Synthetic Brassica napus L.: Development and Studies on Morphological Characters, Yield Attributes, and Yield

1. Introduction

Allopolyploids are widely spread in the plant kingdom. Their success might be explained by positive interactions between homoeologous genes on their different genomes, similar to the positive interactions between different alleles of one gene causing heterosis in heterozygous diploid genotypes [1]. Amphidiploid species are a form of polyploids that have evolved from interspecific hybridization between two or more diploid species, either through the fusion of unreduced gametes or through interspecific hybridization followed by spontaneous chromosome doubling. Many wild species as well as major field crops like wheat, oat, soybean, cotton, and rapeseed are the result of spontaneous interspecific hybridization, showing the high potential of allopolyploid species.

Allotetraploid B. napus (AACC, $2n=38$ ) has evolved from a natural cross between B. rapa (AA, $2n=20$ ) and B. oleracea (CC, $2n=18$ ) along the Mediterranean coast with uncertain evolutionary origin time approximate ranging from 0.12 to 1.37 million years ago [2, 3]. The short domestication history and traditional breeding schedule of B. napus has led to a narrow genetic range in the population. As a whole, although the allopolyploid species has been rapidly and widely cultivated globally as an oilseed due to the advantages of high yield and wide adaptation, rapeseed breeding and heterosis utilization have undergone genetic bottlenecks due to exhaustion of the genetic variation [4, 5]. Artificial synthesis of the naturally occurring amphidiploid B. napus by hybridization between its progenitors followed by chromosome doubling provides a means to increase the usable genetic variability [6]. Artificial B. napus was also synthesized earlier by Schranz and Osborn [7], Albertin et al. [8], and Gaeta et al. [9]. The present investigation was, therefore, aimed for development of synthetic B. napus from the hybrids of its two progenitor species and to study the C₂ (second colchiploid generation) synthetic B. napus compared to its parents regarding some morphological characters, yield attributes, and yield.

2. Materials and Methods

The experiments were conducted during November to February each of 2005-2006, 2006-2007, and 2007-2008 at the Bangladesh Institute of Nuclear Agriculture, Mymensingh, Bangladesh.

2.1. Plant Materials

Binasarisha-6 of B. rapa var. “yellow sarson” and Alboglabra-1 of B. oleracea var. “alboglabra” were used as parental genotypes for the development of interspecific...

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