Abstract
Papaya ringspot virus-P is a major detrimental to papaya cultivation. All cultivars of Carica papaya are found to be susceptible to Papaya ringspot virus disease, meanwhile, the species in Vasconcellea gene pool possess PRSV resistance, conferred by many researchers. Inorder to understand the role of sugars and its partitioning as defence mechanism against PRSV attack, eleven accessions including susceptible cultivated varieties, intergeneric hybrids and wild relatives were inoculated and estimated physiological parameters such as photosynthetic rate (PN), stomatal conductance (gs) and transpiration rate (E) and profile of sugars in LC-MS. The results revealed that physiological parameters remained unchanged in resistant accessions; whereas, in susceptible accessions, PN and gs decreased as disease progressed and E increased upto 14 days post inoculation (dpi) and decline. Major transporter sugar, sucrose increased rapidly in resistant accessions, similar was the case for the glucose and fructose. As a defence mechanism, sucrose attracts towards the wounded site and further converts it into glucose and fructose by invertase, rapid occurrence of these processes act as signalling and resulted in defence related proteins. Due to the destruction of chlorophyll structure, sucrose and hexose sugars failed to elevate rapidly in susceptible accessions. Pentose sugar, ribose was increased immediately in resistant accessions, which might have enhance defence related genes and proteins. However, cell wall pentose sugars remained unaffected in resistant accessions, while in susceptible accessions, they increased at 30 dpi. Sugar alcohol viz., inositol was increased at initial stage in resistant accessions. Trehalose, a disaccharide sugar increased in susceptible accessions after 30 days of inoculation.
Published Version
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