Induction of unstable alleles at the temperature-sensitive Virescent-1 gene of maize using the transposable element Dissociation

SummaryTranspositive mutagenesis was employed to prepare genetic strains useful in cloning theVirescent-1locus (V1) of maize. A stepwise approach was used based on: (1) the isolation of putative insertion phenotypes (62 cases); (2) the verification of the genetic nature of the selected events (36v1-mmutant alleles induced); (3) the accurate genetic study of 11 alleles; (4) the genetic assessment that the allelesv1-m1andv1-m4are due to the insertion ofa Dselement into the locusV1; (5) the proof that aDs-like DNA element induces the inactivation of the wild type function in the allelev1-m1. The phenotype of the unstable alleles, studied by germinating and keeping maize seedlings at the temperature of 18 °C, are the following: allelesv1-m1, v1-m9, v1-m11, v1-m17andv1-m18showing a few revertant green sectors on their leaves;v1-m4exhibiting a reverse type of variegation; allelesv1-m2andv1-m13with a coarse pattern of variegation; allelesv1-m12, v1-m21andv1-m23frequently showing leaves part green with white stripes and part white with green stripes. For the alleles studied, in addition to somatic instability, germinal reversions also occurred. In some cases, these reversions resulted in stable derivatives with a different colour from that of the wild-type ('near green' or pale phenotypes). The results presented not only allow thev1-m1allele to be chosen as a starting material for cloning theV1locus, but also define the molecular strategy to be followed

Allelopathic cover crop of rye for integrated weed control in sustainable agroecosystems

The allelopathic potential of rye ( Secale cereale L.) is mainly due to phytotoxic benzoxazinones, compounds that are produced and accumulated in young tissues to different degrees depending on cultivar and environmental influences. Living rye plants exude low levels of benzoxazinones, while cover crop residues can release from 12 to 20 kg ha –1 . This paper summarizes the results obtained from several experiments performed in both controlled and field environments, in which rye was used as a cover crop to control summer weeds in a following maize crop. Significant differences in benzoxazinoid content were detected between rye cultivars. In controlled environments, rye mulches significantly reduced germination of some broadleaf weeds. Germination and seedling growth of Amaranthus retroflexus and Portulaca oleracea were particularly affected by the application of rye mulches, while Chenopodium album was hardly influenced and Abutilon theophrasti was advantaged by the presence of the mulch. With reference to the influence of agronomic factors on the production of benzoxazinoids, nitrogen fertilization increased the content of allelochemicals, although proportionally less than dry matter. The field trial established on no-till maize confirmed the significant weed suppressiveness of rye mulch, both for grass and broadleaf weeds. A significant positive interaction between nitrogen (N) fertilization and notillage resulting in the suppression of broadleaf weeds was observed. The different behavior of the weeds in the presence of allelochemicals was explained in terms of differential uptake and translocation capabilities. The four summer weeds tested were able to grow in the presence of low amounts of benzoxazolin-2(3H)-one (BOA), between 0.3 and 20 mmol g –1 fresh weight. Although there were considerable differences in their sensitivity to higher BOA concentrations, P. oleracea , A. retroflexus , and Ch. album represented a group of species with a consistent absorption capability. The insensitivity of A . theophrasti to BOA was due to reduced accumulation in seedlings. Overall, results confirm that the use of a rye cover crop in a suitable crop rotation represents a sustainable weed management practice permitting a reduction in the amount of herbicides used in agroecosystems, thus limiting the environmental risks of intensive agriculture

Molecular and phenotypic characterization of a collection of white grain sorghum [Sorghum bicolor (L.) Moench] for temperate climates

AbstractSorghum [Sorghum bicolor (L.) Moench] is a subsistence crop and the main food for populations in arid or semiarid regions and it is appreciated for the production of gluten-free products, forages, raw materials for industrial transformation and packaging. The end-use of different sorghum purposes having various plant or kernel characteristics require specific breeding programs to develop the desired ideotype. Sorghum grains can be classified according to kernel color, tannins and polyphenols content: white, yellow, red, brown, and black. White sorghum is characterized by a low level of total phenolic content and tannins. The advantage of using white sorghum is: increased protein digestibility, nutritional composition and consumer acceptance similar to other cereals. A collection of 117 white grain sorghums was characterized using 10 SSRs and preliminary agronomic observations were made for main traits. SSR analysis revealed from 10 to 33 alleles per locus.Observed heterozygosity was lower than expected according to the reproduction system of sorghum. Phylogenetic analysis revealed 6 main groups of genotypes. Only one group is constituted by genotypes with the same geographical origin (Egypt) while other groups are admixtures of different countries. The principal coordinate analysis revealed good correspondence between genetic profiles and groups evidenced by similar agronomic performances

Test on the effects of reconstituted soil on emergency speed and root growth in maize

Summary Reconstitution is a pedotechnique to counter land degradation and desertification. The reconstitution, patented by the research laboratory m.c.m. Ecosistemi, applies chemical-mechanical actions to a mixture of degraded soil and matrices (such as waste sludge) in order to produce reconstituted soil, a very high fertility soil. This paper is about a pot study in a greenhouse to investigate how reconstituted soil affects emergence speed and seminal roots development of Zea mays L. seedlings, in comparison with a Technosol. 200 seedlings are monitored up to the 16th day after the seeding. The emergence percentage is 98% on reconstituted soil and 91% on Technosol. Average length and weight of fresh seminal roots are higher on reconstituted soil

Aroma quality of fruits of wild and cultivated strawberry (Fragaria spp.) in relation to the flavour-related gene expression.

AbstractExpression profiles of flavour-related genes and the aroma quality of fruit headspace were investigated in the four strawberry genotypes 'Reine des Vallées' (Fragaria vesca), 'Profumata di Tortona' (F mos-chata), 'Onda' and VR 177 selection (F" x ananassa). Differences in the expression level of genes coding of strawberry alcohol acyltransferase (SAAT), F. x ananassa nerolidol synthase 1 (FaNESl) and F vesca monoterpene and sesquiterpene synthases (FvPINS and PINS1, respectively) were detected among these genotypes. In fruits of F. x ananassa the terpenoid profile was dominated by nerolidol, whereas wild spe–cies produced mainly monoterpenes. It was correlated with the higher induction of FaNES1 in cultivated and PINS gene in the wild Fragaria species. The flavour biogenesis in ripening fruits was determined by the expression of SAAT gene, especially visible for 'Profumata di Tortona' and 'Onda' strawberries. The fruit solid-phase microextraction (SPME) headspace was analysed using the Gas Chromatography-Olfac–tometry (GC-O), that allows for the chromatographic separation of volatiles together with their olfactomet-ric evaluation. 'Reine des Vallées' fruits have a peculiar profile characterized by high concentrations of limonene, linalool and mesifurane that resulted in "spiced", "citrus, floral" and "sweet, baked" descriptors. The character impact compound in 'Profumata di Tortona' fruits was ethyl butanoate, responsible for "sweet" and "fruity, strawberry" descriptors. However, it was detected in lower amount in comparison to the data obtained for F. x ananassa strawberries. The sesquiterpene nerolidol was identified in both culti–vated strawberry genotypes

Transcriptome profiling of soybean (Glycine max) roots challenged with pathogenic and non-pathogenic isolates of Fusarium oxysporum

Background Fusarium oxysporum is one of the most common fungal pathogens causing soybean root rot and seedling blight in U.S.A. In a recent study, significant variation in aggressiveness was observed among isolates of F. oxysporum collected from roots in Iowa, ranging from highly pathogenic to weakly or non-pathogenic isolates. Results We used RNA-seq analysis to investigate the molecular aspects of the interactions of a partially resistant soybean genotype with non-pathogenic/pathogenic isolates of F. oxysporum at 72 and 96 h post inoculation (hpi). Markedly different gene expression profiles were observed in response to the two isolates. A peak of highly differentially expressed genes (HDEGs) was triggered at 72 hpi in soybean roots and the number of HDEGs was about eight times higher in response to the pathogenic isolate compared to the non-pathogenic one (1,659 vs. 203 HDEGs, respectively). Furthermore, the magnitude of induction was much greater in response to the pathogenic isolate. This response included a stronger activation of defense-related genes, transcription factors, and genes involved in ethylene biosynthesis, secondary and sugar metabolism. Conclusions The obtained data provide an important insight into the transcriptional responses of soybean-F. oxysporum interactions and illustrate the more drastic changes in the host transcriptome in response to the pathogenic isolate. These results may be useful in the developing new methods of broadening resistance of soybean to F. oxysporum, including the over-expression of key soybean genes

Resistance to Fusarium verticillioides and fumonisin accumulation in maize inbred lines involves an earlier and enhanced expression of lipoxygenase (LOX) genes.

Fusarium verticillioides causes ear rot in maize and contaminates the kernels with the fumonisin myco-toxins. It is known that plant lipoxygenase (LOX)-derived oxylipins regulate defence against pathogensand that the host-pathogen lipid cross-talk influences the pathogenesis. The expression profiles of fif-teen genes of the LOX pathway were studied in kernels of resistant and susceptible maize lines, grownin field condition, at 3, 7 and 14 days post inoculation (dpi) with F. verticillioides. Plant defence responseswere correlated with the pathogen growth, the expression profiles of fungal FUM genes for fumonisinbiosynthesis and fumonisin content in the kernels. The resistant genotype limited fungal growth andfumonisin accumulation between 7 and 14 dpi. Pathogen growth became exponential in the susceptibleline after 7 dpi, in correspondence with massive transcription of FUM genes and fumonisins augmentedexponentially at 14 dpi. LOX pathway genes resulted strongly induced after pathogen inoculation in theresistant line at 3 and 7 dpi, whilst in the susceptible line the induction was reduced or delayed at 14 dpi.In addition, all genes resulted overexpressed before infection in kernels of the resistant genotype alreadyat 3 dpi. The results suggest that resistance in maize may depend on an earlier activation of LOX genesand genes for jasmonic acid biosynthesis

Transcriptome profiling of soybean (Glycine max) roots challenged with pathogenic and non-pathogenic isolates of Fusarium oxysporum.

Abstract Background: Fusarium oxysporum is one of the most common fungal pathogens causing soybean root rot and seedling blight in U.S.A. In a recent study, significant variation in aggressiveness was observed among isolates of F. oxysporum collected from roots in Iowa, ranging from highly pathogenic to weakly or non-pathogenic isolates. Results: We used RNA-seq analysis to investigate the molecular aspects of the interactions of a partially resistant soybean genotype with non-pathogenic/pathogenic isolates of F. oxysporum at 72 and 96 h post inoculation (hpi). Markedly different gene expression profiles were observed in response to the two isolates. A peak of highly differentially expressed genes (HDEGs) was triggered at 72 hpi in soybean roots and the number of HDEGs was about eight times higher in response to the pathogenic isolate compared to the non-pathogenic one (1,659 vs. 203 HDEGs, respectively). Furthermore, the magnitude of induction was much greater in response to the pathogenic isolate. This response included a stronger activation of defense-related genes, transcription factors, and genes involved in ethylene biosynthesis, secondary and sugar metabolism. Conclusions: The obtained data provide an important insight into the transcriptional responses of soybean-F. oxysporum interactions and illustrate the more drastic changes in the host transcriptome in response to the pathogenic isolate. These results may be useful in the developing new methods of broadening resistance of soybean to F. oxysporum, including the over-expression of key soybean genes

Functional genomic analysis of constitutive and inducible defense responses to Fusarium verticillioides infection in maize genotypes with contrasting ear rot resistance.

Background: Fusarium verticillioides causes ear rot in maize (Zea mays L.) and accumulation of mycotoxins, that affect human and animal health. Currently, chemical and agronomic measures to control Fusarium ear rot are not very effective and selection of more resistant genotypes is a desirable strategy to reduce contaminations. A deeper knowledge of molecular events and genetic basis underlying Fusarium ear rot is necessary to speed up progress in breeding for resistance. Results: A next-generation RNA-sequencing approach was used for the first time to study transcriptional changes associated with F. verticillioides inoculation in resistant CO441 and susceptible CO354 maize genotypes at 72 hours post inoculation. More than 100 million sequence reads were generated for inoculated and uninoculated control plants and analyzed to measure gene expression levels. Comparison of expression levels between inoculated vs. uninoculated and resistant vs. susceptible transcriptomes revealed a total number of 6,951 differentially expressed genes. Differences in basal gene expression were observed in the uninoculated samples. CO441 genotype showed a higher level of expression of genes distributed over all functional classes, in particular those related to secondary metabolism category. After F. verticillioides inoculation, a similar response was observed in both genotypes, although the magnitude of induction was much greater in the resistant genotype. This response included higher activation of genes involved in pathogen perception, signaling and defense, including WRKY transcription factors and jasmonate/ ethylene mediated defense responses. Interestingly, strong differences in expression between the two genotypes were observed in secondary metabolism category: pathways related to shikimate, lignin, flavonoid and terpenoid biosynthesis were strongly represented and induced in the CO441 genotype, indicating that selection to enhance these traits is an additional strategy for improving resistance against F. verticillioides infection. Conclusions: The work demonstrates that the global transcriptional analysis provided an exhaustive view of genes involved in pathogen recognition and signaling, and controlling activities of different TFs, phytohormones and secondary metabolites, that contribute to host resistance against F. verticillioides. This work provides an important source of markers for development of disease resistance maize genotypes andmay have relevance to study other pathosystems involving mycotoxin-producing fungi

Real-time determination of photosynthesis, transpiration, water-use efficiency and gene expression of two Sorghum bicolor (Moench) genotypes subjected to dry-down

Plant growth and productivity are strongly affected by limited water availability in drought prone environments. The current climate change scenario, characterized by long periods without precipitations followed by short but intense rainfall, forces plants to implement different strategies to cope with drought stress. Understanding how plants use water during periods of limited water availability is of primary importance to identify and select the best adapted genotypes to a certain environment. Two sorghum genotypes IS22330 and IS20351, previously characterized as drought tolerant and drought sensitive genotypes, were subjected to progressive drought stress through a dry-down experiment. A whole-canopy multi-chamber system was used to determine the in vivo water use efficiency (WUE). This system records whole-canopy net photosynthetic and transpiration rate of 12 chambers five times per hour allowing the calculation of whole-canopy instantaneous WUE daily trends. Daily net photosynthesis and transpiration rates were coupled with gene expression dynamics of five drought related genes. Under drought stress, the tolerant genotype increased expression level for all the genes analyzed, whilst the opposite trend was highlighted by the drought sensitive genotype. Correlation between gene expression dynamics and gas exchange measurements allowed to identify three genes as valuable candidate to assess drought tolerance in sorghum