Traditionally, hybrid seeds are produced by crossing selected inbred lines. Here we provide a proof of concept for reverse breeding, a new approach that simplifies meiosis such that homozygous parental lines can be generated from a vigorous hybrid individual. We silenced DMC1, which encodes the meiotic recombination protein DISRUPTED MEIOTIC cDNA1, in hybrids of A. thaliana, so that non-recombined parental chromosomes segregate during meiosis. We then converted the resulting gametes into adult haploid plants, and subsequently into homozygous diploids, so that each contained half the genome of the original hybrid. From 36 homozygous lines, we selected 3 (out of 6) complementing parental pairs that allowed us to recreate the original hybrid by intercrossing. In addition, this approach resulted in a complete set of chromosome-substitution lines. Our method allows the selection of a single choice offspring from a segregating population and preservation of its heterozygous genotype by generating homozygous founder lines.
Two F2 populations segregating for biomass yield and forage quality traits were developed from two separate crosses of tropically adapted maize inbred lines. The parental, F1 and F2 generations of both crosses were evaluated to estimate broad sense heritability, genetic advance and correlations for these traits to suggest the best traits as selection criteria towards breeding forage maize with high yield and quality.In Cross 1, biomass yield trait with the highest broad-sense heritability was plant height (70.03%), whereas forage quality trait with the highest heritability estimate was crude protein content (66.60%). Heritability estimates in Cross 2 were high for all biomass yield traits and forage quality traits (>50% for all traits). Indigestible cell wall component represented by acid detergent lignin content was found to be highly heritable in both populations. High genetic advance as percent of mean were found for fresh and dry plant yield as well as for lignin content in both populations. Correlation analysis on all traits showed that all biomass yield components were significantly correlated. All traits related to cell wall content were positively correlated and acid detergent lignin was positively correlated with dry plant yield. Traits with high to moderate heritability and high predicted genetic advance, namely plant height, fresh plant yield and protein content can be used as selection criteria to improve maize biomass yield and nutritive quality for forage utilization. Selecting for higher biomass yield would also result in selecting individuals with higher lignin content as shown by the correlation analysis.
Fifteen genotypes of sorghum derived from four different sources of population were evaluated for quality and yield related components. The experiment was conducted at Field 10, Universiti Putra Malaysia in a Randomized Complete Block Design with three replications. The objectives of this study were to evaluate the performance and genetic variation for eight yield and quality traits on selected genotypes sorghum, to estimate the phenotypic correlation between yield and yield related components in sorghum. Genotypes 1-3-5 and 1-4-4 were identified to have high yield for most of the biomass (904.0 g/plant and 880.7 g/plant respectively) and grain yield components (98.1 g and 88.97g respectively). Genotypes 1-1-1, 1-4-1 and 5-3-6 were found to have total soluble solid of more than 16%, which make them suitable for food purposes. Mean for all genotypes for all measured traits, together with the significant genotypic variance indicated substantial amount of genetic variability towards the improvement for fresh biomass weight, stem diameter and total soluble solid content. Biomass and grain yield traits namely plant height, fresh biomass yield, stem diameter and panicle weight indicated significant positive correlation. Thus, selection on any one of these traits will increase in the other traits, thereby improving biomass and grain yield in sorghum for mentioned purpose.
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