Enhancing coffee diversity: Insights into the impact of sodium azide mutagenesis on quantitative and qualitative traits in Coffea arabica L

Crop improvement of coffee (Coffea arabica L.) is limited due to its low genetic variability. Induced mutagenesis is one of the most widely used breeding methods for rapidly increasing genetic diversity in many crops. The present study explored the effect of sodium azide (NaN₃) on quantitative and qualitative fruit and seedling traits of Coffea arabica var Catuaí M2 derived lines. We worked with 81 derived lines obtained from M1 Catuaí seeds, previously treated on M0 during the seed stage with (NaN₃) at 50 mm for eight hours. Morphological characteristics in ripe fruits as well as germination percentages in seeds were measured. In addition to these parents, four lines were used as controls to describe growth parameters of 120-day-old seedlings, established under controlled conditions. Results showed significant differences in the seed and seedling M2 derived lines (p < 0.0001). The qualitative characteristics of fruit level (length, thickness, and width) were significantly higher in 2 out of the 81 lines. The cluster analysis (Wilks, p < 0.0001) revealed divergence of growth variables by classifying evaluated lines into four different groups (p < 0.05). Principal component analysis (PCA) explained more than 80 % of the total variance between lines treated with mutagens and control plants, where all variables showed a positive association, except plant diameter and height. Qualitative characters were classified as morphological alterations in seedling growth. Morphological malformation of three cotyledons obtained the highest frequency of anormal alterations (10.08 %) followed by four cotyledons (4.30 %), and 2.61 % for dwarf plants. Our results showed that the mutagenic treatments induced heterogeneous lines across qualitative and quantitative characteristics in M2 coffee fruits and their seedlings.