The plant root is the primary site of interaction between plants and associated microorganisms and constitutes the main components of plant microbiomes that impact crop production. The endophytic bacteria in the root zone have an important role in plant growth promotion. Diverse microbial communities inhabit plant root tissues, and they directly or indirectly promote plant growth by inhibiting the growth of plant pathogens, producing various secondary metabolites. Mechanisms of plant growth promotion and response of root endophytic microorganisms for their survival and colonization in the host plants are the result of complex plant-microbe interactions. Endophytic microorganisms also assist the host to sustain different biotic and abiotic stresses. Better insights are emerging for the endophyte, such as host plant interactions due to advancements in ‘omic’ technologies, which facilitate the exploration of genes that are responsible for plant tissue colonization. Consequently, this is informative to envisage putative functions and metabolic processes crucial for endophytic adaptations. Detection of cell signaling molecules between host plants and identification of compounds synthesized by root endophytes are effective means for their utilization in the agriculture sector as biofertilizers. In addition, it is interesting that the endophytic microorganism colonization impacts the relative abundance of indigenous microbial communities and suppresses the deleterious microorganisms in plant tissues. Natural products released by endophytes act as biocontrol agents and inhibit pathogen growth. The symbiosis of endophytic bacteria and arbuscular mycorrhizal fungi (AMF) affects plant symbiotic signaling pathways and root colonization patterns and phytohormone synthesis. In this review, the potential of the root endophytic community, colonization, and role in the improvement of plant growth has been explained in the light of intricate plant-microbe interactions.

Rice (Oryza sativa L.) is an important source of nutrition for the world’s burgeoning population that often faces yield loss due to infestation by the brown planthopper (BPH, Nilaparvata lugens (Stål)). The development of rice cultivars with BPH resistance is one of the crucial precedences in rice breeding programs. Recent progress in high-throughput SNP-based genotyping technology has made it possible to develop markers linked to the BPH more quickly than ever before. With this view, a genome-wide association study was undertaken for deriving marker-trait associations with BPH damage scores and SNPs from genotyping-by-sequencing data of 391 multi-parent advanced generation inter-cross (MAGIC) lines. A total of 23 significant SNPs involved in stress resistance pathways were selected from a general linear model along with 31 SNPs reported from a FarmCPU model in previous studies. Of these 54 SNPs, 20 were selected in such a way to cover 13 stress-related genes. Kompetitive allele-specific PCR (KASP) assays were designed for the 20 selected SNPs and were subsequently used in validating the genotypes that were identified, six SNPs, viz, snpOS00912, snpOS00915, snpOS00922, snpOS00923, snpOS00927, and snpOS00929 as efficient in distinguishing the genotypes into BPH-resistant and susceptible clusters. Bph17 and Bph32 genes that are highly effective against the biotype 4 of the BPH have been validated by gene specific SNPs with favorable alleles in M201, M272, M344, RathuHeenati, and RathuHeenati accession. These identified genotypes could be useful as donors for transferring BPH resistance into popular varieties with marker-assisted selection using these diagnostic SNPs. The resistant lines and the significant SNPs unearthed from our study can be useful in developing BPH-resistant varieties after validating them in biparental populations with the potential usefulness of SNPs as causal markers.

Brown planthopper (BPH), one of the most important pests of the rice (Oryza sativa) crop, becomes catastrophic under severe infestations and causes up to 60% yield loss. The highly disastrous BPH biotype in the Indian sub-continent is Biotype 4, which also known as the South Asian Biotype. Though many resistance genes were mapped until now, the utility of the resistance genes in the breeding programs is limited due to the breakdown of resistance and emergence of new biotypes. Hence, to identify the resistance genes for this economically important pest, we have used a multi-parent advanced generation intercross (MAGIC) panel consisting of 391 lines developed from eight indica founder parents. The panel was phenotyped at the controlled conditions for two consecutive years. A set of 27,041 cured polymorphic single nucleotide polymorphism (SNPs) and across-year phenotypic data were used for the identification of marker–trait associations. Genome-wide association analysis was performed to find out consistent associations by employing four single and two multi-locus models. Sixty-one SNPs were consistently detected by all six models. A set of 190 significant marker-associations identified by fixed and random model circulating probability unification (FarmCPU) were considered for searching resistance candidate genes. The highest number of annotated genes were found in chromosome 6 followed by 5 and 1. Ninety-two annotated genes identified across chromosomes of which 13 genes are associated BPH resistance including NB-ARC (nucleotide binding in APAF-1, R gene products, and CED-4) domain-containing protein, NHL repeat-containing protein, LRR containing protein, and WRKY70. The significant SNPs and resistant lines identified from our study could be used for an accelerated breeding program to develop new BPH resistant cultivars.

Varietal identification has attained prime importance at a global level particularly in the context of plant variety protection. In this study, forty-six traits were characterized for the establishment of the sheer distinctness among eighteen rice varieties. Morphologically, out of forty-six traits, twenty-five traits did not display any variation among the varieties studied. Significant variations were observed for 21 traits which are relatively more informative in the identification/characterization. Distinctness, uniformity and stability-based fingerprints specific to the studied varieties were developed based on the variations. A total of 175 simple sequence repeat (SSR) markers were screened for polymorphism; 53 hypervariable polymorphic SSR markers were utilized for fingerprinting of rice varieties. A total of 151 alleles were detected in these 53 SSR markers with an amplification size ranging from 120 to 750 bp and the allelic range of 2–4. The average number of alleles observed was 2.84 per locus. The PIC values of 53 SSRs ranged from 0.03 (RM 12983) to 0.64 (RM 11449) with an average of 0.40. The generated allelic variations of 53 SSR markers for the varieties were translated into DNA barcode profiles by separating the allele size from each SSR locus. Multiplex polymerase chain reaction (PCR) with five markers (RM 21392, RM 1388, RM 6699, RM 25754 and RM 16913) was used to identify rice varieties based on the band positions. This study classifies and identifies rice varieties and is an important reference to test the authenticity and varietal purity of other rice varieties in the future. Supplemental data for this article is available online at https://doi.org/10.1080/13102818.2021.1987324 .

Timely sowing is a critical factor in realizing the yield as it ensures the vegetative growth to crop up during a period of satisfactory temperatures and fits the cultivar maturity length and growing season. In the present investigation, 38 cold tolerant rice genotypes were studied under delayed sowing conditions at College Farm, Professor Jayashankar Telangana State Agricultural University, Hyderabad. The genotypes were evaluated for yield attributing traits with a view of understanding the extent of variability and diversity present among the genotypes that could be suitable for delayed sowing conditions with cold tolerance. Analysis of variance (ANOVA) indicated significant differences for all the characters with high genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) values for tillers per plant, spikelet fertility, filled grains per panicle and seed yield per plant. High heritability coupled with high genetic advance as percent of the mean was observed for plant height, spikelet fertility, filled grains per panicle with higher variability indicating the presence of fixable gene action which may suggest a reliable crop improvement through selection of these traits. As association analysis could help the breeder to design selection strategies to improve grain yield, correlation studies were carried out which revealed the trait to be having positive relation with all the traits except panicle exertion and panicle length. Path coefficient analysis showed all the traits except panicle exertion and test weight to be exhibiting a direct positive effect on yield, selection for which should be emphasized on these positively associated traits for yield enhancement. Principal component analysis and D2 analysis together determined plant height, grain yield, panicle exertion, panicle length and yield per plant having higher contributions to the total variability, which could be taken into consideration in rice breeding programmes for further improvement in production.