Significant Statement

The success of any crop improvement programme largely depends upon the nature and magnitude of the genetic variability existing in breeding material. So the experiment was conducted to study the genetic variability, heritability and genetic advance in F2 segregating population of the cross Surya × Harita.

Introduction

Brinjal also known as eggplant or aubergine is a common vegetable crop grown in tropical and subtropical climates. It is not possible to have one common cultivar to suit different localities. It is therefore required to improve the yield potential of available land races through hybridization, which may yield good hybrids or inbreds. The success of any crop improvement programme largely depends upon the nature and magnitude of the genetic variability existing in breeding material. Effectiveness of selection directly depends on the amount of heritability and genetic advance as per cent of mean for that character. Hence, an insight into the magnitude of variability present in available accessions and hybrids of brinjal is of utmost importance to a plant breeder for starting a judicious breeding program. Therefore, in the current study, an attempt has been made to access the variability in the segregating population of the brinjal hybrid, Surya × Harita.

Material and methods

The present investigation was carried out at the Vegetable Science Block in College of Horticulture, Mudigere, University of Agricultural and Horticultural Sciences, Shivamogga during the rabi season 2018–2019. The experiment consisted of 300 F2 plants derived from the cross Surya × Harita along with their parents, F1 hybrids and four checks viz., Arka Harshitha, Arka Keshav, Arka Kusumakar and Devanur Local which were evaluated for yield and yield components. The experiment was laid out in an Augmented Block Design and 30-days-old seedlings were transplanted in 60 × 45 cm spacing, and all the recommended agronomic package of practices were followed. Data were recorded on all the 300 F2 plants, ten randomly selected plants in each of the checks, parents and F1 hybrids for 16 characters viz., plant height (cm), number of primary branches, plant spread from North to South (cm), plant spread from East to West (cm), days to first flowering, number of flowers per cluster, number of fruits per cluster, fruit set percentage, days to first picking, fruit length (cm), fruit diameter (mm), average fruit weight (g), number of fruits per plant, fruit yield per plant (kg) and TSS (0brix). The genetic parameters of variability like grand mean, range, phenotypic and genotypic coefficient of variation [1], broad-sense heritability, genetic advance and genetic advance as percentage over mean [2] were calculated.

Estimation of Genetic Parameters

Genotypic, Phenotypic and Environmental Variances

Variance due to genotype, phenotype and environment were computed as follows.

$$\begin{aligned} & {\text{Genotypic}}\;{\text{variance}}\left( {\sigma^{2} g} \right) = \frac{{{\text{Treatment}}\;{\text{MSS}} - {\text{Error}}\;{\text{MSS}}}}{r} \\ & {\text{Environmental}}\;{\text{variance}}\left( {\sigma^{2} e} \right) = {\text{Error}}\;{\text{mean}}\;{\text{sum}}\;{\text{of}}\;{\text{squares}}, \\ & {\text{Phenotypic}}\;{\text{variance}}\left( {\sigma^{2} p} \right) = \sigma^{2} g + \sigma^{2} e \\ \end{aligned}$$

where, r is the number of replications.

Phenotypic and Genotypic Coefficient of Variation

Phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) for all the characters were calculated according to the formula provided by [1] based on the estimate of genotypic and phenotypic variance as follows:

  1. (a)
    $${\text{Phenotypic}}\;{\text{coefficient}}\;{\text{of}}\;{\text{variation}}\left( {{\text{PCV}}\% } \right) = \frac{{\sigma^{2} p}}{{\overline{X}}} \times 100$$
  2. (b)
    $${\text{Genotypic}}\;{\text{coefficient}}\;{\text{of}}\;{\text{variation}}\left( {{\text{GCV}}\% } \right) = \frac{{\sigma^{2} g}}{{\overline{X}}} \times 100$$

    where, σ2p = Phenotypic variance of F2, σ2g = Genotypic variance of F2, X = Mean of F2 population.

PCV and GCV were classified as 0–10% as Low, > 10–20% as Moderate and more than 20% and above as High.

Heritability (h2 Broadsense)

Broad-sense heritability was estimated for all the traits using the following formula of [2]

$$h^{2} \left( \% \right) = \frac{{\sigma^{2} g}}{{\sigma^{2} p}} \times 100$$

where, h2 = Heritability (broad sense) expressed in per cent, σ2g = Genotypic variance of F2 population, σ2p = Phenotypic variance of F2 population.

Heritability percentage was categorized, 0–30% as Low, > 30–60% as Moderate and more than 60% and above as High.

Genetic Advance (GA)

The extent of genetic advance expected through selection in the F2 population for each character was estimated by using the following formula of [2].

$${\text{GA}} = h^{2} \times K \times \sigma_{{\text{p}}}$$

where, h2 = Heritability estimate, K = Selection differential at given intensity (which is equal to 2.06 at 5 per cent intensity of selection), σp = Phenotypic standard deviation.

Genetic Advance as Per Cent over Mean

Genetic advance as per cent over mean was worked out as suggested by [2].

$${\text{Genetic}}\;{\text{advance}}\;{\text{as}}\;{\text{per}}\;{\text{cent}}\;{\text{over}}\;{\text{mean}} = \frac{{{\text{GA}}}}{{{\text{Grand}}\;{\text{mean}}}} \times 100$$

The genetic advance as percent mean was categorized as 0–10% as Low, > 10–20% as Moderate and more than 20% and above classified as High.

Analysis of variance in F2 segregating population of the cross Surya × Harita indicated a significant mean sum of squares attributable to ‘treatment’ (F2 progenies + checks), ‘tests’ (F2 progenies), ‘controls’ (checks) and ‘tests vs controls’ for all the traits studied (Table 1). Overall high variability existed for all the characters studied and considerable improvement could be achieved in most of the traits by selection.

Table 1 Analysis of variance in F2 segregating population of the bi-parental cross Surya × Harita for growth and yield parameters
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The estimates of genetic parameters for growth and yield attributes in F2 segregating population of the bi-parental cross Surya × Harita were presented in the Table 2 and Fig. 1. High value of GCV and PCV (> 20 per cent) were observed for number of primary branches per plant (22.10% & 24.91%) and number of fruits per plant (23.89% & 24.97%). The difference between PCV and GCV being very low for majority of the characters suggesting more prevalence of genetic governance of these characters and thus selection on phenotypic basis would hold good. These findings are consistent with those of previous researchers [3,4,5].

Table 2 Estimates of genetic parameters for growth and yield attributes in F2 segregating population of the bi-parental cross Surya × Harita
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Fig. 1
figure 1

Variability in F2 segregating population of the bi-parental cross Surya × Harita

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High estimates of heritability coupled with higher genetic advance as per cent of mean were observed for plant height (80.60% & 32.20%), number of primary branches (78.68% & 66.83%), plant spread from North to South (75.54% & 38.67%), plant spread from East to West (80.90% & 35.94%), fruit length (83.10% & 27.37%), fruit diameter (89.09% & 33.17%), average fruit weight (83.37% & 34.74%), number of fruits per plant (91.54% & 57.44%), fruit yield per plant (96.43% & 98.09%) and TSS (82.43% & 56.32%). This indicates the role of additive gene action in the expression of these characters. Hence, simple selection method can be employed for the improvement of these characters. These results are in agreement with earlier workers [6, 7].