Heterotic groups for identifying of suitable combiners in sunflower using top-cross

The study was conducted in order to identify the suitable parental inbred lines using top cross method for improvement of new sunflower F1 single cross hybrids at research field of Seed and Plant Improvement Institute in Karaj, Iran during two Crop season (2018 and 2019). Experimental materials consisted of 31 restore lines and 43 cytoplasmic male sterile lines which were crossed with A1221 and R14 as the testers respectively. The developed F1 hybrids were evaluated for GCA of three breeding objectives i.e. flowering time, plant height and grain yield during two years replicated trials. Cluster analysis revealed two heterotic groups in which the restorer lines; R22, R24 and R38 (Grain yield of 33, 32 and 31 g head-1 respectively) and three CMS lines; A32, A370 and A110 (Grain yield of 47, 44 and 43 g head-1 respectively) were identified as the suitable restorer and cytoplasmic male sterile line for improvement of new sunflower single cross hybrids. Evaluation of specific combing ability of the resulted combinations will reveal the efficiency of this selection in the following generation.

Comparison of starch granule sizes of maize seeds between parental lines and derived hybrids

Maize starch is an important agricultural commodity that serves as food, feed, and a raw material for industrial purposes. It is organized into starch granules (SG) inside amyloplasts and is highly accumulated in endosperms. Maize hybrids exhibit heterosis over their parents. However, the parental effect on the size of SG in F1 hybrid seeds remains unclear. Here we compared the seed SG sizes among two parental inbred lines (Chang7-2 and Zheng58) as well as their reciprocal hybrids. SG was observed in situ and in vitro with SEM. The size of seed SG in hybrids was more like that of female parents, especially for large SG population. Thus, the control of SG size exhibits a maternal inheritance trend in the context of plastid (amyloplast) inheritance. Our results provide some insight on selecting parental inbred lines for breeding maize hybrids with different SG sizes.

Mating designs commonly used in plant breeding: A review

Mating design represents "rules" for arranging different controlled crossings; a mating design is a procedure of producing progenies. This review describes mating designs commonly used in plant breeding. Biparental is the simplest design in which a number of P plants are paired off to give ½P families; the parents are mated only once in pairs. The design is simple and it provides information needed to determine if significant genetic variation is present in a population for a long term selection program. A polycross is a mating arrangement for interpollinating a group of cultivars or clones using natural hybridization in an isolated crossing block. The design is often used for generating synthetic cultivars. The North Carolina (NC) mating designs permit determination and/or estimation of variance components (additive and dominance components) by using the information from half-sib (HS) families. The experimental material of North Carolina designs I, II and III is developed from F2 generation as a base material. The design III (NCIII) involves backcrossing the F2 plants to the two parental inbred lines from which the F2 were derived. The NCIII design was extended to include a third tester. This third tester is the F1 from the two parental inbred lines; in this extended form, this design is known as the triple test cross (TTC). Line x Tester mating design uses inbred lines as the base population. The design is useful in deciding the relative ability of a number of female and male inbreds to produce desirable hybrid combinations. When the same parents are used as females and males in breeding, the mating design is called diallel. Parents used range from inbred lines to broad genetic base varieties to clones. The design is the most commonly used in crop plants to estimate GCA and SCA and variances. Generally, it should be noted that is not the mating design per se, but the breeder who breeds a new cultivar. Consequently, proper choice and use of a mating design will provide the most valuable information for breeding

MicroRNA transcriptomic analysis of the sixth leaf of maize (Zea mays L.) revealed a regulatory mechanism of jointing stage heterosis

Background Zhengdan 958 (Zheng 58 × Chang 7–2), a commercial hybrid that is produced in a large area in China, is the result of the successful use of the heterotic pattern of Reid × Tang-SPT. The jointing stage of maize is the key period from vegetative to reproductive growth, which determines development at later stages and heterosis to a certain degree. MicroRNAs (miRNAs) play vital roles in the regulation of plant development, but how they function in the sixth leaf at the six-leaf (V6) stage to influence jointing stage heterosis is still unclear. Result Our objective was to study miRNAs in four hybrid combinations developed in accordance with the Reid × Tang-SPT pattern, Zhengdan 958, Anyu 5 (Ye 478 × Chang 7–2), Ye 478 × Huangzaosi, Zheng 58 × Huangzaosi, and their parental inbred lines to explore the mechanism related to heterosis. A total of 234 miRNAs were identified in the sixth leaf at the V6 stage, and 85 miRNAs were differentially expressed between the hybrid combinations and their parental inbred lines. Most of the differentially expressed miRNAs were non-additively expressed, which indicates that miRNAs may participate in heterosis at the jointing stage. miR164, miR1432 and miR528 families were repressed in the four hybrid combinations, and some miRNAs, such as miR156, miR399, and miR395 families, exhibited different expression trends in different hybrid combinations, which may result in varying effects on the heterosis regulatory mechanism. Conclusions The potential targets of the identified miRNAs are related to photosynthesis, the response to plant hormones, and nutrient use. Different hybrid combinations employ different mature miRNAs of the same miRNA family and exhibit different expression trends that may result in enhanced or repressed gene expression to regulate heterosis. Taken together, our results reveal a miRNA-mediated network that plays a key role in jointing stage heterosis via posttranscriptional regulation.

Marker-assisted selection for the gene of β-carotene hydroxylase in maize

Aim. Estimation of the allelic status of marker crtRB1-3'TE of the β-carotene hydroxylase gene and marker-assisted selection by this marker in Ukrainian maize breeding material. Methods. Field method and polymerase chain reaction. Results. The analysis of the allelic state of β-carotene hydroxylase gene for marker crtRB1-3'TE in maize breeding populations (DK23×F2)F2 and (DK23×F2)F3MAS having been obtained after the first and second self-pollinations of single cross DK23×F2 was provided. It was established that the parental inbred lines DK23 and F2 contained respectively 296 bp (unfavorable) and 543 bp (favorable) alleles of marker crtRB1-3'TE. The three kinds of genotypes appeared to present at different frequencies in (DK23×F2)F2 – homozygous for allele 296 bp, homozygous for allele 543 bp and heterozygous with both alleles 296 bp and 543 bp. For further cultivation and self-pollination, only plants with allele 543 bp within (DK23×F2)F2 were selected. All tested plants in population (DK23×F2)F3MAS were homozygous for allele 543 bp. Conclusions. Marker-associated selection in two generations for the β-carotene hydroxylase gene, involved in β-carotene accumulation, allowed to select homozygous plants of maize by favorable crtRB1-3'TE allele. Keywords: Zea mays L., molecular genetic markers, carotenoids, breeding populations, allele.

Genotypic divergence in mouse oocyte transcriptomes: possible pathways to hybrid vigor impacting fertility and embryogenesis

What causes hybrid vigor phenotypes in mammalian oocytes and preimplantation embryos? Answering this question should provide new insight into determinants of oocyte and embryo quality and infertility. Hybrid vigor could arise through a variety of mechanisms, many of which must operate through posttranscriptional mechanisms affecting oocyte mRNA accumulation, stability, translation, and degradation. The differential regulation of such mRNAs may impact essential pathways and functions within the oocyte. We conducted in-depth transcriptome comparisons of immature and mature oocytes of C57BL/6J and DBA/2J inbred strains and C57BL/6J × DBA/2J F1 (BDF1) hybrid oocytes with RNA sequencing, combined with novel computational methods of analysis. We observed extensive differences in mRNA expression and regulation between parental inbred strains and between inbred and hybrid genotypes, including mRNAs encoding proposed markers of oocyte quality. Unique BDF1 oocyte characteristics arise through a combination of additive dominance and incomplete dominance features in the transcriptome, with a lesser degree of transgressive mRNA expression. Special features of the BDF1 transcriptome most prominently relate to histone expression, mitochondrial function, and oxidative phosphorylation. The study reveals the major underlying mechanisms that contribute to superior properties of hybrid oocytes in a mouse model.

Hybrid Purity Testing of Brassica rapa Using SSR Marker Technology

Thirteen Chinese cabbage (Brassica rapa) hybrid cultivars and 26 parental inbred lines were used as experimental materials to screen for primers producing hybrid and parental complementary bands and for primers with high polymorphism information contents and low genotype frequencies. A total of 18 pairs of core primers were designed to identify the purity of Chinese cabbage. There was no significant difference in the purity percentage measured between different loci of the same strain. The fingerprint obtained by the amplification of each locus could be used to identify purity to obtain an authentic purity percentage. Curve mapping and significance analyses were conducted using the purity percentage of eight different seed samples and confirmed a sampling seed number of 96. The results of the purity test were verified by comparison with the grow-out test (GOT) using molecular markers. In conclusion, the simple sequence repeat (SSR) detection system could be used for the rapid identification of the purity of the tested Chinese cabbage hybrids.

Evaluation of quality protein maize crosses through line X testeranalysis for grain yield and quality traits

A set of eighty one genotypes comprising sixty three newly developed single cross quality protein maize hybrids produced by 9 lines x 7 testers crosses along with sixteen parental inbred lines and two standard checks were evaluated for genetic variability, broad sense heritability and genetic advance at CCS, Haryana Agricultural University, Regional Research Station, Karnal, during kharif 2014. Highly significant values of mean sum of squares due to genotypes for all the 17characters studied could be recorded. Close correspondence between GCV and PCV was observed for all the traits except number of cobs per plant and cob diameter. The characters viz., number of grains per cob, tryptophan content, lysine content and grain yield per plant were recorded high estimates of heritability and genetic advance as per cent of mean indicating them to be controlled by additive genes.