2020 Volume 85 Issue 4 Pages 269-274
In vitro propagation of Psidium guajava L. has been significant for breeding programs and conservation. Hereby, distinct explants are chosen and inoculated into media supplemented mainly with the growth regulators 6-benzylaminopurine (BAP) and α-naphthaleneacetic acid (NAA). As growth regulators have been considered the main inducers of somaclonal variation (SV), this study verified the occurrence of karyotype and DNA sequence variation in P. guajava ‘Paluma’ and ‘Cortibel XIII’ plantlets. Plantlets propagated in different media—4.44 µM BAP, 4.44 µM BAP/0.54 µM NAA, or 4.44 µM BAP/2.70 µM NAA—were assessed concerning their nuclear 2C value, karyotype, and DNA sequence. Nuclear DNA content and chromosome number of all plantlets were 2C=0.95 pg and 2n=22, respectively, identical to P. guajava. Therefore, the media did not promote karyotype changes. In contrast, molecular analysis showed appearance and disappearance of allele forms. These alterations in the DNA sequence were found in plantlets propagated in all media, indicating that BAP and especially NAA are related to the event of somaclonal variation (SV). Based on these results, the media most employed for P. guajava induced SV at the DNA-sequence level. This approach provided data about the more appropriate media for propagation of P. guajava.
