Exploring the phenotypic performance of chickpea (Cicer arientinum L.) lines for improved breeding

Introduction

Chickpea (Cicer arietinum L.) is the world's second most important grain legume after dry beans (Phaseolus sp.) (Mir et al., 2021) [6] . It is a self-pollinated diploid species having a chromosome number of 2n = 2x = 16 (Upadhyaya et al., 2008) [11] with a comparatively small genome size of 738 Mbp (Varshney et al., 2013) [12] . The Cicer genus belongs to the family Leguminosae, the sub-family Papilionaceae, and the tribe Cicereae. It is considered to have originated in southeastern Turkey and the adjoining Northern region of Syria (Saxena and Singh, 1987) [9] and evolved from its wild progenitor, Cicer reticulatum L., by selection (Maesen and Pundir, 1984) [5] . The geographic distribution differs for the two types of chickpeas; kabuli chickpeas are grown in temperate regions, whereas the desi type is grown in semi-arid regions. The "kabuli" (also known as macrosperma) types are usually taller and have white flowers, a lack of anthocyanin pigmentation on stems, and large white, beige, or cream-colored seeds with a "ram's head" shape, a thin seed coat, and a smooth seed surface. The "desi" (also known as microsperma) types are generally shorter, possessing small leaflets, pods, seeds, and predominantly pink flowers, anthocyanin pigmentation on stems, and a colored and thick seed coat (Moreno and Cubero, 1978) [7] . Nutritionally, chickpea seed is enriched with protein (20-60%), carbohydrate (62%), fat (4%), essential amino acids, vitamins A, B, and C, minerals, soluble and insoluble fiber (Bodake et al., 2014) [2] . Chickpea can fix the atmospheric nitrogen in the root nodules through biological nitrogen fixation by rhizobium bacteria, which increases the soil fertility in the dry lands (Alyemeni et al., 2016) [1] . The productivity of chickpea is reduced due to different biotic and abiotic stresses under different agroclimatic conditions. The major constraints affecting chickpea production are fusarium wilt, ascochyta blight (AB), dry root rot, botrytis gray mould, pod borer, drought, heat, salinity, and chilling are the major stresses which adversely affect the chickpea production. It faces production limitations due to the adverse impacts of various biotic and abiotic stresses (Mannur et al., 2019; Suthar et al., 2021) [4,10] . Among biotic stresses, Fusarium wilt (FW), a fungal disease caused by the soilborne pathogen Fusarium oxysporum f. sp. ciceri (Foc) (Jamil and Ashraf, 2021) [4] , can lead to complete yield loss in chickpea under favorable conditions (Jendoubi et al., 2017) [5] . With a global annual production of approximately 16.53 million tons, chickpea is cultivated in more than 50 countries. India accounts for the largest share, producing 12.27 million tons from 10.47 million hectares, with an average yield of 1,171.6 kg/ha (FAOSTAT, 2023) [3] . In India, six major chickpea-producing states are Madhya Pradesh, Maharashtra, Rajasthan, Uttar Pradesh, Andhra Pradesh, and Karnataka. Madhya Pradesh leads in chickpea production with a total share of 40.93%, followed by Maharashtra with a total share of 15.84% in chickpea production. Morphological characterization involves the systematic evaluation of observable traits in crop species and serves as a fundamental approach for the identification and classification of breeding lines. In chickpea, it facilitates the differentiation of varieties or breeding lines based on distinct morphological attributes and enables the detection of genetic variation or mutations within populations. Furthermore, this approach provides valuable information that enhances breeders' understanding of the genetic basis underlying morphological traits. In addition, morphological characterization contributes to phylogenetic analysis by offering insights into evolutionary relationships, as well as the origin, development, and functional significance of traits across diverse genotypes (Nandedkar et al., 2021) [10] . Chickpea plants have several stable morphological characters as well as qualitative characters that can be utilized to assess the variability among the breeding lines. The present study was carried out to assess the phonological and morphological variability among the 133 BC 1 F 1 and 196 BC 2 F 1 lines and to identify the best-performing lines based on yield and component traits to be utilized in future breeding programs.

Materials and methods

Plant material

The present investigation was carried out at the Experimental field, Biotechnology Centre, Department of Agricultural Botany, Post Graduate Institute, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, Maharashtra, India, which is situated between 20.70 °N latitude and 77.02 °E longitude and 286 meters above mean sea level. Experimental material comprised of 2 parents, 66 BC 1 F 1 lines, and 123 BC 2 F 1 lines. The recurrent parent PKV Kabuli-4, donor parent WR 315, and BC 1 F 1 seeds were sown in single-row lengths of 3 m with a spacing of 45 cm x 15 cm. The standard agronomic practices were carried out for the better growth and development of the crop. Morphological observations of the backcross populations along with the two parents were recorded on the 8 morphological and yield-attributing traits as per National guidelines for the conduct of tests for Distinctness, Uniformity, and Stability (DUS) (PPV and FR authority, GOI, New Delhi, 2007). The method of taking observation, the appropriate stage, and the measuring scale of various morphological, yield-attributing traits are presented in Table 1. The details of experimental conditions and crop management practices are presented in Table 2. The details of morphological observations Plant height at maturity (cm) was measured from the base of the plant to the tip of the main shoot in five randomly selected plants, and the mean value was calculated. Days to 50% flowering were recorded as the number of days from sowing to the stage when 50% of the plants in each genotype had started flowering. The number of branches per plant was counted at maturity, and the average was worked out. Days to maturity were recorded as the number of days from sowing to full physiological maturity of each genotype. The number of pods per plant was counted at maturity/harvest from selected plants. Seed shape was classified based on chickpea descriptor standards into angular, owl's head, and pea-shaped categories, while seed colour was also recorded according to standard chickpea descriptors for each backcross line. The 100-seed weight (g) was determined by weighing 100 randomly selected seeds; where fewer than 100 seeds were available, the weight was recorded and then converted proportionally to 100-seed weight.

Results and Discussion

Phenotypic performance of chickpea BC1F1 population derived from the cross F1 × PKV Kabuli-4 Phenotypic evaluation for agronomic and yield-attributing traits to identify the plants compared to or superior to the recurrent parent was carried out. BC 1 F 1 plants were evaluated for morphological characters like plant height, days to 50% flowering, number of primary branches, days to maturity, and pods per plant. The morphological observations recorded during the Rabi 2021-2022 and screening of the BC 1 F 1 population are given in Table 3. The field view of the BC 1 F 1 population of chickpea is shown in Figure 1.

Plant height among the backcross lines ranged from 29 cm (BC 1 F 1 -44) to 75 cm (BC 1 F 1 -22), with a mean of 54.83 cm, which was higher than the mean plant heights of the parents, PKV Kabuli-4 (48 cm) and WR 315 (42 cm). The maximum plant height was recorded in BC 1 F 1 -22 (75 cm), and four plants were found to be at par with this genotype. A total of 54 plants exhibited superior plant height compared to the recurrent parent PKV Kabuli-4. The taller plants, namely BC 1 F 1 -22 (75 cm), BC 1 F 1 -37 (71 cm), and BC 1 F 1 -40 (67 cm), may be considered promising for traits associated with vigorous growth and higher biomass production. Days to 50% flowering among the backcross lines ranged from 48 days (BC 1 F 1 -48) to 68 days (BC 1 F 1 -16), in comparison to the parental means of 50 days for PKV Kabuli-4 and 58 days for WR-315. The earliest flowering was observed in BC 1 F 1 -18 (48 days), which was earlier than the recurrent parent, while nine plants were found to be at par, and two plants exhibited fewer days to 50% flowering than PKV Kabuli-4. The early flowering lines identified were BC 1 F 1 -18 (48 days), BC 1 F 1 -21 (49 days), and BC 1 F 1 -1, BC 1 F 1 -10, BC 1 F 1 -12, BC 1 F 1 -17, BC 1 F 1 -26, and BC 1 F 1 -29 (approximately 50 days), which may be useful for early maturity breeding programmes.

The number of primary branches in BC 1 F 1 progenies ranged from 2 (BC 1 F 1 -5) to 9, with a mean of 5.51, compared to the mean values of 3 and 7 observed in the recurrent and donor parents, respectively. The highest number of primary branches (9) was recorded in BC 1 F 1 -25, BC 1 F 1 -33, BC 1 F 1 -35, BC 1 F 1 -45, BC 1 F 1 -52, and BC 1 F 1 -61. A total of 12 plants were found to be at par, while 53 plants exhibited a higher number of primary branches than the recurrent parent, PKV Kabuli-4. This trait is of significance as a greater number of branches provides more potential sites for pod development. Days to physiological maturity among the BC 1 F 1 progenies ranged from 101 days after sowing (DAS) in BC 1 F 1 -12, BC 1 F 1 -33, and BC 1 F 1 -52 to 121 DAS in BC 1 F 1 -14, BC 1 F 1 -35, and BC 1 F 1 -54, compared to 115 and 109 days for the parents PKV Kabuli-4 and WR-315, respectively. The mean days to maturity were 111.37. A total of four plants were found to be at par, while 44 plants matured earlier than the recurrent parent, PKV Kabuli-4. The earliest maturing lines were BC 1 F 1 -12, BC 1 F 1 -33, and BC 1 F 1 -52 (101 DAS), whereas BC 1 F 1 -14, BC 1 F 1 -35, and BC 1 F 1 -54 (121 DAS) were identified as late maturing lines. Early maturing genotypes may be advantageous for drought escape, while late maturing ones may offer higher yield potential due to longer growth duration. The number of pods per plant was recorded and ranged from 4 for (BC 1 F 1 -44) to 176 for (BC 1 F 1 -55), and the mean was 50.33 as compared to 60 (PKV Kabuli-4) and 75 (WR-315) parents. The highest number of pods per plant was observed in plant BC 1 F 1 -28, i.e., 176, and the mean is 50.33; 22 plants had more pods than the PKV Kabuli-4. Top performer lines are BC 1 F 1 -28 (176 pods) (Outstanding), BC 1 F 1 -35 (131 pods), BC 1 F 1 -6 (117 pods), BC 1 F 1 -48 (117 pods), BC 1 F 1 -25 (108 pods), BC 1 F 1 -58 (105 pods), BC 1 F 1 -40 (103 pods), and BC 1 F 1 -41 (102 pods). These are elite yield lines. Seed shape was classified based on chickpea descriptor standards into angular, owl's head, and peashaped categories. Among the BC 1 F 1 progenies, 26 plants exhibited angular seed shape, 22 showed owl's head shape, and 18 displayed pea-shaped seeds. Angular seed shape was the most frequent, followed by pea-shaped (moderately distributed) and owl's head types, which were also significant. The variation in seed shape may be utilized depending on breeding objectives, such as market preference or genetic trait characterization. Seed colour in the BC 1 F 1 population was recorded based on chickpea descriptor standards, revealing considerable variation among the progenies. A total of 9 BC 1 F 1 plants exhibited white seed colour similar to the recurrent parent, PKV Kabuli-4, while the remaining lines showed a wide range of colours, including brown/dark brown, yellow/yellow-brown, beige, and mosaic types. This broad diversity in seed colour is valuable for genetic variability and can be effectively utilized in selection programmes depending on breeding objectives and market preferences.

Best overall BC1F1 backcross lines (Combined traits)

Based on pod number, branching ability, and acceptable maturity duration, several BC 1 F 1 lines were identified as promising. Among these, BC 1 F 1 -28 exhibited the highest yield potential with 176 pods per plant. Other superior lines included BC 1 F 1 -35 (high pod number coupled with a greater number of branches), BC 1 F 1 -25 (combining high branching with high pod production), BC 1 F 1 -40 (high pod number along with good plant height), and BC 1 F 1 -41 (showing overall balanced performance). Additionally, BC 1 F 1 -6 and BC 1 F 1 -48 were also identified as promising due to their strong pod-bearing capacity. These lines may be considered potential candidates for further selection and advancement in breeding programmes. The descriptive statistics of the BC1F1 population are presented in Table 4.

Phenotypic performance of chickpea BC2F1 population derived from cross BC1F1 × PKV Kabuli-4 for different morphological traits

The phenotypic performance of BC 2 F 1 plants was evaluated with respect to plant height, days to 50% flowering, number of primary branches, days to maturity, number of pods per plant, seed shape, seed colour, 100 seed weight, and the results are presented in Table 5. Plant height ranged from 21 cm in BC 2 F 1 -40 to 79 cm in BC 2 F 1 -87, while the recurrent parent PKV Kabuli-4 and the donor parent exhibited plant heights of 48 cm and 42 cm, respectively. The maximum plant height was recorded in BC 2 F 1 -87 (79 cm). In total, three plants were found to be comparable to the recurrent parent, whereas 71 plants showed superior plant height compared to PKV Kabuli3, while the 100-seed weight of BC 2 F 1 progenies along with the donor parent (WR 315) and recurrent parent (PKV Kabuli-4) is shown in Figure 4. Seed shape was assessed as per chickpea descriptors, namely angular, owl's, and pea types. Both parents exhibited an angular seed shape. Among the BC 2 F 1 progenies, 52 plants showed an angular seed shape, 39 plants had an owl's seed shape, and 32 plants exhibited a pea seed shape. A greater proportion of BC 2 F 1 plants expressed the angular seed shape, similar to that of the parents. Seed colour was evaluated based on chickpea descriptors in the BC 2 F 1 population, and 17 BC 2 F 1 plants exhibited white seed colour similar to the recurrent parent PKV Kabuli-4.

Statistical conclusion of the phenotypic performance of the BC2F1 population

"Analysis of variability revealed considerable differences among BC 2 F 1 genotypes for all traits. The highest variability was observed for the number of pods per plant and 100-seed weight, indicating strong scope for selection. Moderate variability was recorded for plant height and number of primary branches, whereas days to 50% flowering and days to maturity showed relatively low variability, suggesting stability of these traits."

Interpretation of the genetic parameters of the BC2F1 population

The analysis of yield and its component traits revealed considerable variability and differing responses to selection. Estimates of genetic variability, heritability, and genetic advance for chickpea traits are presented in Table 6. Pods per plant exhibited very high genotypic and phenotypic coefficients of variation along with high heritability (87%) and very high genetic advance (93%), indicating the predominance of additive gene action and suggesting that this trait is highly amenable to direct selection. Similarly, 100-seed weight showed high GCV and PCV, coupled with high heritability (74%) and substantial genetic advance (43%), reflecting strong genetic control and its suitability for improving seed size, particularly in kabuli-type genotypes. Primary branches per plant displayed moderate to high variability with high genetic advance, emphasizing its importance as a key yield-contributing trait and its effectiveness for selection. Plant height exhibited moderate variability and good heritability, indicating that it can also be improved through selection, albeit with moderate progress. In contrast, flowering and maturity traits recorded low GCV and PCV, along with moderate heritability and low genetic advance, suggesting greater environmental influence and limited scope for improvement through direct selection. Overall, the results indicate that traits governed by additive gene action, particularly pods per plant and 100-seed weight, offer significant potential for genetic improvement through selection, whereas traits like flowering and maturity may require alternative breeding strategies.

Conclusion

Chickpea is a rich source of nutrition and is ranked second amongst food legumes after the common bean. It is considered one of the important sources of proteins, carbohydrates, and minerals, hence called "Poor man's meat". Chickpea has high nitrogen content, due to its ability to fix atmospheric nitrogen (N) through biological nitrogen fixation, and improves soil fertility, particularly in drylands. Chickpea is grown on a large scale, but its productivity and production are reduced due to a variety of biotic and abiotic factors, including Fusarium wilt, Ascochyta blight, insects, nematodes, parasitic weeds, drought, salinity, waterlogging, high temperatures, and chilling. Two fungal diseases, Ascochyta blight and Fusarium wilt, are economically significant diseases of chickpea. Among the biotic stresses, Fusarium wilt caused by Fusarium oxysporum f. sp. ciceris is the major disease limiting chickpea productivity in India.

The phenotypic performance of the BC 1 F 1 population was checked for different agronomic traits. The plant height ranged from 29cm to 75cm, and 54 plants were superior to the recurrent parent PKV Kabuli-4. The lowest days to 50% flowering were observed, i.e., 48 days, which is less than the recurrent parent. The highest number of primary branches was observed, i.e., 9, which is more than the mean value of recurrent and donor parents. The total of 12 plants has an equal number of primary branches, and 53 plants are superior to the recurrent parent PKV Kabuli-4. The lowest days to maturity were recorded, i.e., 101 days, which is less than both parents. The 4 plants were equivalent, and 44 plants had fewer days to maturity than the recurrent parent PKV Kabuli-4. Up to 176 pods per plant were recorded, and 22 plants had more pods than the PKV Kabuli-4.

The 26 plants showed the angular seed shape, 22 plants showed the owl's seed shape, and 18 plants showed the pea seed shape. The 9 BC 1 F 1 plants indicated the white seed colour, as the recurrent parent of PKV Kabuli-4. The phenotypic performance of the BC 2 F 1 population was evaluated for different agronomic traits. The maximum plant height (cm) was seen in plant BC 2 F 1 -87, which measured 79cm, and a total of three plants were found comparable, and 71 plants were superior to the recurrent parent PKV Kabuli-4. The plants BC 2 F 1 -18, BC 2 F 1 -73, and BC 2 F 1 -113 took a minimum days to 50% flowering, i.e., 46 days, which was less than the recurrent parent (50 days), and a total of 14 plants were comparable for the trait, with eight plants having fewer days to 50% flowering than PKV Kabuli-4. The total of 48 plants had an equal number of primary branches, and 51 plants were superior to the recurrent parent PKV Kabuli-4 for this trait. The lowest days to maturity were recorded, i.e., 101 days, which is less than both parents. The 7 plants were equivalent, and 79 plants had fewer days to maturity than the recurrent parent PKV Kabuli-4. The highest number of pods per plant was observed in plant BC 2 F 1 -81, i.e., 86, and the mean of the population was 26.70. The 2 plants were equivalent, and 9 plants had more pods than the PKV Kabuli-4. The highest 100 seed weight was found in BC 2 F 1 -58 and BC 2 F 1 -101. The higher number of BC 2 F 1 plants had an angular seed shape like the parents. The 17 BC 2 F 1 plants indicated the white seed colour, like the recurrent parent PKV Kabuli-4.

Acknowledgement

AcknowledgementsThe authors are thankful for the support and suggestions provided by the Biotechnology Centre, Department of Agricultural Botany, Post Graduate Institute, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, to provide research material, and those who directly or indirectly helped in the research program.

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