Genetic and physiological relationships in N, P and K mobilisation in some sorghum mutants and parents

The mutation breeding program of alteration in plant type in two local Sorghum varieties resulted in several productive mutants of which 16 are far superior to the parents CRP, CBA and recommended hybrids. An earlier analysis of leaf area and photosynthetic efficiency revealed a diversity of mechanisms between mutants of the same yield group. Differences in the transfer of nutrients from leaf to the panicle were also indicated. Further analysis of the partition of nutrients in the panicle, flag leaf and rachis for N, P and K revealed that most of the mutants are at least equal to the parent in grain N but are superior in N content of flag leaf and rachis. Similarly, three mutants had a higher P content in grain than CRP and all other mutants were equal to CRP. Two mutants had more P in the flag leaf but this was not reflected in the grain. However, no differences were observed for the K content in the flag leaf, grain and rachis. The interrelations of the nutrients in different plant parts suggest that each mutant has a different pattern of nutrient accumulation and transfer. It could be concluded that selection for flag leaf N and P can improve grain N and P. There was no negative association between N and P accumulation in different plant parts. No adverse association was observed for other combinations. A study on the grain digestability of the mutants confirmed that the quality of the protein was not adversely affected in this material. This study indicated that simultaneous improvement of grain yield and grain N, P and K can be obtained even among the few mutants generated in this breeding program contrary to the belief of some cereal breeders that grain yield and its N content have a major negative association limiting the improvement of yield and protein content simultaneously.