Mean performance and analysis of variance of germplasm
The result on analysis of variance (ANOVA) for yield component traits revealed significant mean sum of square for studied genotypes for all traits, indicating the existence of sufficient variation among the genotypes and therefore ample scope for effective selection (Table 1).
Mean performance of morphological and essential oil related traits of all the studied germplasm was presented in Table 2. On the basis of morphological, biochemical and oil yield%, PF7 germplasm is superior for most of studied characters followed by PF4 and PF2.
Genetic variability
Genotypic variance (GV), phenotypic variance (PV), genetic coefficient of variation (GCV), phenotypic coefficient of variation (PCV), environment variance (EV), environment coefficient of variation (ECV), heritability (HT) and genetic advance (GV) for the oil yield and yield component traits were furnished in Table 3. These findings revealed maximum range of variability for the plant height (151-191) while minimum range (0.15-0.38) was recorded for the total phenolic content. In the present study, heritability estimates for the studied traits range from (0.649) in stem girth to (1.00) in total phenolic content and total flavonoid content. High estimates of heritability were recorded for all traits excepts stem girth (0.649) which indicate that these characters were less influenced by environment conditions and phenotypic selection would be effective. Similar results were reported by
Zhimomi et al. (2019). Higher estimates of heritability coupled with high to moderate estimates of genetic advance as percentage of mean were observed for different traits in
Perilla by
Hussain et al. (2014)
.
Generally the value of PV and PCV was generally higher than that of GV and GCV for all studies traits indicating the role of environmental variance in controlling the characters along with genetic variability. Similar studies was conducted by Zhimomi and his co-workers in 2019 in landraces collected from Nagaland, India indicating the expression of characters were influenced by the environment factors. The phenotypic variance was partitioned into heritable (genotypic variance and non-heritable- environment variance) components (Table 3). The estimate of genotypic and phenotypic variances in case of plant height were 129.18 and 129.87, respectively and the GCV and PCV were 6.86 and 6.88, respectively (Table 4). The differences between the variances and coefficient of variation quite close indicated that there was a negligible environment influence on plant height of the genotypes. Phenotypic variance and phenotypic coefficient variance was higher than genotypic variance and genotypic coefficient variance in case of length of petiole, stem girth indicating environmental influence (Table 3). In case of leaf length and length of inflorescence, the genotypic and phenotypic variance were 2.46 and 2.95, respectively and the genotypic and phenotypic coefficient of variations were 11.47 and 12.56, respectively. This indicated that a considerable degree of genetic variability prevailed in this character and there was a negligible influence of environment. Estimates of genotypic, phenotypic variance, genotypic coefficient variance and phenotypic coefficient variance indicated that there was moderate environmental influence on leaf breath. For the study of variability in case of total phenolic content and total flavonoid content, the values of genotypic and phenotypic variance (0.006 and 0.006) and genotypic coefficient variance and phenotypic coefficient variance (0.004 and 0.004). These findings indicated that there was no environmental influence on both traits. The genotypic and phenotypic variance of oil yield (%) trait was 12.75 and 12.79, respectively and the genotypic coefficient variance was14.83 and phenotypic coefficient variance was14.85, respectively. These variability values were quite close indicating negligible influence of environment for this trait. Similar results were reported by
Hussain et al. (2013) and
Manggoel et al. (2012).
Heritability, genetic advance and genetic advance as % of mean
High value of Heritability in broad sense are helpful in identify the appropriate characters for selection and enabling the breeder to select superior genotypes on the basis of phenotypic expression of quantitative traits. Heritability is considered low if it is less than 30%, moderate between (30-60%) and high if it is more than 60%
(Johnson et al., 1955).The maximum heritability (broad sense) was observed for oil yield % followed by value of total phenolic content, total flavonoid content, plant height, length of petiole, leaf length, leaf breath, stem girth and length of inflorescence (Table 3). Thus selection for these traits is likely to accumulate more additive genes leading to further improvement of their performance and might also use as selection criteria in
Perilla breeding program. Similar results were reported by
Hussain et al., (2013). Whereas,
Johnson et al., (1955) have showed that a character exhibiting high heritability may not necessarily give high genetic advance. Accordingly, the highest value of genetic advance as per cent of mean was shown for total phenolic content (85.78) and total flavonoid content (62.83), while plant height had lowest value for this estimate. The characters exhibiting moderate estimates of genetic advance in percent of mean (>25% to <50%) were length of inflorescence (43.24) and oil yield % (30.52). However, the low estimates of genetic advance in percentage of mean (<25%) was observed for plant height (14.11), length of petiole (22.54), leaf length (21.54), leaf breath (19.60), stem girth (14.70). On the basis of both variability parameters, high heritability coupled with high genetic advance as percentage of mean was exhibited for total phenolic content, total flavonoid content, oil yield % and length of inflorescence. Thus, this study revealed that these traits can be improve through direct selection. High heritability coupled with moderate genetic advance as per cent of mean were recorded for plant height, length of petiole, leaf width, stem girth. This finding indicated the role of additive gene action and hence selection to be effective for improvement program.
Correlation coefficient
The correlation coefficient of the nine characters of
Perilla were presented in Table 5. In general, phenotypic correlation showed lower values than the corresponding estimate of the genotypic values. Morphological traits such as plant height showed positive significant association with length of petiole, leaf length, leaf width, stem girth and oil yield at phenotypic level. But it showed non-significant association with length of inflorescence, total phenolic content and total flavonoid content. Length of petiole had significant positive association with leaf length, leaf width, total flavonoid content and oil yield. In contrast, it showed negative significant association with stem girth, length of inflorescence and total phenolic content. Leaf length had significant positive association with leaf width, stem girth and oil yield % at phenotypic level. But it showed non-significant association with length of inflorescence, total phenolic content and total flavonoid content. Leaf width showed significant positive association with stem width and oil yield % at phenotypic level and non-significant correlation with length of inflorescence, total phenolic content, total flavonoid content. Stem girth showed significant positive correlation with length of inflorescence and oil yield%. Length of inflorescence had significant positive association with total phenolic content, total flavonoid content and oil yield % at phenotypic level. Total phenolic content showed significant positive correlation with total flavonoid content and showed non-significant correlation with oil yield%. Total flavonoid content showed non- significant correlation with oil yield % at phenotypic level. (
Ansari-mahyari et al., 2019) studied that seed yield per plant was positively correlated with all studied traits except days to 50% flowering, leaf width, petiole length and seed oil content in
Perilla. Contrarily, seed oil content had negative association with inflorescence length, number of inflorescence per plant and 100 seed weight
. Nam et al. (2004) observed positive correlations of seed weight with plant height, flower clusters and inflorescence length
.
Path coefficient analysis
Path analysis uses standardized partial regression coefficients to assess the direct and indirect impacts of independent variables on a dependent variable. By separating correlation coefficients into direct and indirect effects, we can better understand the relationship between observable characteristics (
Ansari-mahyari et al., 2019). In present investigation, path analysis was done as the procedure given by
Dewey et al., (1959) to know the direct and indirect effect of various characters on oil yield of
Perilla. In present study, the characters which has highest positive direct effect on seed yield were due to length of petiole (0.741), leaf width (1.32), stem girth (0.98), length of inflorescence (0.35),total phenolic content (1.69). Similar result were reported by
Hussain et al., (2013) and
Zhimomi et al. (2019).Thus, direct selection for these traits will be beneficial in yield improvement program. While, the characters like plant height, leaf length, total flavonoid content exhibited negative direct effect on seed yield per plant. Similar result were reported by
Rasheed et al., (2008).