Diversity of Antimicrobial Peptide Genes in Bacillus from the Andaman and Nicobar Islands: Untapped Island Microbial Diversity for Disease Management in Crop Plants.

Taxonomic and functional characterization of a total of 90 bacterial isolates representing bulk and rhizosphere soils of diverse niches of Andaman and Nicobar Islands, India were carried out. Twelve bacterial isolates were found promising for the biological suppression of agriculturally important fungal and bacterial plant pathogens such as Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, and Colletotrichum gloeosporioides. The 16S rRNA gene sequence analysis revealed their identity as belonging to Bacillus subtilis, Bacillus amyloliquefaciens, and Lysinibacillus sphaericus. The isolates were positive for plant growth promotion (PGP) traits including siderophore production, and nutrient solubilization especially phosphorous, zinc, and potassium. Interestingly, the PCR test confirmed the presence of 62 antimicrobial peptides (AMP) biosynthesis genes specific to the genus Bacillus. Whilst all tested species of Bacillus harboured the bacD biosynthesis gene, the B. subtilis (Ba_Abi), and B. amyloliquefaciens (Ba_Abi) harboured the maximum AMP biosynthesis genes analysed in the study. Upon in planta evaluation, the biocontrol potential of the bacterial isolates against leaf spot disease of chilli was observed. The study culminated in the isolation and identification of diverse Bacillus species for exploitation as bioinoculants for plant health management programmes.

Enhancing trehalose biosynthesis improves yield potential in marker-free transgenic rice under drought, saline, and sodic conditions.

Edaphic factors such as salinity, sodicity, and drought adversely affect crop productivity, either alone or in combination. Despite soil sodicity being reported as an increasing problem worldwide, limited efforts have been made to address this issue. In the present study, we aimed to generate rice with tolerance to sodicity in conjunction with tolerance to salinity and drought. Using a fusion gene from E. coli coding for trehalose-6-phosphate synthase/phosphatase (TPSP) under the control of an ABA-inducible promoter, we generated marker-free, high-yielding transgenic rice (in the IR64 background) that can tolerate high pH (~9.9), high EC (~10.0 dS m-1), and severe drought (30-35% soil moisture content). The transgenic plants retained higher relative water content (RWC), chlorophyll content, K+/Na+ ratio, stomatal conductance, and photosynthetic efficiency compared to the wild-type under these stresses. Positive correlations between trehalose overproduction and high-yield parameters were observed under drought, saline, and sodic conditions. Metabolic profiling using GC-MS indicated that overproduction of trehalose in leaves differently modulated other metabolic switches, leading to significant changes in the levels of sugars, amino acids, and organic acids in transgenic plants under control and stress conditions. Our findings reveal a novel potential technological solution to tackle multiple stresses under changing climatic conditions.

Harnessing intra-varietal variation for agro-morphological and nutritional traits in a popular rice landrace for sustainable food security in tropical islands.

Introduction: Rice crop meets the calorie and nutritional requirements of a larger segment of the global population. Here, we report the occurrence of intra-varietal variation in a popular rice landrace C14-8 traditionally grown under the geographical isolation of the Andaman Islands. Methods: Based on grain husk color, four groups were formed, wherein the extent of intra-varietal variation was studied by employing 22 agro-morphological and biochemical traits. Results: Among the traits studied, flavonoid and anthocyanin contents and grain yield exhibited a wider spectrum of variability due to more coefficients of variation (>25%). The first five principal components (PCs) of principal components analysis explained a significant proportion of the variation (91%) and the first two PCs explained 63.3% of the total variation, with PC1 and PC2 explaining 35.44 and 27.91%, respectively. A total of 50 highly variable SSR (HvSSR) markers spanning over 12 chromosomes produced 314 alleles, which ranged from 1 to 15 alleles per marker, with an average of 6.28. Of the 314 alleles, 64 alleles were found to be rare among the C14-8 selections. While 62% of HvSSR markers exhibited polymorphism among the C14-8 population, chromosomes 2, 7, 9, and 11 harbored the most polymorphic loci. The group clustering of the selections through HvSSR markers conformed to the grouping based on grain husk coloration. Discussion: Our studies on the existence and pertinence of intra-varietal variations are expected to be of significance in the realms of evolutionary biology and sustainable food and nutritional security under the changing climate.

Marker-assisted enhancement of bacterial blight (Xanthomonas oryzae pv. oryzae) resistance in a salt-tolerant rice variety for sustaining rice production of tropical islands.

Introduction: Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae is a major disease of rice, specially in the tropical regions of the world. Developing rice varieties with host resistance against the disease is the most effective and economical solution for managing the disease. Methods: Pyramiding resistance genes (Xa4, xa5, xa13,and Xa21) in popular rice varieties using marker-assisted backcross breeding (MABB) has been demonstrated as a cost-effective and sustainable approach for establishing durable BB resistance. Here, we report our successful efforts in introgressing four resistance genes (Xa4, xa5, xa13, and Xa21) from IRBB60 to CARI Dhan 5, a popular salt-tolerant variety developed from a somaclonal variant of Pokkali rice, through functional MABB. Results and discussion: Both BB and coastal salinity are among the major challenges for rice production in tropical island and coastal ecosystems. Plants with four, three, and two gene pyramids were generated, which displayed high levels of resistance to the BB pathogen at the BC3F2 stage. Under controlled salinity microplot environments, the line 131-2-175-1223 identified with the presence of three gene pyramid (Xa21+xa13+xa5) displayed notable resistance across locations and years as well as exhibited a salinity tolerance comparable to the recurrent parent, CARI Dhan 5. Among two BB gene combinations (Xa21+xa13), two lines, 17-1-69-334 and 46-3-95-659, demonstrated resistance across locations and years, as well as salt tolerance and grain production comparable to CARI Dhan 5. Besides salinity tolerance, five lines, 17-1-69-179, 46-3-95-655, 131-2-190-1197, 131-2-175-1209, and 131-2-175-1239, exhibited complete resistance to BB disease. Following multilocation testing, potential lines have been identified that can serve as a prospective candidate for producing varieties for the tropical Andaman and Nicobar Islands and other coastal locations, which are prone to BB and coastal salinity stresses.

Genetic enhancement of okra [Abelmoschus esculentus (L.) Moench] germplasm through wide hybridization.

Introduction: The introgression of genetic material from one species to another through wide hybridization and repeated back-crossing, plays an important role in genetic modification and enriching the cultivated gene-pool with novel genetic variations. Okra (Abelmoschus esculentus [(L.) Moench)] is a popular vegetable crop with high dietary fibre and protein, rich in essential amino acids, lysine and tryptophan. The wild Abelmoschus genepool has many desirable traits like ornamental value, short internodal length, more number of productive branches, extended bearing, perennation tendency, reduced fruit length (more consumer preferred trait), high mucilage content (medicinal value), abiotic stress tolerances such as drought, high temperature and biotic stress resistances such as okra Yellow Vein Mosaic Virus (YVMV) and Enation Leaf Curl Virus (ELCV) diseases. The repeated use of elite breeding lines led to narrowing of the genetic base of the okra crop, one of the major factors attributed to breakdown of resistance/ tolerance to biotic stresses. YVMV and ELCV are the two major diseases, causing significant yield loss in okra. Hence, wide hybridization was attempted to transfer tolerance genes from wild species to the cultivated genepool to widen the genetic base. Material and methods: The screening of germplasm of wild Abelmoschus species at hotspots led to the identification of tolerant species (Abelmoschus pungens var. mizoramensis, A. enbeepeegeearensis, A. caillei, A. tetraphyllus and A. angulosus var. grandiflorus), which were further used in a wide-hybridization programme to generate interspecific hybrids with the cultivated okra. Presence of pre- and post-zygotic barriers to interspecific geneflow, differences in ploidy levels and genotype specific variations in chromosome numbers led to varying degrees of sterility in F1 plants of interspecific crosses. This was overcome by doubling the chromosome number of interspecific hybrids by applying Colchicine at the seedling stage. The 113 cross derivatives generated comprising amphidiploids in the F1 generation (30), F3 (14), one each in F2 and F4 generations, back cross generation in BC1F2 (03), BC1F3 (25), and BC2F3 (02), crosses between amphidiploids (27), multi-cross combinations (07) and inter-specific cross (between A. sagittifolius × A. moschatus subsp. moschatus) selfed derivatives at F8 generation (03) were characterized in the present study. Besides they were advanced through selfing and backcrossing. Results and Discussion: The amphidiploids were found to possess many desirable genes with a considerable magnitude of linkage drag. Majority of the wide cross derivatives had an intermediate fruit morphology and dominance of wild characters viz., hispid fruits, stem, leaves, tough fruit fibre, vigorous perennial growth habit and prolonged flowering and fruiting. The fruit morphology of three BC progenies exhibited a high morphological resemblance to the cultivated okra, confirming successful transfer of useful genes to the cultivated okra genepool. The detailed morphological characteristics of the various combinations of Abelmoschus amphidiploids and the genetic enhancement of the genepool achieved in this process is reported here.

A Quick Analysis Method for Protein Quantification in Oilseed Crops: A Comparison With Standard Protocol.

Protein is one of the most abundant substances in plants and plays a major role in human health hence standardization of its analytical quantification method is essential. Various methods for protein quantification exist, such as Kjeldahl, Bradford, Lowry, bicinchoninic acid assay (BCA), Biuret, and total amino acid content methods. These methods are widely applied; however, the development of the rapid and efficient method is the need of the time hence the objective of this research was to analyze and comparing compare the modification of the Kjeldahl method for the determination of protein content in oilseed crops. The study was performed to improve the sample preparation method (processing and digestion) for protein quantification. Generally, the method initially requires homogenization of grains to a fine flour, which involves time and increases the risk of sample cross-contamination and partial loss of oil from the sample during grinding. Moreover at times, it becomes challenging to homogenize oil seeds to fine flour due to high oil content. However, in the present research, the whole grain was digested in place of grounded flour to accomplish quick protein quantification and compared it with the flour matrix of different oil seeds. To further reduce the digestion time and avoid frothing, we have used the modified digestion mixture. The developed method was statistically validated using analysis of variance (ANOVA), Pearson correlation reliability test, paired T-test, and different types of plot analysis. The validation of the sample preparation method in protein quantification demonstrated non-significant differences that the protein content from whole grain of all the five oilseed crops shows 100% non-significant results compared with the flour matrix in both the digestion mixtures. The developed novel method could be used to prepare the sample for protein analysis and reduces the overall analysis time while ensuring the accuracy of the results.