This article correlates colonization with parameters, such as chemotaxis, biofilm formation, and bacterial growth, that are believed to be connected. We show here, by using two varieties of soybean plants that seeds axenically produced exudates, induced a chemotactic response in Bacillus amyloliquefaciens, whereas root exudates did not, even when the exudates, also collected under axenic conditions, were concentrated up to 200-fold. Root exudates did not support bacterial cell division, whereas seed exudates contain compounds that support active cell division and high cell biomass at stationary phase. Seed exudates of the two soybean varieties also induced biofilm formation. B. amyloliquefaciens colonized both seeds and roots, and plant variety significantly affected bacterial root colonization, whereas it did not affect seed colonization. Colonization of roots in B. amyloliquefaciens occurred despite the lack of chemotaxis and growth stimulation by root exudates. The data presented in this article suggest that soybean seed colonization, but not root colonization, by B. amyloliquefaciens is influenced by chemotaxis, growth, and biofilm formation and that this may be caused by qualitative changes of the composition of root exudates.

The purpose of this study was to isolate and select indigenous soil Pseudomonas and Bacillus bacteria capable of developing multiple mechanisms of action related to the biocontrol of phytopathogenic fungi affecting soybean crops. The screening procedure consisted of antagonism tests against a panel of phytopathogenic fungi, taxonomic identification, detection by PCR of several genes related to antifungal activity, in vitro detection of the antifungal products, and root colonization assays. Two isolates, identified and designated as Pseudomonas fluorescens BNM296 and Bacillus amyloliquefaciens BNM340, were selected for further studies. These isolates protected plants against the damping-off caused by Pythium ultimum and were able to increase the seedling emergence rate after inoculation of soybean seeds with each bacterium. Also, the shoot nitrogen content was higher in plants when seeds were inoculated with BNM296. The polyphasic approach of this work allowed us to select two indigenous bacterial strains that promoted the early development of soybean plants.

The spectroscopic changes in reflectance and fluorescence caused by phosphorus (P) starvation in Brassica napus L. young plants were evaluated. P deficiency produced an important decrease in reflectance values between 500 and 650 nm for both intact leaves and cotyledons. Furthermore, cotyledons under P deficiency showed a Chl-F ratio in the red/far-red region (F red /F far-red ) lower than that of non-stressed plants (1.91 and 2.89 respectively). As minimal differences in F red /F far-red were detected in leaves, P deficiencies may be better perceived by measuring changes in Chl-F emission in cotyledons than in leaves. Stressed cotyledons also showed different emission spectra in the blue green (maxima at 470 and 560 nm) from those of non-stressed cotyledons. The results are explained in terms of higher anthocyanin and chlorophyll contents and of damage to photosystem II. We evaluate that measuring variations in fluorescence and reflectance data may be useful to detect early damages induced by P stress.

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Genome engineering using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR associated (Cas) system offers vast potential in the improvement of crop plants. For CRISPR/Cas9 mediated editing in rice, transformation protocols should be standardized for specific genotypes. We standardized the Agrobacterium-mediated transformation protocols for two genotypes -Improved White Ponni (IWP) and WP-22-2, a gamma-ray induced mutant of Improved White Ponni. Three different modifications of MS basal medium, different days old calli and bacterial culture of different optical density were evaluated. Callus induction with IWP-CI-medium-1 followed by callus proliferation for one month in IWP-CI-medium-2 produced transformable calli. Infection with 0.3 OD Agrobacterium culture for 10 min was less damaging and successful than higher density cultures. The transformation efficiency varied between the Improved White Ponni and WP-22-2 emphasizing the need for standardizing tissue culture protocols for every genotype. Transformation efficiency of 9.46 per cent and 3.53 per cent respectively were observed for Improved White Ponni and WP-22-2 which were higher than previous reports.