Lines of Bra.ssica juncea with tetralocular (four-valved) pods were produced by interspecific hybridization between dilocular (two-valved) B. juncea var. Pusa Barani and tetralocular yellow-seeded turnip rape {Brassica rapa ssp. trilocularis) var. YID-1. Some selected lines were significantly superior to their parents for some agronomic traits, including seed yield and harvest index. Line 11 was the best among these and recorded 70% yield advantage in plot yield.The tetralocular condition in Brassicas is considered advantageous because it provides potentially greater seed numbers and a better environment for the development of seed. The tetralocular condition is common in Brassica rapa (Singh 1958) but rarely observed in Brassica juncea. Although attempts have been made, there are no published reports on introgression of this trait into B. juncea. This communication reports on three B. juncea lines with a stable and uniformly expressed tetralocular character obtained by a cross between B. juncea and B. rapa and followed by intermating and selection.A dilocular, brown-seeded, B. juncea var. 'Pusa Barani' was crossed to tetralocular, yellow-seeded, B. rapa (ssp. trilocularis) var. YID-1. The F, hybrid was brown-seeded and resembled the B. juncea parent for most morphological traits. The F, hybrid was backcrossed to YID-1 {B. rapa). The BC, seed was brown and the plants largely resembled B. juncea. The BC, was backcrossed to 'Pusa Barani' {B. juncea parent). This scheme of backcrossing, where the parents alternated, was followed in order to increase both homologous and homeologous recombinations. In the resultant progenies, a number of plants with deformed tri-and tetra-locular siliquae were observed. Partial seed setting sterility was observed but every plant produced sufficient seed. Intermating among plants with multilocular siliquae was performed to fix the variability, reduce the sterility and correct the siliqua defect. The seed of intercrossings was pooled, a population was raised, and selection was made for tetralocular siliqua and B. juncea plant type. After three cycles of selection, a number of tetralocular B. juncea lines were recovered. Three lines (6, 11 and 16) were stable for locule habit.To confirm the stability ofthe siliqua trait and assess the performance of these 3 lines, they were sown, along with their parents, in field plots of 3 X 2.4 m on the Institute Experimental Farm at Delhi in the 1996-97 season. Recommended agronomical practices were followed. Data on quantitative traits, listed in Table 1. were recorded on five plants drawn randomly from every plot. Means, critical difference (CD) and standard deviation (SD) were calculated. Observations on plot biomass, seed yield per plot and plot harvest index were also recorded.The results obtained are presented in Table 1. These data indicate that tetralocular hnes had significantly higher biomass compared with both parents. This points to their potential for Fig. 1: A tetralocular Brassica juncea line 6 (middle) derived from the parents diloc...

No abstract

To assess the effect of alien cytoplasm and fertility restorer genes on agronomic and physiological traits in Brassica juncea, cytoplasmic male sterile (CMS) and fertility restorer lines involving five alloplasms in three nuclear backgrounds were constituted through repeated backcrossing. These lines were evaluated along with euplasmic lines for agronomic traits in field experiments. Respiration efficiency of in vitro cultured hypocotyls, and chlorophyll content in leaves were also estimated. Significant adverse effects of trachystoma and catholica cytoplasms on yieldcontributing traits and yield were noticed. The restorer gene corrected the floral defects in CMS trachystoma and restored yield to the level of euplasmic line, while it did so only partly in CMS catholica. Restorer genes had no adverse effect on traits in any of the systems. On the contrary, the Rf gene of moricandia CMS system exerted a positive effect on leaf chlorophyll content. Likewise, in vitro assay indicated the moricandia CMS system as vigorous. The moricandia CMS plants gave higher seed yield perhaps due to overall better vigour and higher leaf chlorophyll content.

Haploids and doubled haploids are invaluable for basic genetic studies and in crop improvement. A novel method of haploid induction through genetic engineering of the Centromere Histone Protein gene, CENH3, has been demonstrated in Arabidopsis. The present study was undertaken to develop haploid inducer (HI) lines of Brassica juncea based on the principles elaborated in Arabidopsis. B. juncea was found to carry three copies of CENH3 which generated five different transcripts, of which three transcripts resulted from alternative splicing. Unlike Arabidopsis thaliana where native CENH3 gene was knocked out for constructing HI lines, we used RNAi approach to knockdown the native CENH3 genes. Further, to rescue CENH3 silenced cells, a GFP-CENH3-tailswap construct having N terminal GFP fused to H3.3 tail sequences and synthetic CENH3 histone fold domain sequences was devised. A total 38 transgenic B. juncea plants were regenerated following co-transformation with both silencing and rescue cassettes and transgenics carrying either or both the constructs were obtained. Transgenic status was confirmed through PCR, Southern and qRT-PCR analyses. Co-transformed lines were crossed to untransformed B. juncea or a line expressing only GFP-tailswap. FACS and cytological analyses of progenies revealed partial or complete elimination of B. juncea chromosomes thereby giving rise to aneuploids and haploid. This is the first report in a polyploid crop demonstrating that CENH3 engineering could be used to develop HI lines.