Enhancing defense against rice blast disease: Unveiling the role of leaf endophytic firmicutes in antifungal antibiosis and induced systemic resistance.

Rice remains the primary staple for more than half of the world's population, yet its cultivation faces numerous challenges, including both biotic and abiotic stresses. One significant obstacle is the prevalence of rice blast disease, which substantially diminishes productivity and increases cultivation costs due to frequent fungicide applications. Consequently, the presence of fungicide residues in rice raises concerns about compliance with international maximum residue limits (MRLs). While host resistance has proven effective, it often remains vulnerable to new variants of the Magnaporthe oryzae pathogen. Therefore, there is a critical need to explore innovative management strategies that can complement or enhance existing methods. An unexplored avenue involves harnessing endophytic bacterial communities. To this end, the present study investigates the potential of eleven endophytic Bacillus spp. in suppressing Pyricularia oryzae, promoting plant growth, and eliciting a defense response through phyllobacterization. The results indicate that the secreted metabolome and volatilome of seven tested isolates demonstrate inhibitory effects against P.oryzae, ranging from a minimum of 40% to a maximum of 70%. Bacillus siamensis L34, B. amyloliquefaciens RA37, B. velezensis L12, and B. subtilis B18 produce antifungal antibiotics targeting P.oryzae. Additionally, B. subtilis S4 and B. subtilis S6 emerge as excellent inducers of systemic resistance against blast disease, as evidenced by elevated activity of biochemical defense enzymes such as peroxidase, polyphenol oxidase, and total phenol content. However, a balance between primary metabolic activity (e.g., chlorophyll content, chlorophyll fluorescence, and photosynthetic rate) and defense activity is observed. Furthermore, specific endophytic Bacillus spp. significantly stimulates defense-related genes, including OsPAD4, OsFMO1, and OsEDS1. These findings underscore the multifaceted potential of endophytic Bacillus in managing blast disease through antibiosis and induced systemic resistance. In conclusion, this study highlights the promising role of endophytic Bacillus spp. as a viable option for blast disease management. Their ability to inhibit the pathogen and induce systemic resistance makes them a valuable addition to the existing strategies. However, it is crucial to consider the trade-off between primary metabolic activity and defense response when implementing these bacteria-based approaches.

Linking genome wide RNA sequencing with physio-biochemical and cytological responses to catalogue key genes and metabolic pathways for alkalinity stress tolerance in lentil (Lens culinaris Medikus).

BACKGROUND: Alkaline soils cause low productivity in crop plants including lentil. Alkalinity adaptation strategies in lentil were revealed when morpho-anatomical and physio-biochemical observations were correlated with transcriptomics analysis in tolerant (PDL-1) and sensitive (L-4076) cultivars at seedling stage. RESULTS: PDL-1 had lesser salt injury and performed better as compared to L-4076. Latter showed severe wilting symptoms and higher accumulation of Na+ and lower K+ in roots and shoots. PDL-1 performed better under high alkalinity stress which can be attributed to its higher mitotic index, more accumulation of K+ in roots and shoots and less aberrantly dividing cells. Also, antioxidant enzyme activities, osmolytes' accumulation, relative water content, membrane stability index and abscisic acid were higher in this cultivar. Differentially expressed genes (DEGs) related to these parameters were upregulated in tolerant genotypes compared to the sensitive one. Significantly up-regulated DEGs were found to be involved in abscisic acid (ABA) signalling and secondary metabolites synthesis. ABA responsive genes viz. dehydrin 1, 9-cis-epoxycarotenoid dioxygenase, ABA-responsive protein 18 and BEL1-like homeodomain protein 1 had log2fold change above 4.0. A total of 12,836 simple sequence repeats and 4,438 single nucleotide polymorphisms were identified which can be utilized in molecular studies. CONCLUSIONS: Phyto-hormones biosynthesis-predominantly through ABA signalling, and secondary metabolism are the most potent pathways for alkalinity stress tolerance in lentil. Cultivar PDL-1 exhibited high tolerance towards alkalinity stress and can be used in breeding programmes for improving lentil production under alkalinity stress conditions.

Molecular mapping of aluminium resistance loci based on root re-growth and Al-induced fluorescent signals (callose accumulation) in lentil (Lens culinaris Medikus).

Development of aluminium (Al) resistant genotypes through molecular breeding is a major approach for increasing seed yield under acidic conditions. There are no available reports on mapping of Al resistance loci and molecular breeding for Al resistant varieties in lentil. The present study reports a major quantitative trait loci (QTL) for Al resistance using simple sequence repeat (SSR) markers in F2 and F3 mapping populations derived from contrasting parents. Phenotypic response to Al was measured on the bases of root re-growth (RRG), fluorescent signals (callose accumulation) and Al contents in hydroponic assay. After screening 495 SSR markers to search polymorphism between two contrasting parents, 73 polymorphic markers were used for bulk segregation analysis. Two major QTLs were identified using seven trait linked markers, one each for fluorescent signals and RRG mapped on linkage group (LG) 1 under Al stress conditions in F2 mapping population of cross BM-4 × L-4602. One major QTL (qAlt_fs) was localised between PLC_88 and PBA_LC_373, covering 25.9 cM with adjacent marker PLC_88 at a distance of 0.4 cM. Another major QTL (qAlt_rrg) for RRG was in the marker interval of PBA_LC_1247 and PLC_51, covering a distance of 45.7 cM with nearest marker PBA_LC_1247 at a distance of 21.2 cM. Similarly, in F3 families of BM-4 × L-4602 and BM-4 × L-7903, LG-1 was extended to 285.9 and 216.4 cM respectively, having four newly developed genic-SSR markers. These QTLs had a logarithm of odd (LOD) value of 140.5 and 28.8 along with phenotypic variation of 52% and 11% for fluorescent signals and RRG respectively, whereas, qAlt_rrg had LOD of 36 and phenotypic variance of 25% in F3 population of BM-4 × L-4602. Two major QTLs identified in the present study can be further dissected for candidate gene discovery and development of molecular markers for breeding improved varieties with high Al resistance.

Spermidine exogenous application mollifies reproductive stage heat stress ramifications in rice.

Introduction: Rice productivity is severely hampered by heat stress (HS) which induces oxidative stress in this crop. This oxidative stress can be alleviated using various exogenous chemicals, including spermidine (Spd). Therefore, the present study was carried out to characterize HS components and to elucidate the role of exogenous Spd application in rice at the flowering stage. Methods: Two contrasting rice genotypes, i.e. Nagina22 (N22) and Pusa Basmati-1121 (PB-1121) were placed in temperature tunnels and exposed to HS (38-43°C) with and without Spd (1.5 mM) foliar application during the heading stage till the end of the anthesis stage. Result: Heat stress induced the production of H2O2 and thiobarbituric acid reactive substances, which resulted in lower photosynthesis, spikelet sterility, and reduced grain yield. Interestingly, foliar application of Spd induced antioxidant enzyme activities and thus increased total antioxidant capacity resulting in higher photosynthesis, spikelet fertility, and improved grain yield under HS in both genotypes. Under HS with Spd, higher sugar content was recorded as compared to HS alone, which maintained the osmotic equilibrium in leaf and spikelets. Spd application initiated in vivo polyamine biosynthesis, which increased endogenous polyamine levels. Discussion: This study corroborates that the exogenous application of Spd is promising in induction of antioxidant defence and ameliorating HS tolerance in rice via improved photosynthesis and transpiration. Thereby, the study proposes the potential application of Spd to reduce HS in rice under current global warming scenario.

Evaluation of cultivated and wild genotypes of Lens species under alkalinity stress and their molecular collocation using microsatellite markers.

In this study, 285 lentil genotypes were phenotyped under hydroponic and alkaline field conditions. Significant genotypic variation for alkalinity stress was observed among the six Lens species screened hydroponically and in the field having pH up to 9.1. The crucial parameters, like whole Na+ and K+ contents and the Na+/K+ ratio at 40 mM NaHCO3 were found significantly correlated with seedling survivability under hydroponics (r = -0.95, r = 0.93 and -0.97). Genotypes, ranked on the bases of seed yield, restricted uptake of Na+ with thick pith area, increased vascular bundles, less H2O2 production and low Na+/K+ ratio, were found important physio-anatomical traits for alkalinity stress tolerance. The proper regulation of Na+ uptake was found for maintaining higher K+. This relationship is probably the main factor responsible for a better mechanism for tolerance to high pH up to 9.1 in tolerant breeding lines PDL-1 and PSL-9 (cultivars) and ILWL-15, ILWL-192 and ILWL-20 (wild accessions). Based on UPGMA dendrogram, all the genotypes were clustered into four diverse groups. DMRT was implied within the group to differentiate genotypes based on phenotypic response under alkalinity stress. These results can be utilized for selecting diverse parents for developing alkalinity tolerant genotypes.

Discerning morpho-anatomical, physiological and molecular multiformity in cultivated and wild genotypes of lentil with reconciliation to salinity stress.

One hundred and sixty two genotypes of different Lens species were screened for salinity tolerance in hydroponics at 40, 80 and 120 mM sodium chloride (NaCl) for 30 d. The germination, seedling growth, biomass accumulation, seedling survivability, salinity scores, root and shoot anatomy, sodium ion (Na+), chloride ion (Cl-) and potassium ion (K+) concentrations, proline and antioxidant activities were measured to evaluate the performance of all the genotypes. The results were compared in respect of physiological (Na+, K+ and Cl-) and seed yield components obtained from field trials for salinity stress conducted during two years. Expression of salt tolerance in hydroponics was found to be reliable indicator for similarity in salt tolerance between genotypes and was evident in saline soil based comparisons. Impressive genotypic variation for salinity tolerance was observed among the genotypes screened under hydroponic and saline field conditions. Plant concentrations of Na+ and Cl- at 120 mM NaCl were found significantly correlated with germination, root and shoot length, fresh and dry weight of roots and shoots, seedling survivability, salinity scores and K+ under controlled conditions and ranked the genotypes along with their seed yield in the field. Root and shoot anatomy of tolerant line (PDL-1) and wild accession (ILWL-137) showed restricted uptake of Na+ and Cl- due to thick layer of their epidermis and endodermis as compared to sensitive cultigen (L-4076). All the genotypes were scanned using SSR markers for genetic diversity, which generated high polymorphism. On the basis of cluster analysis and population structure the contrasting genotypes were grouped into different classes. These markers may further be tested to explore their potential in marker-assisted selection.

Correction: Discerning morpho-anatomical, physiological and molecular multiformity in cultivated and wild genotypes of lentil with reconciliation to salinity stress.

[This corrects the article DOI: 10.1371/journal.pone.0177465.].

Molecular Scanning and Morpho-Physiological Dissection of Component Mechanism in Lens Species in Response to Aluminium Stress.

Aluminium (Al) stress was imposed on 285 lentil genotypes at seedling stage under hydroponics to study its effects on morpho-physiological traits where resistant cultigens and wilds showed minimum reduction in root and shoot length and maximum root re-growth (RRG) after staining. Molecular assortment based on 46 simple sequence repeat (SSR) markers clustered the genotypes into 11 groups, where wilds were separated from the cultigens. Genetic diversity and polymorphism information content (PIC) varied between 0.148-0.775 and 0.140-0.739, respectively. Breeding lines which were found to be most resistant (L-7903, L-4602); sensitive cultivars (BM-4, L-4147) and wilds ILWL-185 (resistant), ILWL-436 (sensitive) were grouped into different clusters. These genotypes were also separated on the basis of population structure and Jaccard's similarity index and analysed to study Al resistance mechanism through determination of different attributes like localization of Al and callose, lipid peroxidation, secretion of organic acids and production of antioxidant enzymes. In contrast to sensitive genotypes, in resistant ones most of the Al was localized in the epidermal cells, where its movement to apoplastic region was restricted due to release of citrate and malate. Under acidic field conditions, resistant genotypes produced maximum seed yield/plant as compared to sensitive genotypes at two different locations i.e. Imphal, Manipur, India and Basar, Arunanchal Pradesh, India during 2012-13, 2013-14 and 2014-15. These findings suggest that Al stress adaptation in lentil is through exclusion mechanism and hybridization between the contrasting genotypes from distinct clusters can help in development of resistant varieties.