CREA Journals (Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria)
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The complex and multiform relationship between Nematoda and Bacteria
Get PDFThe relationship between nematodes and bacteria has taken place in different ways, from the simple trophic relation to the most sophisticated forms of symbiosis. Such symbiosis is not a primitive condition but it appeared and was established, being advantageous, during the evolution of different nematode taxa, independently and with different, sometimes complex, modalities ranging from mutualism to parasitism. The most significant modalities of mutualism are exposed here with particular stress on the highly specific relationship between entomopathogenic nematodes of the families Heterorhabditidae and Steinernematidae and their symbionts. This relationship, fruit of co-evolution between the nematodes and their bacteria, is treated from different points of view and at the light of the most recent genetic research
Nitrogen use efficiency in corn (Zea mays L) genotypes under different conditions of nitrogen and seeding date
Get PDFMany factors can contribute the nitrogen use efficiency in corn (Zea mays L) genotypes, like weather and soil, for instance. This present study aimed to identify efficient genotype using nitrogen across three seeding date and two covered nitrogen level at Tocantins-Brazil, during the season 2009/2010. The assessment characteristic were through: ear of corn yield and grain yield (kg ha-1), they were correct for 13% of humidity; agronomic nitrogen use efficiency (NUEA), partial by Moll et al and Low N index by Fischer et al. It was done through analysis of variance, considering the fixed genotype effect and the other random. Significant genotype, seeding date, covered nitrogen level, genotype x seeding date and genotype x covered nitrogen level were observed for ear of corn yield, grain yield, NUEA. The NUEA was significantly lower at LN than at HN for all genotypes. At LN the genotypes showed an average of 206 kg of produced grains for each N kg applied (kg kg-1). At HN they showed an average of 39 kg kg-1. The genotypes GEN 03, GEN 10 and GEN 16 were the most efficient that used the nitrogen, in both assessments methods above. It could be concluded that the choice of the methodology may be function of the study purpose, nitrogen level or seeding date effect
Characterization of the maize b-32 ribosome inactivating protein and its interaction with fungal pathogen development
Get PDFPlants respond to attack by pathogenic fungi with a complex network of responses, including the production and accumulation of proteins, such as the Ribosome Inactivating Proteins (RIPs) that are toxic or inhibitory to pathogens. In maize endosperm, a cytosolic albumin termed b-32 (RIP1) is synthesized in temporal and quantita¬tive coordination with the deposition of storage proteins. Research has shown that b-32 is able to i) enzymati¬cally inactive ribosomes modifying rRNA inhibiting protein synthesis in vitro, ii) inhibit the growth of Rhizoctonia solani mycelia in an in vitro and in planta assays, iii) reduce Fusarium culmorum head blight in wheat transgenic plants expressing b-32, and iv) diminish Fusarium verticillioides attack symptoms in leaf tissues assays of maize transgenic expressing ectopically b-32 protein. Similarly to other RIPs, maize b-32 is accumulated in the seed as an inactive precursor, which is converted into an active form by proteolytic processing which removes peptide segments from the N (residues 1-16 of pro-RIP) and C (residues 295-301) termini and also from the center (linker domain) of the polypeptide. In this review we will summarize evidence and advances related to the ability of the b-32 protein in contrasting pathogen attacks by considering and describing i) in vivo b-32 antifungal activity and ii) in vitro fungal development inhibition. These data provide information for assessing b-32 in developing plants with a higher capacity to contrast damages induced by pathogens
Genomic localization of the maize cross-incompatibility gene, Gametophyte factor 1 (ga1)
Get PDFGametophyte factors in maize (Zea mays L) mediate pollen-pistil interactions that confer preferential fertilization of some pistil genotypes by pollen carrying compatible alleles. Non-Mendelian segregation ratios caused by game¬tophyte factors have been observed in maize since the early 1920’s. In this study, we mapped the ga1 locus by analyzing segregation distortion and QTL for seed set in recombinant inbred lines from the cross B73 × Hp301. The dent corn parent of this cross, B73, carries ga1, whereas the popcorn parent Hp301 carries the Ga1-s al¬lele conferring preferential fertilization and cross-sterility. High density genotyping-by-sequencing markers were used to delineate the position of ga1 to a 2.6 Mbp region of the B73 reference sequence (AGP version 2). We also mapped ga1 based on its inheritance in backcross between W22 (ga1) and a near-isogenic line carrying Ga1-s on a chromosome segment introgressed from a popcorn variety. The chromosome blocks introgressed from popcorn into W22 were identified with a high-density SNP assay. We created simple sequence repeat markers targeting sequences linked to ga1 to track its inheritance in the W22 backcross populations. Recently, other researchers independently mapped ga1 in crosses of Chinese dent and popcorn lines, and we compared our results to theirs with reference to the B73 reference sequence. All lines of evidence were consistent, with the intervals containing ga1 among all studies overlapping in a 2.2 Mbp interval on chromosome 4 containing 13 predicted genes in the B73 reference sequence
Assessing sorghum [Sorghum bicolor (L) Moench] germplasm for new traits: food, fuels & unique uses
Get PDFSorghum [Sorghum bicolor (L) Moench] is the fifth most important cereal crop in the world; however, it has a wide range of other applications that are being explored with worldwide interest in renewable resources. The USA sorghum germplasm collection contains over 41,000 accessions that represent landraces and cultivars from over 115 countries. Traditionally, this collection has been evaluated for such traits as abiotic or biotic stress and other agronomic characteristics and little work has been done on the collection to characterize it for what might be considered “non-traditional” uses. Sorghum is a gluten-free cereal and recent research has begun to evaluate it for flour characteristics that would make it more amenable to baking and other processing technologies. New technologies are allowing sorghum germplasm to be screened for high levels of anti-oxidants that show promise in cancer research and glycemic control. In Europe, broomcorns continue to be grown for a unique market. Most recently, various forage accessions have been evaluated for their potential for renewable fuel production. Near infrared technologies have been developed to quickly and cost-effectively screen large numbers of accessions for such compositional characteristics as ash, lignin, glucan, xylan, galactan, and arabinan, all of which have unique properties related to various bioconversion technologies. Given its genetic variability, a known genomic sequence, and a robust seed industry, new utilization of sorghum within the health food market, niche utilization markets and the bioenergy arena make sorghum an attractive renewable resource for future generations
Exogenously applied RbCl revealed the role of potassium in the regulation of directional cell growth in the primary root of maize (Zea mays)
Get PDFRubidium was applied to the maize root system as a potassium antagonist. Exogenously applied RbCl dramatically decreased primary root length and caused radial expansion. However, the decrease in fresh weight was not prominent. The endogenous level of potassium decreased accompanying accumulation of rubidium following RbCl treatment. The altered root growth caused by RbCl was restored by KCl, suggesting that potassium is required for directional regulation of root cell growth. Microscopic observations of cells in the elongation zone of control and RbCl-treated roots supported this idea. Gravitropic curvature, which is dependent on ἀne regulation of differential cell elongation, was also impaired in RbCl-treated roots, indicating that potassium is not simply in volved in cell elongation itself, but is necessary for directional regulation of cell growth
Comparison of disease resistance of maize varieties from the 1950s to the 2000s in China
Get PDFThe objective of this investigation was to analyze trends in diseases resistance along with genetic gain. Experimental materials consisted of maize varieties selected from each decade beginning with the 1950s. These varieties were evaluated for resistance to maize dwarf mosaic virus (MDMV), maize rough dwarf virus (MRDV), common smut disease (CSD) and head smut disease (HSD) in several different locations. Artificial inoculation was adopted for infection with MDMV and HSD, whereas natural infection was used for infection MRDV and CSD. Results indicated that resistance of the newer varieties to MDMV, CSD, and HSD was greater than that of older varieties, but the correlation to decades was not significant. To date, no variety tested in China has shown resistance to MRDV, which is likely due to a lack of maize germplasm resources resistant to MRDV in China. So the next goal will be to import new germplasm resources and select resistant germplasm as the basis of breeding resistant varieties
The homeologous Zea mays gigantea genes: characterization of expression and novel mutant alleles
Get PDFThe two homeologous Zea mays gigantea (gi) genes, gi1 and gi2, arose from the last genome duplication event in the maize lineage. Homologs of these genes in other species are required for correct circadian rhythms and proper regulation of growth and development. Here we characterized the expression of these two maize gi genes. Although gi1 and gi2 shared comparable 24-hour rhythmic expression profiles, gi1 levels were consistently higher than gi2. Furthermore, short day photoperiods repressed gi2 expression. The transcriptional unit for gi1 is established based on 5’-RACE analysis. Two independent mutant alleles for gi1 are described that are caused by transposons of the Mutator (Mu) class inserted into the 5’-end of the gene. The type of Mu element and position of the transposon in gi1 was different for each gi1 allele. Mutant plants had a marked reduction in gi1 expression and carried transcripts interrupted by the Mu element. Together, these results provide a deeper understanding of the gi genes in maize. In addition, the novel gi1 mutant alleles described here will be valuable tools to study gi1 function in maize, as well as the role of circadian clock regulation in maize metabolism, growth, and development
Gamasid soil mites (Arachnida Acari) as indicators of the conservation status of forests
Get PDFThe Gamasida of 8 study areas in 5 different Sites of Community Interest (SCI of the Nature 2000 network) of Central Italy, characterized by beech forest and by mixed forests, were investigated to collect information for define the conservation status of the investigated sites. Samples were taken in autumn from the forest ground of the study sites (litter and soil till 7 cm in depth) during the three years of the study. Collected adult specimens were identified at species level and data were used to calculate the following indices: Shannon, Simpson, Eveness and Maturity index. On the whole, in the 8 study sites were recorded 63 species of Gamasida, belonging to 17 families, and some species seems to be a rare component of the fauna. Among study sites, diversity indices ranged from 2.20 to 2.57 for the Shannon index and from 0.82 to 0.90 for the Simpson, while the Maturity index ranged from 0.69 to 0.85; no substantial differences were observed among different study areas