Chickpea is a crop containing high protein and has a vital role in the diet of food security in the world, especially in developing countries. An experiment was conducted to evaluate the genetic diversity, heritability, and path analysis in chickpea cultivars, based on the Randomized Complete Block Design with three replications in 2023. The geographical coordinates are north latitude 34°58′ longitude 18°48′ and altitude was 1607. Calculation of genetic correlation in both environmental conditions showed that traits of plant height, number of seeds per plant, number of pods per plant, single plant biomass, seed yield of single plant without pods, the total number of main branches of the plant, grain yield of single plant with pods, grain yield (m2), biomass (m2), the stubble weight and harvest index, had high genetic correlation with each other. The highest percentage of heritability in irrigated conditions was related to biomass (m2) (0.96), number of pods per plant, and SPAD chlorophyll index at the fruiting stage (0.98). The highest percentage of heritability of grain yield (m2) under irrigated was (0.97), biomass, and SPAD chlorophyll index (0.99). The grain yield, biomass, and SPAD chlorophyll index at the fruiting time had the highest amount of heritability under rainfed conditions and also had the highest level of genetic gain. In normal conditions, traits the total number of main branches of the plant (0.06) and grain yield (0.09), had the lowest heritability and genetic gain. Under drought stress, trait the total number of main branches of the plant (0.16) had the lowest heritability and also had the lowest genetic gain (1.07). These results can be used in breeding programs to select for drought tolerance. The first four principal components accounted for 90.966% of the variance under irrigated and 95.362% of variance under rainfed conditions.
Research Article
Analysis of genetic parameters, heritability, and path analysis in chickpeas under irrigated and rainfed conditions
https://doi.org/10.21203/rs.3.rs-4976169/v1
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Chickpeas
Drought stress
Genetic analysis
Path analysis
Chickpeas (Cicer arientinum L.) with 15–25% protein, 41-50.8% carbohydrates, a high percentage of other mineral nutrients, and unsaturated linoleic and oleic acid is one of the most important crops for human consumption. Chickpea, with low production cost, wide climate adaptation, uses in crop rotation, and atmospheric nitrogen fixation ability is one of the most important legume plants in sustainable agriculture (Latham 1997, Wood and Grusak 2007, Kakaei et al. 2024). Chickpea has high variation for different quality and quantity traits, including ideal plant type (tall type), shape and color grain, flower color, podding, the color of seed coat, earliness, resistance to disease and pests, which helps breeders to release improved and advanced lines and varieties (Kakaei and Moosavi 2017). To avoid genetic erosion and releasing new varieties, cultivars, and recombinant lines, the genetic variation for desirable traits should be broadened. Genetic parameters such as heritability, gene action, genetic and phenotypic correlation, etc., should be studied (Farshadfar and Farshadfar 2018, Singh and Chaudhary1979). Plant genetic resources are the basis of global food security. They comprise diverse genetic material in traditional varieties, modern cultivars, and crop wild relatives.
Increasing genetic diversity plays an important role in meeting the nutritional needs of humans (Karagoz and Zencirci 2005). In general, important parameters, such as high heritability and selection intensity play a key role in plant breeding programs (Falconer 1989). The optimal selection for the desired trait can be done when the heritability is appropriate, and the additive genetic effects are high (Philips and Abbey 1989). Before choosing any breeding method, especially in self-fertilizing plants, it is necessary to identify the degree of transfer of traits from one generation to the next (heritability value). General heritability provides a reasonable estimate of genetic variance and provides more information for plant improvement (Phudenpa et al. 2004). Kakaei et al. (2015) reported the highest and the lowest heritability belonged to harvest index, and number of seeds per plant, respectively. They explained that due to the high variability of these traits, they can be used as an important source of diversity to increase yield and select superior genotypes. Genetic variability and path analysis of 360 chickpea landraces and lines were calculated. The highest correlation coefficient (r = 78%) was between seed yield per plant and pod number. The direct and indirect effects of different morphological traits on grain yield were estimated (Farshadfar and Farshadfar 2008).
In general, to evaluate the genetic diversity between different cultivars of chickpea, the evaluation and determination of genetic parameters, such as heritability, genotypic coefficient of variation, phenotypic coefficient of variation, H2 heritability, genetic advance, genetic gain, and the identification of the most suitable traits affecting the yield were designed and carried out.
To evaluate the genetic parameters of morphological traits, seven chickpea cultivars (1: Yadegar, 2: Adel, 3: Ana, 4: Kasra, 5: Mansour, 6: Kavian, and 7: Arman) were selected in this study (Table 1). An experiment based on the randomized complete blocks design (RCBD) with three replications in 2023, with the north latitude (34°58′), longitude (18°48′), and altitude was 1607 m geographical coordinates. The experiment was carried out in two conditions, including supplementary irrigation at the final stage of seeding and rainfed conditions (only rainfall moisture). The variety was sown in two-meter five rows, and the distance between the rows of each plot was 40 cm, and the distance between the plants on the row was 10 cm. Planting was done at the end of March 2023. Tillage operations such as plowing, disking, leveling, and making furrows were done before planting. The measured traits, including plant height at the harvest time, the main root length, the number of seeds per plant, the number of seeds per pod, the biomass of a single plant, the seed yield of a single plant, the total number of plant branches (including secondary and main branches), 100 seeds weight, grain yield of a single plant with pod, grain yield (per m2), biomass (per m2), stubble weight, chlorophyll index of SPAD during pod yield and harvest index (Table 2). Harvesting was done manually in the first half of July 2023. Genotypic Coefficient of Variation (GCV), Phenotypic Coefficient of Variation (PCV), Heritability (H2), Genetic Advance (GA), and Genetic Gain (GG) were calculated. Statistical calculations were done using SPSS 26 and Excel 2013 software.
Genotypic Coefficient of Variation (GCV); Phenotypic Coefficient of Variation (PCV); Heritability (H2); Genetic Advance (GA); Genetic Gain (GG).
Table 1 Name of chickpea cultivars
|
Cultivar Name |
No. |
|
Yadegar |
1 |
|
Adel |
2 |
|
Ana |
3 |
|
Kasra |
4 |
|
Mansour |
5 |
|
Kavian |
6 |
|
Arman |
7 |
Table 2 Morpho-physiological measured traits
|
Traits |
Row |
|
Plant height |
1 |
|
The length of the main root of the plant |
2 |
|
Number of seeds per plant |
3 |
|
Number of pods per plant |
4 |
|
Single plant biomass |
5 |
|
Seed yield of single plant without pods |
6 |
|
The total number of main branches (per plant) |
7 |
|
100 grains weight |
8 |
|
The number of sub-branches |
9 |
|
Seed yield of single plant with pods |
10 |
|
Grain yield (per m2) |
11 |
|
biomass (per m2) |
12 |
|
The weight of the stubble |
13 |
|
SPAD chlorophyll |
14 |
|
Harvest index |
15 |
Genetic parameters in irrigated conditions
The different types of variation in significant traits in two environmental conditions were revealed in (Tables 3 and 4).
According to Table 3, the heritability of the number of pods per plant (0.92), biomass (0.96), and chlorophyll index (0.98) had high values. Regarding the three traits mentioned, genetic gain (G.G) with 103.48, 366.39, 307.38, and genetic advanced (G.A) with 9.39, 258.6, and 52.93 respectively had high values indicating the high additive component of variance.
The amount of genotypic variance was high compared to other traits for the number of pods per plant (22.73), biomass (1645.9), and chlorophyll index (678.9). Also, regarding these traits, the environmental variance was very small, which indicates the greater effect of genetic variance and low environmental effect on the mentioned traits. In general, the environmental coefficient of variations was very low for traits the length of the main root of the plant (12), number of pods per plant (15), and SPAD chlorophyll index (17) at the time of fruiting. However other traits had more values for these parameters, which indicates the environmental effect. The grain yield of a single plant with pods (30.01), biomass/m2 (70.58), and SPAD chlorophyll index (17) had the highest amount of phenotypic coefficient variation indicating the emergence of these traits in the phenotype of the plant. Of course, biomass (m2) and SPAD chlorophyll index simultaneously had a high genotypic coefficient of variation (262.62) and high phenotypic coefficient variation parameter (152.26), which indicates the effect of genetic characteristics on the morphology of the plant.
Genetic parameters under drought stress conditions
Table 4 shows the genetic parameters in chickpea plants under drought-stress conditions. The heritability of grain yield (0.97), biomass (0.99), and SPAD chlorophyll index (0.99) at the fruiting time was very high. These traits had high genetic gain and genetic advance compared to other traits. The grain yield, biomass, and SPAD chlorophyll index had a high amount of genotypic variance and a high genotypic coefficient of variation (GCV).
Genetic correlation between the studied traits in chickpea cultivars
Table 5 shows the genetic correlation of characters in different chickpea cultivars under dry conditions. In rainfed conditions, the maximum value of the positive correlation coefficient (100%) was calculated between the grain yield per plant, with the number of pods per plant, the number of seeds per plant, and the biomass of a single plant. Also, a 100% positive correlation was observed between the number of pods per plant and the number of seeds per plant.
The lowest value of the correlation coefficient (0.02) was measured between the biomass (m2) of a single plant and the total biomass (m2). This value between the harvest index (HI) and the 100 seeds weight was − 0.02. It was also calculated between sub-branches and the harvest index with 0.007 value. A negative coefficient correlation (-0.008) between total biomass (m2) and the number of sub-branches was observed. The genetic correlation of characters in different chickpea cultivars under irrigated conditions was revealed in Table 6. In irrigated conditions, the maximum positive value of the correlation coefficient, i.e. (100%), was calculated between the seed yield per plant and the number of seeds per plant. Also, this coefficient between the number of pods per plant with seed yield was 0.78, and the harvest index (HI) was equal to %100. The correlation coefficient between the number of main branches and the number of sub-branches was evaluated as -100%. The lowest value of the correlation coefficient between the number of seeds per plant with the number of pods and the height of the plant was observed as -0.007. Also, the coefficient between the 100 seeds weight and the number of sub-branches was − 0.03. SPAD and HI were − 0.30 while the correlation between stubble weight and sub-branches was − 0.02.
Path analysis
The direct and indirect effects of chickpea yield components under irrigated and rainfed conditions are shown in Table 7.
The direct effects of plant height, the number of seeds per plant, the number of pods per plant, and the weight of 100 seeds are 1.423, 0.353, -1.533, and 2.153. The largest indirect effect on grain yield is the number of pods through the 100-grain weight (2.035). The lowest value of the indirect impact of the path coefficient is related to the effect of plant height through the number of seeds per plant with a coefficient of -0.021.
The direct effects of plant height, the number of seeds per plant, the number of pods per plant, and the weight of 100 seeds are 1.456, 0.814, 0.106, and 0.553. The largest indirect effect on seed yield is the number of pods through the number of seeds per plant (-0.952). The lowest value of the indirect effect of the path coefficient is related to the impact of the 100-grain weight through the number of pods per plant with a coefficient of -0.009.
Principle component analysis
To determine the contribution of traits to genetic diversity, Principal Component Analysis (PCA) was performed under both irrigated and rainfed conditions. The results of the PCA under irrigated conditions are presented in Table 8. The first four principal components accounted for 90.966% of the variance under these conditions. The contribution of each trait to the principal components is provided in Table 9. The trait grouping is shown in Fig. 1. In this analysis, 15 measured traits were categorized into four groups. The traits of the number of pods, number of seeds, number of seeds without pods, and with pods were grouped in the first category. Traits such as plant biomass, SPAD, and the number of sub-branches were placed in the second group, while traits like yield, plant height, hay, and total biomass were classified in the third group. Additionally, traits such as the main branch, harvest index (HI), and 100-seed weight were placed in the fourth group.
The results of the Principal Component Analysis (PCA) under rainfed conditions are presented in Table 10. The first four principal components accounted for 95.362% of the variance in these conditions. The contribution of each trait to the principal components is provided in Table 9. The trait grouping is shown in Fig. 2. In this analysis, 15 measured traits were categorized into four groups. The traits of yield, 100-seed weight, height, total biomass, hay, number of main branches, sub-branches, and SPAD were grouped in the first category. The trait of harvest index (HI) was placed alone in the second group. The plant biomass, root length, the number of seeds in plants with and without pods, and the total number of seeds were categorized in the third group.
Based on Table 5, which shows the genetic correlation between the traits studied in the investigated chickpea cultivars under rainfed conditions, shows a suitable genetic correlation between the traits related to yield. Regarding the trait of plant height at the time of harvesting, the traits of biomass and stubble weight show a positive and high correlation. In this regard, it can be noted that the higher the height of the plant at the time of harvest, the higher the biomass and stubble weight, which is a logical result in this study. The main root length trait of the plant shows a positive and high correlation with the chlorophyll index of the plant at the time of plant maturity (physiological maturity). The more the plant manages to extend the length of the root, it means it has a good establishment, which means that it has managed to create a plant with appropriate vegetative parts, on the other hand, a plant that has acceptable photosynthesis can have a more appropriate and longer underground organ (root). So, the results obtained are reasonable and expected. The trait number of seeds per plant showed a positive and high correlation with the trait number of pods per plant, the seed weight of a single plant without pods, and the seed weight of a single plant with pods. In other words, if the number of seeds in a plant is more it requires more pods, which the result is obtained in this study. The trait of the number of pods in a plant showed a very high and positive correlation with the characteristics of seed weight of a single plant without pods and seed weight of a single plant with pods. The biomass trait of a single plant showed a positive and significant correlation with traits of seed yield of a single plant without pods, seed yield of a single plant with pods, and the trait of the number of sub-branches in a plant, which was also fully expected. The seed weight trait of a single plant without pods had a positive correlation with the traits of seed weight of a single plant with pods and the harvest index trait, which was also expected. The trait of the number of main branches in the plant showed a positive and high genetic correlation with the stubble weight trait. The grain yield trait showed a positive and high genetic correlation with biomass and stubble weight traits, which was completely reasonable and expected. Table 5 and Table 6, show the genetic correlation of traits in normal humidity conditions and drought conditions, respectively. It should be noted that the trait Plant height at harvest time showed a high genetic correlation with traits Grain yield (in square meter area) and biomass (in square meters) in both environmental conditions. Also, the trait Number of seeds per plant showed a positive and high correlation with the trait Number of pods per plant, Seed yield of single plant without pods, and Seed yield of a single plant with pods in both environmental conditions. Trait Number of pods per plant showed a positive and high correlation with the trait Seed yield of the single plant without pods and the Seed yield of the single plant with pods in both environmental conditions. Trait Single plant biomass and trait Seed yield of a single plant with pods showed the ability to create positive and high genetic correlation in both environmental conditions. Trait Seed yield of the single plant without pods showed a positive and high correlation with the trait Seed yield of a single plant with pods and Harvest index and trait the total number of main branches of the plant showed a high and positive correlation with trait the weight of the stubble in both environmental conditions. Trait Grain yield (m2) showed a high genetic correlation with trait biomass (m2) and the weight of the stubble in both environmental conditions. Trait biomass (m2) showed a high genetic correlation with a trait the weight of the stubble in both environmental conditions.
In general, according to the results of this research, it was found that the diversity of most of the assessed traits among the studied chickpea cultivars was of genetic parameters and environmental factors did not have much effect on their occurrence. In their study, Kakaei and Mazahery Laqab (2023), stated that correlation analysis is a suitable parameter for studying the relationship between traits in plant breeding programs. Chickpeas are an affordable source of protein, carbohydrates, minerals and vitamins, dietary fiber, folate, beta-carotene, and health-promoting fatty acids. Therefore, by using the genetic diversity of this valuable plant, it is possible to choose a species that has more nutrients and help to produce it for the health of the human society who are concerned about health (Kakaei et al. 2024). Diagnosing drought-tolerant genotypes has been one of the basic goals of breeders, and this work is associated with many difficulties (Kakaei et al. 2011). In such a way, there was high diversity in some evaluated traits and less diversity in others. In general, the greater diversity in the investigated traits, naturally, the selection in them will result in a more appropriate selection response (Falconer 1989).
Plant Height with 1.423 positive direct effects of plant height on grain yield suggests that taller plants contribute to increased yield. This correlation might be due to the enhanced ability of taller plants to capture more sunlight, which is crucial for photosynthesis and biomass accumulation. Recent studies have confirmed that plant height is a significant trait in crop yield improvement strategies. For example, in chickpeas (Cicer arietinum L.), plant height was found to be positively associated with yield due to better canopy coverage and light interception (Yadav et al., 2023). The number of seeds per plant with a 0.353 coefficient has a positive effect, its relatively small coefficient indicates that it has a modest impact on overall yield. This suggests that while increasing seed numbers can contribute to higher yields, it is not as significant as other traits like seed weight. This finding aligns with research in which the number of seeds was shown to have a lower direct impact on yield compared to seed weight in legumes (Singh et al., 2022). The number of pods per plant (-1.533) has a negative direct effect on yield is intriguing. This could be due to a resource allocation trade-off, where a higher number of pods might lead to reduced resources available for each pod, resulting in lower yield per plant. This phenomenon has been observed in studies where excessive pod numbers led to a decrease in the individual pod and seed size, thus negatively impacting total yield (Kumar & Sharma 2021). 100-grain weight (2.153) has the most substantial direct effect on yield, indicating that heavier seeds significantly boost grain yield. This is consistent with breeding programs that focus on increasing seed size to improve yield. Grain weight has been identified as a critical factor in yield improvement in various crops, including chickpeas, as heavier seeds generally contain more stored energy, leading to more robust seedling growth and higher yields (Patil et al. 2022). The largest indirect effect (2.035) belongs to the number of pods per plant has a significant indirect effect on grain yield through its impact on the 100-grain weight. This suggests a complex interaction where the increase in pod number might initially reduce the yield but, through its influence on seed weight, can lead to an overall increase in yield. This indirect relationship emphasizes the importance of considering multiple traits simultaneously in breeding programs to maximize yield (Ghosh & Singh 2023). The lowest indirect effect is the minimal and negative indirect effect of plant height (-0.021) through the number of seeds per plant suggesting that the relationship between these two traits does not significantly impact yield. This finding implies that while plant height is important, its influence on yield via seed number is negligible. This aligns with findings in recent studies, where indirect effects through seed number were found to be less critical compared to other pathways (Ali et al. 2023). The analysis indicates that breeding programs should prioritize traits like seed weight and manage pod numbers carefully to optimize yield. Plant height and seed number, while important, should be considered secondary traits that complement the primary focus on enhancing grain weight. This approach is supported by recent research that advocates for a multi-trait selection strategy to improve yield potential in crops (Rani et al. 2022, Meena et al. 2021).
The PCA under irrigated conditions revealed that the first four principal components accounted for 90.966% of the total variance. This percentage, although slightly lower than that under rainfed conditions (95.362%), still indicates a significant dimensionality reduction, effectively capturing most of the variability in the dataset.
Under irrigated conditions, the first group primarily consists of reproductive traits related to seed production (number of pods, seeds, seeds without pods, and seeds with pods).
Under rainfed conditions, this group was different, with yield, 100-seed weight, and biomass-related traits being predominant. This indicates that under rainfed conditions, traits related to yield and biomass are more critical, possibly due to water stress influencing overall plant productivity.
Plant biomass, SPAD, and secondary branches are grouped in irrigated conditions, suggesting that vegetative growth traits are more closely linked when water is not a limiting factor.
In contrast, this grouping was different under rainfed conditions, with traits like HI and plant biomass separated, indicating different stress responses and the importance of specific characteristics under limited water availability. Traits like yield, plant height, and biomass are grouped under irrigated conditions, reflecting their importance for overall plant growth and yield potential when water is readily available. The PCA performed under rainfed conditions revealed that the first four principal components (PCs) accounted for 95.362% of the total variance, indicating that these components effectively captured most of the variation within the dataset. This high percentage suggests a strong dimensionality reduction, where most information is retained within fewer components.
When comparing these results with other studies, it is evident that PCA is a common technique in agricultural research to identify key traits that contribute significantly to yield and other important agricultural outcomes. Similar studies have found comparable groupings of traits, although the specific characteristics and their associations can vary based on environmental conditions, crop type, and experimental design. For instance, Ghaffari et al. (2020) conducted a PCA on wheat traits under drought conditions finding yield components such as grain weight and number of grains per spike were highly correlated and grouped, similar to the grouping observed in this study under rainfed conditions. Mandal et al. (2018) studied maize diversity under stress conditions by PCA. Traits such as plant height, biomass, and yield, showed significant variability in the first principal component, mirroring the results in this study with similar grouping. This analysis aligns with findings from other studies where environmental conditions significantly impact trait associations and their contributions to genetic diversity. Ali et al. (2021) conducted similar research in chickpeas under irrigated and rainfed conditions. They found that under irrigated conditions, reproductive traits such as pod and seed number dominated the first principal components, while under rainfed conditions, traits related to yield and biomass were more critical.
Similarly, Zhang et al. (2019) reported that traits like grain number and biomass were consistently important under different water regimes in wheat. Still, grouping and contribution varied depending on water availability, reflecting the findings in this analysis. The fourth group under irrigated conditions includes traits such as the main branch, HI, and 100-seed weight, which may play a more secondary role in genetic diversity under optimal water conditions. Interestingly, under rainfed conditions, HI was placed in a separate group, reflecting its distinct role under water stress where it might be a more critical determinant of yield efficiency.
This comparison offers a clear understanding of how environmental factors alter the significance and grouping of traits, which is critical for breeding programs to improve crop performance under varying conditions.
| Traits | CV% | ECV | GCV | PCV | G. a | G. g % | Hb | Var. G.% | Var. P.% | Var. E.% |
|---|---|---|---|---|---|---|---|---|---|---|
| Plant height | 28 | 28 | 42.31 | 33.45 | 4.1 | 20.67 | 0.3 | 13.22 | 44.11 | 30.9 |
| Length of the main root | 12 | 12 | 28.75 | 19.27 | 5.12 | 24.21 | 0.61 | 10.2 | 16.66 | 6.46 |
| Number of seeds per plant | 29 | 29.01 | 80.32 | 52.07 | 6.53 | 74.01 | 0.69 | 14.58 | 21.14 | 6.56 |
| Number of pods per plant | 15 | 15 | 29.23 | 54.6 | 9.39 | 103.48 | 0.92 | 22.73 | 24.58 | 1.86 |
| Single plant biomass | 19 | 19 | 39.32 | 27.5 | 6.88 | 29.45 | 0.52 | 21.59 | 41.33 | 19.73 |
| Seed yield of single plant without pods | 24 | 24 | 43 | 32.07 | 1.63 | 29.06 | 0.44 | 1.435 | 3.26 | 1.83 |
| Total number of main branches | 2 | 20 | 20.08 | 19.37 | 0.1 | 2.39 | 0.06 | 0.05 | 0.76 | 0.81 |
| 100 grains weight | 18 | 18.11 | 4204.16 | 33.65 | 6.22 | 41.5 | 0.71 | 18.11 | 25.49 | 7.38 |
| The number of sub-branches | 22 | 11.63 | 17.98 | 14.064 | 1.46 | 8.98 | 0.31 | 1.65 | 5.23 | 3.58 |
| Seed yield of single plant with pods | 30 | 30.01 | 65.37 | 1497.97 | 2.94 | 50.97 | 0.55 | 3.74 | 6.74 | 3 |
| Grain yield ((m2)) | 20 | 20 | 110.85 | 66.05 | 6.91 | 12.24 | 0.09 | 1263.3 | 1390.84 | 127.548 |
| biomass (m2) | 36 | 70.58 | 316.83 | 185.27 | 258.6 | 366.39 | 0.96 | 16453.9 | 17099.53 | 645.635 |
| The weight of the stubble | 36 | 36 | 69.13 | 49.57 | 83.57 | 47.99 | 0.47 | 3520.6 | 7450.5 | 3929.9 |
| SPAD chlorophyll index | 17 | 17 | 262.62 | 152.26 | 52.93 | 307.38 | 0.98 | 678.9 | 687.47 | 8.57 |
| Harvest index | 16 | 16.05 | 45.4 | 27.8 | 0.074 | 37.8 | 0.66 | 0.002 | 0.003 | 0.001 |
| Traits | CV% | ECV | GCV | PCV | G. a. | G. g. % | H2 | Var. G.% | Var. P.% | Var. E.% |
|---|---|---|---|---|---|---|---|---|---|---|
| Plant height | 25 | 11.98 | 54.36 | 48.92 | 7.38 | 42.42 | 0.55 | 23.516 | 42.46 | 18.944 |
| Length of the main root | 19 | 19 | 37.35 | 26.56 | 2.1 | 26.26 | 0.48 | 2.22 | 4.55 | 2.33 |
| Number of seeds per plant | 35 | 35 | 91.96 | 60.27 | 6.42 | 81.94 | 0.66 | 14.8 | 22.33 | 7.533 |
| Number of pods per plant | 32 | 31.96 | 80.88 | 53.51 | 5.64 | 70.51 | 0.64 | 11.77 | 18.31 | 6.54 |
| Single plant biomass | 34 | 34.02 | 55.74 | 42.51 | 5.05 | 31.52 | 0.36 | 16.7 | 46.44 | 29.74 |
| Seed yield of single plant without pods | 32 | 32.8 | 63.12 | 44.86 | 1.98 | 45.29 | 0.49 | 1.9 | 3.88 | 1.98 |
| Total number of main branches | 24 | 2.87 | 3.63 | 3.14 | 0.258 | 1.07 | 0.166 | 0.095 | 0.571 | 0.476 |
| 100 grains weight | 20 | 20 | 62.03 | 85.42 | 3.48 | 26.39 | 0.15 | 20 | 126.96 | 6.96 |
| The number of sub-branches | 32 | 31.98 | 25.19 | 40.71 | 34.35 | 536.78 | 0.39 | 2.6 | 6.79 | 4.19 |
| Seed yield in a plant with pods | 35 | 3.93 | 81.25 | 54.93 | 0.74 | 14.76 | 0.59 | 4.52 | 7.61 | 3.09 |
| Grain yield (m2) | 22 | 22 | 212.98 | 124.27 | 72 | 248.3 | 0.97 | 1258.07 | 1298.78 | 40.71 |
| Biomass (m2) | 37 | 37.01 | 1101.2 | 199.214 | 267.92 | 1298.07 | 0.99 | 17200.63 | 17258.99 | 58.365 |
| Stubble weight | 39 | 39 | 74.88 | 53.69 | 84.88 | 52.74 | 0.47 | 3528.4 | 7468.35 | 3939.95 |
| SPAD chlorophyll index | 27 | 27 | 464.28 | 267.59 | 53.31 | 548.51 | 0.99 | 676.55 | 683.44 | 6.89 |
| Harvest index | 21 | 21.08 | 66.66 | 42.16 | 0.097 | 64.66 | 0.75 | 0.003 | 0.004 | 0.001 |
| Traits | Plant height | Length of the main root | Number of seeds per plant | Number of pods per plant | Single plant biomass | Seed yield in a plant without pods | Total number of main branches | 100 grains weight | The number of sub-branches | Seed yield in a pant with pods | Grain yield (m2) | Biomass (m2) | Stubble weight | SPAD chlorophyll index |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Plant height | ||||||||||||||
| Length of the main root | -0.29 | |||||||||||||
| Number of seeds per plant | -0.54 | 0.57 | ||||||||||||
| Number of pods per plant | -0.7 | 0.52 | 1 | |||||||||||
| Single plant biomass | 0.18 | 0.06 | 0.31 | 0.44 | ||||||||||
| Seed yield in a plant without pods | -0.19 | 0.28 | 1 | 1 | 1 | |||||||||
| Total number of main branches | 0.35 | 0.31 | -0.43 | -0.46 | 0.07 | -0.61 | ||||||||
| 100 grains weight | 0.57 | -0.59 | -0.44 | -0.28 | 0.72 | 0.4 | 0.45 | |||||||
| The number of sub-branches | 0.16 | -0.23 | 0.1 | -0.12 | 0.75 | 0.16 | -1 | -0.08 | ||||||
| Grain yield per single plant with pods | -0.13 | 0.28 | 1 | 1 | 1 | 1 | -0.42 | 0.41 | 0.17 | |||||
| Grain yield (m2) | 0.75 | 0.35 | -0.09 | -0.27 | 0.25 | -0.14 | 0.46 | 0.11 | 0.08 | -0.07 | ||||
| Biomass (m2) | 0.81 | 0.03 | -0.34 | -0.44 | 0.02 | -0.45 | 0.34 | 0.17 | -0.008 | -0.36 | 0.77 | |||
| Stubble weight | 1 | -0.14 | -0.45 | -0.69 | 0.07 | -0.56 | 1 | 0.32 | -0.07 | -0.41 | 0.95 | 1 | ||
| SPAD chlorophyll index | 0.27 | 0.75 | 0.31 | 0.08 | 0.31 | 0.23 | 0.33 | -0.13 | 0.16 | 0.19 | 0.64 | 0.34 | 0.5 | |
| Harvest index | -0.65 | 0.18 | 0.44 | 0.5 | 0.41 | 0.73 | -0.31 | -0.02 | 0.007 | 0.63 | -0.60 | -0.80 | -0.83 | -0.09 |
| Traits | Plant height | Length of the main root | Number of seeds per plant | Number of pods per plant | Single plant biomass | Seed yield in a plant without pods | Total number of main branches | 100 grains weight | The number of sub-branches | Seed yield in a pant with pods | Grain yield (m2) | Biomass (m2) | Stubble weight | SPAD chlorophyll index |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Plant height | 1 | |||||||||||||
| Length of the main root | -0.14 | 1 | ||||||||||||
| Number of seeds per plant | -0.67 | 0.22 | 1 | |||||||||||
| Number of pods per plant | -0.66 | 0.12 | 0.85 | 1 | ||||||||||
| Single plant biomass | 0.27 | -0.03 | 0.21 | 0.18 | 1 | |||||||||
| Seed yield in a plant without pods | -0.26 | 0.17 | 1 | 0.77 | 0.63 | 1 | ||||||||
| Total number of main branches | 1 | 0.46 | -0.11 | -0.22 | 0.81 | -0.26 | 1 | |||||||
| 100 grains weight | 0.83 | -0.28 | -0.49 | -0.23 | 0.58 | 0.22 | 0.5 | 1 | ||||||
| The number of sub-branches | 0.21 | -0.2 | 0.07 | -0.2 | 0.56 | 0.17 | -1 | -0.03 | 1 | |||||
| Seed yield per single plant with pods | -0.007 | 0.1 | 1 | 0.78 | 0.92 | 1 | 0.09 | 0.40 | -0.01 | 1 | ||||
| Grain yield (m2) | 0.92 | 0.09 | 0.03 | -0.05 | 0.24 | -0.13 | 0.01 | 0.18 | -0.11 | 0.15 | 1 | |||
| Biomass (m2) | 1 | -0.03 | -0.37 | -0.32 | -0.04 | -0.65 | 0.32 | 0.19 | -0.05 | -0.34 | 0.75 | 1 | ||
| Stubble weight | 1 | -0.08 | -0.8 | -0.5 | 0.07 | -0.78 | 1 | 0.35 | -0.02 | -0.33 | 0.92 | 0.98 | 1 | |
| SPAD chlorophyll index | 0.35 | 0.3 | 0.35 | 0.04 | 0.27 | 0.2 | 0.42 | -0.14 | 0.05 | 0.22 | 0.61 | 0.29 | 0.5 | 1 |
| Harvest index | -1 | 0.1 | 0.67 | 0.56 | 0.39 | 1 | -0.87 | -0.10 | -0.01 | 0.86 | -0.45 | -0.98 | -0.99 | -0.03 |
Table 7 Path coefficient analysis of yield component in chickpeas under irrigated conditions
| Component | Initial Eigenvalues (Extraction Sum of Squared Loadings) | ||||||
|---|---|---|---|---|---|---|---|
| Total | Variance % | Cumulative variance % | |||||
| 1 | 4.864 | 32.428 | 32.428 | ||||
| 2 | 4.098 | 27.320 | 59.748 | ||||
| 3 | 3.094 | 20.629 | 80.377 | ||||
| 4 | 1.588 | 10.589 | 90.966 | ||||
| Characteristics | PCAs | ||||||
| 1 | 2 | 3 | 4 | ||||
| Plant-seed-with-pod | .924 | − .099 | .100 | .278 | |||
| Plant-seed-without-pod | .914 | − .313 | .133 | .008 | |||
| SPAD | .833 | .493 | − .095 | .185 | |||
| Plant-biomass | .770 | .452 | .005 | .019 | |||
| seedweight100 | − .576 | − .446 | − .574 | .168 | |||
| Height | − .058 | .983 | .065 | .135 | |||
| Biomass | − .435 | .758 | .216 | .394 | |||
| Pod no. | .438 | − .695 | .386 | .306 | |||
| Yield | − .103 | .621 | .471 | .604 | |||
| Hay | − .141 | .534 | .393 | − .238 | |||
| R-length | .009 | − .057 | .901 | − .415 | |||
| HI | − .584 | − .273 | .701 | .067 | |||
| Main-branch | − .603 | − .249 | .698 | .078 | |||
| Seed-no | .557 | − .521 | .572 | .163 | |||
| Sub-brach | .355 | .487 | .187 | − .742 | |||
based on the PCA1 and PCA2
| Component | Eigenvalues (Extraction Sum of Squared Loadings) | ||||||
|---|---|---|---|---|---|---|---|
| Total | Variance % | Cumulative % | |||||
| 1 | 5.357 | 39.60 | 39.60 | ||||
| 2 | 3.546 | 25.90 | 65.5 | ||||
| 3 | 3.145 | 15.966 | 81.466 | ||||
| 4 | 2.084 | 13.896 | 95.362 | ||||
| Characteristics | PCAs | ||||||
| 1 | 2 | 3 | 4 | ||||
| Yield | .194 | .057 | .067 | .035 | |||
| Height | .150 | − .092 | .081 | − .137 | |||
| Root length | .094 | .268 | .001 | .039 | |||
| Seed no. | − .016 | .264 | − .034 | − .025 | |||
| Pod no. | − .059 | .187 | .014 | .057 | |||
| 100 Seed weight | .010 | − .288 | .310 | .180 | |||
| Biomass | .179 | .022 | − .029 | .030 | |||
| HI | − .156 | − .024 | .103 | − .014 | |||
| SPAD | .151 | .209 | .011 | − .014 | |||
| Plant biomass | .044 | − .075 | .321 | − .062 | |||
| Plant seedwithoutpod | − .038 | .043 | .240 | .003 | |||
| Mainbranch | .037 | .006 | .057 | .465 | |||
| Sub-mainbranch | .039 | .019 | .043 | − .452 | |||
| Plant-seedwithpod | − .026 | .026 | .266 | .023 | |||
| Hay | .189 | .042 | − .022 | .018 | |||
Table 10. Principle component analysis under rainfed conditions
|
Component |
Eigenvalues (Extraction Sum of Squared Loadings) |
||||||
|
Total |
Variance % |
Cumulative % |
|||||
|
1 |
5.357 |
39.60 |
39.60 |
||||
|
2 |
3.546 |
25.90 |
65.5 |
||||
|
3 |
3.145 |
15.966 |
81.466 |
||||
|
4 |
2.084 |
13.896 |
95.362 |
||||
|
Characteristics |
PCAs |
||||||
|
1 |
2 |
3 |
4 |
||||
|
Yield |
.194 |
.057 |
.067 |
.035 |
|||
|
Height |
.150 |
-.092 |
.081 |
-.137 |
|||
|
Root length |
.094 |
.268 |
.001 |
.039 |
|||
|
Seed no. |
-.016 |
.264 |
-.034 |
-.025 |
|||
|
Pod no. |
-.059 |
.187 |
.014 |
.057 |
|||
|
100 Seed weight |
.010 |
-.288 |
.310 |
.180 |
|||
|
Biomass |
.179 |
.022 |
-.029 |
.030 |
|||
|
HI |
-.156 |
-.024 |
.103 |
-.014 |
|||
|
SPAD |
.151 |
.209 |
.011 |
-.014 |
|||
|
Plant biomass |
.044 |
-.075 |
.321 |
-.062 |
|||
|
Plant seedwithoutpod |
-.038 |
.043 |
.240 |
.003 |
|||
|
Mainbranch |
.037 |
.006 |
.057 |
.465 |
|||
|
Sub-mainbranch |
.039 |
.019 |
.043 |
-.452 |
|||
|
Plant-seedwithpod |
-.026 |
.026 |
.266 |
.023 |
|||
|
Hay |
.189 |
.042 |
-.022 |
.018 |
|||
In this study, traits Plant height at harvest time, number of seeds per plant, number of pods per plant, single plant biomass, seed yield of single plant without pods, the total number of main branches of the plant, seed yield of single plant with pods, grain yield (m2), biomass (m2), the weight of the stubble and harvest index had a suitable genetic correlation with other traits, which could be applied in breeding programs. The highest percentage of heritability in normal moisture conditions was related to traits biomass (m2), the number of pods per plant, and SPAD chlorophyll index at the fruiting time, and the highest percentage of heritability in drought stress was related to traits grain yield (m2), biomass (m2) and SPAD chlorophyll index at the time of fruiting, consequently, these traits can also be used in chickpea breeding programs. Considering that these traits have been evaluated in both normal and drought-stress environmental conditions. They would be used in breeding for tolerance to drought stress. To identify drought-tolerant cultivars and investigate traits that can survive drought, researchers use the calculation of genetic parameters such as heritability for all morphological, physiological, and phenological traits, of course, significant and diverse. The path analysis approach advocates for a multi-trait selection strategy to improve yield potential in crops. The PCA results under irrigated and rainfed conditions provide a comprehensive understanding of how different traits contribute to genetic diversity. The variation in trait grouping under different conditions highlights the influence of environmental factors, particularly water availability, on the importance and relationships of agronomic traits.
Author Contribution
Mehdi kakaei's contribution: Set up experiment, Collection data, wrote the manuscript textMohsen farshadfar's contribution: wrote part of the manuscript text, prepared tables and figures, reviewed the manuscript
Acknowledgement
We would like to thank the authority of Payame Noor University of Assadabad for providing us with the facilities to complete this experiment.
Data Availability
The original date has been prepared in the Excel file. Whenever this data is needed, it will be provided to you.
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No competing interests reported.
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