Effect of in vivo plant preservation on the fertility and chromosome configuration of a quadri-specific hybrid derived from 4 cultivated cotton species

Abstract

A quadri-specific hybrid F1 (G. arboreum, G. herbaceum, G.hirsutum, and G.barbadense) was produced by crossing the doubled-chromosome (G.arboretum × G. herbaceum) F1 with (G.hirsutum × G.barbadense) F1. The hybrid plants were preserved for 15 years via the method of grafting. The hybrid flowers were self-crossed and back-crossed every year, and the pollen vigor was tested as well. The results showed that the percentage of fertile pollens and weak-vigor pollens increased with the time of plant preservation, especially for those of weak-vigor that occupied about 10% of the total pollens after 15 years of growth. Meanwhile, the percentage of the sterile pollens decreased with the plant preservation, and the fertility of the quadri-specific hybrid was recovered partially. After plant preservation for more than 10 years, some backcrossed seeds were obtained via backcrossing with upland cotton parents, and a few self-crossed seeds were produced finally. The characteristics of chromosome behavior and the chromosome configuration during the meiosis were studied and the results showed that the chromosome configuration of the quadri-specific hybrid plant grown for 15 years was 2n = 52 = 4.92I + 14.62II + 2.29III + 1.56IV + 0.71V+ 0.19VI, while that from the plants of 15 years ago was 2n = 52 + 8.4I + 8.1II + 5.7III + 1.9IV + 0.6V. It was showed that the univalents decreased to 3.5 per cell, bivalents increased up to 6.5 per cell, and the number of multivalents decreased obviously as well. It was found from this experiment that extending the growth period by the method of grafting would be helpful to harmonize the relationship among the different chromosome groups which came from different species, and balance the chromosome configuration, which led to the partially recovering in plant fertility of the interspecific hybrids.