CREA Journals (Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria)
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Notes on Drosophila suzukii Matsumura (Diptera Drosophilidae): field survey in Tuscany and laboratory evaluation of organic products
Get PDFReported for the first time in Italy in 2009, the Spotted Wing Drosophila (SWD), Drosophila suzukii (Matsumura) (Diptera Drosophilidae), has rapidly spread throughout the country, causing serious damage on many fruit crops. The potential of infestation rate by D. suzukii is enormous: the females can complete many generations per year, and are able to attack the fresh, ripe fruit of many hosts by laying eggs under the soft skin; the larvae grow in the fruits and destroy the commercial value of them. The host range of SWD is reportedly wide, including both cultivated (soft fruits, sweet cherry, stone fruits etc…) and wild plants. In 2013, field surveys aimed at monitoring the presence of the insect on Tuscany territory, were regularly carried out: on an important district for the sweet cherry production with differently managed in control, on a biological blueberry orchard and even on other host plants neighboring the samples’ areas. D. suzukii was present in the monitored areas and its numerically large populations and heavy infestations on sweet cherries have shown that the species has settled in these areas. In laboratory tests, labeled organic products and substances of natural origin - in accordance with the requirements of EU regulations which provides for the reduction of chemicals - were evaluated as concern toxicity and residual effect on the pest. As regards effects of direct toxicity, products based on Beauveria bassiana have shown some effectiveness in the control of SWD, other organic products have shown interesting results. The evidences acquired are discussed
Alien insects on Eucalytpus spp.: an australian biocenosis in Tuscany
Get PDFDespite the diffusion of eucalypts in Italy, the community of insects hosted by these trees is scantily studied, while information about the presence of these pests is crucial for their potential threats to economic activities. This study aims at investigating and evaluating the status of Australian insects hosted by eucalypts in Tuscany (Central Italy). We found six established species and, among them, two species recently discovered in the study area were noteworthy for their potential impacts and diffusion: Gonipterus scutellatus complex and Glycaspis brimblecombei. We provided a distribution map on Tuscan coast for both these species and revised data on biology and presence of these and other alien insects Eucalyptus-linked species
Effect of drought on yield components of maize hybrids (Zea mays L)
Get PDFWhen investigating drought tolerance, it must not be forgotten that drought stress is a complex phenomenon ex¬hibiting quite different characters in different years and locations. For this reason, the plant response to drought is also a complex process. In our study, 83 maize hybrids originating from various countries were investigated over a period of two years, under irrigated and non-irrigated conditions. The drought tolerance of plants in the non-irrigated plots was analysed in terms of flowering synchrony and yield components. It could be concluded from the results that in response to long-term water deficit the period between tasselling and silking became longer, while the analysis of yield components revealed the greatest reductions in the number of kernels per ear and in the proportion of seed set. As the degree of proterandry increased, there was a decline in the grain yield, confirming that the analysis of this trait could be a way of predicting drought tolerance. Considerable differences in drought tolerance were observed between the genetic materials included in the analysis, suggesting the presence among these parental lines and hybrids of genotypes resistant to long-term water deficit, suitable for cultivation under dry conditions. An analysis of correlations between the traits revealed that proterandry should be treated as a priority trait when investigating drought stress tolerance, as better predictions can be made of both drought tolerance and potential yields, leading to more reliable selection for higher yields
Quantitative Trait Loci for Leaf Angle, Leaf Width, Leaf Length, and Plant Height in a maize (Zea mays L) B73 × Mo17 population
Get PDFMorphological traits affecting the canopy architecture of maize (Zea mays L) in high density cultivation can affect productivity. To identify quantitative trait loci affecting some of these traits, including leaf angle, leaf width, leaf length, and plant height, I analyzed these traits in the intermated B73 × Mo17 recombinant inbred line population, IBM-94, a maize population that other researchers developed for genetic studies by the scientific community. I collected data for the traits in replicated trials of IBM-94 grown in 2007, 2008, and 2009 at Sioux Falls, SD, USA. Means ± standard errors were for leaf angle = 26 ± 2.6°, leaf width = 91.0 ± 2.95 mm, leaf length 764.6 ± 20.76 mm, plant height = 2231.3 ± 101.24 mm. There was significant (a = 0.01) genotypic variation for each trait. Herita¬bility for height = 74.5%, leaf width = 86.2%, leaf length = 85.3%, and leaf angle = 90.5%. Phenotype data were combined with genetic maps and molecular marker haplotypes from the Maize Genetics and Genomics Database to analyze for quantitative trait loci by composite interval mapping using PLABMQTL computer software. One to three quantitative trait loci with logarithm of odds equivalent to a = 0.05 were identified for each trait. Three quanti¬tative trait loci were identified for leaf angle on chromosomes 1, 5, and 9, two for leaf width on chromosomes 2 and 8, one for leaf length on chromosome 2, and one for plant height on chromosome 4. Regression models explained 27.1% of leaf angle, 25.0% of leaf width, 9.1% of leaf length, and 8.4% of plant height variation
Genetic relatedness and population structure within the public Argentinean collection of maize inbred lines
Get PDFGenetic diversity of an Argentinean public temperate inbred maize collection has not been previously assessed. This collection includes mainly locally developed orange flint germplasm and a group of temperate inbred lines introduced from the US or derived from selection of crosses to genetic stocks from other countries, providing representativeness of exotic gene pools. To establish heterotic groups and patterns for breeding purposes and to assess genetic structure and relatedness for association-mapping studies, a public panel of a 103 maize inbreds was characterized using 50 microsatellite markers and pedigree information. By means of clustering-based and model-based methods the flint germplasm collection was split into two subpopulations that were separated from the BSSS-BS13-related lines. Relatedness estimates with coancestry and kinship coefficients provided additional information in the case of structured mixed membership of some germplasm. These three main subpopulations were in agreement with prior pedigree records. Allele diversity was high and sufficient to give major, minor and specific allele profiles to characterize inbred lines. Convenience of the use of minor allele frequency for structure and relatedness assessment is also discussed. In addition, molecular characterization provided useful information to elucidate inbred ancestry origins of germplasm with unknown pedigree records and to group them into known heterotic groups to define heterotic patterns
Molecular phylogenetic characterization and analysis of the WRKY transcription factor family responsive to Rhizoctonia solani in maize
Get PDFIn this study we have identified, based on the maize genome, 85 WRKY genes that were phylogenetically clustered into three families formed by 8 distinct subfamilies. The exon/intron structures and motif compositions of these WRKY genes were highly conserved in each subfamily suggesting their functional conservation. Moreover, based on qTelller analyses, the majority of these WRKY genes showed a specific temporal and spatial expression pattern. These WRKY genes, within the same group, manifested a distinct expression, indicating a similar function in their expression during the evolutionary process; this is reflected by their sub-functionalizations in their expression pattern concerning leaf developmental gradient, while mature bundle sheath, and mesophyll cells had a similar cellular localization and modality of expression. This study has also provided evidence of the presence of a subset of WRKY genes exhibiting a putative functional role in leaf sheath when infected with Rhizoctonia solani. This finding appears helpful for future functional investigations to unravel the roles of WRKY genes in plant pathogen resistance. Interestingly, in this study we have identified three WRKY genes that are predicted to be potential targets of miR160 and miR171b families. Therefore, this finding appears relevant in elucidating the biological functions of these transcription factors to clarify the molecular mechanisms affecting leaf sheath growth and development during fungal infection and plant resistance
A high-throughput regeneration protocol for recalcitrant tropical Indian maize (Zea mays L) inbreds
Get PDFImmature embryos from five select recalcitrant maize (Zea mays L) inbreds used as explants were evaluated for their ability to form callus, somatic embryos and subsequent regeneration into plants. The embryos were placed on N6 basal media with varying levels of 2,4-D (0.5, 1.0, 1.5, 2.0, and 2.5 mg l-1) and were regenerated on MS me¬dium supplemented with BAP (2 - 10 mg l-1), 2,4-D (0.25 mg l-1) and silver nitrate (0.85 mg l-1). Explants cultured on N6 medium supplemented with 2,4-D (2.0 mg l-1) were associated with the highest frequency of embryogenic calli and that of UMI 29 were highly embryogenic (78.67%). When synergism between dicamba and 2,4-D on Type II callus production in UMI 29 was sought to be investigated using 2,4-D (1 or 2 mg l-1) individually and in combina¬tion with dicamba (3.7 mg l-1) production of Type II callus with the greatest frequency of 83.33% was observed on N6 medium containing 3.7 mg l-1 dicamba + 1 mg l-1 2,4-D. The greatest percentage of shoot induction (82.67%) was observed on MS medium supplemented with BAP (10 mg l-1). Among the five genotypes tested, UMI 29 was associated with the highest percentage of callus initiation, shoot induction and mean number of developed shoots. The protocol described in this study can reliably be used to transform tropical maize inbreds as a routine
Characterizing corn hybrids (Zea mays L) for water shortage by principal components analysis
Get PDFIdentifying drought tolerant genotypes is very important for increasing corn yield. Thus four simple corn hybrids were submitted to periods of water shortage, at three phenological stages of the crop, to discriminate for drought tolerance by principal components analysis and identify their main differentiating characteristics under limited water conditions. Assessments were made of the leaf water potential, gas exchange, photochemical activity, grain yield and total dry matter. Analysis of variance was carried out and the mean values were compared by the Tukey test at 5% probability. Water shortage at the three phenological stages of the corn crop reduced the leaf water potential (Ψw), stomata conductance (gs), photosynthesis (Ai), transpiration (Ei), potential quantum efficiency of the PSII (Fv/Fm), apparent rate of electron transport (ETR), photochemical dissipation coefficient (qP) and increased the non-photochemical dissipation coefficient (NPQ), mainly when there was drought at the vegetative and flower¬ing stages. The data obtained for grain yield (GY) showed that the TOL1 hybrid was outstanding for drought toler¬ance at all the phenological stages of the crop, while the SENS1 hybrid demonstrated greatest sensitivity to water shortage, proving the pattern of tolerance and sensitivity of these respective hybrids to drought. The result of the principal components analysis showed that the corn hybrids could be separated into diversity groups for irrigation treatment at the vegetative stage, and that integrated photosynthesis (Ai) was considered the best characteristic to discriminate the irrigation treatments and hybrids when submitted to water shortage at this phenological stage of the crop
Bt transgenes minimally influence maize grain yield and lodging across plant populations
Get PDFAdoption of maize (Zea mays L) hybrids containing Bt (Bacillus thuringiensis) transgenes and increased plant population is widespread but little scientific research exists on their interactions with production environments in the Western Maize Belt of the United States. Two pairs of near-isogenic Bt and non-Bt maize hybrids were grown under rainfed and irrigated conditions from 2008 to 2010 at target populations from 49,300 to 111,100 plants ha-1 near Mead, NE. The objective was to determine the influence of the presence/absence of Bt transgenes for European corn borer [Ostrinia nubilalis (Hübner) - ECB] and corn rootworm [Diabrotica spp. - CRW] on maize yield and lodging across a range of target populations. Bt maize hybrids produced 0.6 Mg ha-1 more grain, 0.2 more ears m-2, and 1.3 g heavier 100-kernel weight than non-Bt hybrids in absence of visible ECB and CRW rootworm pressure. Yield of Bt and non-Bt hybrids responded similarly to increasing target population, with Dekalb DKC 58-16 and 58-19 increasing from 11.0 to 13.1 Mg ha-1 and Dekalb DKC 61-69 and 61-72 from 11.8 to 12.7 Mg ha-1 as the target population increased from 49,300 to 111,100 plants ha-1. Lodging increased linearly with increasing target population, with a greater increase in rainfed than irrigated environments. Lodging of Bt and non-Bt maize hybrids was inconsistent. Grain yield, seed and insecticide cost, likelihood of ECB and CRW infestation, and en¬vironmental concerns related to soil insecticide use should be the drivers when determining if Bt maize hybrid use is justified. If CRW resistance occurs, planting non-Bt maize hybrids along with application of soil insecticide is a viable alternative
Grain yield, photosynthesis and water relations in two contrasting maize landraces as affected by high temperature alone or in combination with drought
No full textOn a global basis, high temperature in conjugation with coincident drought poses the most important environmen¬tal constraint to plant survival and to crop productivity. Two experiments were conducted to investigate the effect of drought, heat, and the combined stresses on stress-tolerant C-3014 and stress-susceptible C-3015 maize landraces. The objective of the first experiment was to compare the effects of drought, heat, or the combined stresses on photosynthesis and water relations on two contrasting maize landraces under controlled conditions; the objective of the second experiment was to determine the effects on drought and heat stress on agronomic traits and grain yield in field. Results indicated that dry matter production, RWC, and Ψ was significantly reduced by the combination of high temperature and drought by 66, 38, and 105% respectively, which was greater and more severe than the reduction under drought or heat alone. In tolerant genotype the Ψ was reduced in 84%, how¬ever in the susceptible genotype the reduction was in 126%. The combined stresses also significantly decreased the A and gs in C-3015 more rapidly than C-3014. Under field, the combined stresses caused a severe decline in all agronomic traits, but the response was higher in the susceptible than tolerant genotype. The field evaluation confirmed the observation in controlled conditions, that C-3014 is more tolerant to high temperature and water stress combined, than C-3015