Characterization and evaluation of putative polyploid progenies of guava (Psidium guajava L.) through flow cytometry

Introduction - An attempt was made to assess the relationship between nuclear DNA content and various phenotypic characters among putative polyploid progenies of guava. Ploidy analysis using conventional chromosome counting method is time-consuming and requires lot of practice. In this study, an attempt was made to determine indirect method for ploidy level identification that can be used satisfactorily. Materials and methods - Eighty-six putative ploidy progenies were obtained by treating the seeds and seedlings of guava cultivars 'Arka Mridula' and 'Arka Kiran' with different concentrations of colchicine and established in the field. Morphological, anatomical traits and total soluble solids were recorded. Flow cytometry analysis was undertaken using Marie's nuclear extraction buffer for estimating nuclear DNA content among the progenies. Results and discussion - The flow cytometric data revealed that the mean nuclear DNA content was significantly different across the progenies with 2.97% and 3.95% coefficient of variation in 'Arka Kiran' and 'Arka Mridula', respectively. The absolute genome size varied from 0.493-1.333 pg/2C (482.88-1304 Mb/2C) in 'Arka Mridula' and 0.460-1.293 pg/2C (499.88-1,204.88 Mb/2C) in 'Arka Kiran' progenies. The variability present in progenies of maternal parents 'Arka Mridula' and 'Arka Kiran' was 0.960 and 0.957 pg/2C, respectively. The 2C DNA content showed a significant positive correlation with leaf size, stomatal size and TSS whereas significantly negative correlation with shoot internodal length and stomatal density. Results suggested that intraspecific variation in nuclear DNA content plays an important role in determining the phenotypic differences among ploidy-manipulated progenies of guava.