Brace roots in C 3 Poaceae: where have they gone?

Brace roots are common in large C 4 Poaceae species, such as maize and sorghum. However, in other species, these roots were either never reported, or the existence of the trait was neglected. Here we report the presence of brace roots in a high-performing Avena sativa L. (oat) line.

Leaf manganese and phenolics as proxies of soil acidification and phosphorus acquisition mechanisms in lentil cultivars on alkaline soil.

Leaf manganese (Mn) concentration has been used as a proxy for root exudation and phosphorus (P) uptake under controlled conditions, but there are limited field studies that confirm its validity. On an alkaline, P-poor soil, four lentil cultivars ('Samos', 'Thessaly', 'Flip', 'Algeria') received two P rates (0 and 26.2kgPha-1 ), for two growing seasons, to study whether aboveground assessments [leaf P, Mn, phenolic concentration (TPhe)] can approximate rhizosphere physiological traits related to P acquisition [soil acidification (ΔpH), arbuscular mycorrhizal fungi (AMF) colonisation, acid phosphatase activity (APase)]. Phosphorus addition had no effect on the determined traits. Cultivars differed in leaf P, Mn, TPhe and AMF, but there was no clear pattern relating aboveground traits to rhizosphere traits related to P acquisition, thus not confirming that leaf Mn can be a proxy of root exudation. Of three growth stages [V 7-8, R1 (first bloom), R4 (flat pod)], R1 seemed to be critical, showing the highest leaf P, ΔpH, AMF and TPhe. Precipitation and temperatures over the growing season were determinants of lentil responses affecting rhizosphere activity, soil P availability and finally leaf traits. In conclusion, in lentil on alkaline and P-limiting soils, high leaf Mn and phenolic concentration are not reliable indicators of rhizosphere P-acquiring mechanisms.

Phosphorus fertilisation may induce Zn deficiency in cotton (Gossypium hirsutum) on calcareous Mediterranean soils.

On a P-poor, calcareous soil, three upland cotton (Gossypium hirsutum L.) cultivars (ST 402, ST 405, Zeta 2) were tested for 2years under three P rates (0, 13.1, 26.2kgPha-1 ). Leaf traits (SPAD values; specific leaf area, SLA; carbon isotope discrimination, Δ; 15 N natural abundance, δ15 N) and elements (N, P, K, C, Na, Zn) along with arbuscular mycorrhizal (AM) colonisation were measured at first open flower, full bloom and first open boll stages. Phosphorus addition decreased yield, but had no effect on fibre quality, a response attributed to P-induced Zn deficiency, previously reported for cereals. The best-performing cv., ST 405, had high SPAD and SLA, but the lowest P, N and Zn concentrations, an indication of cultivar's high use efficiency for these nutrients. At full bloom, SPAD was lowest, while SLA was highest. AM increased gradually with growth stages, while N, P, K and Zn concentrations showed an opposite trend, possibly due to a dilution effect. On Mediterranean calcareous soils, P fertilisation should take into account soil Zn levels in order to avoid P-Zn antagonistic relationships, which could impact negatively on yield.

Diversity and nodulation effectiveness of rhizobia and mycorrhizal presence in climbing dry beans grown in Prespa lakes plain, Greece.

The Prespa lakes plain is an isolated area where about 1000 ha are seeded to Phaseolus vulgaris L. and Phaseolus coccineus L. Nodulation, arbuscular mycorrhizal fungal (AMF) presence and the genetic diversity of rhizobia were evaluated by 16S-ITS-23S-RFLP patterns and by sequencing. The bean rhizobial population in the region was diverse, despite its geographic isolation. No biogeographic relationships were detected, apart from a Rhizobium tropici-related strain that originated from an acidic soil. No clear pattern was detected in clustering with bean species and all isolates formed nodules with both bean species. Most strains were related to Rhizobium leguminosarum and a number of isolates were falling outside the already characterized species of genus Rhizobium. Application of heavy fertilization has resulted in high soil N and P levels, which most likely reduced nodulation and AMF spore presence. However, considerable AMF root length colonization was found in most of the fields.

In the wild hybridization of annual Datura species as unveiled by morphological and molecular comparisons.

BACKGROUND: The present work aimed to verify whether intermediate variants were natural crosses between Datura species (D. stramonium forms and D. ferox). Their existence has been long ago insinuated but has not been studied using morphological features and molecular tools. The variants differed in stem coloring, upper bearing forks, and fruit characters. RESULTS: Principal Components Analysis of 11 morphological characteristics showed that D. ferox and D. stramonium (forms stramonium and tatula) were quite different and the putative hybrids were intermittent. The D. ferox × D. stramonium f. tatula was closer to the latter of its parents. Sequencing analysis revealed identical amplified trnL intron in all variants and a 100% homology with D. stramonium accession number EU580984.1 suggested that this plastid cannot discern Datura variants. However, genomic analysis with URP markers indicated that the hybrids had >60% genetic makeup similarity with both parents suggesting that the intermediate variants were putative inter-specific hybrids. Moreover, the dendrogram stemmed from cluster analysis of the fingerprint profile of variants placed D. stramonium and D. ferox in different branches indicating their genetic differentiation from each other as well as from their hybrids. CONCLUSIONS: The findings suggest that the natural hybridization of annual Datura species occurs. Extrapolating, this hybridization could be the first step for speciation. More possibly, it can alter population composition, its weediness and adaptability to local conditions.