster
and therefore, could be called as a vegetative component. The second component axis (PC2) explained 6.1% of the total variability and was positively associated with days to marketable maturity, whereas, for plant height, it was found to be highly negative. The results for the qatar zone followed a similar trend. The PC1 accounted for 96.75% of the total variation and was also positively and highly associated with days to marketable maturity, plant height and fruit weight, whereas, negatively associated with yield per plant, fruit shape index and fruits per cluster. The PC2 explained 1.68% of the total variation and was positively related to plant height and fruit weight, whereas, days to marketable maturity and yield per plant was negative. The genetic diversity studies about tomato quantitative traits based on the multivariate analysis using PCA involved days to marketable maturity, plant height, fruit weight as the most discriminating traits in both zones explaining greater variability in tomato (Fig 1).
Correlation and path coefficient analysis
Correlation studies and path coefficient analysis were carried out for phenotypic traits of genotypes in Qatar climatic zone (Table 5,6). Number of fruits per plant and fruit width had significant positive correlation with fruit yield per plant. Number of fruits per cluster and ascorbic acid had significantly positive association with number of primary branches per plant and days to 50% flowering. Number of fruits per plant had negative correlation with acidity. Fruit weight had negative correlation with TSS. Ascorbic acid had negative association with TSS. Similar type of results was tabulated by several other researchers
(Kumar et al., 2006; Dhankhar and Dhankar, 2006;
Singh et al., 2007; Singh, 2009;
Kumar and Dudi, 2011).
The path coefficient studies (Table 3) revealed that plant height (PH), number of fruits per plant (FPP) and ascorbic acid (AA) had high positive direct effects on fruit yield per plant (FYP). High negative direct effects on fruit yield per plant had been observed for days to 50% flowering (DoF), fruits per cluster (FPC) and fruit weight (FW). The results are in accordance with the conclusions of other workers
(Asati et al., 2008; Kumar and Thakur, 2007).
The above information revealed that highly significant positive correlation with highest positive direct effect was observed in days to 50% flowering, days to marketable maturity and fruits per plant which can be considered as selection criteria for improvement in tomato production in Qatar.
