Analysis of morphological traits in different host plants associated with resistance to Phenacoccus solenopsis- an invasive pest in Pakistan
Phenacoccus solenopsis Tinsley (Pseudococcidae: Hemiptera) is a sucking insect pest and is polyphagous in nature. Twenty five (25) different host plants were screened against P. solenopsis and their physicomorphic traits were determined to correlate their role against pest population. Among the tested plant species, most favorable host plants of mealy bug on the basis of population were Gossypium hirsutum (69.74±10.5), Solamum melongena (62.41±10.0), Helianthus annuus (61.83±10.0), Hibiscus rosa-sinensis (61.1±10.0) and Lantana camara (55.83±9.75), but the least preferred plants were tandla Digera arvensis (1.57±1.00) and Conyza bonariensis (3.83±1.75). Significant variations were observed in all the morphological plant characters recorded from different plant species. The maximum leaf thickness per plant was 2.04±0.23 ìm in plant species S. melongena while minimum thickness of leaf was recorded from lehli (0.25±0.02 ìm). Maximum trichome density per plant was 444±72.4 in sunflower followed by 411.6±19.6, 399±52, 391.6±22.0, in C. bonariensis, Abelmoschus esculentus and Withania somnifera respectively but minimum were 2.33±1.45 in Chinopodium morale, followed by 2.66±1.4, and 3±2.08 in Portulaca oleracea and Trianthema portulacastrum respectively. The maximum hair length per plant (2.62±0.07 mm) was of sunflower followed by 2.55±0.03 mm in okra, 2.53±0.06 mm in both S. melongena and G. hirsutum. It was concluded that plant characters including trichome density and hair length favor mealy bug population showing r-values of 0.357* and 0.190 respectively but leaf size and leaf width (leaf area and leaf thickness) exerted negative effect on pest population showing r-values of -0.172 and -0.285 respectively.
Key words: Phenacoccus solenopsis, invasive species, physicomorphic traits, resistance.