Enhancing virus resistance through pre-breeding and crossability experiments in okra (Abelmoschus esculentus (L.) Moench)

Wild relatives of okra serve as donors for resistance breeding programs, particularly for viral diseases. In this study, the cultivated okra variety Abelmoschus esculentus cv. 'Pusa A-4' was crossed with four wild accessions: A. moschatus (IC-141055), A. manihot var. tetraphyllus (IC 90476-1), A. caillei (Sikkim), and A. ficulneus (Sel-1). Cross-compatibility experiments revealed that A. ficulneus (Sel-1) exhibited better compatibility with cultivated okra than other wild relatives. Both cultivated and wild parents showed high pollen viability and low variability in pollen diameter compared to their interspecific F1 hybrids and BC1F1S. Interspecific F1 hybrids were screened for okra yellow vein mosaic diseases (OYVMD) and okra enation leaf curl disease (OELCuD) under natural conditions, showing that the interspecific lines derived from A. moschatus were highly resistant, while interspecific lines derived from A. ficulneus were susceptible. Backcross was attempted in resistant F1s and the only successful BC1F1 population developed was Pusa A-4 x (Pusa A-4 x A. moschatus (IC 141055)) with 24 survived individuals. Eight simple sequence repeat (SSR) markers were identified as polymorphic between Pusa A-4 and A. moschatus (IC 141055). These eight markers were used for hybridity confirmation and molecular characterization of 24 BC1F1 individuals, which confirmed the genetic closeness of BC1F1 individuals to the cultivated parent Pusa A-4 compared to the wild parent A. moschatus (IC 141055), indicating the restoration of cultivated characteristics on backcrossing. Screening of BC1F1 individuals against viral diseases grouped 20 individuals as highly resistant to OYVMD and all 24 were highly resistant to OELCuD, confirming the resistance of A. moschatus (IC 141055). These resistant lines and insights into crossability can serve as valuable pre-breeding lines for developing durable multiple disease-resistant okra cultivars.