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Genetic variability; Eruca sativa mill; Taramira; Genotypic coefficient of variation; Heritability; Phenotypic coefficient of variation and genetic advance as per cent of mean

Introduction

Taramira (Eruca sativa Mill) is an important rainfed winter season oil seed crop in the Brassicaceae family. Taramira is believed to have originated in South Europe and North Africa before being introduced to India [1]. It contains a diploid number of chromosomes (2n=22) and chromosomes are very small. Taramira possesses excellent characteristics, especially resistance to powdery mildew, which can be transmitted to Brassica campestris and Brassica juncea, both of which are important crops [2]. In India, it is known by many names such as tara, trara, schwan, duan, turra, tirwa, merha, merkai, chara, ushan and sondha Singh [3]. The oil content of taramira varies between 31.60 to 41.31 per cent [4]. Taramira oil is mostly used to increase the pungency of mustard oil. Taramira cake may be used as manure to improve soil physical condition and fertility, as well as nutritional feed for animals. The success of any breeding programme relies on genetic variability for economically important traits in the population and its management for exploitation. Germplasm with genetic variation are able to adapt themselves in changeable environment and insured the plants to meet the harsh environment conditions. Study of variability, heritability and genetic advance in the germplasm will help to ascertain the real potential value of the genotype. Hence an experiment was planned to assess the variability, heritability and genetic advance for yield and other characters in a set of taramira germplasm.

Materials and Methods

Genetic material

The material for the present investigation were consist of a set of 30 germplasm lines including five checks which were released varieties i.e. RTM-314, RTM-1351, RTM-1355, RTM-1624, RTM-2002 obtained from the collection being maintained at the AICRP Rapeseed-Mustard (Taramira Unit), Department of Plant Breeding and Genetics, S.K.N.

College of Agriculture, Jobner (Table 1). This investigation was conducted during rabi, 2022-23 at Research Farm, S.K.N. College of Agriculture, Jobner (Rajasthan). Jobner is located at 26.97°N and 75.38°E. It has an average elevation of 400 metres above mean sea level (1312 feet).

Table 1:List of germplasm lines.

These 30 germplam was sown in four different environments created by manipulating sowing date and Orobanche infestation. Envionment-1 (timely sown Orobanche free field), Envionment-2 (timely sown Orobanche infested field), Envionment-3 (late sown Orobanche free field), Envionment-4 (late sown Orobanche infested field) in randomized block design with three replications in each environment during rabi, 2022-23. The date of timely sown environment was 17th October, 2022 and date of late sown was 5th November, 2022. The inter row spacing’s followed would be 80 cm and plant to plant distance were maintained at 15 cm by thinning after 15 days of sowing.

Five plants were randomly selected and tagged before flowering from each plot and data were taken on plant height (cm), primary branches per plant, height of first branch emergence (cm), siliqua on main shoot, siliqua density, siliqua length (cm), seeds per siliqua, chlorophyll content 35 DAS (SPAD), chlorophyll content 70 DAS (SPAD) and 1000-seed weight (g) while data relating to days to 50 per cent flowering and days to maturity was recorded on whole plot basis.

Statistical analysis

The data were subjected to analysis of variance as per the procedure suggested by Panse VG and Sukhatme PV [5]. The genotypic coefficient of variation (GCV) and phenotypic coefficient Variation (PCV) computed by the formula suggested by Burton GW [6]. The PCV and GCV values were ranked as low (0-10%), medium (10-20%) and high (>20%). Heritability (h²) in the broad sense was calculated according to the formula given by Johnson HW et al. [7]. Heritability values are categorized on the basis of range of percentage as low (<30%), moderate (30-60%) and high (>60%). Genetic advance for each character was predicted by the formula given by Johnson HW, et al. [7]. Genetic advance as percent of mean was classified as low (0-10%), moderate (10-20%) and high (>20%).

Results and Discussion

The pooled analysis of variance was estimated from pooled data of three replications of four environments for all germplasm. Pooled analysis of variance showed highly significant difference among the germplasm for each character. The environmental effects were, also highly significant for all characters. The majority of the parameters with the exception of days to maturity, primary branches per plant and siliqua length (cm) were, significantly influenced by G x E interactions. It indicated differential effects of environments on the germplasm for all the traits. These results showed presence of substantial amount of G × E interaction (Table 2). Therefore, analysis of variance was carried out environment wise which revealed significant variance due to germplasm for all the characters indicating the presence of ample amount of variability in the germplasm (Table 3). These results are similar with earlier findings of [8-10].

Table 2: Pooled analysis of variance for yield and yield determining traits in taramira germplasm.

Table 3: Environment wise analysis of variance for 30 germplasm of taramira tested under four environments.

Comparative study of different environments depicted that mean values in E2 and E4 were lower in relation to E1 and E3 for all the traits except height of first branch emergence (cm) indicated that late sowing, Orobanche infested had adverse effect on the performance of taramira germplasm for most of the traits. Further it was also observed that E1 had higher mean in comparison to E3 for most of the traits except height of first branch emergence and siliqua on main shoot whereas, E2 in comparison to E4 had similar trend for all traits except height of first branch emergence (Table 4). Based on the above result, it can be concluded that taramira germplasm should be tested under a timely sown, Orobanche free environment for a clear distinction between superior and inferior germplasm because this environment was found to be better for the expression of most of the component traits. Comparison of range over environments for all the traits indicated that E1 was most favourable for the expression of traits viz. days to maturity, height of first branch emergence (cm), siliqua length (cm), 1000-seed weight (g) and Seed yield per plant (g) which revealed that these traits had higher range in this environment. Similarly, E3 was favourable for expression of siliqua on main shoot, siliqua density, seeds per siliqua and chlorophyll content 35 DAS (SPAD meter) and E4 had wider range for the traits days to 50 per cent flowering, plant height (cm) and primary branches per plant. E2 wider range for only trait Chlorophyll content 70 DAS (SPAD meter) (Table 4). Conclusively it can be advocated that to obtain clear-cut discrimination in screening of taramira germplasm for different traits should be carried out under timely sown, Orobanche free (E1) conditions.

Table 4: Range and mean for yield and related traits in taramira germplasm in different environments.

In all four environments, the phenotypic coefficient variation was higher than the genotypic coefficient of variation for all characters. High PCV and GCV were observed for height of first branch emergence in E1 and E3 (Table 5). Similar findings pertaining to presence of high genetic variability were reported by Kumar S et al. [11] for first branch initiation height. Moderate GCV and PCV were recorded for plant height (cm) in E2 and E4, also for traits siliqua on main shoot, seeds per siliqua, 1000- seed weight (g) and seed yield per plant (g) in all four environment. Similar findings have also been reported by Kumar S et al. [11] for plant height (cm), [12] for siliqua on main shoot, [13] seeds per siliqua, [14] for 1000-seed weight and [15] for seed yield per plant (g). The results demonstrated a significant level of genetic variability in the examined germplasm for the primary yield contributing characteristics, as well as seed yield, suggesting that further improvement for these traits is possible. Likewise, lower GCV and PCV were recorded for days to 50 per cent flowering, days to maturity, siliqua length (cm), chlorophyll content 35 DAS (SPAD meter) and chlorophyll content 70 DAS (SPAD meter) (Table 5). These similar findings were reported by Choudhary RR et al. [16] for days to 50 per cent flowering, days to maturity, [17] for days to 50 per cent flowering and days to maturity, [18] for siliqua length and [19] for chlotrophyll content.

Table 5: Genotypic coefficient of variation and phenotypic coefficient variation for yield and related traits in     taramira germplasm in different environments.

Johnson HW et al. [7] suggested the heritability estimates combined with genetic advance would be more effective in estimating yield under phenotypic selection than heritability estimates alone. In the present investigation, estimate of high heritability along with high genetic advance as per cent of mean were reported for characteristics such as height of first branch emergence (cm), seeds per siliqua, 1000- seed weight (g) and seed yield per plant (g) in all the environments (Table 6). As a result, they might be under the control of additive gene action. Therefore, selection for these characters will be highly responsive. Similar findings have been recorded by Padra N and Lal GM [19] for test weight (g) and seed yield (g), [18] for seeds/siliqua, seed yield per plant (g) in, [20] for seeds per siliqua, test weight (g) and seed yield (g). The trait siliqua on main shoot and siliqua density showed high heritability along with moderate genetic advance (except in E1 for siliqua density) in all the four environments. This result was also reported by Choudhary RR et al. [16] for siliqua on main shoot.

Table 6: Heritability (%) and Genetic advance as per cent of mean for yield and related traits in taramira germplasm in different environments.

Conclusion

The current study indicated that there was sufficient genetic variability present in the experimental material for most of the traits in all the environments. Therefore, this variability could be used to establish segregating generations by using these germplasm for both timely and late planting situations. After comparing the mean and range (over the germplasm and replications) for yield and different yield attributing traits in all four environments, it was found that both were highest in E1 for most of the traits. A review of heritability and genetic advance as per cent of mean for all four environments revealed that characteristics such as height of first branch emergence, seeds per siliqua, 1000-seed weight and seed yield per plant had high value. This suggested that these traits governed by additive gene action and direct selection based on these traits could be beneficial.

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