Structure of variation among morphological and physiological traits in three pearl millet composites

The plant breeder's task of improving and stabilizing many plant traits simultaneously is complicated by interrelationships that occur among the traits. Factor analyses were conducted on three phenotypically diverse pearl millet [Pennisetum glaucum (L.) R. Br.] composites to describe the structure of relationships among yield, morphological, and physiological traits. Approximately 1000 S0 spaced-plants from each composite were evaluated for 20 traits, and random samples of 289 S1 progenies from each composite were evaluated for 18 of these traits. Factors extracted in S0 and S1 populations identified unique sets of traits that were interrelated along axes of (a) biological yield, (b) panicle size, (c) dry matter partitioning and (d) compensation between number and size of seeds. Several plant traits had large loading coefficients on the ‘Biological Yield’ and also, but with opposite signs, on the ‘Dry Matter Partitioning’ factor. The traits having large loading on these two factors differed between space-planted and normal-density stands, showing that environmental conditions contributed to the associations observed among traits. Correlations of S1 with parental S0 factor scores for the ‘Biological Yield’, ‘Panicle Size’ and ‘Seed Paramters’ factors produced significant correlation coefficients, indicating that these trait complexes had a genetic basis. The implications of these results for millet breeding are discussed