Cristian Dal Cortivo

Genetic and phenotypic characterization of a novel brachytic2 allele of maize

The maize brachytic2 (br2) gene encodes a protein homologous to the Arabidopsis ABCB1 protein, which actively transports chemically diverse substrates across cellular membranes. This includes indole-3-acetic acid (IAA), the most abundant natural form of auxin, a key regulator of plant growth and tropisms. Defects in auxin transport are responsible for the short stature of br2 mutants. We describe a novel br2 mutant allele present in NC238, an inbred maize of medium stature and demonstrate that the mutant allele br2-NC238 is caused by the insertion of a novel transposon in intron IV of the br2 gene. A tall revertant of NC238 (NC238-rev) appeared spontaneously as a result of excision of the transposon from the br2 gene. This event yielded two completely isogenic versions of the NC238 inbred, one brachytic (NC238-ref) and one tall (NC238-rev). The presence of the transposon in br2-NC238 alters normal splicing of the transcript, producing several splicing forms. One splicing form, ABCB1-T02, was abundantly expressed in NC238-ref, while its expression was very weak in tall NC238-rev plants. Differences between NC238-rev and NC238-ref were also detected in the expression pattern of auxin transporter genes. Morphological changes associated with the br2-NC238 mutant allele included reduced length and increased diameter of the lower internodes. The shortening of plant stature was confirmed in the B73 genetic background by introgression of the br2-NC238. Our results demonstrate that br2-NC238 reduces plant height without altering other morphological traits, and might thus be useful in maize breeding programs when reduction of stature is desired.

16S rDNA Profiling to Reveal the Influence of Seed-Applied Biostimulants on the Rhizosphere of Young Maize Plants

In an open field trial on two agricultural soils in NW Italy, the impact of two seed-applied biostimulants on the rhizosphere bacterial community of young maize plants was evaluated. The 16S rDNA profiling was carried out on control and treated plant rhizosphere samples collected at the 4-leaf stage and on bulk soil. In both soils, the rhizospheres were significantly enriched in Proteobacteria, Actinobacteria, and Bacteriodetes, while the abundances of Acidobacteria, Cloroflexi and Gemmatimonadetes decreased compared with bulk soil. Among the culturable bacteria genera that showed an increase by both biostimulants, most are known to be beneficial for nutrient uptake, such as Opitutus, Chryseolinea, Terrimonas, Rhodovastum, Cohnella, Pseudoduganella and the species Anaeromyxobacter dehalogenans; others are known to be involved in root growth, such as Niastella, Labrys, Chloroflexia and Thermomonas; or in plant defence, such as Ohtaekwangia, Quadrisphaera, Turneriella, and Actinoallomurus. Both biostimulants were also found to stimulate gen. Nannocystis, a potential biocompetitive agent against aflatoxigenic Aspergillus moulds. Under controlled conditions, both biostimulants enhanced the shoot and root biomass at the 4–5 leaf stage. We conclude that the biostimulants do not decrease the biodiversity of the microbial community rhizosphere of young maize plants, but stimulate rare bacterial taxa, some involved in plant growth and pathogen resistance, a result that may have implications in improving crop management.

Wood biochar produces different rates of root growth and transpiration in two maize hybrids (Zea mays L.) under drought stress

ABSTRACT This study investigated the effects of wood-derived biochar (BC) applied at 1% to a C-poor silty-loam soil in the drought-tolerant (D24) and in the drought-sensitive (P1921) Pioneer Hi-Bred maize hybrids in pot and field trials (NE Italy). D24 had better growth than P1921 under rain-fed conditions without irrigation and soil amendment. The addition of biochar increased root growth in D24 (+38% root area) and decreases it in P1921 (−9%) at the silking stage, while the fraction of finer roots (<250 µm diam.) was reduced in D24 and increased in P1921. This led both hybrids to maintain the maximum transpiration at a lower fraction of transpirable soil water (from 82% to 45% in D24, and from 46% to 22% in P1921). There were no significant variations in plant nutrient contents, productivity and in the protein and starch contents of the grains, whereas the lipid content was reduced by biochar, particularly in P1921 (2.6% vs. 3% DW, −13%). We conclude that biochar can be profitably used to enhance drought tolerance in maize, possibly due to improvements in the physicochemical characteristics and the water content of treated soils, although maximum benefits are expected in drought-tolerant hybrids through increased root elongation and transpiration.

Biostimulant effects of seed-applied sedaxane fungicide: morphological and physiological changes in maize seedlings

Most crops are routinely protected against seed-born and soil-borne fungal pathogens through seed-applied fungicides. The recently released succinate dehydrogenase inhibitor (SDHI), sedaxane®, is a broad-spectrum fungicide, used particularly to control Rhizoctonia spp., but also has documented growth-enhancement effects on wheat. This study investigates the potential biostimulant effects of sedaxane and related physiological changes in disease-free maize seedlings (3-leaf stage) at increasing application doses (25, 75 and 150 μg a.i. seed-1) under controlled sterilized conditions. We show sedaxane to have significant auxin-like and gibberellin-like effects, which effect marked morphological and physiological changes according to an approximate saturation dose-response model. Maximum benefits were attained at the intermediate dose, which significantly increased root length (+60%), area (+45%) and forks (+51%), and reduced root diameter as compared to untreated controls. Sedaxane enhanced leaf and root glutamine synthetase (GS) activity resulting in greater protein accumulation, particularly in the above-ground compartment, while glutamate synthase (GOGAT) activity remained almost unchanged. Sedaxane also improved leaf phenylalanine ammonia-lyase (PAL) activity, which may be responsible for the increase in shoot antioxidant activity (phenolic acids), mainly represented by p-coumaric and caffeic acids. We conclude that, in addition to its protective effect, sedaxane can facilitate root establishment and intensify nitrogen and phenylpropanoid metabolism in young maize plants, and may be beneficial in overcoming biotic and abiotic stresses in early growth stages.

Effects of drought and salinity on maize phenology, morphology and productivity in a semi-arid environment

in rainfall patterns and temperature dynamics can seriously affect field crops and compromise productivity, due to increased drought and salinisation of agricultural land (Sarr et al., 2011). According to scenarios for climate change (IPCC, 2007), all these perturbations are predicted to become more accentuated in semi-arid areas, where competition for water resources for other human activities is also expected. Drought and salt stress are common threats for plant growth, development and survival in several Effects of drought and salinity on maize phenology, morphology and productivity in a semi-arid environment Romdhane Leila1,2, Dal Cortivo Cristian3, Vamerali Teofilo3*, Radhouane Leila2