Introduction
Chickpea is the world's most important grain legume crop. Micro-nutrient malnutrition has several ill-effects on human health and high healthcare costs all over the world (Welch and Graham, Reference Welch and Graham2002). Chickpea is a good source of minerals; it has the potential to contribute to daily Fe and Zn intake and can help to alleviate hidden hunger (Jukanti et al., Reference Jukanti, Gaur, Gowda and Chibbar2012). A few studies conducted earlier using different market classes of chickpea confirmed that chickpea possess higher seed Fe and Zn content as compared to staple cereals (Jukanti et al., Reference Jukanti, Gaur, Gowda and Chibbar2012). Different market classes like desi versus Kabuli types have been evaluated for nutrient concentrations in earlier studies (Aliu et al., Reference Aliu, Kaul, Rusinovci, Shala-Mayrhofer, Fetahu and Zeka2016). Recently, a study has also evaluated a set of wild relatives including lines from primary gene pool species and a few lines from secondary gene pool species for seed nutrient content (Von Wettberg et al., Reference Von Wettberg, Chang, Başdemir, Carrasquila-Garcia, Korbu, Moenga and Cordeiro2018). However, reports on all gene pools of chickpea for comparative nutrient densities are meagre (Kahraman et al., Reference Kahraman, Pandey and Khan2017). In addition, there is hardly any report available where nutrient concentrations in chickpea have been evaluated from North-Western Himalayas of the state Jammu and Kashmir, India despite the fact that the state high hills of Jammu and Kashmir are the natural habitat for tertiary gene pool species of chickpea. Therefore, there is an urgent need to evaluate chickpea genotypes belonging to all gene pools to fill the gaps in the available literature. We evaluated a set of 40 chickpea genotypes including members of both cultivated chickpea as well as wild chickpea from all gene pools for key micro- and macro-nutrients. Most promising genotypes with high micro-nutrient concentration have been identified for chickpea breeding programmes, transcriptomics, applied genomics and crop biotechnology programmes.
Experimental details
A set of 40 Chickpea genotypes including desi chickpea, desi stay green, Kabuli chickpea and wild relatives belonging to different gene pools were evaluated for nutrient concentrations (online Supplementary Table S1). The wild relatives included Cicer reticulatum, Cicer echinospermum and Cicer microphyllum. The seed material of tertiary gene pool species C. microphyllum was collected from its wild natural habitat in Leh Ladakh region of the state of Jammu and Kashmir, India. All standard agronomic practices were followed in order to raise a good crop.
The micro-nutrient concentrations in a set of 40 genotypes were estimated and involved following procedure briefly.
(i) Seeds of 5–10 representative plants were selected and surface cleaned with 70% ethanol to remove soil and dust and further oven dried at 55–60°C. (ii) Random sample of 20 seeds from each genotype was finely ground to flour. (iii) Ground seed samples (500 mg) were digested using 9:4 diacid mixture (HNO3:HClO4) (Dutta et al., Reference Dutta, Chatterjee, Sarkar, Singh, Boopathi, Kuotsu, Vikramjeet, Akoijam, Saha, Vanlalhmangaiha, Malsawmzuali, Chowdhury and Lungmuana2016). The aliquot was used to quantify micro- (Zn, Fe, Cu, Mn) and macro- (Mg, Ca, K) nutrients by atomic absorption spectrophotometer against standard solutions of known concentration. (iv) Data were statistically analysed using MS-Excel 2007.
Discussion
Chickpea is one of the most important legume crops inherently loaded with micro- and macro-nutrients for nutritional security in the world. Our results revealed significant variation for seed Zn and Fe concentrations among different genotypes including cultivated and wild genotypes. The wild genotypes possessed higher seed Zn, Fe and K concentration than cultivated chickpeas (Table 1). Among the cultivated gene pool, desi chickpeas possessed significantly higher Zn concentration as compared to Kabuli types while the reverse was true for Fe concentration (Table 1). These findings got support from some earlier studies (Ibáñez et al., Reference Ibáñez, Rincón, Amaro and Martínez1998; Wang et al., Reference Wang, Hatcher, Tyler, Toews and Gawalko2010). Our results indicated that black-seeded chickpea are best for alleviating seed Zn deficiency. The pea-shaped chickpea possess highest seed Zn concentration than both desi and Kabuli types indicating transgressive segregation for seed Zn content in pea-shaped chickpeas.
Variation for micro- and macro-nutrients in different cultivated versus wild gene pools and among different cultivated chickpea types/colour classes
Similarly, for seed Fe concentration within desi types indicated that desi brown types are best for alleviating Fe deficiency. The pea shaped was found to possess intermediate seed Fe concentration (between desi and Kabuli types) (Table 1).
The cultivated chickpeas have Cu concentration much higher than wild types (Table 1). Seed Cu concentration in desi chickpeas was found to be more than Kabuli chickpeas. Similar results were also reported in some earlier studies (Chavan et al., Reference Chavan, Kadam, Salunkhe and Beuchat1986).
Seed Mn concentration revealed that the average Mn concentration in desi chickpeas was less than Kabuli chickpeas (Table 1). The variation in results in different studies may be attributed to different germplasm used under different environmental conditions and different estimation procedures.
The analysis of the macro-nutrients between cultivated and wild gene pools indicated that wild chickpeas possess more K than cultivated but the other two macro-nutrients such as seed Ca and Mg showed a reverse trend (Table 1). The results indicated positive domestication effects on seed Ca and seed Mg concentration while as negative domestication effects on seed K concentration and this also indicates that K could be improved by involving wild gene pools in crossing programmes with cultivated chickpeas.
The nutrient analysis among wild relatives revealed some important facts such as C. microphyllum is inferior in terms of nutrient availability (Zn, Fe, Cu, Mn K, Ca and Mg) than both C. reticulatum and C. echinospermum (Table 2). However, more efforts need to be made in future to collect more accessions of C. microphyllum from their natural habitat to test their nutrient status. Cicer echinospermum was found to possess more seed Fe, Mn, Ca and Mg than C. reticulatum; C. reticulatum was found to possess more seed Zn and K. For seed Cu concentration, the two species did not show any difference (Table 2). The results of seed K and Zn content got support from an earlier study involving the same material from UC-Davis (von Wettberg et al., Reference Von Wettberg, Chang, Başdemir, Carrasquila-Garcia, Korbu, Moenga and Cordeiro2018).
Variation for micro- and macro-nutrients in different wild chickpea gene pools
In summary, cultivated chickpea was found much superior to wild chickpeas in terms of nutrient density indicating positive domestication effect. Among cultivated types, desi chickpea genotypes were found superior to Kabuli types and these findings got support from some earlier studies (Veenakumari et al., Reference Veenakumari, Kasturiba and Vijaykumar2017).
The best genotypes identified from our study (online Supplementary Table S2) can be selected as potential donors for targeted micro-/macro-nutrient bio-fortification programmes in future. However, it is advised to evaluate these genotypes for micro and macro-nutrients again under the range of environments before their use in future breeding or genomics programmes.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/S147926211900025X
