Delineating the elusive BaMMV resistance gene rym15 in barley by medium-resolution mapping

Barley mild mosaic virus (BaMMV), transmitted by the soil-borne protist Polymyxa graminis, has a serious impact on winter barley production. Previously, the BaMMV resistance gene rym15 was mapped on chromosome 6HS, but the order of flanking markers was non-collinear between different maps. To resolve the position of the flanking markers and to enable map-based cloning of rym15, two medium-resolution mapping populations Igri (susceptible) × Chikurin Ibaraki 1 (resistant) (I × C) and Chikurin Ibaraki 1 × Uschi (susceptible) (C × U), consisting of 342 and 180 F2 plants, respectively, were developed. Efficiency of the mechanical inoculation of susceptible standards varied from 87.5 to 100% and in F2 populations from 90.56 to 93.23%. Phenotyping of F2 plants and corresponding F3 families revealed segregation ratios of 250 s:92r (I × C, χ2 = 0.659) and 140 s:40r (C × U, χ2 = 0.741), suggesting the presence of a single recessive resistance gene. After screening the parents with the 50 K Infinium chip and anchoring corresponding SNPs to the barley reference genome, 8 KASP assays were developed and used to remap the gene. Newly constructed maps revealed a collinear order of markers, thereby allowing the identification of high throughput flanking markers. This study demonstrates how construction of medium-resolution mapping populations in combination with robust phenotyping can efficiently resolve conflicting marker ordering and reduce the size of the target interval. In the reference genome era and genome-wide genotyping era, medium-resolution mapping will help accelerate candidate gene identification for traits where phenotyping is difficult.

Extreme resistance to potato virus A in potato cultivar Barbara is independently mediated by Ra and Rysto

Potato virus A (PVA) and potato virus Y (PVY) are two common members of Potyvirus genus infecting potato crops worldwide. Host resistance offers an economical and effective means for the control and/or management of these viruses. In this study, 20 potato clones were screened for their resistance against PVA and PVY by mechanical and/or graft inoculation assay, and were explored for the relationship between extreme resistance genes Ra and Ry by the detection of molecular markers linked respectively to Ryadg, Rysto, and Rychc. Six clones, including Barbara, Jizhangshu 8, Longshu 7, Longshu 8, M6, and Solara, were found to be extremely resistant to both PVA and PVY; three clones (AC142, Eshu 3, and Shepody) were deemed to be extremely resistant to PVA but susceptible to PVY. To further reveal the inheritance of the extreme resistance (ER) against PVA, a tetraploid F1 population of Barbara × F58050 (susceptible to both PVY and PVA) and a tetraploid BC1 population of BF145 (a PVA-resistant but PVY-susceptible progeny of Barbara × F58050) × F58050 were obtained, and phenotyping of the F1 and BC1 population by graft-inoculation with PVA showed segregation ratios of 3:1 and 1:1 (R:S), respectively. These results suggested that two independent loci control ER against PVA in Barbara: one confers ER to both PVA and PVY, and the other confers ER to PVA only. The deduced genotype of Barbara is RyryryryRararara.

Interspecific Hybrids Between Pelargonium × hortorum and Species From P. Section Ciconium Reveal Biparental Plastid Inheritance and Multi-Locus Cyto-Nuclear Incompatibility

The genetics underlying Cyto-Nuclear Incompatibility (CNI) was studied in Pelargonium interspecific hybrids. We created hybrids of 12 closely related crop wild relatives (CWR) with the ornamental P. × hortorum. Ten of the resulting 12 (F1) interspecific hybrids segregate for chlorosis suggesting biparental plastid inheritance. The segregation ratios of the interspecific F2 populations show nuclear interactions of one, two, or three nuclear genes regulating plastid function dependent on the parents. We further validated that biparental inheritance of plastids is common in section Ciconium, using diagnostic PCR primers. Our results pave the way for using the diverse species from section Ciconium, each with its own set of characteristics, as novel sources of desired breeding traits for P. × hortorum cultivars.

qRf8-1, a Novel QTL for the Fertility Restoration of Maize CMS-C Identified by QTL-seq

C-type cytoplasmic male sterility (CMS-C), one of the three major CMS types in maize, has a promising application prospect in hybrid seed production. However, the complex genetic mechanism underlying the fertility restoration of CMS-C remains poorly understood. The maize inbred line A619 is one of the rare strong restorer lines carrying the restorer gene Rf4, but different fertility segregation ratios are found in several F2 populations derived from crosses between isocytoplasmic allonucleus CMS-C lines and A619. In the present study, the segregation ratios of fertile to sterile plants in the (CHuangzaosi × A619) F2 and BC1F1 populations (36.77:1 and 2.36:1, respectively) did not follow a typical monogenic model of inheritance, which suggested that some F2 and BC1F1 plants displayed restored fertility even without Rf4. To determine the hidden locus affecting fertility restoration, next-generation sequencing-based QTL-seq was performed with two specific extreme bulks consisting of 30 fertile and 30 sterile rf4rf4 individuals from the F2 population. A major QTL related to fertility restoration, designated qRf8-1, was detected on the long arm of chromosome 8 in A619. Subsequently, qRf8-1 was further validated and narrowed down to a 17.93-Mb genomic interval by insertion and deletion (InDel) and simple sequence repeat (SSR) marker-based traditional QTL mapping, explaining 12.59% (LOD = 25.06) of the phenotypic variation. Thus, using genetic analyses and molecular markers, we revealed another fertility restoration system acting in parallel with Rf4 in A619 that could rescue the male sterility of CHuangzaosi. This study not only expands the original fertility restoration system but also provides valuable insights into the complex genetic mechanisms underlying the fertility restoration of CMS-C.

An Approach to Micro Segregation Level and Presence of Quench Cracks in Medium Carbon Low Alloy Steels

Samples from forged and heat-treated steel products with known quench crack histories have been mapped in order to study a possible relation between banding segregation and quench cracking. The steels were medium carbon low alloy steels, ingot and continuous cast, as well as vacuum arc remelt D6AC. EDS X-ray mapping was applied to characterize the banding segregation pattern from casting i.e. gradient of chemical composition that creates direction dependent properties. Trends for segregation ratios followed the expectations: the segregation ratios were higher for the quench sensitive steels.34CrNiMo6, ingot- and continuous cast, was then supplied for testing. Segregation level was pre-checked for decision for heat treatment and testing of as quenched tensile properties. There is an indication of 90 % reduction of the difference between Rm and Rp0.2, the work hardening, for the steel with lowest quality.

Mendel’s pea crosses: varieties, traits and statistics

A controversy arose over Mendel’s pea crossing experiments after the statistician R.A. Fisher proposed how these may have been performed and criticised Mendel’s interpretation of his data. Here we re-examine Mendel’s experiments and investigate Fisher’s statistical criticisms of bias. We describe pea varieties available in Mendel’s time and show that these could readily provide all the material Mendel needed for his experiments; the characters he chose to follow were clearly described in catalogues at the time. The combination of character states available in these varieties, together with Eichling’s report of crosses Mendel performed, suggest that two of his F3 progeny test experiments may have involved the same F2 population, and therefore that these data should not be treated as independent variables in statistical analysis of Mendel’s data. A comprehensive re-examination of Mendel’s segregation ratios does not support previous suggestions that they differ remarkably from expectation. The χ2 values for his segregation ratios sum to a value close to the expectation and there is no deficiency of extreme segregation ratios. Overall the χ values for Mendel’s segregation ratios deviate slightly from the standard normal distribution; this is probably because of the variance associated with phenotypic rather than genotypic ratios and because Mendel excluded some data sets with small numbers of progeny, where he noted the ratios “deviate not insignificantly” from expectation.

Estimation of Gene Frequencies in Clinical Research

Biometrics is a branch of statistics in which various mathematical and statistical techniques can be applied to biological research problems. These are two main areas of specialization of Biometry namely, Bioassays and Quantitative Genetics. Genetics concerns with Heredity and variation. Quantitative Genetics is concerned with the inheritances of quantitative differences between individuals.The essence of Quantitative Genetics is to estimate the genetic parameters such as Gene frequencies, segregation Ratios, Recombination of Genes and so on. Among them, the estimation of Gene Frequencies in the population is an important one. The proportion or percentage of genes in the population is called gene Frequency. In the present research articles, the ABO blood group system of man has been described by discussing the multiple alleles; genotypes, Frequencies and phenotypes of blood groups. The various estimation methods for estimating gene frequencies have gene presents in the present study.

The genetics and genome-wide screening of regrowth loci, a key component of perennialism in Zea diploperennis

Perennialism is common among the higher plants, yet little is known about its inheritance. To address this, six hybrids were made by reciprocally crossing perennial Zea diploperennis Iltis, Doebley & R. Guzman with inbred lines B73 and Mo17 and Rhee Flint, a heirloom variety, of Z. mays L. ssp. mays. All the F1 plants demonstrated several cycles of growth, flowering, senescence and regrowth into normal flowering plants, indicating a dominant effect of the Z. diploperennis alleles. The regrowability (i.e. the plants' ability to regrow after senescence) was stably transmitted to progeny of the hybrids, so we focused on this trait. Segregation ratios in the F2 generations are consistent with the trait controlled by two dominant, complementary loci, but do not exclude the influence of other modifiers or environment. Genome-wide screening with genotyping-by-sequencing (GBS) indicated two major regrowth loci, regrowth 1 and regrowth 2, were on chromosomes 2 and 7, respectively. These findings lay the foundation for further exploration of the molecular mechanism of regrowth in Z. diploperennis.