Non-homologous meiotic pairing in the A and B genomes of Brassica: its breeding significance in the production of variable amphidiploids

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Abstract
Brassica juncea Coss (2n = 36) is a naturally occurring allotetraploid. In the progenies of F1 hybrids of its constituent parents B. campestris sub.sp. oleifera var. toria × B. nigra and B. campestris sub.sp. japonica × B. nigra, the majority of the plants were parthenogenetic homozygous amphidiploids like B. juncea whereas a few differed in morphological and physiological characteristics. The latter, presumed to have arisen partheno-genetically, were suspected to be homozygous for chromosomes changed by allosyndetic recombination. One of these derived plants with curley leaves was crossed first with one of the homozygous amphidiploids and secondly with B. c. sub.sp. oleifera var. toria. Sporocytes of the two hybrids were studied at meiosis. The presence of one or two quadrivalents in the first hybrid and two trivalents in the second suggested that allosyndetic recombination had occurred in the 18-chromosome hybrid. The progeny was presumed to have arisen through pseudo-diploid parthenogenesis and this in association with allosyndetic recombination may provide a means of breeding higher yielding genotypes.