Oryza rufipogon (Griff.), a conduit for rapid evolution of rice under stress-prone environments: a test case of UV-B resistance and exoferalization

In general, wild relatives of cultivated rice are a repository of stress-tolerant genes and have been used to introduce resistance into cultivated rice. Compared to other abiotic stresses like drought, heat, cold, salinity, and disease resistance, UV stress emerged late in the biosphere, and there has been minuscule research on its trait location for resistance among rice genotypes for a possible way of introgression into cultivated species. Wild rice O. rufipogon (Griff.) which is sensitive to UV stress was facilitated to cross-pollinate naturally with a UV stress-resistant traditional cultivated rice Meghadambaru and the hybridization impact on stress tolerance was assessed on the progeny as well as the progenitors. UV stress affects vegetative growth by the downregulation of photosynthetic activity of leaf, lemma + palea, and awns because of its inhibitory effects on SPAD index, Fv/Fm ratio, and ETR (rel), photochemical quenching qP (rel), maximal fluorescence Fm (rel) and release of fluorescence energy (OJIP curve) in all three genotypes. However, these indices in O. rufipogon were found more vulnerable. The Intergrade genotype resulted from the parental cross-inherited weedy characters of O. rufipogon and UV tolerance attributes of Meghadambaru of the F1 generation followed by the F2 generation. O. rufipogon exhibited rapid evolution to gain UV stress resistance in the natural cross, while Meghadambaru resurged in exo-feralization and resurrected to devolution to weedy attributes.