Autotetraploids are generally:
Autotetraploids contain four homologous chromosome sets of same species genome, AAAA, derived from doubling of diploid AA genome via colchicine treatment that inhibits spindle formation. Presence of four allele copies increases cell size, nuclear volume, and organ dimensions termed gigas effect due to increased gene dosage and protein production per cell. Leaves become thicker, stomata larger, flowers bigger, fruits heavier, and biomass enhanced, contributing to increased vigor in forage crops like alfalfa and rye grass and ornamental flowers. Photosynthetic rate may rise due to larger chloroplast number and increased water content. However fertility may decline because quadrivalent formation at meiosis I causes irregular segregation, producing aneuploid gametes and reduced seed set requiring selection for regular bivalent pairing. Successful autotetraploid cultivars are selected for improved seed set and stability. Examples include tetraploid potato varieties and tetraploid rye that outperform diploids in vegetative yield and stress buffering due to greater heterozygosity and allelic diversity per locus. Breeding strategies exploit gigas effect for larger fruits in apple tetraploids and ornamental flowers with increased petal size and intense color; however tetraploid sterility barriers limit crossing, requiring interploid crosses and
Ref: Randolph LF. 1932 Autopolyploid vigor; Stebbins GL. Gigas effect. Acquaah Autotetraploid breeding