Inheritance of supernumerary spikelets in a tetraploid wheat cross

The supernumerary spikelet (SS) trait of durum wheat (Triticum turgidum L.), including the four-rowed and ramified spike types, is characterized by an increased number of spikelets per spike. To determine the inheritance of this trait, the tetraploid ramified spike cultivar PI349056 was crossed reciprocally to normal-spike 'Langdon' durum, and the F1 was backcrossed to each parent. The F1, F2, F3, BC1F1, and BC1F2 were classified for SS expression. Additionally, PI349056 was crossed to the 'Langdon' 2D(2A) disomic substitution line to study linkage of SS genes. The SS trait was recessive to normal spike, and both four-rowed spike and ramified spike progeny were observed in the segregating generations. Segregation in F3 and BC1F2 families indicated that SS in PI349056 was quantitatively inherited, controlled by a major recessive gene and numerous minor genes. Normal-spiked plants selected in families homozygous for the major gene indicated that the major gene did not produce SS when the minor genes were absent. Selection of normal-spiked plants in the F3 and F4 of 'Langdon' 2D(2A) disomic substitution/PI349056 indicated that the minor SS genes were not linked to the major gene on chromosome 2A.Key words: Triticum, branched spike, ramified spike, four-rowed spike.

Influence of time of sowing, photoperiod, and temperature on supernumerary spikelet expression in wheat (Triticum)

Three tetraploid (Triticum turgidum L. emend, gr. turgidum and gr. durum) and six hexaploid wheats (Triticum × aestivum L. emend aestivum) with reported tendencies for "branched" heads (supernumerary spikelets) exhibited variation for this character when grown under different photoperiod and temperature regimes. Wheats with a weak vernalization response under short photoperiod in an outdoor (low temperature) environment and those with a strong vernalization response under a long-photoperiod outdoor (low temperature) environment developed more supernumerary spikelets than under other photoperiods and temperatures. There was a variation among the nine wheats in the level and stability of supernumerary spikelet expression and in their fertility and grain number per head over the different times of sowing. This indicates the feasibility for selecting high and stable expression of supernumerary spikelets in breeding to increase spikelet number per head in wheat.