Transgressivity in Key Functional Traits Rather Than Phenotypic Plasticity Promotes Stress Tolerance in A Hybrid Cordgrass

Hybridization might promote offspring fitness via a greater tolerance to environmental stressors due to heterosis and higher levels of phenotypic plasticity. Thus, analyzing the phenotypic expression of hybrids provides an opportunity to elucidate further plant responses to environmental stress. In the case of coastal salt marshes, sea level rise subjects hybrids, and their parents, to longer tidal submergence and higher salinity. We analyzed the phenotypic expression patterns in the hybrid Spartina densiflora x foliosa relative to its parental species, native S. foliosa, and invasive S. densiflora, from the San Francisco Estuary when exposed to contrasting salinities and inundations in a mesocosm experiment. 37% of the recorded traits displayed no variability among parents and hybrids, 3% showed an additive inheritance, 37% showed mid-parent heterosis, 18% showed best-parent heterosis, and 5% presented worst-parent heterosis. Transgressivity, rather than phenotypic plasticity, in key functional traits of the hybrid, such as tiller height, conveyed greater stress tolerance to the hybrid when compared to the tolerance of its parents. As parental trait variability increased, phenotypic transgressivity of the hybrid increased and it was more important in response to inundation than salinity. Increases in salinity and inundation associated with sea level rise will amplify the superiority of the hybrid over its parental species. These results provide evidence of transgressive traits as an underlying source of adaptive variation that can facilitate plant invasions. The adaptive evolutionary process of hybridization is thought to support an increased invasiveness of plant species and their rapid evolution

Analysis of reproductive performances during the formation of a synthetic rabbit strain

[EN] In 1995, a synthetic rabbit strain ('2666') was formed at INRA for commercial meat purposesby crossing the INRA '2066' strain and the 'V' strain from the Polytechnical University of Valencia (Spain).The development of some reproductive traits and body weight at palpation of the '2666' does was studiedfrom the F1 (first generation cross) to the F4 generation in comparison with the 'V' does. This developmentwas quantified in terms of Dickerson's crossbreeding parameters. The base strains did not differ significantlyfor any of the studied traits, either overall or in their direct and maternal genetic value. F1 does exhibitedsignificant individual heterosis for body weight (5.5% of the parental average), pregnancy rate (13.3%),total born (18.3%), born alive (24.4%) and weaned (21.0%) per litter born. Concerning body weight, asignificant crossbred superiority over the 'V' line was retained in the F2 but not thereafter. The rate ofpregnancy showed no crossbred advantage from the F2 on. Concerning litter size traits, the benefit ofcrossbreeding was maintained until the F4, but at a lower magnitude than in the F1. Body weight andpregnancy rate exhibited maternal heterosis, while litter size did not. Direct epistatic losses were significantfor body weight, tended towards significance for pregnancy rate, but did not affect litter size. Overall, thecomparison between the synthetic strain and the founders was favourable to the synthetics.Brun, J.; Baselga, M. (2005). Analysis of reproductive performances during the formation of a synthetic rabbit strain. World Rabbit Science. 13. doi:10.4995/wrs.2005.514SWORD1

Combining abilities and heterotic groups in Pisum sativum L.

The objective of this research was to investigate the use of heterosis and estimates of the general combining ability (GCA) and specific combining ability (SCA) for yield and the yield-related traits for identifying suitable parents and forming heterotic groups for pea- breeding programs. Seventy-six F1 hybrids derived from crosses between nineteen female lines and four male testers were evaluated during two seasons. Estimates of variance due to GCA and SCA effects and their relationship revealed predominantly additive effects for all traits. Parents with higher GCA values were "ZAV20" (female parent) and "ZAV23" (male parent).The cross "ZAV5 x ZAV23" showed the highest value for seed yield. Days to flowering and number of seeds per plot were the variables with the highest values for broad and narrow-sense heritability (0.93 and 0.65, respectively), indicating that these traits are highly heritable. The highest best parent heterosis for seed yield was observed in the "ZAV17 x DDR14" hybrid. Four heterotic groups were formed and validated by estimating the intra and inter group heterosis.Fil: Espósito, María Andrea. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Gatti, Ileana. Universidad Nacional de Rosario; ArgentinaFil: Cravero, Vanina Pamela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Lopez Anido, Fernando Sebastian. Universidad Nacional de Rosario; ArgentinaFil: Cointry Peix, Enrique Luis. Universidad Nacional de Rosario; Argentin

Parental Selection for Productivity Improvement in Indian Tropical Tasar Silkworm, Antheraea mylitta Drury (Lepidoptera: Saturniidae)

Global demand for Vanya silks in general and tasar silk in particular, call-for sustainable utilization of the country’s seri-biodiversity potential. Viability and productivity proportion of tasarculture in terms of seeds, cocoons and essentially raw silk, need attention for its vital role in reforming the livelihood and economic condition of tribal farmers. The conventional approaches on basic stock maintenance, commercial seed production, selective use of parental races or parents for heterosis and heterobeltiosis, method of backcrossing to exploit the traits of commercial importance and applying the advantage of genotype x environment (G x E) interactions are indispensable. In spite of current knowledge on sophisticated transgenic silkworm, appropriate application of on-hand parental resource material and methodologies can expedite tasar silk productivity improvement in addition to up-keep of the agro based cottage industry’s cost-effectiveness

Growth and slaughtering performance, carcase fleshiness and meat quality according to the plumage colour in Padovana male chickens slaughtered at 18 weeks of age

The aim of this trial was to investigate on the growth and meat quality of Padovana male chickens with different plumage varieties, chamois (PC - light brown feathers with white edge), silver (PS - white feathers with black edge), and their cross. The body weight of PC during the growth period was higher (p<.01) than PS, and it was 1.7 and 1.5 kg, respectively, at 126 d of age. At slaughter, PC showed higher weight of carcase (p<.05), breast and total fleshiness (breast, wings and legs) (p<.01), and thigh meat:bone ratio (p<.05). PS showed higher shanks weight on carcase weight (p<.01), Ilio tibialis a value (p<.01), water losses (p<.01) and shear force (p<.05) in breast meat than PC. Crossing PC males to PS females gave birds with white (Cross- W) and silver (Cross-S) plumage (3:1 ratio, respectively). The offspring genotypes showed similar body weight, and almost all slaughtering, carcase and meat quality traits studied. Cross-W and Cross-S showed significantly higher final body weight, breast and leg weight, total fleshiness and thigh meat:bone ratio than PS. For the Padovana breed, the plumage colour can involve productive and slaughtering performance, and carcase and meat quality, throughout the growing period. At 18 weeks of age, the Padovana male chickens show body weight and carcase fleshiness similar to that of a hybrid laying hen belonging to a light strain

The pattern and distribution of deleterious mutations in maize

Most non-synonymous mutations are thought to be deleterious because of their effect on protein sequence. These polymorphisms are expected to be removed or kept at low frequency by the action of natural selection, and rare deleterious variants have been implicated as a possible explanation for the "missing heritability" seen in many studies of complex traits. Nonetheless, the effect of positive selection on linked sites or drift in small or inbred populations may also impact the evolution of deleterious alleles. Here, we made use of genome-wide genotyping data to characterize deleterious variants in a large panel of maize inbred lines. We show that, in spite of small effective population sizes and inbreeding, most putatively deleterious SNPs are indeed at low frequencies within individual genetic groups. We find that genes showing associations with a number of complex traits are enriched for deleterious variants. Together these data are consistent with the dominance model of heterosis, in which complementation of numerous low frequency, weak deleterious variants contribute to hybrid vigor

Hybrid Varieties for Organic Cereals? Prospects and acceptance of hybrid breeding for organic production

Hybrid breeding utilizes the advantages characterizing F1 plants in a targeted manner: Vigour, uniformity, and a combination of all dominant traits of the parental lines. It gives breeders secure licences, as farmers can not save seed from hybrid varieties with a view to replanting. Regarding rye, the current advantages of hybrid varieties are primarily the higher yields but also improved resistances to lodging and sprouting. However, farmers can only benefit from higher yields if the limited market for organic rye in Switzerland can be expanded. The currently available hybrid rye varieties have higher susceptibility to leaf rust and ergot infections. The criticism of hybrid breeding and hybrid varieties concerns four areas: Firstly, the area of intrinsic quality: There are concerns, especially in the biodynamic movement, that continued inbreeding and pollen sterility as part of the breeding process will lead to losses regarding the more subtle ripening and nutritional qualities. This poses the question of adequate research methods. There is still considerable need for research. Secondly, the area of socio-economics: The fact that seed from hybrid varieties can not be saved and replanted leads to greater dependence on breeders and seed producers on the part of the farmers. At present this is not regarded as a problem in Switzerland as most farmers purchase new seed every year in any case but in the long term it renders agriculture liable to corruption. Thirdly, the ethical field: Some people have concerns regarding the breeders’ intervention into the flowering biology of the relevant cereal species. These interventions are at variance with the basic ethical-philosophical tenets of organic agriculture. Moreover, the fact that the hybrid varieties can not be saved and replanted effectively constitutes “patent protection” and promotes the ethically questionable change in meaning of seed from a cultural asset to a mere means of production. Fourthly: Hybrid varieties of self-sterile plants (e.g. rye) are genetically more vulnerable to environmental influences which were not considered during selection. This point is less relevant as regards self-fertile plants (oilseed rape, barley, wheat) as even today’s pureline varieties are already very uniform. It must be noted that amongst all hybrid varieties which are based on male sterility many so-called “different” varieties may share the same cytoplasm. As the criticisms regarding dependencies and genetic vulnerability only concern the future and the ethical concerns are not shared by everyone, it is the quality issue which is of particular relevance regarding the pending decision on whether or not to ban hybrid varieties in organic bread cereal production in Switzerland. Further research is essential. However, if one is to wait for the relevant results before taking a decision, this will certainly be too late. It would be more realistic to integrate a review clause into a potential decision to refrain from the use of hybrid varieties. Abstaining from the use of hybrid varieties in organic bread cereal production in Switzerland would give a clear signal to upstream and downstream sectors (breeders/trade and consumers respectively) that organic farming strives to consider long-term and future aspects of independence, quality, and diversity and that it would be ready to forego current agronomic advantages to this end. This would need to be clearly communicated to the trade sector when it comes to discussions on market prices