Genetic variation for perenniality in O. sativa/ O. rufipogon derivatives

Introgression of perenniality genes from Oryza rufipogon to O. sativa would help upland rice farmers reduce soil erosion from their fields. Parental upland cultivars and 51 O. sativa/O. rufipogon F1 combinations were evaluated for 12 mo in an upland field. None of the 14 parental upland cultivars survived the experiments, indicating that they were not highly perennial. In contrast, 95 interspecific progenies (19%) survived, indicating that perenniality genes from O. rufipogon were expressed in some of the hybrids. The choice of O. rufipogon as parental material had a large and highly significant effect on the survival rate of the interspecific progenies. Phenotypic selection for perenniality should be done more than a year after planting. The percentage of surviving individuals in F1 families at 12 mo was moderately and significantly correlated with the vigor of the O. rufipogon parent at 20 mo posttransplanting but not with parental vigor at 9 mo. These observations were consistent with a strong and significant correlation between the percentages of surviving individuals within O. rufipogon accessions at 15 mo with data taken at 21 mo. Moreover, the percentage of surviving individuals within O. rufipogon accessions at 9 mo was not significantly correlated with percent survival at 15 mo or 21 mo, indicating that early selection for perenniality is not efficient. Selectable genetic variation for perenniality has been found in O. rufipogon and its progenies with O. sativa. Combining agronomically desirable traits with perenniality should be feasible but will be time-intensive.