Document Type : Research Paper
Authors
1 Department of Plant Breeding and biotechnology, College of Agriculture, Shahrekord University, Shahrekord, Iran
2 Department of Plant Breeding and Biotechnology, Faculty of Agriculture, Shahrekord University,Shahrekord, Iran
3 Associate Professor of Dep. of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111, Iran.
4 Department of Horticulture, Science Shahrekord University, Shahrekord, Iran
Abstract
Background and objectives: Nigella sativa L. is an important medicinal plant widely used in the food and pharmaceutical industries. Considering the increasing demand for medicinal plants worldwide and the need to produce cultivated and breeding varieties, it is necessary to study the genetic resources. The gain from selection for a trait depends on the relative importance of genetic factors in the occurrence of phenotypic differences among genotypes; in other words, the success of breeding programs depends on the genetic variation and heritability of traits. Therefore, this study investigated the genetic variation and inheritance of seed yield and yield component traits in different black cumin genotypes and identified desirable genotypes for use in breeding programs.
Methodology: This study investigated the genetic variation in 20 different black cumin genotypes (Iranian and foreign) regarding different agronomic traits as a randomized complete block design with three replications at the research farm of Shahrekord University. The genotypes were planted in the middle of March. Each genotype in every repetition was cultivated in four rows, each 1.5 meters long. The distance between the rows of cultivation was 30 cm, with seeds planted 15 cm apart within the row at a depth of 1-2 cm. The traits studied included seed yield, number of capsules per plant, number of seeds per capsule, thousand seed weight, capsule diameter, number of branches per plant, and plant height. Based on the expectation of mean square components, environmental, genetic, and phenotypic variance were calculated, and then the genotypic and phenotypic coefficient of variation and broad-sense heritability were estimated. Statistical analyses, including analysis of variance and comparison of the mean traits between genotypes, were performed using the least significant difference (LSD) test using SAS 9.0 software. Pearson correlation between traits and cluster analysis based on Ward's method according to squared Euclidean distance using R 3.6.1 software. Also, to ensure the correctness of grouping, multivariate tests and analysis of variance tests were performed based on a completely random, unbalanced design.
Results: The analysis of variance showed a significant difference between the studied genotypes for all the agronomic traits (p<0.01). The plant height in the studied genotypes varied from 22 cm (Nige7) to 58.4 cm (Nige1). The highest number of capsules per plant was observed in the Nige 53 genotype, with 20.45 capsules, and the lowest number of capsules per plant was observed in the Nige63 genotype, with 5.3 capsules. The number of branches per plant ranged from 3.9-11.5 per plant. The yield ranged from 263.56 kg/ha (Nige3) to 1409.39 kg/ha (Nige78 genotype). The phenotypic coefficient of variation varied from 48.58% (seed performance) to 5.20 (capsule diameter), and the genotypic coefficient of variation varied from 48.29% (seed performance) to 4.7 (capsule diameter). The highest genetic coefficient of variation (48.29%) belonged to the grain yield trait. The estimated heritability for the assessed traits ranged from 73.81% for number of branches per plant to 98.8% for seed yield. Heritability was 91.91% for the number of capsules per plant trait. According to the correlation coefficient results, seed yield per plant showed a positive and significant correlation with the number of capsules per plant (r=0.87**) and branches per plant (r=0.54*). In the cluster analysis, the studied genotypes were divided into four different groups, and the results of the multivariate analyses indicated appropriate grouping and significant differences in the amount of grain yield and yield components among the groups resulting from the cluster analysis.
Conclusion: The high genetic variation among the studied genotypes indicates the high efficiency of this germplasm for improving grain yield and various traits and the high efficiency of selection in black cumin. Genotypes Nige53, Nige78, and Nige60 had high grain yields compared to other genotypes, which can be used to improve and increase grain yield in black cumin.
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