Contribution of bacterial cell nitrogen to soil humic fractions

Summary Living cells ofSerratia marcescens, uniformly labelled with¹⁵N, were added to samples of maple (Acer saccharum) and black spruce (Picea mariana) forest soils. After different periods of incubation from zero time to 100 days, the soils were subjected to alkali-acid and phenol extraction to provide humic acid, fulvic acid, humin and humoprotein fractions. Significant amounts of the cell nitrogen were recovered in the humic and fulvic acids immediately after addition. After incubation, less cell, nitrogen appeared in the humic acid and more in the fulvic acid. The amount of cell nitrogen recovered in the humin fraction increased with incubation. Roughly 5 to 10 per cent of the added cell nitrogen was found as amino acid nitrogen from humoprotein in a phenol extract of the humic acid. The data are consistent with the occurrence of co-precipitation of biologically labile biomass nitrogen compounds with humic polymers during the alkaline extraction procedure involved in the humic-fulvic fractionation.     

Regulation of ovule initiation by gibberellins and brassinosteroids in tomato and Arabidopsis: two plant species,two molecular mechanisms

Ovule primordia formation is a complex developmental process with a strong impact on the production of seeds. In Arabidopsis this process is controlled by a gene network, including components of the signalling pathways of auxin, brassinosteroids (BRs) and cytokinins. Recently, we have shown that gibberellins (GAs) also play an important role in ovule primordia initiation, inhibiting ovule formation in both Arabidopsis and tomato. Here we reveal that BRs also participate in the control of ovule initiation in tomato, by promoting an increase on ovule primordia formation. Moreover, molecular and genetic analyses of the co‐regulation by GAs and BRs of the control of ovule initiation indicate that two different mechanisms occur in tomato and Arabidopsis. In tomato, GAs act downstream of BRs. BRs regulate ovule number through the downregulation of GA biosynthesis, which provokes stabilization of DELLA proteins that will finally promote ovule primordia initiation. In contrast, in Arabidopsis both GAs and BRs regulate ovule number independently of the activity levels of the other hormone. Taken together, our data strongly suggest that different molecular mechanisms could operate in different plant species to regulate identical developmental processes even, as for ovule primordia initiation, if the same set of hormones trigger similar responses, adding a new level of complexity.     

Effective Identification of Low-Gliadin Wheat Lines by Near Infrared Spectroscopy (NIRS): Implications for the Development and Analysis of Foodstuffs Suitable for Celiac Patients

Scope

The aim of this work was to assess the ability of Near Infrared Spectroscopy (NIRS) to distinguish wheat lines with low gliadin content, obtained by RNA interference (RNAi), from non-transgenic wheat lines. The discriminant analysis was performed using both whole grain and flour. The transgenic sample set included 409 samples for whole grain sorting and 414 samples for flour experiments, while the non-transgenic set consisted of 126 and 156 samples for whole grain and flour, respectively.

Methods and Results

Samples were scanned using a Foss-NIR Systems 6500 System II instrument. Discrimination models were developed using the entire spectral range (400–2500 nm) and ranges of 400–780 nm, 800–1098 nm and 1100–2500 nm, followed by analysis of means of partial least square (PLS). Two external validations were made, using samples from the years 2013 and 2014 and a minimum of 99% of the flour samples and 96% of the whole grain samples were classified correctly.

Conclusions

The results demonstrate the ability of NIRS to successfully discriminate between wheat samples with low-gliadin content and wild types. These findings are important for the development and analysis of foodstuff for celiac disease (CD) patients to achieve better dietary composition and a reduction in disease incidence.     

Molecular and cytological characterization of an extra acrocentric chromosome that restores male fertility of wheat in the msH1 CMS system

A new CMS system designated as ‘msH1’ has been reported in bread wheat using the cytoplasm of H. chilense. While testing this system in different wheat backgrounds, a highly fertile line with chromosome number 42 plus an extra acrocentric chromosome was obtained. The extra chromosome did not pair with any wheat chromosome at meiosis, and progeny from this line which lack the acrocentric chromosome showed pollen abortion and male sterility. In order to establish the origin of this chromosome, FISH using H. chilense genomic DNA as probe was used and showed that it had originated from H. chilense chromosome(s). The novel chromosome did not possess sequences similar to wheat rDNA; however, the probe pSc119.2 from S. cereale containing the 120 bp family was found to occur at the end of its long arm. Data obtained from FISH and EST molecular markers confirm that the long arm of the acrocentric chromosome is indeed, the short arm of chromosome 1H^ch from H. chilense. We suggest that the novel chromosome originated from a deletion of the distal part of the long arm of chromosome 1H^ch. Neither the 1H^chS short arm, nor the whole chromosome 1H^ch restores pollen fertility of the alloplasmic wheat. Therefore, the restorer gene on the acrocentric chromosome must be located on the retained segment from the hypothetical 1H^chL, while some pollen fertility inhibitor could be present on the deleted 1H^chL distal segment. Disomic addition of the acrocentric chromosome was obtained and this line resulted fully stable and fertile.     

Host Plant and Biotype Density Interactions – Their Role in the Establishment of the Invasive B Biotype of Bemisia tabaci

Bemisia tabaciis a complex of closely related genetic types of whiteflies, few of which are invasive. One of these, B biotype, has proven to be particularly adapted to invading new areas, but the underlying reasons as to why it has a well-developed capacity to invade is not known. To develop an understanding of factors that may be contributing to B’s invasive capacity, inter-biotype mating interactions and host plant suitability for the exotic B (B. tabaci Mediterranean/Asia Minor/Africa) and the indigenous Australian (AN) biotype (B. tabaci Australia) were examined. The results suggest that when confined to a mutually acceptable host, B cannot establish when the ratio of AN : B exceeds 20 : 1. However, when simultaneously provided with a host that only it prefers, B is able to establish even at 50 : 1 (AN : B). Further, when both biotypes occur together the number of progeny per female increases (relative to the number produced when only one biotype is present). The response is observed for both biotypes, but is considerably greater in the case of B. In addition, B performs better in the presence of the AN biotype B. tabaci Australia while AN perform worse in coexistence with B, but only if the demographics allow B to mate without significant interference. This leads to the prediction that B will invade in circumstances where its unique hosts are of sufficient number to escape the full negative impact of inter-biotype mating interactions and reduced competitiveness in terms of reproductive rate, while exposing the indigenous biotype to the full effects of the interaction.     

The marker SCK13<Subscript>603</Subscript> associated with resistance to ascochyta blight in chickpea is located in a region of a putative retrotransposon

The sequence characterized amplified region (SCAR) marker SCK13(603), associated with ascochyta blight resistance in a chickpea recombinant inbred line (RIL) population, was used as anchored sequence for genome walking. The PCRs performed in the walking steps to walk in the same direction produced eight bands in 5' direction and five bands in 3' direction with a length ranking from 530 to 2,871 bp. The assembly of the bands sequences along with the sequence of SCK13(603) resulted in 7,815 bp contig. Blastn analyses showed stretches of DNA sequence mainly distributed from the nucleotides 1,500 to 4,500 significantly similar to Medicago truncatula genomic DNA. Three open reading frames (ORFs) were identified and blastp analysis of predicted amino acids sequences revealed that ORF1, ORF2 and ORF3 had significant similarity to a CCHC zinc finger protein, to an integrase, and to a precursor of the glucoamylase s1/s2, respectively, from M. truncatula. The high homology of the putative proteins derived from ORF1 and ORF2 with retrotransposon proteins and the prediction of the existence of conserved domains usually present in retrotransposon proteins indicate that the marker SCK13(603) is located in a region of a putative retrotransposon. The information generated in this study has contributed to increase the knowledge of this important region for blight resistance in chickpea.     

Characterization of ��/��- and ��-Gliadins in Commercial Varieties and Breeding Lines of Durum Wheat Using MALDI-TOF and A-PAGE Gels

In this work, gliadin composition has been analyzed in 33 accessions of durum wheat using MALDI-TOF MS and compared with A-PAGE results. The MALDI-TOF MS spectra were 29,900-42,500 Da, which corresponds to the α/β- and γ-gliadin regions in A-PAGE. The average of gliadin peaks per line was 23 for MALDI-TOF MS and only 14.8 bands for A-PAGE. MALDI-TOF MS identified 33 gliadin peaks in the durum wheat collection, 20 of which were unique peaks present in 7 lines. A-PAGE analysis identified 30 bands, of which only 4 were unique. Thus, the MALDI-TOF MS method was more sensitive than A-PAGE for identifying α/β- and γ-gliadins in the 33 durum wheat lines studied. Phylogenetic analyses performed using MALDI-TOF MS data assigned the durum wheat lines to two groups. The utility of MALDI-TOF MS to determine relationships among genotypes and for identification of durum wheat accessions is discussed.     

Suitability of Bemisia tabaci (Hemiptera: Aleyrodidae) instars for the parasitization by Encarsia bimaculata and Eretmocerus sp. nr. furuhashii (Hymenoptera: Aphelinidae) on glabrous and hirsute host plants

The host instar preferences of Encarsia bimaculata and Eretmocerus sp. nr. furuhashii parasitizing Bemisia tabaci and their development on four host plants, collard, eggplant, cucumber and tomato, were studied in the laboratory. Both of the parasitoids accepted all nymphal stages of B. tabaci, but E. bimaculata preferred third and fourth instars while Er. sp. nr. furuhashii preferred second and third instars under both choice and no choice conditions. Regardless of host stage parasitized, adults of parasitoids emerged only from fourth instars. When given the simultaneous choice of all instars, E. bimaculata reduced parasitization of first and second instars (3.73 and 4.76%, respectively) while increasing parasitization of third and fourth instars (5.44 and 6.93%, respectively), in contrast Er. sp. nr. furuhashii increased its parasitization of second and third instar nymphs (1.27 and 3.17%, respectively) and decreased that of first and fourth instars (7.0 and 3.06%, respectively). Host plants did not significantly influence instar preference for either parasitoid. Developmental periods of both the parasitoids from egg to adult emergence were longest when first instars were parasitized and shortest when fourth instars were selected. Parasitoid developmental time was generally shorter on glabrous plants than on hirsute plants.