Estimation of variability parameters for growth, yield and yield traits in chilli (Capsicum annuum L.)

Introduction

Chilli (Capsicum annuum L.) is one of the most important commercial spice crops belonging to the family Solanaceae, widely cultivated throughout India for its pungent fruits that are used as vegetables, spices, condiments, pickles, and in pharmaceutical industries. India is the world's largest producer, consumer, and exporter of chilli. The crop exhibits ample variability in morphological characters throughout India, particularly in the south peninsular region, North Eastern foot hills of Himalayas, and Gangetic plains (Pradheep and Veeraragavatham, 2006) [13] . The evaluation of germplasm is immensely important in genetic improvement of the crop for achieving higher yields and productivity (Munshi et al., 2000) [11] . The magnitude of variability and its genetic components are the most important aspects of breeding material. Hence, the basic understanding of genetic variability is a prerequisite for the planning of breeding programmes. Variability helps to choose the potential genotype, since it indicates the extent of recombination for implementing effective selection. Genotypic coefficient of variability (GCV) and phenotypic coefficient of variability (PCV) are measured to study the variability (Burton and De Vane, 1953) [2] . Heritability estimates give a measure of transmission of characters from one generation to another, thus giving an idea of heritable portion of variability and enabling the plant breeder in isolating the elite genotype (Lush, 1949; Hanson et al., 1956) [9,6] . Heritability coupled with genetic advance is an important selection parameter. Johnson et al. (1955) [8] reported that heritability along with genetic gain is more useful than heritability alone in predicting the resultant effect for selecting the best individuals. The present investigation was undertaken to estimate variability parameters for growth, yield and yield traits in diverse chilli germplasm.

Materials and Methods

Experimental Site and Climate

The field experiment was conducted on red soil with coarse texture at the P.G research block, Sri Konda Laxman Telangana State Horticultural University, College of Horticulture, Rajendranagar, Hyderabad during Kharif 2018. The site of the experiment is situated in semi arid tropical zone at an altitude of 542.6 m above mean sea level. Geographically, it lies at latitude of 17°19' N and a longitude of 78°23" E.

Experimental Material

The experimental material comprising of 40 chilli genotypes, homozygous accessions obtained from NBPGR Regional Station, Rajendranagar, Hyderabad and one local variety collected from Warangal district of Telangana state and few released varieties from RARS, Lam, Guntur, Andhra Pradesh were systematically evaluated for 20 quantitative traits (Table 1).

Experimental Design

The experiment was laid out in a Randomized Block Design with 40 chilli accessions as treatments during Kharif, 2018-19. Each treatment was randomly replicated thrice. Six weeks old healthy seedlings were transplanted in the main field. Each germplasm line was grown in a plot of 1.8 m × 3.15 m (5.67 Sq. meters), 8 plants per row with spacing of 60×60 cm per replication.

Estimation of Genetic Variability Parameters

Phenotypic and genotypic components of variance were estimated using the formula given by Cochran and Cox (1957) [4] . Genotypic variance (σ²g) = [MSS due to genotypes -MSS due to error] / r. Phenotypic variance (σ²p) = Genotypic variance (σ²g) + Error variance (σ²e). Both phenotypic and genotypic coefficients of variability were estimated using the formula of Burton and De Vane (1953) [2] . PCV and GCV were classified as per Sivasubramanian and Menon (1973) [17] as: Low (<10%), Moderate (10-20%), and High (>20%). Broad sense heritability (h²bs) was estimated as the ratio of genotypic variance to phenotypic variance expressed in percentage (Lush, 1949; Hanson et al., 1956) [9,6] . Heritability was categorized as per Johnson et al. (1955) [8]: Low (<30%), Moderate (30-60%), and High (>60%). Genetic advance was estimated using the formula GA = h²bs × σp × K, where K is the standard selection differential at 5% intensity (2.06). Genetic advance as percent of mean was classified as: Low (<10%), Moderate (10-20%), and High (>20%).

Results and Discussion

Analysis of Variance

The analysis of variance in 40 chilli genotypes indicated highly significant differences among the genotypes for all the 20 quantitative characters studied (Table 2), indicating the existence of adequate genetic variability among the genotypes. This was in accordance with the reports of Sarma and Roy (1995) [15] . The significant variation among genotypes suggests ample scope for selection of superior genotypes for yield improvement in chilli breeding programmes.

Estimates of Variability, Heritability and Genetic Advance

The estimates of variability parameters including range, mean, phenotypic variance, genotypic variance, PCV, GCV, heritability, genetic advance and genetic advance as percent of mean for twenty characters are presented in Table 2. The PCV was higher than GCV for all characters, indicating that all characters interacted with environment to some degree. However, the narrow differences between PCV and GCV values for most characters suggest that environmental influence was minimal and the traits were predominantly under genetic control. High PCV and GCV values (>20%) were recorded for plant height (23.59%, 23.00%), number of primary branches per plant (23.99%, 23.41%), number of flowers per axil (25.06%, 23.52%), average fruit weight (54.69%, 53.32%), fruit length (37.61%, 37.53%), fruit diameter (41.86%, 41.03%), fruit yield per plant (44.54%, 44.40%), fruit yield per plot (44.35%, 44.07%), oleoresin content (23.47%, 23.38%), capsaicin content (39.21%, 39.14%), and chlorophyll content (28.37%, 28.01%), indicating the existence of wider genetic variability for these traits and the potential for improvement through selection. Similar findings were reported by Sharma et al. (2010) [16] , Suryakumari et al. (2010) [18] , Datta and Das (2013) [5] , and Amit et al. (2014) [1] in chilli. Moderate PCV and GCV values (10-20%) were observed for days to 50% flowering (14.83%, 13.32%), days to fruit set (14.20%, 13.09%), ascorbic acid content (19.98%, 19.94%), and capsanthin content (14.50%, 14.47%). Low PCV and GCV values (<10%) were recorded for days to first fruiting, days to first harvest, days to last harvest, duration of crop, and recovery percentage, indicating narrow range of genetic variability for these traits. High heritability estimates (>60%) were observed for all the characters except recovery percentage (58.4%), which showed moderate heritability. Very high heritability (>95%) was recorded for plant height (95.0%), number of primary branches per plant (95.2%), average fruit weight (95.0%), fruit length (99.6%), fruit diameter (96.1%), fruit yield per plant (99.4%), fruit yield per plot (98.7%), ascorbic acid content (99.6%), oleoresin content (99.2%), capsanthin content (99.5%), capsaicin content (99.6%), and chlorophyll content (97.5%). These findings are in agreement with the reports of Chattopadhyay et al. (2011) [3] , Priyanka and Naidu (2015) [14] , and Udachappa et al. (2017) [19] . High heritability coupled with high genetic advance as percent of mean (>20%) was observed for plant height, number of primary branches per plant, number of flowers per axil, days to 50% flowering, days to fruit set, average fruit weight, fruit length, fruit diameter, fruit yield per plant, fruit yield per plot, ascorbic acid content, oleoresin content, capsanthin content, capsaicin content, and chlorophyll content, indicating the predominance of additive gene action in the expression of these traits and suggesting that these characters could be improved through direct selection. Similar findings were reported by Sharma et al. (2010) [16] , Suryakumari et al. (2010) [18] , Datta and Das (2013) [5] , Amit et al. (2014) [1] , Priyanka and Naidu (2015) [14] , and Mallikarjun et al. (2003) [10] . Moderate heritability coupled with moderate genetic advance as percent of mean was observed for days to first fruiting (74.7%, 15.30%), days to first harvest (61.9%, 11.82%), days to last harvest (79.7%, 15.05%), and duration of crop (72.1%, 12.28%), indicating the role of both additive and non-additive gene action in the expression of these traits. Recovery percentage showed moderate heritability (58.4%) with low genetic advance as percent of mean (6.84%), indicating the predominance of nonadditive gene action and environmental influence on this trait.

Conclusion

The present investigation on estimation of variability parameters in forty diverse chilli genotypes revealed the existence of substantial genetic variability for all the twenty characters studied. The phenotypic coefficient of variation was consistently higher than genotypic coefficient of variation for all characters; however, the narrow differences suggest that environmental influence was minimal. High PCV and GCV recorded for plant height, number of primary branches per plant, number of flowers per axil, average fruit weight, fruit length, fruit diameter, fruit yield per plant, fruit yield per plot, oleoresin content, capsaicin content, and chlorophyll content indicate the presence of wider genetic variability. High heritability coupled with high genetic advance as percent of mean observed for these characters indicates the predominance of additive gene action, suggesting that simple selection based on phenotypic performance would be effective for genetic improvement. Hence, breeders are recommended to adopt mass selection, pure line selection, or pedigree method of breeding for improving these traits in chilli.

Acknowledgement

AcknowledgementThe author is thankful to SKLTSHU, for providing financial assistance in the form of a fellowship for perusing the PG program. Authors also thank's the other authors for supporting the research work in relevant field and for proof reading the manuscript. Assistance received from ICAR-NBPGR, RS Hyderabad for providing germplasm is also acknowledged by the author. The studies were conducted with the help of financial support aided by SKLTSHU.

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