Dissecting the genetics of cold tolerance in a multiparental maize population.

KEY MESSAGE: We identify the largest amount of QTLs for cold tolerance in maize; mainly associated with photosynthetic efficiency, which opens new possibilities for genomic selection for cold tolerance in maize. Breeding for cold tolerance in maize is an important objective in temperate areas. The objective was to carry out a highly efficient study of quantitative trait loci (QTLs) for cold tolerance in maize. We evaluated 406 recombinant inbred lines from a multi-parent advanced generation intercross (MAGIC) population in a growth chamber under cold and control conditions, and in the field at early and normal sowing. We recorded cold tolerance-related traits, including the number of days from sowing to emergence, chlorophyll content and maximum quantum efficiency of photosystem II (Fv/Fm). Association mapping was based on genotyping with near one million single nucleotide polymorphism (SNP) markers. We found 858 SNPs significantly associated with all traits, most of them under cold conditions and early sowing. Most QTLs were associated with chlorophyll and Fv/Fm. Many candidate genes coincided between the current research and previous reports. These results suggest that (1) the MAGIC population is an efficient tool for identifying QTLs for cold tolerance; (2) most QTLs for cold tolerance were associated with Fv/Fm; (3) most of these QTLs were located in specific genomic regions, particularly bin 10.04; (4) the current study allows genetically improving cold tolerance with genome-wide selection.

Effect of Testosterone Administration and Spiking on Reproductive Success of Broiler Breeder Flocks.

Age negatively affects reproductive success of broiler breeder flocks. One of the main hormones involved in the change of fertility with the age is testosterone (TT). The introduction of young males at later production stages of broiler flocks is known as spiking and is expected to reduce the fertility decline with age. The aim of this study was to determine the effect of injection of different levels of TT and the effect of spiking on reproductive fitness of broiler breeder flocks. Two experiments were conducted on Ross 308 breeder flocks for 10 weeks (41-50 weeks of age). The experiment 1 included a control and three treatments corresponding to three doses of TT (0.1, 0.2 and 0.3 cc), while the experiment 2 included a control and one treatment corresponding to spiking. The lower dose of TT (0.1 cc) and the spiking clearly slowed down the decline in hatchability. Therefore, either the external administration of TT to the males when the natural concentration of TT starts to decline or spiking the breeder flock with young roosters could contribute to improve reproductive success in later stages of the production cycle in broiler breeder flocks.

Knowledge, attitudes and tobacco use among nursing and physiotherapy students.

BACKGROUND: As future health educators, nursing and physiotherapy students will play an essential role in the prevention of smoking. AIM: To determine the prevalence of smoking among students and to analyse their knowledge of and attitudes towards smoking. METHOD: This was a descriptive cross-sectional study using an anonymous questionnaire and conducted in a Spanish Faculty of Health Sciences in 2013. FINDINGS: 247 nursing and physiotherapy students (82.33%) participated in the study. The global prevalence of smoking (18.2%) was lower compare with the general population group of the same age. We have observed statistical significance in relation to previous studies. Nursing and physiotherapy students showed a low nicotine dependence. We found a lack of knowledge about the harmful effects of cigarette consumption on health. Statistically significant results were also found in relation to degree courses (p < 0.01) as regards students' opinions about their knowledge of strategies and methods to help patients stop smoking. CONCLUSION: Most students started smoking before commencing their university studies; consequently, interventions should focus on cessation programmes. An analysis of university curricula leading to the award of a degree in the health sciences could serve to identify educational deficiencies in order to implement the necessary modifications. IMPLICATIONS FOR NURSING AND HEALTH POLICY: This paper presents an update in tobacco use characteristics amongst nursing and physiotherapy students. Those results have showed a need to improve the curricula in order to develop specific programmes to improve knowledge, attitudes and beliefs. Measures to prevent smoking must be taken at school.

Relationship between time to flowering and stalk and ear damage by second generation corn borers.

In the Mediterranean area, the main corn borer species are Sesamia nonagrioides Lefebvre (Mediterranean corn borer) and Ostrinia nubilalis Hübner (European corn borer). In the overall context of integrated pest control, it is possible to reduce the effect of a pest without having a negative effect on the environment by varying the sowing date. Benefits are possible if the most susceptible stages of the crop no longer coincide with the peak of the pest. We used different cycles of selection (0, 6, 8, 10, and 12) of two populations (Purdue A and Purdue B) of maize selected for early flowering to get a more precise estimation of the relationship between maturity of plant tissues and corn borer damage. We found a relationship between the damage produced by corn borers and the number of days from flowering to infestation. We conclude that, after flowering, a later stage of plant development at the moment of the infestation by corn borers reduces the damage caused by the larvae. Based on our results, we recommend to plant as early as possible so the tissues would be as mature as possible at the moment of insect attack.

Comparison of two methods of reciprocal recurrent selection in maize (Zea mays L.).

Reciprocal recurrent selection (RRS) was proposed for simultaneously improving two populations and their cross. A modification of the classical full-sib RRS (FS-RRS) was proposed in which the performance of full-sibs and S(2) families is combined in a selection index (FS-S(2)-RRS). The Mediterranean corn borer (MCB) is the main corn borer species in the Mediterranean and adjacent areas and produces important yield losses. We started two RRS programs (FS-RRS and FS-S(2)-RRS) from the same maize population in which the selection criterion was grain yield under artificial infestation with MCB eggs. Original populations, two cycles of selection derived from them by both RRS methods, and population crosses were evaluated under MCB attack and under insecticide treatment in three different environments. The objective was to compare the efficiency of the FS-RRS and the FS-S(2)-RRS methods for improving grain yield. We found that the FS-S(2)-RRS method was successful for improving the yield of the population cross under optimum conditions (the regression coefficient over cycles was b = 0.87** Mg ha(-1) cycle(-1)) without losing yield under high pressure of MCB attack (b = 0.07). On the contrary, FS-RRS failed to improve the yield of the population cross under optimum conditions (b = 0.65) and tended to decrease the yield under high levels of MCB attack (b = -0.26). We conclude that for developing high yielding and stable varieties, FS-S(2)-RRS is more efficient than the classical FS-RRS method.

Evaluation of the European Union Maize Landrace Core Collection for resistance to Sesamia nonagrioides (Lepidoptera: Noctuidae) and Ostrinia nubilalis (Lepidoptera: Crambidae).

Two corn borer species are the principal maize insect pests in Europe, the European corn borer, Ostrinia nubilalis (Hübner), and the pink stem borer, Sesamia nonagrioides (Lefebvre). Hence, it would be advisable to evaluate the European maize germplasm for corn borer resistance to generate European varieties resistant to corn borer attack. The creation of the European Union Maize Landrace Core Collection (EUMLCC) allowed the screening of most of the variability for European corn borer resistance present among European maize local populations from France, Germany, Greece, Italy, Portugal, and Spain, testing a representative sample. The objective of this study was the evaluation of stem and ear resistance of the EUMLCC to European corn borer and pink stem borer attack. Trials were made at two Spanish locations that represent two very different maize-growing areas. Populations that performed relatively well under corn borer infestation for stem and ear damage were 'PRT0010008' and'GRC0010085', among very early landraces; 'PRT00100120' and 'PRT00100186', among early landraces; 'GRC0010174', among midseason landraces; and 'ESP0070441', among late landraces. Either the selection that could have happen under high insect pressure or the singular origin of determined maize populations would be possible explanations for the higher corn borer resistance of some landraces. Landraces 'PRT0010008', 'FRA0410090', 'PRT00100186', and 'ESP0090214' would be selected to constitute a composite population resistant to corn borers and adapted to short season, whereas populations 'ESP0090033', 'PRT00100530', 'GRC0010174', and 'ITA0370005' would be used to make a resistant composite adapted to longer season.

Antibiosis of the pith maize to Sesamia nonagrioides (Lepidoptera: Noctuidae).

Thirteen inbred lines of maize (Zea mays L.) with different levels of stem resistance to the stem borer Sesamia nonagrioides Lefevbre were evaluated in the field and the laboratory to determine the antibiotic resistance to this pest. Inbreds CM151, CO125, and EP39 had antibiotic pith as well as stem resistance, so the pith could play a role in stem resistance. Inbreds A509, F473, and PB130 did not have antibiotic pith but had stem resistance; therefore, other mechanisms could confer stem resistance. Finally, the inbred MS1334 had antibiotic pith and did not show stem resistance; thus, other factors could compensate the effect of the pith. Therefore, although pith antibiotic compound seems to play a role in the defense against S. nonagrioides attack, it is not the only possible mechanism of defense.