# Diversity in Selected Grain Mineral and Protein among Pigeonpea Landraces
## 4 Discussion
Some of the pigeonpea landraces also contained significantly higher Zn than chickpea (21.1-28.3 mg/kg). Zn is essential for different biological functions such as wound healing, protection from oxidative damage by reactive oxygen species and prevention of both pancreatic and prostate cancer [37]. The two landraces ('G-13' and 'G-09') which contained significantly high Cu and Zn could also be useful in mineral biofortification in pigeonpea. Various studies reported successful improvements in micronutrients such as Fe and Zn in legumes including pigeonpea through biofortification [38; 39; 40; 41]. The highest grain protein content (23.50%), which was attained by the landrace 'G10', was comparable but lower than the variability (23.35-29.50%) which was observed among 600 pigeonpea genotypes from a regional genebank in India [42]. Nonetheless, this study identified useful landraces that contain a good balance of protein and mineral content; hence, they can be use as donor parental materials in pigeonpea breeding programs aimed at enhancing grain protein content to benefit end-users, particularly in poor rural communities that are prone to malnutrition. Correlation analysis is critical for detecting the relationship between nutritional features that can be used to determine effective breeding strategies [43]. In this regard, positively correlated mineral elements could make concomitant biofortification with multiple minerals easy. However, significant negative correlations were observed between grain protein and Fe and Mn. Nonetheless, the improvement of Ca content in pigeonpea is favoured by Mg selection since a significant positive correlation between Ca and Mg was evident among the landraces. Various studies reported that Fe and Mn are cofactors in several enzymes (such as arginase, glutamine synthetase, Mn superoxide dismutase and pyruvate carboxylase), thus suggesting that, perhaps, deficiencies in these minerals could diminish grain protein content [44; 45]. In contrast, excess Mn was reported to decrease some proteins associated with signalling pathways as well as negatively affect the utilization of other minerals such as Ca and Fe and eventually cause oxidative stress [45]. Principal component analysis (PCA) is an important tool for determining the significance of various traits and genotypes based on their contribution to the overall variation. Mineral elements such as Ca, Mg, Mn and P could be considered = the most informative for evaluating genetic diversity for the grain and protein content among the pigeonpea landraces due to their strong association with the first principal component (PC1). In this regard, the landraces such as 'G-03', 'G-04' and 'G-05' which were strongly associated with Ca, P, Mg and Mn could be considered for introgression genes that control the accumulation of these nutrient elements. Similar studies involving PCA showed that pigeonpea and lentil were characterized by high calcium and protein contents, respectively [35; 42]. The six landraces ('G-03', 'G-04', 'G-10', 'G-01', 'G-09' and 'G-14') which were positioned far from the origin of the biplot indicated that they were the most distinct and probably possessed unique genes associated with the grain traits. The cluster analysis partitioned the landraces into three major groups, revealing considerable intra-cluster variability. Two landraces ('G-04' and 'G-09'), which were grouped as singletons, were among the most divergent for the traits. Similar studies in pigeonpea also revealed high genetic diversity based on cluster analysis [42]. The pigeonpea genotypes that were grouped together may not be recommended for hybridization as they could be related. However, molecular tools can be used to validate the genetic similarity of the landraces with regard to the grain mineral and protein content. This is partly because phenotypic expression is influenced by the environment and provides a proxy indicator of genetic variation, but molecular markers are more reliable.