Within-Row Spacing Influences on Diverse Sorghum Genotypes: I. Morphology

Plant morphology influences forage quality. Plant population has been shown to influence sorghum [Sorghum bicolor (L.) Moench.] morphology, but morphology also is affected by the genetic diversity in sorghum. Our objective was to determine changes in morphology of four diverse sorghum genotypes as influenced by within-row spacing. Four sorghum genotypes (IS-0469, IS-0865, IS-954063, and IS-2952) designated G1, G2, G3, and G4, were sown at five within-row spacings of 5, 10, 15, 30, and 60 cm at two field locations in 1986 and 1987. Differences among genotypes and within-row spacings were significant (P > 0.05) for most morphological characteristics. Number of shoots per plaint increased as within-row spacing increased by 4.8 shoots plant⁻¹ for GI, compared to an increase of only 1.6 shoots plant⁻¹ for the genotype with the lowest tillering potential (G3). Shoot diameter also increased 53.2% and 128.9% for main shoot and tillers, respectively, averaged over genotypes as within-row spacing increased. As within-row spacing increased from 5 to 60 cm, height declined from 2.0 to 1.7 m, across genotypes. As within-row spacing imcreasied from 5 to 60 cm, leaf/steam ratio increased linear by from 0.9 to 1.2 across genotypes. Morphological characteristics responded in varying degrees to changes in within row spacing, and were Significantly influenced by genotype. Increased within-row spacing: resulted in increased light penetration and reduced within-row competition. Consequently, sorghum morphology was altered through changes in within-row spacing and these changes were influenced by genetic diversity among sorghum genotypes. Breeders selecting for forage quality in diverse sorghum genotypes need to be aware of plant population effects on morphology. Contribution from the Purdue Univ. Agric. Exp. Stn., West Lafayette, IN 47907. Journal Paper no. 11,521.