Genetic correlations between culm length, grain yield and seedling elongation within tall (rht1) and semi-dwarf (Rht1) spring wheat (Triticum aestivum L.)

The purpose of this study was to obtain information on the genetic correlations between culm length, grain yield and seedling elongation within tall (rht1) and semi-dwarf (Rht1) nearly isogenic spring wheat genotypes. Thirty random F₇ families and 25 of their offspring in F₈ were tested in field experiments in the absence of lodging. Coleoptile and leaf lengths of F₉ seedlings were examined in a growth room at 18°C. Each family was descended from a single F₅ plant, heterozygous at the Rht1 locus. Within each family, the homozygous tall (rht1) and homozygous semi-dwarf (Rht1) were identified; the differences between the families represent the effect of background variation. A significantly high positive genetic correlation between culm length and grain yield was found in the Rht1 genotype. Based on our results, we suggest that spring wheat breeders first select for long culms within the semi-dwarf population. This shOUld be followed by selection for resistance to lodging arid high grain yield, with a special emphasis on genotypes excelling in high grain number per area, due to the highly significant positive genetic correlation, found between this character and grain yield. The markedly significant positive correlation found between seedling elongation and culm length suggests the advantage of selecting for long culm genotypes within the semi-dwarf population by using the seedling-elongation test. This selection is accompanied by indirect selection for long coleoptiles, which are advantageous in the event of seedling-emergence difficulties.