Opuntia ficus-indica (L.) Mill.), is called "beles" in the Tigray region of Ethiopia, where it is used for multiple purposes, such as food, fodder, and fences; however, in recent years the introduction of the cochineal (Dactylopius coccus Costa) to this region has caused it to become a plague that has affected thousands of hectares, causing an economic and social problem. Six cultivars: three from Opuntia ficus-indica (‘Atlixco’, ‘Chicomostoc’, and ‘Rojo Pelón’) and three others O. cochenillifera (‘Nopalea’ and ‘Bioplástico’) and O. robusta (‘Robusta’) were tested for resistance to D. coccus in completely randomized design (CRD) experiment with six replications under greenhouse conditions, for two seasons (cycles). Matured cladodes were infested by attaching a paper bag with ten ovipositing female D. coccus. The number of insects at different stages and yields were recorded, log transformed (insect count data), and subjected to statistical analysis. The number of nymphs (stages I and II) was significantly different in both cycles (P=0.0000). The insects died at the nymph I stage at ‘Rojo Pelón’ and ‘Robusta’, in contrast, they completed their life cycle at ‘Atlixco’, ‘Chicomostoc’, and ‘Nopalea’ cultivars. Insects at ‘Bioplástico’ cultivar remained in the nymph I stage the whole experimental period; the molting was hampered. Although some crawlers started settling (nymph I) at ‘Rojo Pelón’, they couldn’t survive and developed, and this confirms that this O. ficus-indica cultivar is resistant to D. coccus.
Multipurpose cactus pear plant with great potential as a source of food and livestock faced a threat from Dactylopius spp in different countries. Specifically, D. coccus is an important pest damaging significant areas in Tigray-Ethiopia. Using pest-resistant cultivars is an important element of an integrated pest management strategy, and studying the mechanisms of resistance is vital. It can be chemical or physical such as oxalate crystals and other cladode characteristics. Cladode features of six cultivars (three O. ficus-indica, two O. cochenillifera, and one O. robusta) were examined for resistance to D. coccus in a completely randomized design (CRD) with three replications. 'Rojo Pelón' (O. ficus-indica), 'Robusta' (O. robusta), and 'Bioplástico' (O. cochenillifera) are resistant cultivars; and 'Atlixco' and 'Chicomostoc' (O. ficus-indica) and 'Nopalea' (O. cochenillifera) are susceptible. Cultivars showed asignificant difference in cladode weight in g, and cladode length, cladode width, and cladode thickness in cm, where cladode thickness was higher in 'Rojo Pelón' followed by 'Robusta'. Calcium oxalates number per mm was higher in 'Bioplástico' (20.7 ± 2.08) followed by 'Robusta' (18.9 ± 2.31) and 'Rojo Pelón' (15.9 ± 0.34); and similarly, epidermis thickness found higher in 'Bioplástico' (0.21 ± 0.032) and 'Robusta' (0.19 ± 0.014), but similar with 'Rojo Pelón' (0.18 ± 0.026). However, cuticle thickness didn't show a difference among cultivars. Cladode thickness, calcium oxalate number, and epidermis thickness had positive correlations with resistance. These results demonstrate that calcium oxalate number and epidermis thickness might have a positive role in
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