Hybrid between durum wheat and diploid Thinopyrum bessarabicum

Abstract

Gross morphological features and chromosome association of the first triploid intergeneric hybrid (2n = 3x = 21; ABJ genomes) between durum wheat, Triticum turgidum L. (2n = 4x = 28; AABB), and diploid wheatgrass, Thinopyrum bessarabicum (Savul. &Rayss) A. Löve (2n = 2x = 14; JJ), are described. Genome relationships are assessed in the presence of the pairing homoeologous gene, Ph1. The hybrid was intermediate in phenotype between the two parents. It inherited the tillering habit, perennial growth habit, and glaucous leaves and stems from the male Thinopyrum parent; spike density and awns of wheat were partially expressed. An average of 13.67% of the chromosome complement paired in metaphase I cells of the hybrid. Mean chromosome associations were 0.07 III + 0.03 ring II + 1.30 rod II + 18.13 I and 1.51 chiasmata per cell, with a mean arm-pairing frequency, c, of 0.107. Because chromosomes of the A and B genomes show very little pairing with each other in the polyhaploids of T. turgidum, it was inferred that most of the bivalents in the hybrid were formed between chromosomes of the A and J and (or) B and J genomes, a welcome feature from the breeding standpoint. Trivalent frequency, albeit low, further indicated intergenomic pairing among A, B, and J. Associations between wheat and Thinopyrum chromosomes may permit intergeneric transfer of genes, which may be accelerated by the use of the ph1c ph1c homoeologous pairing mutant of durum wheat.Key words: intergeneric hybrid, chromosome pairing, genome relationship, Triticum, Ph1 pairing regulator.