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Papaya Ring Spot Virus disease is wide spread across papaya growing countries ofthe world and is one ofthe major impediments in successful papaya cultivation. Genetically engineered papaya varieties viz., SunUp and Rainbow have already been developed and commercialized in USA using coat protein mediated resistance. However, transgenic papaya conferring resistance to papaya ringspot virus has not been developed in India till date due to lack of suitable genetic transformation protocol for Indian papaya varieties and unavailability of coat protein gene construct for harbouring broad-spectrum resistance. The current study reports an efficient gene delivery mechanism in papaya. Young globular embryos infected for 30 minutes with Agrobacterium tumefaciens strain LBA 4404 harbouring hairpin loop of truncated coat protein gene and subsequently co-cultivated in presence of 100 pM acetosyringone and ImM spermidine in dark for 72 hours gave rise to independent transgenic events characterized by PCR, dot blot hybridisation and RT-PCR. [ABSTRACT FROM AUTHOR]

Cassava brown streak disease (CBSD) has occurred in the Indian Ocean coastal lowlands and some areas of Malawi in East Africa for decades, and makes the storage roots of cassava unsuitable for consumption. CBSD is associated with Cassava brown streak virus (CBSV) and the recently described Ugandan cassava brown streak virus (UCBSV) [picorna-like (+)ssRNA viruses; genus Ipomovirus; family Potyviridae]. This study reports the first comprehensive analysis on how evolution is shaping the populations of CBSV and UCBSV. The complete genomes of CBSV and UCBSV (four and eight isolates, respectively) were 69.0-70.3 and 73.6-74.4% identical at the nucleotide and polyprotein amino acid sequence levels, respectively. They contained predictable sites of homologous recombination, mostly in the 3'-proximal part (NIb-HAM1h-CP-3'-UTR) of the genome, but no evidence of recombination between the two viruses was found. The CP-encoding sequences of 22 and 45 isolates of CBSV and UCBSV analysed, respectively, were mainly under purifying selection; however, several sites in the central part of CBSV CP were subjected to positive selection. HAM1h (putative nucleoside triphosphate pyrophosphatase) was the least similar protein between CBSV and UCBSV (aa identity approx. 55%). Both termini of HAM1h contained sites under positive selection in UCBSV. The data imply an on-going but somewhat different evolution of CBSV and UCBSV, which is congruent with the recent widespread outbreak of UCBSV in cassava crops in the highland areas (>1000 m above sea level) of East Africa where CBSD has not caused significant problems in the past.