Pre-fertilization Barrier, Crossability and Meiotic Behavior of Interspecific Hybrids Among Brassica Species

Inter-specific hybridization is an important driving force in plant evolution, speciation and creation of novel genetic variations those are not available with the naturally occurring species. Present investigation includes study of pre-fertilization barriers, phenotypic characterization and the meiotic abnormalities during microsporogenesis in the interspecific hybrids. Mean pollen tube germination percent in interspecific hybrids was recorded to be highest in case of B. carinata x B. nigra (33.67±11.35) and lowest between B. carinata x B. napus (18.68±6.62) whereas in the reciprocal crosses it was highest for B. napus x B. carinata (33.06±13.41). Siliqua set ranged from 33% in B. carinata x B. napus to 72% in selfedB. carinata. Seed set % ranged from 0% in B. rapa x B. carinata and B.nigra x B.carinatato 25.64 % for B. carinata x B.nigra. Mean pollen tube growth was recorded highest in B. carinata x B. nigra (21.23±5.33) while was lowest in B. carinata x B. napus (10.18±3.17) and among reciprocals it was highest for B. nigra x B. carinata (21.39±7.53). Pollen tube abnormalities viz., coiling and bending of pollen tube, hairpin shaped pollen tube, swelling of tube tip, tube bifurcation, more than one tube emerging from pollen, tubes growing in wrong direction were observed. B. carinata as pollen parent showed highest mean pollen tube abnormality percent with B. napus (36.32±8.62) whereas lowest with B. nigra (18.09±6.73). It was observed highest with B. rapa (49.170 ±13.55) when B. carinata was used as pollen parent. Some of the pre fertilization barriers related to stylar and ovule region can also be observed through fluroscent microscopy. As per the observations B. carinata performed better as a seed parent with B. nigra, B. juncea and B. rapa whereas, with B. napus it performed good as a pollen parent. Correlation study gave the association the above traits with each other. The meiotic abnormalities showed improper alignment at M-I, M-II, A-I, A-II and Telophase.

Pollen fertility differences in the progenies obtained from a cross between eggplant (Solanum melongena L.) as a seed parent and eggplant cytoplasmic substitution lines as pollen parents

To the best of our knowledge, there is no report about pollen fertility of the progenies developed using eggplant (Solanum melongena L.) as a seed parent and eggplant cytoplasmic substitution lines as pollen parents. Pollen fertility of these progenies is very important to use as restorer line in the eggplant’s hybrid breeding program. In this study, pollen fertility was investigated for the progenies which were produced using S. melongena ‘Uttara’ as a seed parent and the eggplant cytoplasmic substitution lines as pollen parents. To assess pollen fertility, pollen stainability and in vitro germination ability were investigated. Although the nuclear and the cytoplasmic genome of the progenies were almost identical to eggplant ‘Uttara’, a clear difference was observed in the pollen fertility due to the difference in the pollen parents having different wild Solanum cytoplasms. The progenies produced using the functional cytoplasmic male sterile (CMS) lines as a pollen parent, whose cytoplasm donor were S. kurzii, S. violaceum and S. virginianum, showed pollen release type and high pollen fertility almost equal to eggplant ‘Uttara’. It is considered that the characteristics of these progenies were almost the same as eggplant. On the other hand, the progenies that produced using the fertility restored lines of the pollen non-formation type CMS lines as a pollen parent, whose cytoplasm donors were S. aethiopicum, S. anguivi and S. grandifolium, showed pollen release type and low pollen fertility, i.e., pollen staining ability was about 54% and pollen germination ability were about 35%. It is considered that the cause of this low pollen fertility was the incompatibility between the eggplant cytoplasm and the eggplant nuclear genome, which seems to be modified in the process of continuous backcrossing under the wild Solanum cytoplasms. It is suggested that complete nuclear substitution is difficult by continuous backcrossing with eggplant in the alloplasmic lines with S. aethiopicum, S. anguivi and S. grandifolium cytoplasm donors. Incompatibility between the normal eggplant cytoplasm and the modified eggplant nuclear genomes of the alloplasmic lines with S. aethiopicum, S. anguivi and S. grandifolium cytoplasms might be a cause for the low pollen fertility of the investigated progenies

Sequenced-based paternity analysis to improve breeding and identify self-incompatibility loci in intermediate wheatgrass (Thinopyrum intermedium)

Key Message Paternity assignment and genome-wide association analyses for fertility were applied to aThinopyrum intermediumbreeding program. A lack of progeny between combinations of parents was associated with loci near self-incompatibility genes. Abstract In outcrossing species such as intermediate wheatgrass (IWG, Thinopyrum intermedium), polycrossing is often used to generate novel recombinants through each cycle of selection, but it cannot track pollen-parent pedigrees and it is unknown how self-incompatibility (SI) genes may limit the number of unique crosses obtained. This study investigated the potential of using next-generation sequencing to assign paternity and identify putative SI loci in IWG. Using a reference population of 380 individuals made from controlled crosses of 64 parents, paternity was assigned with 92% agreement using Cervus software. Using this approach, 80% of 4158 progeny (n = 3342) from a polycross of 89 parents were assigned paternity. Of the 89 pollen parents, 82 (92%) were represented with 1633 unique full-sib families representing 42% of all potential crosses. The number of progeny per successful pollen parent ranged from 1 to 123, with number of inflorescences per pollen parent significantly correlated to the number of progeny (r = 0.54, p < 0.001). Shannon’s diversity index, assessing the total number and representation of families, was 7.33 compared to a theoretical maximum of 8.98. To test our hypothesis on the impact of SI genes, a genome-wide association study of the number of progeny observed from the 89 parents identified genetic effects related to non-random mating, including marker loci located near putative SI genes. Paternity testing of polycross progeny can impact future breeding gains by being incorporated in breeding programs to optimize polycross methodology, maintain genetic diversity, and reveal genetic architecture of mating patterns.

Effects of Metaxenia on Stone Cell Formation in Pear (Pyrus bretschneideri) Based on Transcriptomic Analysis and Functional Characterization of the Lignin-Related Gene PbC4H2

The deposition of lignin in flesh parenchyma cells for pear stone cells, and excessive stone cells reduce the taste and quality of the fruit. The effect of metaxenia on the quality of fruit has been heavily studied, but the effect of metaxenia on stone cell formation has not been fully elucidated to date. This study used P. bretschneideri (Chinese white pear) cv. ‘Yali’ (high-stone cell content) and P. pyrifolia (Sand pear) cv. ‘Cuiguan’ (low-stone cell content) as pollination trees to pollinate P. bretschneideri cv. ‘Lianglizaosu’ separately to fill this gap in the literature. The results of quantitative determination, histochemical staining and electron microscopy indicated that the content of stone cells and lignin in YL fruit (‘Yali’ (pollen parent) × ‘Lianglizaosu’ (seed parent)) was significantly higher than that in CL fruit (‘Cuiguan’ (pollen parent) × ‘Lianglizaosu’ (seed parent)). The transcriptome sequencing results that were obtained from the three developmental stages of the two types of hybrid fruits indicated that a large number of differentially expressed genes (DEGs) related to auxin signal transduction (AUX/IAAs and ARFs), lignin biosynthesis, and lignin metabolism regulation (MYBs, LIMs, and KNOXs) between the CL and YL fruits at the early stage of fruit development. Therefore, metaxenia might change the signal transduction process of auxin in pear fruit, thereby regulating the expression of transcription factors (TFs) related to lignin metabolism, and ultimately affecting lignin deposition and stone cell development. In addition, we performed functional verification of a differentially expressed gene, PbC4H2 (cinnamate 4-hydroxylase). Heterologous expression of PbC4H2 in the c4h mutant not only restored its collapsed cell wall, but also significantly increased the lignin content in the inflorescence stem. The results of our research help to elucidate the metaxenia-mediated regulation of pear stone cell development and clarify the function of PbC4H2 in cell wall development and lignin synthesis, which establishes a foundation for subsequent molecular breeding.

Inheritance of a Novel Heterozygous Peanut Mutant, 5-Small Leaflet

ABSTRACT An unusual 5-Small Leaflet mutant plant was found within the ‘Georgia Green' runner-type peanut (Arachis hypogaea L.) cultivar. Subsequent selfing has not established a true-breeding 5-Small Leaflet genotype. It continues to segregate normal and 5-Small Leaflet plants but with a reduced number of normal leaf plants upon selection for 5-Small Leaflet phenotypes after several self-generations. F1, F2, F3, and F4 data suggests that the 5-Small Leaflet trait is dominant or possibly pseudo-dominant. Likewise, the 5-Small Leaflet mutant can only be used as a pollen parent in crosses, and it has approximately a 1:1 ratio of elongated to normal stigmas, respectively, on individual plants. This is an example of a novel heterozygous peanut mutant plant found within the cultivated allotetraploid peanut.