14.
A quadri-specific hybrid F
1 (
G. arboreum,
G. herbaceum,
G.hirsutum, and
G.barbadense) was produced by crossing the doubled-chromosome (
G.arboretum ×
G. herbaceum) F
1 with (
G.hirsutum ×
G.barbadense) F
1. 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 2
n = 52 = 4.92I + 14.62II + 2.29III + 1.56IV + 0.71V+ 0.19VI, while that from the plants of 15 years ago was 2
n = 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.
__________
Translated from
Cotton Science, 2007, 19(6): 461–466 [译自: 棉花学报]
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