Genetic and agronomic studies of non-elongating sub-crown internode in spring barley (Hordeum vulgare L.).

Abstract

This dissertation reports on studies of non-elongating subcrown internode (NE) in spring barley and its role in plant performance under reduced water use. Chapter 1 covers the inheritance study of NE. Chapter 2 reports a two year study of seeding depth and subcrown internode length (SIL) effects in performance of barley, wheat and durum genotypes. Chapter 3 reports on genetic and environmental factors that affect crown depth and crown root development under a one-irrigation cultural regime. The research was conducted between 1990 and 1993 under field and greenhouse conditions. The NE character appears to be controlled by a major recessive gene. Selecting the NE trait is relatively easy by conventional plant breeding. SIL variation is continuous and seems regulated by several modifiers that interact strongly with the environment. Expression of genes for SIL require deep seeding. Under field conditions and regardless of genotype, shallow seeding inhibited SIL but produced shallow crowns while deep seeding stimulated SIL but produced deeper crowns. Deep seeding increased yield, 100-seed weight, seeds/spike, an days to anthesis, but reduced tillers/m² and plant height in most genotypes. Short SIL genotypes (≤2.6 mm) were more favored by deep seeding than long SIL genotypes (≥8.2 mm). The correlations of SIL and crown depth with yield and yield components increased with deep seeding. The time of crown root initiation varied tremendously among barley plants of CC XXXIX. Crown roots/plant could be predicted by leaves/plant (r = 0.92; P ≤ 0.01). Most plants in CC XXXIX had crown root initiation around the 3-leaf stage. The rate of soil moisture decreased with soil depth. Soil moisture between day 7 and day 21 after the planting irrigation was depleted by 77% at 0-2.5 cm and by 40% at 12.5-15 cm depth. The construction of specific soil water tension curves based on soil moisture distribution over a dry period after the planting irrigation could be of great value in determining optimal seeding depth, choice of variety, and establishment of selection criteria for crown depth, and time of crown root initiation in a breeding program for reduced water use. Line P4 had no-SIL regardless of light and population density. Light deficiency increased SIL of Seco and the Yemen line more than high population density. The internodes below the crown in P4 are insensitive to light and population density, but internodes above the crown in the same line are as sensitive as Seco and the Yemen line. Screening for NE can be very efficient in the greenhouse at the seedling stage.