Characterization of some Nigerian pawpaw (Carica papaya L.) accessions using pomological traits

Abstract

Genetic diversity assessment is fundamental for crop improvement, particularly in underutilized tropical species like papaya (Carica papaya L.). This study evaluated 60 papaya accessions collected from southern Nigeria using pomological traits. Significant genotypic differences (p < 0.01) were observed across all traits measured. Fruit length ranged from 23.10 to 31.53 cm (mean = 26.92 cm), while fruit pulp diameter varied between 8.13 and 14.53 cm. Fruit circumference spanned 30.10 to 38.53 cm, and fruit weight exhibited the highest variability, ranging from 0.73 to 2.78 kg (mean = 1.63 kg; CV = 50.90%). Seed number varied widely, from 298 to 945 seeds per fruit, with a mean of 609.00. Fruit shapes were diverse, with elliptic and reniform shapes most common (13.33% each), followed by elongated and plum-shaped (11.67% each), and less frequent shapes like pear, lengthened cylindrical, and globular (1.67% each). Mature fruit skin colour was predominantly green (62.71%), followed by yellowish-green (25.42%) and yellow (11.86%). Fruit flesh colour was mainly deep yellow to orange (33.33%), light yellow (26.67%), bright yellow (23.33%), and reddish-orange (16.67%). This diversity has potential implications for breeding programs. Correlation analysis revealed a strong positive association between fruit length and circumference (r = 0.97), suggesting simultaneous improvement potential. Cluster and heatmap analyses grouped accessions into five distinct clusters, indicating substantial genetic divergence. Accessions such as IMNO01 (high fruit weight) and ASUN02 (low seed number) were identified as promising for breeding programs targeting larger fruit size and improved edible yield. The findings provide a foundation for selecting elite genotypes and enhancing papaya breeding efforts in Nigeria.