Chromosome number is not fixed unlike in other crops, its a range for example 2n= 40-120
its because of polyploidy during the cause of their evolution
They are polyploid aneuploid hybrids with unequal contribution from S. officinarum (80–90%) and S. spontaneum (10–20%) parental genomes and a small percentage of recombinant chromosomes. Sugarcane hybrids have ploidy levels of 10 or more and have a much larger total genome size (R570 cultivar, 10,000 Mb and 2n = 115) than that of maize (5500 Mb, 2n = 20), sorghum (1600 Mb, 2n = 20) or rice (860 Mb, 2n = 24) reflecting the high polyploidy level of sugarcane cultivars.
The topical Vireya in the genus Rhododendron have a wide variation in flow cytometry scores including some in the normal diploid range for Asia mainland species but increasing linearly to the triploid, tetraploid, pentaploid, and hexaploid ranges as the Vireya migrated to the more subtropical and tropical islands.
Although it is not clear whether these increases in flow cytometry scores are due to increased chromosome count or chromosome length, what is clear is the selected pressure towards a stabilized genome size decreased as the Vireya moved into conditions similar to those found in greenhouse environments.
Our hand crosses with 3x by 4x deciduous azaleas illustrates that aneuploids between 3x and 4x are viable when germinated in greenhouse conditions. Moreover such aneuploids can be fertile. We have found that pentaploid seedlings that result from 3x by 4x are very fertile.
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