Final answer:
The cultivated cotton species Gossypium hirsutum and Gossypium barbadense are tetraploid with a chromosome number of 2n = 52. (option 2)
Step-by-step explanation:
Gossypium hirsutum and Gossypium barbadense, two major cultivated cotton species in the new world, share a tetraploid genome, indicating a chromosome number of 2n = 52. This tetraploidy arises from the hybridization of diploid cotton species, leading to a doubling of the chromosome sets. In their genomic composition, each cell of G. hirsutum and G. barbadense possesses four sets of 13 chromosomes. The tetraploid nature of these cotton species is of great significance in agriculture as it contributes to their resilience, adaptability, and the expression of desirable traits.
Tetraploidy in cotton has implications for breeding programs, as it introduces a higher level of genetic diversity and complexity. It allows for the incorporation of favorable traits from different diploid species, leading to improved varieties with enhanced fiber quality, disease resistance, and other agronomically important characteristics. Understanding the ploidy level, specifically 2n = 52, is fundamental for cotton researchers and breeders, guiding their efforts to develop cotton varieties that meet the demands of the textile industry and global agriculture.
The tetraploid status (2n = 52) of G. hirsutum and G. barbadense is a defining feature that underlies their genetic diversity and agricultural importance.