Expression of short hairpin RNA (shRNA) targeting AC2 gene of Mungbean yellow mosaic India virus (MYMIV) reduces the viral titre in soybean

Mungbean yellow mosaic India virus (MYMIV) belonging to the family Geminiviridae and the genus Begomovirus is a severe pathogen of tropical legumes including soybean. The absence of genetically mapped loci conferring resistance together with the genetic diversity of begomoviruses infecting soybean warrants the utilization of RNA interference (RNAi) technology to develop virus resistance. However, viral suppressors of RNAi (VSRs) reduce the effectiveness of RNA silencing. Here, we report the effectiveness of Agrobacterium-mediated transient expression of shRNA, targeting a conserved region of AC2 ORF (a VSR) of MYMIV, in conferring virus resistance in soybean. Transient expression of shRNA showed progressive reduction of the viral titre estimated by the MYMIV-derived AC2 gene copy numbers from the initial inoculum by approximately 80-fold 20 days post-application. In addition, the newly emerging leaves exhibited symptom recovery. Thus, this study proves that AC2 of MYMIV is a potent target gene for obtaining RNAi-mediated virus resistance in soybean. Agro-infiltration-based delivery of shRNA was an efficient means of gene silencing and could pave way for the development of transgenic virus-resistant soybean genotype.

Quantification of a legume begomovirus to evaluate soybean genotypes for resistance to yellow mosaic disease

Mungbean yellow mosaic India virus (MYMIV) infecting soybean and other legumes causes yellow mosaic disease (YMD). Evaluation of soybean genotypes for YMD resistance involves field screening at disease hot spots or in a protected environment using infectious clones or viruliferous whiteflies as sources of virus inocula. Development of efficient virus inoculation and quantification protocols to screen soybean genetic stocks against YMD is imperative for breeding resistant varieties. Binary plasmids harbouring complete, tandem dimeric genomic components DNA A and DNA B of MYMIV-soybean isolate were engineered. The infectivity of the clones was demonstrated in soybean genotypes JS335 and UPSM534 that display contrasting YMD resistance. As a follow-up, soybean germplasm lines, breeding lines, and representative cultivars that were initially screened at an YMD hot-spot were then subjected to Agrobacterium-based infection with MYMIV. Quantitative real time polymerase chain reaction (qRT-PCR) based copy number analysis of MYMIV genomic components allowed soybean genotypes to be classified into three discrete categories; resistant, moderately resistant and susceptible to the viral infection. Thus, a soybean germplasm disease screening system based on agro-infection and qRT-PCR based quantification of MYMIV was developed to facilitate breeding YMD resistant soybean. The implications of this study for obtaining YMD resistant soybean cultivars are discussed.

Ultrasonic study to see the effect of topical pilocarpine and homatropine on anterior chamber depth in phakic cases

Pilocarpine and Homatropine are the drugs having known effect on the depth of anterior chamber. The purpose of this study was to demonstrate the time of onset, peak effect and its duration of action as well as shallowing/deepening of the anterior chamber, after single instillation of pilocarpine 2% or homatropine bromide 2%, topically in one eye. Also we tried to see if there is any effect on the contralateral eye, due to systemic absorption of pilocarpine, homatropine after topical instillation of the drug in one eye. Pilocarpine causes a measurable shallowing of the anterior chamber with onset of effect with in 20 minutes and a peak in 60 minutes, the average narrowing being 0.26 mm. (range 0.20-0.29 mm.). Homatropine has a measurable deepening effect on the anterior chamber, due to axial flattening of the lens because of cycloplegia, with a range of 0.33 to 0.36 mm. In 70% of the cases the effect passes away with in 24 hours., but in 30% it comes to normal in 48 hours.

Kajal eye staining for early detection of vitamin A deficiency in the field

Staining of the eyes with carbon black ("kajal") was tried out in 500 children, age 1--15 years, partly urban and partly rural, in Jaisalmer District. Of the eyes of 280 rural boys 21.4% took the stain, of 50 girls 16.0%. In the urban groups the figures were 5.7% of 88 and 9.7% of 82, respectively. These figures conincided nearly wholly with the cases diagnosed X1A (conjunctival xerosis) or X1B (conjunctival xerosis with Bitot's spots) clinically. All Bitot's spots were stained black; in addition also 2.6% of cases diagnosed X1A. Eight cases presenting only nightblindness also stained. Since kajal application is harmless, cheap, and acceptable to Indian custom it is proposed as a diagnostic procedure suitable for the general duty doctor and paramedical staff in the field.