Research Notes : India : Induced parthenogenesis in soybean

A field of research currently gaining much interest is the irradiated-pollen-induced ovule transformation in plants. The interest lies mainly in the possibility of modifying the plant genome in a quicker and more economical way. The successful demonstration of such gene transfers have been achieved in Nicotiana (Pandey, 1975; Jinks et al., 1981), Brassica (Banga et al., 1983) and Lycopersicum (Zamir, 1983) for both qualitative and metric traits

Research Notes : India : Potential of an off-season soybean nursery

In India, soybean is generally sown during summer (June-October). However, due to tremendous variability in climatic conditions of the country, there is a scope for growing soybean in more than one season. The efficacy of yield improvement projects could be substantially enhanced by rapid genera-tion turnover

Heterosis as Investigated in Terms of Polyploidy and Genetic Diversity Using Designed Brassica juncea Amphiploid and Its Progenitor Diploid Species

Fixed heterosis resulting from favorable interactions between the genes on their homoeologous genomes in an allopolyploid is considered analogous to classical heterosis accruing from interactions between homologous chromosomes in heterozygous plants of a diploid species. It has been hypothesized that fixed heterosis may be one of the causes of low classical heterosis in allopolyploids. We used Indian mustard (Brassica juncea, 2n = 36; AABB) as a model system to analyze this hypothesis due to ease of its resynthesis from its diploid progenitors, B. rapa (2n = 20; AA) and B. nigra (2n = 16; BB). Both forms of heterosis were investigated in terms of ploidy level, gene action and genetic diversity. To facilitate this, eleven B. juncea genotypes were resynthesized by hybridizing ten near inbred lines of B. rapa and nine of B. nigra. Three half diallel combinations involving resynthesized B. juncea (11×11) and the corresponding progenitor genotypes of B. rapa (10×10) and B. nigra (9×9) were evaluated. Genetic diversity was estimated based on DNA polymorphism generated by SSR primers. Heterosis and genetic diversity in parental diploid species appeared not to predict heterosis and genetic diversity at alloploid level. There was also no association between combining ability, genetic diversity and heterosis across ploidy. Though a large proportion (0.47) of combinations showed positive values, the average fixed heterosis was low for seed yield but high for biomass yield. The genetic diversity was a significant contributor to fixed heterosis for biomass yield, due possibly to adaptive advantage it may confer on de novo alloploids during evolution. Good general/specific combiners at diploid level did not necessarily produce good general/specific combiners at amphiploid level. It was also concluded that polyploidy impacts classical heterosis indirectly due to the negative association between fixed heterosis and classical heterosis

Research Notes : India : Induced parthenogenesis in soybean

A field of research currently gaining much interest is the irradiated-pollen-induced ovule transformation in plants. The interest lies mainly in the possibility of modifying the plant genome in a quicker and more economical way. The successful demonstration of such gene transfers have been achieved in Nicotiana (Pandey, 1975; Jinks et al., 1981), Brassica (Banga et al., 1983) and Lycopersicum (Zamir, 1983) for both qualitative and metric traits.</p

Research Notes : India : Potential of an off-season soybean nursery

In India, soybean is generally sown during summer (June-October). However, due to tremendous variability in climatic conditions of the country, there is a scope for growing soybean in more than one season. The efficacy of yield improvement projects could be substantially enhanced by rapid genera-tion turnover.</p

Mean square values in analysis of variance for combining ability in resynthesized <i>B. juncea</i> and its progenitor species.

<p>*Significant at P = 0.05;</p><p>**Significant at P = 0.01.</p

Pictorial representation of the manifestation of relative mid parent (A) and high parent (B) heterosis for seed yield in F₁ hybrids of resynthesized <i>B. juncea</i> (red) and progenitor species, <i>B. rapa</i> (blue) and <i>B. nigra</i> (yellow).

<p>Pictorial representation of the manifestation of relative mid parent (A) and high parent (B) heterosis for seed yield in F₁ hybrids of resynthesized <i>B. juncea</i> (red) and progenitor species, <i>B. rapa</i> (blue) and <i>B. nigra</i> (yellow).</p

Multiple correlation coefficient (R²), constant and partial regression coefficients from multiple regression analysis.

<p>Multiple correlation coefficient (R²), constant and partial regression coefficients from multiple regression analysis.</p

Association between fixed and classical heterosis for resynthesized <i>Brassica juncea</i> and progenitor species for biomass yield over absolute high parent (A) and relative high parent (B) values.

<p>Association between fixed and classical heterosis for resynthesized <i>Brassica juncea</i> and progenitor species for biomass yield over absolute high parent (A) and relative high parent (B) values.</p

Pictorial representation of the manifestation of relative mid parent (A) and high parent (B) heterosis for biomass yield in F₁ hybrids of resynthesized <i>B. juncea</i> (red) and progenitor species, <i>B. rapa</i> (blue) and <i>B. nigra</i> (yellow).

<p>Pictorial representation of the manifestation of relative mid parent (A) and high parent (B) heterosis for biomass yield in F₁ hybrids of resynthesized <i>B. juncea</i> (red) and progenitor species, <i>B. rapa</i> (blue) and <i>B. nigra</i> (yellow).</p