Detection of beneficial genes from wild accessions of cultivated crops is becoming increasingly important for crop improvement, especially for traits lost during domestication. A set of wild introgression lines derived from advanced back cross breeding of Swarna with Oryza nivara species were characterized for grain size and seedling vigor related traits. Grain length in the population varied between 7.23 and 8.22 mm, while width varied from 2.66 to 3.13 mm. The length-to-width ratio (LWR) ranged from 2.41 to 3.06 mm, showing various grain shapes in the population. Simultaneously, seedling vigor-related traits were studied, and a significant correlation was observed between seedling vigor traits and grain size parameters. Further mapping of quantitative trait loci (QTL) using simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) genotyping identified 18 QTL for seedling vigor- and grain size-related traits. Among these QTL, three major QTL (qAS7.1, qPL7.1 and qL7.1) were detected for grain size-related traits on chromosome 7, explaining 21.44

Aim: The present study aimed to investigate the inter-relation of different light and nutritional sources on the sporulation of fungus. Methodology: Two isolates of Bipolaris oryzae collected from IIRR, Hyderabad and Lonavala were used in the present study. These isolates were cultured on routine culture media-potato dextrose agar for five days and irradiated with different regimes of near ultraviolet (NUV), ultraviolet and visible light to assess their ability to induce sporulation in fungus. With standardized light source (exposure of fungus to NUV 12hr and 12 hr of darkness), different stresses such as nutrient stress, cold and heat stresses were assessed for its ability to support the abundant sporulation. Results: The enhanced sporulation in B. oryzae (55.9x104 and 36.2x104 spores ml-1, respectively, in IIRR and Lonavala isolates) was obtained by culturing fungus on rabbit food agar media for five days under darkness and later 12 hr alternate exposure of near ultraviolet light and darkness. Interpretation: The maximum sporulation obtained in the present study used in pathogenesis test can be employed in screening programme for identification of resistant genotype for brown spot disease. Key words: Brown spot, Bipolaris oryzae, Nutrition, Rice, Sporulation

Wild and related species are a source of wide genetic diversity. Back cross inbred line 166-2S derived from Swarna/Oryza nivara was crossed with Swarna to generate F3 population. This F3 population was raised in wet season of 2018 and data was collected for ten yield traits. Among all ten yield traits, single plant yield was highly associated with PH, TN, PTN, BM, TDM, HI, PL, PW and GW. HI was observed with a highly significant negative association with PH and BM. Positive skewness was observed for TN, PTN, SPY, BM, TDM and GW with platykurtic distribution and complementary gene action, suggesting an intense selection for better genetic gain. The panicle weight showed positive skewness with leptokurtic distribution, indicating the genetic regulation by only a few segregating genes. The negatively skewed and platykurtic distribution of PH, PL and HI indicated the governance of large number of dominant genes with duplicate interaction in the inheritance of these traits.

The wild species of Oryza are an important source of genetic variability for the improvement of yield and tolerance to biotic and abiotic stresses. Phosphorus (P) is the second most important key nutrient, vital for plant growth and development at all stages. Phosphorous deficiency is one of the factors limiting rice yields and farmer’s profitability so it is necessary to identify genotypes with stable yield and tolerance to P deficiency. Keeping in view the unlimited potential of wild species for yield enhancement and stress tolerance, interspecific population between Oryza rufipogon in the back ground of Oryza sativa genotype KMR3 was developed by advanced back cross breeding strategy. DRR Dhan 65 (IET 27641) (RP Bio 4919-B-B NSR86) is an interspecific wild introgression line, a derivative of KMR 3 / O rufipogon with short bold grains which is high yielding under both normal and low soil phosphorous conditions. It has seed to seed maturity of 130- 135 days and gives an average yield of 6.5 t/ ha (under normal conditions; 60 kg/ha of P, i.e., recommended dose) and 4.7 t/ ha (under low Phosphorus; 40 kg/ha of P). It was released for cultivation in Andhra Pradesh, Telangana, Karnataka, Chhattisgarh, Jharkhand and Maharashtra states through Central Sub-committee on Crop Standards, Notification and Release of Varieties for Agricultural Crops vide S.O. 4065(E) dated 31st August, 2022 [CG-DL-E-31082022-238490].

In the present study, 868 SSR and 475 InDel markers were selected to study parental polymorphism of two different crosses between recipient parent Samba Mahsuri and false smut donor linesIC379047 and IC334233 at ICAR-Indian Institute of Rice Research, Rajendranagar, Hyderabad. Out of 1343 markers used for parental polymorphism, 100 markers were polymorphic between parental lines Samba Mahsuri and landrace IC379047 and the total polymorphism percentage recorded was 7.44%. Ninety-nine markers exhibited polymorphism between parental lines Samba Mahsuri and IC334233 and 7.37% of total polymorphism percentage was recorded between the parents. The identified polymorphic markers could be further used for QTL mapping studies in false smut resistance.

Rice false smut disease is gaining importance because of its impact on the grain yield and its toxin production ability. Fifty-eight isolates of Ustilaginoidea virens were collected from different rice-growing regions of India. DNA of U. virens was isolated by the CTAB method and fifty ISSR primers were screened for molecular variability studies. Twelve primers viz., UBC series 807, 808, 809, 810, 811, 812, 834, 835, 836, 840, 841, and 842 were selected to study the genetic variability. Different parameters of tested primers viz., heterozygosity (Hn), polymorphism information content (PIC), effective multiplex ratio (EMR), marker Index (MI), and resolving power (RP) were calculated. Primers UBC 812 and UBC 809 recorded maximum heterozygosity (Hn). The PIC values ranged from 0.10 to 0.27 and UBC 807 recorded the maximum value of 0.27. The EMR value varied from 6.75 to 24.0, Similarly, UBC 807 recorded the highest value of MI (24) and RP (8.55). A dendrogram was generated using the DARwin software (version 6.0.21A) based on the unweighted neighbor-joining cluster method. All the fifty-eight U. virens isolates were grouped into three major clusters. Clusters I and II had 21 and 35 U. virens isolates respectively. Cluster III had only two isolates. The isolates showed genetic variations and there was no specific grouping based on the geographical distance.

DRR Dhan 53 was released for commercial cultivation in Samba Mahsuri/Improved Samba Mahsuri growing regions of Telangana, Andhra Pradesh, Tamilnadu, Karnataka, Chhattisgarh, Orissa, Jharkhand, Bihar, Gujarat and Maharashtra by Central Sub-committee on Crop Standards, Notification and Release of Varieties in 2020. It is a cross between Improved Samba Mahsuri*3/PAU 3554. DRR Dhan 53 (IET 27294) is a marker assisted selection (MAS) derived product in the genetic background of Improved Samba Mahsuri. DRR Dhan 53 is a durable bacterial blight resistant, high-yielding, fine-grain type rice variety having the major bacterial blight resistance genes, Xa21+xa13+xa5+Xa38 with seed to seed maturity of 130-135 days and average yield of 5.5- 6 t/ ha.

Heteroduplex mobility assay (HMA) is based on the principle that DNA heteroduplexes formed between related sequences have a reduced mobility in polyacrylamide gels proportional to their degree of divergence. HMA has been reported as a reliable means for identification and classification of phytoplasmas. Recently, the 16/23S spacer region has been demonstrated to be the best choice, when using the heteroduplex mobility assay (HMA) to differentiate closely related phytoplasmas and to group field isolates into well characterized phytoplasmas. The rice samples of varieties BPT 5204, White Ponni, CO 39 and ADT 43 produced no heteroduplex with assay, signifying that they are very closely related to each other.

Survey was conducted during 2013-2014 (August 2013-February 2014) in the grapes growing areas of Tamil Nadu viz., Coimbatore, Dindigul and Theni districts to assess the disease incidence of downy mildew.Accordingly, the per cent incidence ranged between 30.74 and 78.17 in all the districts surveyed.Among the different districts surveyed, maximum incidence of downy mildew was recorded in Cumbum area of Theni (78.17 per cent) during inflorescence stage and the lowest incidence of 30.74 per cent was observed in the village Uthupatty of Dindugal district during fruiting stage.Among the area surveyed in Coimbatore district, Mathampatty recorded maximum incidence of 72.55 per cent at 35-45 days after pruning.

Phytoplasmas are phloem-limited pleomorphic bacteria which lacks the cell wall, mainly transmitted through leafhoppers but also by plant propagation materials and seeds. In India evidences showed that phytoplasma have been found associated with 129 plant species including Cereals, vegetables, fruits, trees, ornamental, sugarcane, grasses and weeds which is increasing at alarming rate. Sesame phyllody, brinjal little leaf, sugarcane grassy shoot, sandal spike, coconut root wilt, areca nut yellow leaf and many diseases in ornamental plants which causes the most severe economic losses in India. In earlier days, very few phytoplasma diseases were identified in India merely based on the bright-field, fluorescence, electron microscope observations, tetracycline treatment and to a lesser extent by serological assays. Recently detection of phytoplasma based on molecular methods including nested PCR assays are efficiently carried out and on that basis several plant species are reported to have phytoplasma infections. Identified phytoplasmas are related to ‘Candidatus Phytoplasma asteris’, ‘Ca. P. pruni’, ‘Ca. P. ziziphi’, ‘Ca. P. trifolii’, ‘Ca. P. solani’, ‘Ca. P. cynodontis’, ‘Ca. P. oryzae’, ‘Ca. P. phoenicium’, ‘Ca. P. australasia’ and ‘Ca. P. pini’. At present the suggested effective management practices in India includes growing resistant varieties, control of insect vectors, weed species as alternative hosts and use of healthy planting materials. It is moreover essential to understand the molecular basis of phytoplasma-vector interaction and other factors involved in disease development in order to reduce the outbreak of phytoplasma. In this chapter, we have discussed overall progress on phytoplasma disease on plant species in India in terms of detection, transmission and management of phytoplasma.

Plant growth-promoting bacteria (PGPB) include bacteria isolated from rhizosphere, phyllosphere, marine, rock surface, and from different ecosystems. PGPB enhance plant growth by promoting nitrogen fixation, phosphorus solubilization, and production of phytohormones such as indole acetic acid (IAA), gibberellins, polyamines, nitric oxide, and stress-mitigating enzyme viz., 1-aminocyclopropane-1-carboxylate deaminase. Further, they protect plant health through the synthesis of antibiotics and hydrolytic enzymes and induction of resistance in plants. Conspicuously, the mixtures of PGPB strains have been reported for their synergistic action in enhancing plant growth and protection. Due to their wide range of properties in maintaining crop health, PGPB can be an integral component in sustainable crop production practices. The effect of PGPB has been demonstrated successfully against many plant diseases and pests affecting crop cultivation. PGPB are also used in wastewater treatment and soil conservation. The current review discusses the mechanisms of action of PGPB and their usefulness in pest and disease management practices.

Based on the nature of symptoms, 16SrDNA sequence identity and phylogenetic relationships, the association of ‘Candidatus Phytoplasma asteris’ with Rice Orange Leaf (ROL) phytoplasma disease in South India was confirmed recently. This disease was transmitted by the Zigzag leafhopper, Recilia dorsalis as persistent manner in nature. The population fluctuation of hoppers played significant role in the incidence of rice orange leaf phytoplasma in rice ecosystem.

Rice, Oryza sativa (Graminae) was domesticated earlier than 5000 B.C. in North East of India. Its cultivation then spread throughout Southeast Asia and Southern China. Rice is the most important staple or subsistence food of world and India. China, India, Indonesia, Bangladesh, Vietnam, Thailand and Myanmar are the biggest rice producers and account for over 75 per cent of the production (Thottapalli, 2003). Annually, more than 40 per cent of the world‟s rice crop is lost owing to biotic stresses like insects, pests, pathogens and weeds (Hossain and Fischer, 1995). Several diseases caused by bacterial, fungal and viral pathogens devastate rice yields all over the world. Among the diseases blast, bacterial blight and rice Tungro are important because of economic yield loss which they cause.

Phytoplasmas are intracellular obligate prokaryotes that lack cell walls and have very small genomes (680–1,600 kb). Since the first report by Doi et al., (1967), phytoplasmas have been identified as pathogens in different plant genera and in some cases have caused severe epidemics in major crops (Bertaccini et al., 2014). Phytoplasmas cause complex syndromes with symptoms such as stunting, proliferating auxiliary shoots, forming sterile deformed flowers, virescence and phyllody in several hundred plant species (Lee et al., International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 8 Number 10 (2019) Journal homepage: http://www.ijcmas.com

RNAi mediated silencing of pectin degrading enzyme of R. solani gives a high level of resistance against sheath blight disease of rice. Rice sheath blight disease caused by Rhizoctonia solani Kuhn (telemorph; Thanatephorus cucumeris) is one of the most devastating fungal diseases which cause severe loss to rice grain production. In the absence of resistant cultivars, the disease is currently managed through fungicides which add to environmental pollution. To explore the potential of utilizing RNA interference (RNAi)-mediated resistance against sheath blight disease, we identified genes encoding proteins and enzymes involved in the RNAi pathway in this fungal pathogen. The RNAi target genes were deciphered by RNAseq analysis of a highly virulent strain of the R. solani grown in pectin medium. Additionally, pectin metabolism associated genes of R. solani were analyzed through transcriptome sequencing of infected rice tissues obtained from six diverse rice cultivars. One of the key candidate gene AG1IA_04727 encoding polygalacturonase (PG), which was observed to be significantly upregulated during infection, was targeted through RNAi to develop disease resistance. Stable expression of PG-RNAi construct in rice showed efficient silencing of AG1IA_04727 and suppression of sheath blight disease. This study highlights important information about the existence of RNAi machinery and key genes of R. solani which can be targeted through RNAi to develop pathogen-derived resistance, thus opening an alternative strategy for developing sheath blight-resistant rice cultivars.

Brown spot disease caused by Bipolaris oryzae results in the yield loss of paddy in the recent years. In the present study, isolates were collected from nine rice growing states of India. Based on colony morphology and growth pattern, the 17 isolates of B. oryzae were characterized and formed four groups. These were (Group I) black with fluffy growth, (Group II) grey with fluffy growth and white spots, (Group III) grey with fluffy growth and (Group IV) grey with suppressed growth. Further the morphological characterization was studied on different media and spectral values for all isolates.