Incompatible Hybrids Research Articles

Ammonium and nitric oxide condition the establishment of Arabidopsis Ler/Kas-2 immune-related hybrid incompatibility

Main ConclusionHigh ammonium suppresses hybrid incompatibility between Ler and Kas-2 accessions through lowering nitric oxide levels and nitrate reductase activity required for autoimmunity.The immune-related hybrid incompatibility (HI) between Landsberg erecta (Ler) and Kashmir-2 (Kas-2) accessions is due to a deleterious genetic interaction between the RPP1 (RECOGNITION OF PERONOSPORA PARASITICA1)-like Ler locus and Kas-2 alleles of the receptor-like kinase SRF3 (STRUBBELIG RECEPTOR FAMILY 3). The genetic incompatibility is temperature-dependent and leads to constitutive activation of the salicylic acid (SA) pathway, dwarfism and cell death at 14–16 °C. Here we investigated the effect of nutrition on the occurrence of Ler/Kas-2 HI and found that high ammonium suppresses Ler/Kas-2 incompatible phenotypes independently of the ammonium/nitrate ratio. Ammonium feeding leads to compromised disease resistance to Pseudomonas syringae pv. tomato DC3000, lower total SA, nitric oxide and nitrate reductase activity in Ler/Kas-2 incompatible hybrids. In addition, we find that Ler/Kas-2 incompatibility is dependent on NPR1 (NONEXPRESSER OF PR GENES 1) and nitric oxide production. Overall, this work highlights the effect of nutrition on the expression of incompatible phenotypes independently of temperature.

Sizing of an Islanded Wind-Solar-Battery Hybrid Power System for a Zero-Energy House in Afyon Turkey

Renewable energy systems offer sustainable solutions for the energy need of the world. Hybrid systems can be an alternative for remote off-grid houses that do not have connection to the electricity grid. This study examines sizing of an islanded wind-solar-battery power system for a zero-energy house that does not have a grid connection in Afyon Turkey. For this remote house, continuous power supply is an essential requirement and the designed system must guarantee reliable uninterrupted supply of power to the house. In an off-grid wind-solar-battery hybrid system, if different rated wind turbines and/or different number of solar panels are used in the system, the minimum number of batteries needed in the hybrid system would be different in order the meet the uninterrupted continuous power supply requirement. In practice it is the usual case that, due to incompatible hybrid system components the consumers suffer from no electric power occasionally. In this study, using power consumption data of the considered remote house and actual wind and solar measurement data of Afyon site, sizing analysis for a hybrid wind-solar-battery power system is done. For a sizing analysis, calculations that use actual small time interval data are essential to ensure uninterrupted continuous power from a hybrid system.

Perturbation of parentally biased gene expression during interspecific hybridization.

Interspecific hybridization often induces epigenetic remodeling that leads to transposon activation, gene expression changes, and loss of imprinting. These genomic changes can be deleterious and contribute to postzygotic hybrid incompatibility. In Arabidopsis, loss of genomic imprinting of PHERES1 and presumed failure of Polycomb Repressive Complex contributes to seed inviability observed in A. thaliana X A. arenosa interspecific hybrids. We used this species pair to further analyze the relationship between parentally biased gene expression and postzygotic hybrid incompatibility using two A. thaliana accessions, Col-0 and C24, with differential seed survival. We found that parentally biased expression was perturbed to a similar degree in both A. thaliana hybrids for PHERES1, HDG3, and six other normally paternally expressed genes. We propose that early genome remodeling and loss of imprinting of seed development genes induces lethality in both compatible and incompatible hybrids.

Early Disruption of Maternal–Zygotic Interaction and Activation of Defense-Like Responses inArabidopsisInterspecific Crosses

Seed death resulting from hybridization between Arabidopsis thaliana and Arabidopsis arenosa has complex genetic determination and involves deregulation 5 to 8 d after pollination (DAP) of agamous-like genes and retroelements. To identify causal mechanisms, we compared transcriptomes of compatible and incompatible hybrids and parents at 3 DAP. Hybrids misexpressed endosperm and seed coat regulators and hyperactivated genes encoding ribosomal, photosynthetic, stress-related, and immune response proteins. Regulatory disruption was more severe in Columbia-0 hybrids than in C24 hybrids, consistent with the degree of incompatibility. Maternal loss-of-function alleles for endosperm growth factor transparent testa glabra2 and HAIKU1 and defense response regulators non-expressor of pathogenesis related1 and salicylic acid induction-deficient2 increased hybrid seed survival. The activation of presumed polycomb repressive complex (PRC) targets, together with a 20-fold reduction in expression of fertilization independent seed2, indicated a PRC role. Proximity to transposable elements affected natural variation for gene regulation, but transposon activation did not differ from controls. Collectively, this investigation provides candidates for multigenic orchestration of the incompatibility response through disruption of endosperm development, a novel role for communication between endosperm and maternal tissues and for pathways previously connected to immunity, but, surprisingly, does not identify a role for transposons.

Production of peanut hybrid seeds in an intersectional cross through post-pollination treatment of flower bases with plant growth regulators

To broaden the narrow gene base of the cultivated peanut and utilize sources of resistance to abiotic/biotic stresses, quality-related traits and high yielding factors, much attention has been paid to wild relatives of the oilseed crop since 1980s. Species outside section Arachis are cross-incompatible with A. hypogaea L.; even some of the species from section Arachis, which are supposed to be compatible, may also encounter obstacles when crossed with the peanut cultigen. The objective of the present communication is to study the effects of simple hormone treatment on production of true incompatible hybrids in peanut to replace the tedious and lengthy in vitro embryo rescue procedures currently in use. In the incompatible cross, A. hypogaea cv Qunyu 101 × A. paraguariensis, post-pollination application of a hormone aqueous solution (IAA 4 mg/L + GA 2 mg/L) at flower bases resulted in 42 seeds, of which 26 were identified as true hybrids by allele-specific PCR for FAD2A genotyping. As a desirable alternative to in vitro embryo/ovules/peg culture, the present method may facilitate the utilization of wild species in peanut breeding. The method described here for peanut may be of reference to other crop plants where embryo abortion is also a problem.

Molecular marker systems for Oenothera genetics.

The genus Oenothera has an outstanding scientific tradition. It has been a model for studying aspects of chromosome evolution and speciation, including the impact of plastid nuclear co-evolution. A large collection of strains analyzed during a century of experimental work and unique genetic possibilities allow the exchange of genetically definable plastids, individual or multiple chromosomes, and/or entire haploid genomes (Renner complexes) between species. However, molecular genetic approaches for the genus are largely lacking. In this study, we describe the development of efficient PCR-based marker systems for both the nuclear genome and the plastome. They allow distinguishing individual chromosomes, Renner complexes, plastomes, and subplastomes. We demonstrate their application by monitoring interspecific exchanges of genomes, chromosome pairs, and/or plastids during crossing programs, e.g., to produce plastome-genome incompatible hybrids. Using an appropriate partial permanent translocation heterozygous hybrid, linkage group 7 of the molecular map could be assigned to chromosome 9.8 of the classical Oenothera map. Finally, we provide the first direct molecular evidence that homologous recombination and free segregation of chromosomes in permanent translocation heterozygous strains is suppressed.

Study on morphological, rheological, and mechanical properties of PP/SEBS‐MA/SGF hybrid composites

AbstractHybrid composite samples composed of polypropylene as matrix, 20% short glass fibers (SGF) as reinforcement and varying amount of maleic anhydride (MA) grafted SEBS as compatibilizer and impact modifier were prepared by melt mixing in a modular twin screw extruder. The SEM examination performed on cryogenically fractured surfaces of hybrid samples showed a three‐phase type morphology in which SGF and rubber phase finely distributed in the PP matrix. SEM results also revealed that in the hybrid samples containing SEBS‐MA, the surface of the SGF are coated with a thin layer of SEBS‐MA, indicating a strong adhesion between SGF and matrix materials. The results of rheological studies showed nearly equal viscosity for compatible and incompatible hybrid samples. Tensile yield strength enhanced with increasing rubber content up to 10% above which it decreased and highest impact strength enhancement was obtained for sample containing 20% rubber. The impact strength of composites was found to be increased with increasing the SGF content. In final, it was shown that a good balance between stiffness and toughness could be achieved by adjusting the SGF and rubber content in this ternary system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2704–2710, 2007