Sex determination of papaya var. ‘Maradol’ reveals hermaphrodite-to-male sex reversal under greenhouse conditions

Abstract

Papaya is a nutritious fruit cultivated worldwide under suitable climate conditions. This plant is polygamous, bearing female, male, and hermaphrodite sex types determined by sex chromosomes XX, XY, and XY h , respectively. In this paper, a molecular sex determination of papaya var. 'Maradol' was carried out based on PCR and specific primers. Specific molecular markers resulted in sixty-nine hermaphrodites and twenty-one female plants, matching 100% to the flower morphology. Nevertheless, since the summer stressing conditions rose in the greenhouse, sex reversal to male phenotype was observed in 43% of hermaphrodite plants due to high-temperature conditions. A specific male marker could not detect that change, supporting the proposal that sex reversal is caused by harsh environmental conditions aimed at epigenetic modification and genes related to hormones. Our study demonstrates the effectiveness of molecular sex determination and the importance of controlling the growing requirements of papaya to avoid sex reversal.

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“…The experiment was conducted in an 8 × 8 m greenhouse at Cinvestav, Irapuato Campus facilities in Guanajuato, Mexico (20 • 43 N, 101 • 19 W) at an elevation of 1780 m. The greenhouse is a dome-shaped structure covered with plastic polystyrene on the top, antiaphid mesh on three sides, and only one side with a transparent polycarbonate wall on the back [51], where it adjoins to another greenhouse, creating a light gradient from the front to the greenhouse's interior. The greenhouse has three corridors in its interior with mud bricks on the floor.…”

“…The greenhouse was naturally ventilated. Conditions like temperature and relative humidity were not controlled; however, these parameters were monitored at 2 m above the ground with a digital thermometer Loriskors ® (Los Angeles, CA, USA) with a temperature precision of ±1 • C and humidity of ±2~3% with a 24 h record of minimum and maximum [51].…”