Genetic Diversity in Brassica integrifolia

Brassica integrifolia also named Cai Ngot in Vietnam belongs to the Brassicaceae family. This family contains about 350 genus and 3,500 species. B. integrifolia is originates to India and China and is often grown as a vegetable. In Vietnam, the cultivation area of B. integrifolia is very large and it is one of the main crops because it brings high economic efficiency. By 2024, the area of B. integrifolia cultivation nationwide will reach 200,000 hectares, with a productivity of about 3,000,000 tons/year. Therefore, research related to B. integrifolia breeding is very interested.
       
Can Giuoc District, Long An Province is a large vegetable farm in Vietnam with an area of over 2000 hectares. Can Giuoc district is a rare place in Vietnam that still cultivation local B. integrifolia varieties with large farm. Because this is a local germplasm source mainly produced by farmers the B. integrifolia variety is currently morphologically degraded. Evaluation of the genetic diversity parameters of this local B. integrifolia variety is the first step in improving B. integrifolia populations to conserve and develop local B. integrifolia germplasm.
       
Nowadays plant breeders are exerting to develop new varieties. For this, breeders must have a good knowledge of genetic variability and heritability. In addition, locally collected B.integrifolia varieties are also a good source of genetic material to start breeding programs because they have higher genetic variability. This genetic variation can be improved during breeding to develop varieties with high yield potential (Sidra Iqbal et al., 2014).
       
Certain morphological traits serve as tools for estimating genotypic variance (Ali et al., 2013) and heritability (Azam et al., 2013). Environmental factors can influence these parameters due to the polygenic inheritance of the genes involved. The heritability coefficient can calculate the relative influence of genetic and environmental  effects, This indicates the extent to which a trait will be transmitted to the next generations. Thus, the expression of the next generations can be predicted and selection can be carried out Khan et al., (2003).
       
Heritability and response to selection show a direct relationship to genetic progress. The expected response to selection is also known as genetic advance (GA). Therefore, to estimate genetic advances breeders often use heritability to calculate, which measures the extent of increase in any trait under a particular selection pressure. Therefore, genetic advance is one of the important parameters that help breeders select genotypes Shukla et al., (2004). To select effectively for certain traits high genetic advance along with high heritability is required. Heritability along with selection efficiency should be considered in breeding processes.
               
The genetic variability present in the available germplasm of a particular crop determines the success of any breeding program in general and the improvement of specific traits through selection. The traits for variability traits must have high heritability because the selection process depends on the heritability and genetic advance and helps the breeder to select an appropriate selection programme in the crop improvement process (Yadava et al., 2011). High heritability in the initial breeding material ensures better chances of producing new desirable crops (Raturi et al., 2014).

The experiment was conducted at the College of Agriculture, Can Tho university from October 2023 to January 2024. The experimental materials were 36 samples of B. integrifolia collected from different areas of Can Giuoc district, Long An province, Vietnam. The criteria for selecting 36 samples were from farmers with seed production areas of over 500 m2 and using locally B. integrifolia resources for seed production. The experiment was arranged in a completely randomized block design with 36 treatments corresponding to 36 accession of B. integrifolia collected and 3 replications. Eleven quantitative traits were collected and evaluated (Table 1) as such as seed weight (g/plant), seed weight at the bottom of the panicle (g), number of seeds/10 silique at the bottom of the panicle, number of seeds/10 silique at the top of the panicle, number of seeds/10 silique at the middle of the panicle, number of seeds per 10 silique/plant, seed filling time (day), plant width (cm), number of secondary branches, number of primary branches, thousand seed weight (g) were collected to assess genetic diversity. The method of collecting morphology criteria is shown through (Table 1). After the traits were collected, variance will be estimated and calculate genetic parameters (Table 2). Correlation coefficient analysis 11 quantitaive trait (Pearson,1939). Cluster analysis (Ward, 1963). The data are presented in a statistical format SPSS 22.0.

Genetic diversity parameters of 36 B. integrifolia accessions
 
The parameter of genetic variance (GV), phenotypic variance (PV), genetic coefficient variation (GCV), Phenotypic coefficient variation (PCV), heritability (h2) and Genetic advance (GA) were calculated for all 11 quantitative traits under study are presented in (Table 3), showing that genotypic variance (GV) ranges from 0.006 for thousand seed weight to 1,674.98 for number of seed.10 siliques at the top of panicle. Phenotypic variance (PV) ranges from 0.007 for thousand seed weight to 1,693.47 for number of seed/10 siliques at the top of panicle. The low difference between genotypic and phenotypic variance in a trait indicates that these traits are less influence of environment factor. Genetic variation is one of the most important requirements for crop improvement because it provides a wider range of choices (Pal et al., 2019).


       
The genotypic coefficient of variation (GCV) ranged from 15.96 (medium) for thousand seed weight to 67.05 (high) for seed weight (g). According to the classification of Deshmukh et al., (1986), all traits had high genotypic coefficients of variation, except for thousand seed weight which had a medium genotypic coefficient of variation. The genotypic coefficient of variation is considered a measure used to compare genetic variations occurring in different types of traits and a high genotypic coefficient of variation helps in more effective selection and improvement of traits.
       
The phenotypic coefficient of variation (PCV) ranged from 16.58 (medium) for thousand seed weight to 67.27 (high) for seed weight. Overall, all 11 quantitative traits had high phenotypic coefficients of variation according to the classification of Deshmukh et al., (1986), except the thousand seed weight (16.58) which was average. The results of high genotypic coefficients of variation and phenotypic coefficients of variation in this experiment were similar of Patel et al., (2021); Nishad et al., (2022); Mandal et al., (2022) and Sur et al., (2023) on seed weight/plant of B. juncea L.
       
High genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) also help in the effective selection and improvement of traits. In this experiment, high phenotypic coefficient of variation and genotypic coefficient of variation were observed for all quantitative traits, which shows that environmental factors have little impact on trait expression and that traits are mainly controlled by genotype (Jagaonkar et al., 1990).
       
The heritability (h2) in this experiment was very high for 11 quantitative traits such as seed weight (99.0%), seed weight at the bottom of the panicle (97.0%), number of seeds/10 silique at the end of the panicle (97.0%), number of seeds/10 silique at the top of the panicle (99.0%), number of seeds/10 silique at the middle of the panicle (99.0%), number of seeds/10 silique/plant (99.0%), grain filling time (95.00%), plant width (99.0%), number of secondary branches (92.0%), number of primary branches  (80.0%), thousand seed weight (93.0%). Nh­n ðËnh Thus, based on the classification of very high heritability, population improvement is possible because these traits are mainly determined by genotype and are less affected by the environment. The heritability reflects the contribution rate of the genotype to the quantitative trait. The heritability was higher the less influenced the trait by environmental factors (Singh, 2001).
       
The percentage of genetic advance for all quantitative traits ranged from 31.69% for thousand seed weight (g) to 100% for seed weight and Seed weight at bottom of panicle was rated high according to the classification of as according to the classification of Johnson et al., (1955). This result is consistent with the study of Yadava et al., (2011); Kumar et al., (2013); Rout et al., (2019); Patel et al., (2019); Jat et al., (2019); Yadav et al., (2020); Patel et al., (2021); Nishad et al., (2022); Mandal et al., (2022) và Sur et al., (2023) reported high heritability and genetic advance values for seed/plant weight in Brassicaceae. High heritability and high genetic advance across traits suggest that direct selection can improve through breeding programs. (Pal et al., 2019). According to Burton (1951) suggested that combining the genotypic coefficient of variation with heritability allows for a better assessment of genetic variation.  Johnson et al., (1955) suggested that combining heritability with genetic advance as a percent of means (GAM) would help evaluate the selected phenotypes more effectively. Thus, combining heritability and genetic advance, all 11 quantitative traits showed that selection through these traits would be useful in improving the B. integrifolia population.
       
High heritability coefficients show that these traits are not affected by environmental factors. High GA shows that the ability to select the desired B. integrifolia lines is very high. Thus, high heritability combined with a high genetic advance for local B. integrifolia varieties in this study is very useful for breeding local B. integrifolia varieties.
 
Cluster analysis
 
The results of hierarchical cluster analysis of 36 B. integrifolia accessions collected based on 11 quantitative traits such as seed weight, seed weight at the bottom of the panicle, the number of seeds/10 silique at the bottom of the panicle, the number of seeds/10 silique at the top of the panicle, the number of seeds/10 silique at the middle of the panicle, the number of seeds/10 silique per plant, grain filling time, plant width, the number of secondary branches, the number of primary branches and thousand seed weight were divided into 4 clusters (Fig 1).


       
Cluster I consist of 9 accessions (3, 5, 12, 28, 34, 2, 13, 16, 30) accounting for 25% of the total number of accessions. Cluster II consists of 14 accessions (6, 10, 4, 14, 8, 36, 29, 7, 19, 15, 35, 17, 33, 1) accounting for 39% of the total number of accessions. Cluster III consists of 2 accessions (31, 32) accounting for 5.6% of the total number of accessions. Cluster IV consists of 11 accessions (9, 20, 11, 25, 23, 18, 26, 27, 21, 24, 22) accounting for 30.5% of the total number of accessions.
       
Thus, based on the means of quantitative traits of 4 clusters (Table 4), it shows that Cluster III has the highest growth, yield components and yield such as plant width (27.7 cm), number of secondary branch (22.8), number of primary branch (13.5), seed weight (9.1 g/plant), number of 10 seeds/plant (157.2), thousand seed weight (1.7 g). Cluster I, Cluster II have the average growth, yield components and yield. Cluster IV has the lowest growth, yield components and yield. It is possible to use germplasm resources from Cluster III as materials for future breeding programmes.



Correlations between quantitative traits
 
The correlation coefficients between quantitative traits are presented in (Table 5), showing that some traits have good correlation coefficients (r > |0.5|). Seed weight trait has a good correlation with seed weight at bottom of panicle, number of seed of 10 silique at bottom of panicle, number of seed of 10 silique at top of panicle, number of seed of 10 silique at medium of panicle, number of seed of 10 silique per plant, thousand seed weight. Number of seed of 10 silique at bottom of panicle positive correlation with number of seed of 10 silique at top of panicle, number of seed of 10 silique at medium of panicle, number of seed of 10 silique per plant. Correlation analysis shows that yield components and yield are positively correlated, the higher the yield component, the higher the yield.

All collected local sources of B. integrifolia showed differences for most of the traits. The results of the study showed that the heritability was very high (>80%) combined with high genetic advance (>20%) for 11 quantitative traits, indicating that these traits are under the control of genetics and are not affected by environmental factors, while the remaining traits showed a tendency to change due to environmental factors. Through hierarchical cluster analysis, the quantitative traits of 36 B. integrifolia accession were divided into 4 clusters. Cluster III contained good germplasm sources. This study showed a great diversity in growth, yield and yield component traits, contributing a valuable genetic source for B. integrifolia breeding.
 
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The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.
 
Informed consent
 
All animal procedures for experiments were approved by the Committee of Experimental Animal care and handling techniques were approved by the University of Animal Care Committee.

The authors declare that there are no conflicts of interest regarding the publication of this article. No funding or sponsorship influenced the design of the study, data collection, analysis, decision to publish or preparation of the manuscript.