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Early duration rice culture CB 06 535, a derivative of the cross ADT 43 / RR 272 -1745 was released as TNAU Rice CO 51 during the year 2013 as an alternate variety to ADT 43 with 105 -110 days duration with additional desirable features like high yield, physiological efficiency and better adaptability. This culture with semi dwarf stature has efficient tillering capacity, long droopy panicles with highly acceptable plant characters and is a good replacement for the rice variety ADT 43 due to its high grain yield and pest and disease resistance. In the overall performance, the culture, CB 06 535 recorded a mean productivity of 6623 kg/ha in seven years of trials with 10.72 per cent increase over ADT 43. At Nallampalli, Dharmapuri district, the culture has recorded the highest yield of 11,377 kg/ha among the trials conducted, demonstrating the highest yield potential of this variety. The culture CB 06 535 is moderately resistant to blast, BPH and GLH under artificial condition. It produces medium slender white rice with intermediate amylose, soft gel consistency and moderate gelatinization temperature. It produces good quality cooked rice besides high milling and head rice recovery. CB 06 535 with higher yield, better pest and disease resistance and good cooking quality in comparison to the check ADT 43 is suitable for cultivation during Kar/ Kuruvai /Sornavari /Navarai and the seasons / tracts wherever early maturing rice varieties are cultivated throughout Tamil Nadu.

Rice crops in South and Southeast Asian countries suffer critical yield losses due to rice tungro disease caused by joint infection with rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV). Previously, for generating RNA interference-based transgenic resistance against tungro viruses, RTBV ORF IV was used as a transgene to develop RTBV resistance in a popular high-yielding scented rice variety. The transgene from this line was then introgressed into five popular high-yielding but tungro-susceptible rice varieties by marker-assisted backcross breeding with a view to combine the resistant trait with the agronomic traits. The present work includes a resistance assay of the BC3F5 lines of these varieties under glasshouse conditions. Out of a total of 28 lines tested, each consisting of 12 individual plants, eight lines showed significant amelioration in height reduction and 100- to 1000-fold reduction in RTBV titers. The RNAi-mediated resistance was clearly manifested by the presence of virus-derived small RNA (vsRNA) specific for RTBV ORF IV in the transgenic backcrossed lines.

Cassava mosaic disease is a widespread disease of cassava in south Asia and the African continent. In India, CMD is known to be caused by two single-stranded DNA viruses (geminiviruses), Indian cassava mosaic virus (ICMV) and Sri Lankan cassava mosdaic virus (SLCMV). Previously, the diversity of ICMV and SLCMV in India has been studied using PCR, a sequence-dependent method. To have a more in-depth study of the variability of the above viruses and to detect any novel geminiviruses associated with CMD, sequence-independent amplification using rolling circle amplification (RCA)-based methods were used. CMD affected cassava plants were sampled across eighty locations in nine districts of the southern Indian state of Tamil Nadu. Twelve complete sequence of coat protein genes of the resident geminiviruses, comprising 256 amino acid residues were generated from the above samples, which indicated changes at only six positions. RCA followed by RFLP of the 80 samples indicated that most samples (47) contained only SLCMV, followed by 8, which were infected jointly with ICMV and SLCMV. In 11 samples, the pattern did not match the expected patterns from either of the two viruses and hence, were variants. Sequence analysis of an average of 700 nucleotides from 31 RCA-generated fragments of the variants indicated identities of 97–99% with the sequence of a previously reported infectious clone of SLCMV. The evidence suggests low levels of genetic variability in the begomoviruses infecting cassava, mainly in the form of scattered single nucleotide changes. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13337-018-0432-x) contains supplementary material, which is available to authorized users.

The feasibility of controlling peanut stem necrosis disease caused by Tobacco streak virus (TSV) in groundnut (Arachis hypogaea L.) was explored by expressing double-stranded RNA of the replicase (Rep) gene of TSV in groundnut through genetic engineering. A hairpin (hp) RNAi construct containing 535-bp sense and antisense TSV-Rep sequences flanking a 742-bp spacer sequence (Pdk intron) under the control of the constitutive Cauliflower mosaic virus 35S promoter was made in the binary vector pART27. This chimeric gene construct was then mobilized into Agrobacterium tumefaciens strain LBA4404 via triparental mating using pRK2013 as a helper. Cotyledon explants of groundnut cultivar TMV-7 were transformed with A. tumefaciens harboring the hpRNA cassette. The presence of the transgene in the transgenic plants was confirmed up to T3 generation by PCR amplification of the 535-bp fragment of TSV-Rep gene. The bioassay results indicated that necrotic lesions were observed on the leaves of the wild-type plants 7–9 days after inoculation with TSV and stem necrosis appeared 16–20 days after inoculation, whereas the transgenic plants did not develop symptoms until harvest. ELISA results indicated that the wild-type plants inoculated with TSV recorded the highest virus concentration as compared to the transgenic lines.

Severe losses of rice yield in south and southeast Asia are caused by Rice tungro disease (RTD) induced by mixed infection of Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV). In order to develop transgene-based resistance against RTBV, one of its genes, ORF IV, was used to generate transgenic resistance based on RNA-interference in the easily transformed rice variety Pusa Basmati-1, and the transgene was subsequently introgressed to rice variety ASD 16, a variety popular in southern India, using transgene marker-assisted selection. Here, we report the evaluation of BC3F4 and BC3F5 generation rice plants for resistance to RTBV as well as for agronomic traits under glasshouse conditions. The BC3F4 and BC3F5 generation rice plants tested showed variable levels of resistance, which was manifested by an average of twofold amelioration in height reduction, 1.5-fold decrease in the reduction in chlorophyll content, and 100- to 10,000-fold reduction in the titers of RTBV, but no reduction of RTSV titers, in three backcrossed lines when compared with the ASD 16 parent. Agronomic traits of some of the backcrossed lines recorded substantial improvements when compared with the ASD 16 parental line after inoculation by RTBV and RTSV. This work represents an important step in transferring RTD resistance to a susceptible popular rice variety, hence enhancing its yield in areas threatened by the disease.

The post genomic era of biological research is directed towards understanding of gene expression and function. Proteome studies of plant-pathogen interactions help us to identify pathogenicity and defense related proteins involved in compatible (successful) and incompatible (un-successful) phyto-pathogen interactions. Mungbean (Vigna radiata), an important pulse crop known for its dietary protein is majorly affected by Mungbean Yellow mosaic disease. Proteomics of Mungbean-MYMV interaction was studied through 2D-PAGE using leaf protein extracts at virus stressed flowering phase of uninfected (control) and MYMV-infected susceptible (Cv VBN Gg2), resistant (Cv KMG 189) parents and their susceptible (CM 15-1-1-F2S) and resistant (CM 15-7-13-F2R) F2 progenies. Our analysis detected more than 200 protein spots in each sample with 68% of differential expression. High differences in protein abundance between control and infected were seen in 14 spots within F2's and 24 spots within parents. Out of these, we have analyzed 12 protein spots that were common between F2's and parents by MALDI-TOF MS. The spots identified were classified under six categories based on their putative functions viz., Stress/defense (Metallothionin like protein, Aminocyclopropan –1– carboxylate oxidase and OBERON 2), Signal transduction (two acyl-carrier proteins and a receptor kinase), Photosynthesis (PS I assembly protein), viral transport (Nucleic acid binding protein and RNA recognition motif containing protein), mRNA processing (Maturase k and F-box protein) and photorespiration (Flavin Mono-oxygenase). Statistical analysis, such as ANOVA and Principle component analysis (PCA) of differentially expressed proteins also suggested that proteins of stress/defense and signaling/transport were involved in re-programming the defense mechanism.

Mungbean yellow mosaic virus (MYMV) is a disastrous pathogen of mungbean. It is widespread in most of southern India and no complete resistance has been identified among its commercial cultivars. Two isolates of MYMV, representing its diversity, were used to assess and characterize the susceptibility reaction of all the three species of Vigna. The seeds were agroinoculated with the virus and the presence of the viral DNA was confirmed after 12 d by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis after which the plants were monitored for the expression of symptoms. All of the 20 accessions of Vigna radiata and ten accessions of Vigna mungo were systemically infected with MYMV, and they all produced typical symptoms. On the other hand, the 24 accessions of Vigna umbellata were found to be resistant to both the isolates. For additional affirmation, three representative accessions of V. radiata and V. mungo and all the accessions of V. umbellata were agroinoculated, and quantitative RT-PCR was performed for the quantitative detection of the MYMV. The mRNA transcripts of MYMV were detected in V. radiata and V. mungo plants but not in the V. umbellata plants. Researching the molecular basis of the resistance in V. umbellate against MYMV might definitely be very constructive for developing resistant varieties of mungbean on a commercial scale. This genetic quality offering resistance to MYMV could also be incorporated into V. radiata/V. mungo by means of interspecific crosses.

Blast disease caused by the pathogen Pyricularia oryzae is a serious threat to rice production. Six generations viz., P1, P2, F1, F2, B1 and B2 of a cross between blast susceptible high-yielding rice cultivar ADT 43 and resistant near isogenic line (NIL) CT13432-3R, carrying four blast resistance genes Pi1, Pi2, Pi33 and Pi54 in combination were used to study the nature and magnitude of gene action for disease resistance and yield attributes. The epistatic interaction model was found adequate to explain the gene action in most of the traits. The interaction was complementary for number of productive tillers, economic yield, lesion number, infected leaf area and potential disease incidence but duplicate epistasis was observed for the remaining traits. Among the genotypes tested under epiphytotic conditions, gene pyramided lines were highly resistant to blast compared to individuals with single genes indicating that the nonallelic genes have a complementary effect when present together. The information on genetics of various contributing traits of resistance will further aid plant breeders in choosing appropriate breeding strategy for blast resistance and yield enhancement in rice.

The effect of elicitor from mycelial walls of Magnaporthe grisea, the rice blast fungus and α-picolinic acid, one of the toxins produced by M. grisea on induction of peroxidase (PO), polyphenol oxidase (PPO) in suspension-cultured rice (Oryza sativa L.) cells was studied. Cultured cells of blast resistant (Usen) and susceptible (CO39) rice genotypes were treated with elicitor (50 μg of glucose equivalents per ml) or α-picolinic acid (400 ppm). The cells were harvested at different time intervals and analysed for the induction of PO and PPO. PO isozyme analysis indicated that the elicitor strongly induced the activities of PO-2 and PO-3 in cultured cells of Usen 3 days after treatment. In Usen, toxin also induced the activities of PO-3 and PO-4. However, similar levels of activities corresponding to these isozymes were recorded 7 days after treatment. In CO39, the activities of PO-1 and PO-2 were induced 3 days after elicitor treatment. In contrast, the toxin suppressed the activity of PO-2. The elicitor i...

Blast disease is considered as a major limiting factor in the global rice production because of its wide distribution and destructiveness. Near Isogenic Lines (NILs) harboring different blast resistant Pi genes were surveyed for blast resistance along with resistant and susceptible varieties. These genotypes were randomly crossed to transfer disease resistance to agronomically superior varieties ADT 43, Improved White Ponni and BPT5204. Disease reaction was recorded in both artificial as well as natural epiphytotic conditions and differential response to blast disease incidence was observed. The minimum blast incidence was observed in F1s of ADT 43/CT13432-3R, ADT 43/C101A51 and ADT 43/C101LAC across the environments. Advanced back cross inbred lines developed from the cross combination ADT 43/CT13432-3R were also screened against blast disease. Gene pyramided back cross lines exhibited higher resistance than susceptible genotypes. Among the genotypes tested under epiphytotic conditions at different environments, lines with gene combinations Pi1 + Pi2 + Pi33 + Pi54 and Pi1 + Pi2 + Pi33 were highly resistant to blast disease than those with single genes indicating that these non-allelic genes have a complementary effect. Variation in resistance reaction was observed for the same gene when it acts alone or in combinations and also when the same genes were present in different genetic backgrounds. The gene pyramided lines developed in this study can serve as excellent donors for blast resistance in rice improvement and also for basic studies on gene-race interactions.

Seventy-eight mungbean genotypes were grown in the field and 28 genotypes were found to be resistant to Mungbean yellow mosaic virus, while the remainder were susceptible. All genotypes were further subjected to agroinoculation to confirm their resistance/susceptibility against MYMV using two different MYMV strains, namely VA 221 and VA 239. The results showed that only three genotypes, namely ML 1108, KMG 189 and SP 84, exhibited resistance to the VA 221 strain while 77 genotypes were found to be susceptible to strain VA 239. Only one genotype, namely ML 818, showed resistance to strain VA 239, but it was susceptible to strain VA 221. The accumulation of the viral genome in the host was confirmed by PCR amplification of the coat protein gene of MYMV using gene-specific primers.

Yellow mosaic disease is the major limitation in the production of grain legumes in India. This disease is caused by bipartite begomovirus, Mungbean yellow mosaic virus. In addition to the bipartite genomic components, the yellow mosaic disease affected urdbean plants which contain satellite like DNA-1 component called as alphasatellites. The present study has been attempted to characterise the alphasatellites associated with Mungbean yellow mosaic virus. Nucleotide sequence analysis of alphasatellites showed 98% identity with Vernonia yellow vein Fijian alphasatellite, VYVFA (JF733780). Since the sequence identity is more than 98%, the threshold value for demarcation of alphasatellites species, the alphasatellites of the present study are named as Vernonia yellow vein Fijian alphasatellite. Comparison with other, alphasatellites shared 51–55% identity with alphasatellites associated with monopartite begomovirus and it shared only 41–42% identity with an unusual alphasatellites, DNA-2. This is the first r...

The coat protein (CP) gene of Tobacco streak virus (TSV) from sunflower (Helianthus annuus L.) was amplified, cloned and sequenced. A 421 bp fragment of the TSV coat protein gene was amplified and a gene construct encoding the hairpin RNA (hpRNA) of the TSV-CP sequence was made in the plasmid pHANNIBAL. The construct contains sense and antisense CP sequences flanking a 742 bp spacer sequence (Pdk intron) under the control of the constitutive CaMV35S promoter. A 3.6 kb Not I fragment containing the hpRNA cassette (TSV-CP) was isolated from pHANNIBAL and sub-cloned into the binary vector pART27. This chimeric gene construct was then mobilized into Agrobacterium tumefaciens strain LBA4404 via triparental mating using pRK2013 as a helper. Sunflower (cv. Co 4) and tobacco (cv. Petit Havana) plants were transformed with A. tumefaciens strain LBA4404 harbouring the hpRNA cassette and in vitro selection was performed with kanamycin. The integration of the transgene into the genome of the transgenic lines was confirmed by PCR analysis. Infectivity assays with TSV by mechanical sap inoculation demonstrated that both the sunflower and tobacco transgenic lines exhibited resistance to TSV infection and accumulated lower levels of TSV compared with non-transformed controls.

A mapping population comprising 220 F2 individuals was developed by raising the selfed F1 seed of a single hybrid plant, White Ponni x Moroberekan. Two hundred and twenty two F3 families were phenotyped for blast resistance under artificial condition. Fifty random amplified polymorphic (RAPD) primers were used to identify parental polymorphism. Twelve RAPD markers which showed clear polymorphism were scored in the F2 mapping population. Out of 12 markers, 11 loci (91.97 %) fitted into the expected segregation ratio of 3:1 based on c2 - test at 0.05% probability value. Four hundred microsatellite primer pairs were used in the parental survey, Out of which 52 simple sequence repeats (SSR) primers were polymorphic. Out of 52 marker loci, 44 marker loci (84.61%) fitted into the expected Mendelian segregation ratio of 1:2:1 based on c2 - test at 0.05% probability value. The multipoint analysis resulted in the construction of preliminary genetic linkage map with 40 loci. One way analysis of variance (ANOVA) was performed to identify the marker phenotype association which resulted in the identification of 23 SSR markers putatively associated for the six traits studied. Three SSR markers (RM 5757, RM 451 and RM 492 from chromosomes four and two) were linked for leaf blast resistance, six markers for days to flowering, nine markers for pigmentation trait, two markers for plant height, four markers for panicle length and seven markers linked for grain yield per plant. Out of 12 RAPD markers studied, 7 were found to be linked to three traits viz., leaf blast resistance (OPBB 5258, OPBB 5194, OPAL 16940 and OPBD 12680), five markers for glume purple tip (GPT) and one marker for grain yield per plant based on single marker analysis. Key words: Magnaporthe grisea (Hebert) Barr, Oryza sativa. L., marker assisted selection (MAS).

In Department of Rice, Tamil Nadu Agricultural University, Coimbatore, a medium duration fine grain rice variety CO52 was released for cultivation in transplanted situation for late samba / thaladi season . CO52 rice variety recorded a mean grain yield of 6191 kg/ha and possessess quality grain traits comparable to the predominantly cultivated fine grain types. It is a derivative of the cross between BPT 5204 and CO(R) 50 which matures in 130-135 days. The variety was tested in the station trial for three (2009-2011)years, Multi Location Trial for two (2011-12 and 2012-13) years, Adaptive Research Trial for two (2013-14 and 2014-15) years, OFT for three (2013-14, 2014-15 and 2015-16) years and in AICRIP trial for two (2011 and 2015) years. CO52 variety is moderately resistant to insect pests viz., plant hoppers and leaf hoppers and diseases viz., blast, sheath rot, brown spot and sheath blight. It produces medium slender white rice with high milling percentage, high head rice recovery, high linear elongation ratio, intermediate amylose content, soft gel consistency and moderate gelatinization temperature indicating its suitability for cooking with a remunerative market price and consumer preference similar to Improved White Ponni and BPT 5204.

Marker assisted selection was employed to pyramid three bacterial blight resistance genes Xa21, xa13 and xa5 into high yielding susceptible rice cultivars ADT43 and ADT47. With the assistance of PCR markers, homozygous and heterozygous genotypes were identified in F2 generation of two crosses (ADT43 × IRBB60 and ADT47 × IRBB60) and goodness of fit was tested. Eighty nine plants from F3 generation of ADT43 × IRBB60 were also screened for resistance genes. The genotypes carrying resistance genes in different combinations were identified. The pyramided lines showed a wider spectrum and higher level of resistance against two Xoo isolates under field conditions.

Oxalic acid (1 mM) when applied as a foliar spray to rice plants induced resistance to challenge infection with Rhizoctonia solani, the rice sheath blight pathogen. Maximum reduction in sheath blight incidence was observed when the plants were sprayed with oxalic acid three days before inoculation with the fungus. The biochemical alterations in rice plants treated with oxalic acid was also investigated. When rice plants were treated with oxalic acid, a two-fold increase in phenolic content in leaf sheaths was recorded three days after treatment. Phenylalanine ammonia-lyase and peroxidase activities increased significantly starting from two days after treatment. Peroxidase (PO) isozyme analysis indicated that PO-3 and PO-4 were induced two days after treatment with oxalic acid. Western blot analysis revealed that two chitinases (28 and 35 kDa) and two β-1,3-glucanases (30 and 32 kDa) were strongly induced in rice sheaths four to six days after treatment with oxalic acid. Immunoblot analysis of pro...

Five different Indian cassava mosaic virus (ICMV) specific primers were used to screen the virus from CMD affected samples collected from the different parts of Tamil Nadu. Out of five specific primers, three were designed to amplify the specific viral genes of ICMV and two were used for detection of ICMV. All primers amplified specific regions of the virus in all samples. The specific primer for amplification of coat protein gene of ICMV amplified 800 bp of coat protein gene from both ICMV and Sri Lankan cassava mosaic virus (SLCMV) infected samples invariably. The specific primer for amplifying movement protein (MP) gene amplified about 900 bp of movement protein gene from all CMD infected cassava samples. Likewise, 800 bp of nuclear shuttle protein (NSP) gene was amplified from all the samples. The primer ICMV A amplified 700 bp of PCR product from mosaic diseased cassava samples. A 300 bp product from DNA A of the virus amplified in all samples using the primer ICMV A1.

Bitter gourd Yellow Mosaic Virus (BGYMV) is a Whitefly transmitted geminivirus. BGYMV causes yellow mosaic disease in bitter gourd. This disease attains significance because the virus causing this disease is capable of attacking the crop at all stages. There was a severe yield loss in bitter gourd plants due to the infection of BGYMV. Bitter gourd plants treated with Bougainvillea spectabilis challenge inoculated with BGYMV reduced the disease incidence and increased the plant growth. In the above treatment the disease incidence was 33.33% at 75 Days After Sowing (DAS). But in the inoculated untreated control the disease incidence was 100% at 75 DAS. The mean maximum plant height was 92.24 cm in plants inoculated at 65 DAS. Bougainvillea spectabilis treated plants challenge inoculated with BGYMV showed an increased activity of peroxidase, polyphenoloxidase and phenol content from 4 Days After Inoculation (DAI) to 12 DAI. The activity of all the enzymes was reduced from 16 DAI in all the treatments.

Polymerase chain reaction of Cassava mosaic virus revealed that out of the 50 samples analysed only two samples, one from Musiri (Trichy district) and other from Mallur (Salem district), were detected with ICMV infection as 904 bp fragment of DNA-A amplified. All the other samples from various districts of Tamil Nadu were detected invariably with SLCMV as they amplified 599 bp of DNA-A. A 599 bp fragment of DAN-A was cloned and sequenced from the sample collected from Mallur. The nucleotide sequence has been submitted to GenBank under the accession number DQ303479. The nucleotide sequence was compared with other cassava infecting geminiviruses and other geminiviruses in GenBank. Cluster dendrogram revealed that the cloned sequence was most closely related to ICMV, Maharastra strain rather than SLCMV, forming one cluster. Comparative sequence analyses showed that the cloned fragment shared a maximum sequence identity with ICMV at nucleotide levels (93%) than with SLCMV (88%).

A survey was conducted to record the occurrence of whitefly-transmitted gemini viruses (WTGs) in four districts of Tamil Nadu. Various plant and weed species infected by WTGs were collected during the survey, and preliminary studies conducted revealed that the bitter gourd plant exhibiting the yellow mosaic symptom was new and it was devastating for bitter gourd in all the places where the survey was conducted. This virus was characterized as bitter gourd yellow mosaic virus (BGYMV). Cassava (Monihot esculenta) and three weed species viz., Acalypha indica L., Croton sparsiflorus, Bail, and Malvastrum coromandelianum (L.) Gracke, respectively, were found to be the hosts of BGYMV. BGYMV was purified from the infected bitter gourd plants and it was found that the purified particles contained a single major protein of an estimated molecular weight of 35 KDa.

Serodiagnosis of BGYMV revealed that ACMV polyclonal antibody and ICMV monoclonal antibody trapped the particles from the extracts of BGYMV infected bitter gourd plants. Optimum antigen and ICMV monoclonal antibody dilution to detect BGYMV was 1:10 and 1:1, respectively. A405 value at 1.10 and 1:100 antigen dilution for BGYMV infected sample was 0.949 and 0.544, respectively. A405 value at 1:1 and 1:5 ICMV monoclonal antibody dilution was 0.993 and 0.696, respectively. Polymerase chain reaction technique using Deng's degenerate primer for gemini virus amplified 560 bp fragment from BGYMV infected bitter gourd plants.

Studies were conducted to evaluate two specific strains of the novel plant growth promoting rhizobacterium (PGPR), Pseudomonas fluorescens for induced systemic resistance (ISR) against urdbean leaf crinkle virus (ULCV) in blackgram (Vigna mungo) under controlled conditions. Results of the studies revealed that the pre-inoculation application of blackgram plants with the strains of P. fluorescens viz., Pf1 and CHAO were found to reduce ULCV infection significantly. Soil and foliar application of P. fluorescens (Pf1) induced the accumulation of phenolics and enhanced the activities of peroxidase, phenylalanine ammonia lyase and polyphenol oxidase. New isoforms of peroxidase and polyphenol oxidase were also induced by the treatment. The induced defense mechanism might have played a role in reducing the disease.

The effect of chemicals on the induction of systemic resistance in blackgram (Vigna mungo) against urdbean leaf crinkle virus (ULCV) was studied. Pre-inoculation spraying of blackgram plants with resistance-inducing chemicals, namely salicylic acid and benzothiadiazole at 100 ppm concentration was found to be effective in reducing ULCV infection and increasing the incubation period of the virus under controlled conditions. The treatment of blackgram plants with salicylic acid and benzothiadiazole significantly increased the phenylalanine ammonialyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO) activities. New isoforms of peroxidase and polyphenol oxidase were also induced by these treatments. A two-fold increase in accumulation of total phenol was observed in plants treated with salicylic acid and benzothiadiazole.

The complete nucleotide sequence of Sri Lankan cassava mosaic virus (SLCMV) DNA-A isolated from cassava in southern India was analyzed, a phylogenetic analysis with other begomoviral nucleotide sequences was performed and an efficient inoculation method of Nicotiana benthamiana with the cloned DNA was developed utilizing a biolistic device. The nucleotide sequence showed the conservation of all functional begomoviral protein domains and aligned most closely with begomoviruses reported from the Indian subcontinent, except for begomoviruses of cucurbits and legumes. Upon biolistic inoculation of N. benthamiana with the cloned DNA, most plants became symptomatic and showed the accumulation of viral DNA within 21-28 days post-inoculation.

The wild rice species (Oryza rufipogon, O. latifolia), thermogenic male sterile lines (TGMS) and Cuddalore rice accessions were evaluated for their reaction to the sheath rot pathogen (Sarocladium oryzae) under field conditions. The resistant TGMS line TS 47, Jeragasala 1, 2 and 3 (Cuddalore accessions) exhibited reduced disease symptoms. These field-screened cultivars were further confirmed for their resistance under in vitro conditions. The efficiency to grow in the toxin-containing medium was appraised. The medium was supplemented with toxin as crude, diluted preparation and culture filtrate. All the field identified genotypes except TS 47 showed better callus proliferation in vitro. Indeed they produced plantlets in toxin free medium further confirm their resistance. The germination test conducted in toxin containing culture tube also endorsed the suitability of Jeragasala 1, 2 and 3 as resistance donor. In addition, the difference in the protein profile of disease susceptible and resistant cultivars ...

Rice(Oryza sativa L.,)isone ofthemostimportant cerealcropsworldwide.Inthisstudy,phytoplasmashavebeen detected in symptomatic leaves of four varieties of rice using nested-PCR with primer pairs P1/P7 and R16F2n/R16R2, which amplified a 1.2 kb fragment of the 16S rRNA gene. The nucleotide sequence analysis of the fragment had 100 % identity among the sequences from the four varieties (GenBank Accession numbers: JX290545, JX290546, JX290547 and JX290548) and 99 % nucleotide sequence identity with 16S rRNA gene sequences of the Rice orange leaf disease phytoplasmas from the Philippines and Thailand, Maize bushy stunt phytoplasma and Wheat blue dwarf phytoplasma belonging to the 'Candidatus Phytoplasma asteris' (16SrI) group. This is the first report of 16SrI group phytoplasmas infecting rice in India.

Mirabilis jalapa and Harpulia cupanioides remain as an unexploited potential to be tapped, as sources of antiviral principles. The antiviral protein from M. jalapa (MAP) and H. cupanioides (HAP) were highly effective in inhibiting TSWV at 60 and 80% saturation. A minimum concentration of 400 μg/ml of MAP was sufficient to inhibit TSWV. HAP at 800 μg/ml recorded 98.41% inhibition of lesion formation. The plants treated with M. jalapa and H. cupanioides challenged with TSWV did not show significant variation in absorbance values when compared to uninoculated healthy plants, indicating the absence of detectable virus through indirect DAS ELISA thus indicating the effectiveness of AVPs. Pre-application of MAP and HAP induced the activity of phenols, PO, PPO and PAL leading to the suppression of TSWV on local lesion and systemic host.

A polymerase chain reaction (PCR) assay was used to detect the Indian iso­late of banana bunchy top virus at early stages of infection in banana suckers before symptom expression. The viral DNA was detected from a single viruliferous banana aphid (Pentalonia nigronervosa) at 1.0 kb. The six plant species viz., Zingiber officinale, Colocasia esculenta, Cathe­ranthus roseus, Canna indica, Hedychium coronarium and Alphi­nium sp. upon inoculation with BBTV showed negative results in PCR assay. Using PCR assay the BBTV could be detected in meristem tip cultured banana plants before symptom expression. In field condition the meristem tip cultured banana plants expressed BBTV symptom 45 days after planting.

Sugar beet (Beta vulgaris L. subsp. vulgaris var. altissima) is a biennial, sugar-producing tuber crop grown in different parts of the world. Diseased sugar beets with symptoms of little leaf were observed during 2008 in Tamil Nadu, India. Phytoplasmas were detected in symptomatic leaves of three separate plants using PCR with primer pair fU5/rU3, which amplify an 880-bp fragment of the 16S rRNA region of phytoplasmas. The nucleotide sequence analysis of a 766-bp fragment had 100% identity among the sequence from the three plants (GQ184437) and 96% nucleotide sequence identity with 16S ribosomal RNA gene sequences of eggplant phyllody phytoplasma.

Yellow mosaic disease caused by mungbean yellow mosaic virus (MYMV) belonging to the genus Begomovirus (the family Geminiviridae) is a major constraint in cultivation of grain legumes in India. The urdbean (Vigna mungo (L.) Hepper) and mungbean (Vigna radiata (L.) R. Wilczek) samples affected with yellow mosaic disease exhibits yellow mosaic symptoms along with leaf puckering and leaf distortion in Tamil Nadu. Hence the study was performed to find out if there was any association and influence of betasatellite DNA on the symptom expression of MYMV. Full length viral clones of DNA A and DNA B were obtained through rolling circle amplification from YMD infected samples and identified as mungbean yellow mosaic virus. Interestingly, betasatellite was found to associate with MYMV, and its nucleotide sequence analysis showed its 95% identity with papaya leaf curl betasatellite (DQ118862) from cowpea. The present study represents the first report about the association of papaya leaf curl betasatellite with MYMV and represents a new member of the emerging group of bipartite begomovirus associated with betasatellite DNA.

Twenty one rice genotypes were selected and screened under artificially controlled conditions to identify the rice blast disease reaction. Sixteen genotypes which were already reported to have resistance genes reacted negatively to the blast disease. Four genotypes were found to be susceptible. Highly significant, lower mean disease reaction score and mean PDI (potential disease incidence) % was recorded for Moroberekan, followed by Columbia 2 and ARBN 142 (Asian rice biological network). All the 21 genotypes along with 64 hybrids were evaluated for nine traits in a randomized block design over five replications. Genetic variability, character association and path-coefficient analysis were studied. Grain yield was kept as a dependant character and the results were analyzed. Analysis of variance revealed considerable variability among the genotypes for all the characters. The phenotypic correlation coefficient (PCV) values were slightly greater than genotypic correlation coefficient (GCV), revealing negligible influence of environment in character expression. High heritability coupled with high genetic advance and high GCV were observed for number of tillers/plant followed by number of productive tillers per plant, plant height and grain yield / plant. Characters like plant height, number of tillers / plant, number of productive tillers / plant, panicle length, filled grains per panicle and test weight had significant positive association with grain yield. Results of path-coefficient analysis revealed that, test weight exhibited maximum positive direct effect on grain yield / plant followed by filled grains / panicle, plant height, panicle length, number of tillers / plant and days to 50% flowering and they contributed primarily to yield and could be relied upon for selection of genotypes to improve genetic yield potential of rice. Key words: Oryza sativa, direct effect, heritability, genetic advance, association, Magnaporthe grisea, phenotypic correlation coefficient, genotypic correlation coefficient.

The complete nucleotide sequence of an isolate of rice tungro bacilliform virus (RTBV), collected from Kanyakumari, India, where RTBV was reported recently for the first time, has been analyzed. Sequence comparison revealed that the RTBV isolate from Kanyakumari (RTBV-KK) has a high degree of identity to the two previously reported RTBV sequences from India, RTBV-AP and RTBV-WB, which had been collected from field locations about 10 years ago and 1000–2000 km away from the collection site of RTBV-KK. Most of the sequence domains reported previously in other RTBV isolates were found to be conserved in RTBV-KK. Closer inspection revealed RTBV-KK to be a possible recombinant between RTBV-AP and RTBV-WB in the genomic region encompassing the coat protein gene.

Marker assisted backcrossing breeding has become one of the essential tools in transferring novel genes to adapted varieties and was employed to pyramid three blast resistance genes Pi1, Pi2 and Pi33 to a popular susceptible rice variety ADT43. Gene pyramiding process was facilitated by marker aided selection for both foreground as well as background genotype. Previously reported linked molecular markers were deployed to survey resistant and susceptible genotypes. In the BC3F1 generation four lines viz, AC-B3-11-7, AC-B3-11-36, AC-B3-11-57, AC-B3-11-83 were identified to be pyramided with three genes and subjected to background analysis and a genome recovery up to 95 % was observed and advanced to further generations. Morphological, yield and grain quality traits were significantly similar to ADT43. The introgressed lines with three gene combinations were highly resistant to the blast pathogen compared to genotypes with single genes and the susceptible checks under blast nursery screening at two epiphytotic locations; Coimbatore and Gudalur. The selected three gene pyramided backcross lines in the desirable background were advanced to obtain an improved ADT 43 with resistance to blast disease.