Genetic Similarity Between Donor And Recurrent Parents Can Reduce The Number of Backcross Generation In Marker-Assisted Backcross

The marker assisted backcross (MABC) method is the most used to obtain transgenic hybrid and transgenic inbred lines in maize with few backcrosses (BC) generations. It is possible that the use of donor parents with greater genetic similarity with recurrent parents can further reduce the number of BC generation to recover recurrent parent genome. The objective of this study was to evaluate the influence of genetic distance between parents and the percentage of recurrent parent genome recovery, as well as the similarity of BC plants and recurrent parent. Nine maize BC populations were evaluated, with genetic distances between donors and recurrent parents ranging from 0.238 to 0.499. In the backcross generations, molecular markers were used to identify the plants with the highest percentage of recurrent genome recovery and with greater similarity to the recurrent parent. There was no difference in the recurrent genome recovery among populations after three BC generations. In the first two BC generation the similarity between BC plants and recurrent parents was positively correlated with the similarity between donor and the populations recurrent parent. BC populations with higher similarity among parents could be finished with two BC generations, and BC populations with lower similarity could just be finished after three generation of MABC. The use of donor parents with higher similarity with recurrent parent can reduce one BC generation in MABC approach.

Third Backcross Generation Indonesian Indigenous Chicken Kampong Broiler-Type (Kambro) SOX5 Gene Polymorphism

The comb is an accessory organ on the head of chicken which is influenced by testosterone hormone and can be used as an indicator of chicken’s fertility. Comb shape is related to climate adaptation and associated with a dominant mutation in chicken chromosome 1. Therefore this research was aimed to study the association between Pea-comb shape and SOX5 gene polymorphism in the population of progenies (BC-III Kambro) derived from a crossbreed between females Pelung and males second backcross generation Kampong Broiler-Type (BC-II Kambro). Chicken (Gallus gallus) SOX5 gene was acquired from NCBI GenBank with the Ref. Seq. 418195. Primers used to amplify the SOX5 gene are (F):5’-AGGTAGCCATGGTGACAAGC-3’,(R):5’-GATCTGTGAGGCAGCCAGTT-3’. Progenies showed 100% Pea-comb shape, while parental generation composed of Pea-comb shape and Single-comb shape. PCR-RFLP and endonuclease restriction enzyme HindIII were unable to determine the genotype of the female parent with Pea-comb. The result of SOX5 gene polymorphism showed the comb shape uniformity between progenies and parental of Kambro backcross generation. This study concluded that the genotype of Pea-comb shape female Pelung was undetermined and there was no polymorphism of the SOX5 gene between pea and single comb. PCR-RFLP using endonuclease restriction enzyme HindIII produced both target products and non-target/artifact products. The sequencing procedure was required to provide nucleotide sequences.

Marker-Assisted Backcross Breeding for Improvement of Submergence Tolerance and Grain Yield in the Popular Rice Variety, ‘Maudamani’

Background: Submergence stress due to flash flood reduces rice yield drastically in sensitive varieties. Maudamani is a high yielding popular rice variety but highly susceptible to submergence stress. The Sub1 and yield component QTL, GW5 were transferred into the popular high yielding variety for enhancing submergence tolerance and yield. Methods: Sub1 and GW5 QTLs were transferred into Maudamani variety by adopting marker-assisted backcross breeding method. The target QTLs were selected by foreground selection in each backcross generation progenies to track the target QTLs. Recipient parent’s genome recovery was accelerated by adopting background selection in each backcross generation progenies carrying the target QTLs. Results: The two target QTLs were tracked in each backcross generation progenies by employing the tightly linked and direct markers. Background screening was performed in each backcross generation progenies carrying the target QTLs by using 57 background markers for enhancing the recovery of recipient parent’s genome content. The selected progenies containing highest genome recovery of the parent was hybridized with recipient parent, Maudamani. Finally, the selected BC3F1 plant containing highest recipient parent genome content and the two target QTLs was self-pollinated. In BC3F2 generation, two QTLs, Sub1 and GW5 along with recipient parent’s yield component QTLs, OsSPL14, Gn1a and SCM2 were tracked for their homozygous state in the progenies. Amongst the developed pyramided lines, six lines showed tolerance to submergence for 14 days and also exhibited higher grain yield than both the parents. The pyramided lines, MSS 607-116-541-117 and MSS 607-116-541-436 produced >9 t/ha grain yield showing an advantage of >5% over the popular recipient variety. Few pyramided lines were similar in appearance and quality traits with the recipient parent. Conclusion: The pyramided lines will be useful as potential donors for the QTLs Sub1+ OsSPL14+ Gn1a + GW5 + SCM2 and also as cultivars.

Transfer of Downy Mildew Resistance from Wild Basil (Ocimum americanum) to Sweet Basil (O. basilicum)

Sweet basil (Ocimum basilicum) is susceptible to downy mildew caused by the oomycete foliar pathogen Peronospora belbahrii. No resistant varieties of sweet basil are commercially available. Here, we report on the transfer of resistance gene Pb1 from the highly resistant tetraploid wild basil O. americanum var. americanum (PI 500945, 2n = 4x = 48) to the tetraploid susceptible O. basilicum ‘Sweet basil’ (2n = 4x = 48). F1 progeny plants derived from the interspecific hybridization PI 500945 × Sweet basil were resistant, indicating that the gene controlling resistance (Pb1) is dominant, but sterile due to the genetic distance between the parents. Despite their sterility, F1 plants were pollinated with the susceptible parent and 115 first backcross generation to the susceptible parent (BCs1) embryos were rescued in vitro. The emerging BCs1 plants segregated, upon inoculation, 5:1 resistant/susceptible, suggesting that resistance in F1 was controlled by a pair of dominant genes (Pb1A and Pb1A’). Thirty-one partially fertile BCs1 plants were self-pollinated to obtain BCs1-F2 or were backcrossed to Sweet basil to obtain the second backcross generation to the susceptible parent (BCs2). In total, 1 BCs1-F2 and 22 BCs2 progenies were obtained. The BCs1-F2 progeny segregated 35:1 resistant/susceptible, as expected from a tetraploid parent with two dominant resistant genes. The 22 BCs2 progenies segregated 1:1 resistant/susceptible (for a BCs1 parent that carried one dominant gene for resistance) or 5:1 (for a BCs1 parent that carried two dominant genes for resistance) at a ratio of 4:1. The data suggest that a pair of dominant genes (Pb1A and Pb1A’) residing on a two homeologous chromosomes is responsible for resistance of PI 500945 against P. belbahrii.

Haplo-deficiency of ODF1/HSPB10 in mouse sperm causes relaxation of head-to-tail linkage

The small heat shock protein ODF1/HSPB10 is essential for male fertility in mice. Targeted deletion ofOdf1resulted in acephalic sperm in homozygous mice of mixed background (C57BL/6J//129/Sv), whereas heterozygous animals are fully fertile. To further elucidate the function of ODF1, we generated incipient congenic mice with targeted deletion ofOdf1by successive backcrossing on the 129/Sv background. We observed that fecundity of heterozygousOdf1+/−male mice was severely reduced over backcross generations. However, neither aberrant sperm parameters nor sperm anomalies could be observed. Ultra-structural analyses of sperm from incipient congenic heterozygousOdf1+/−males of backcross generation N7 revealed no obvious pathological findings. However, we observed an enlargement of the distance between nuclear membrane and capitulum, indicating a weakening of the sperm head-to-tail coupling. Severe male subfertility provoked by haplo-deficiency of ODF1 is therefore most probably caused by impaired head-to-tail coupling that eventually might induce sperm decapitation on the specific conditions ofin vivofertilisation. As subfertility in haplo-deficient ODF1 male mice could not be diagnosed by semen analysis, it seems to be a paradigm for unexplained infertility that is a frequent diagnosis for male fertility impairment in humans.

Adaptation of Trifolium repens × T. uniflorum hybrid clovers to drought stress

White clover (Trifolium repens L.) is valued for its contribution to pasture quality and utilisation by animals, compatibility with grass, and fixation of nitrogen. However, it is limited by poor adaptation to drought. Hybridisation with Trifolium uniflorum L. may have potential to improve the drought resistance of white clover. An experiment in a rain shelter facility with contrasting moisture treatments, and a field evaluation under dryland conditions, were used to compare the agronomic potential of these interspecific hybrids (ISH) with white clover in moisture limited conditions. In the rain shelter experiment, there were smaller effects of water stress on shoot dry weight (DW), leaf area, internode length and senescence of first backcross generation hybrids compared with white clover and second backcross generation hybrids. Differences in photosynthetic responses were possibly influenced by the effect of root DW allocation on water uptake. In the field evaluation, growth scores of a wider range of hybrid families during summer moisture stress concurred with the results under water stress in the rain shelter. Growth of some ISH families outperformed the best white clover cultivars, particularly in the third and most stressful summer and this result was a key performance indicator of the value of the hybrids for drought prone areas. These findings using early, unselected, hybrid populations indicate the potential for further selection of elite, adapted cultivars from ISH breeding strategies. Keywords: Interspecific clover hybrid, drought resistance, rain shelter, field evaluation