Evaluation of cactus pear clones subjected to salt stress

Cactus pear is an important source of fodder for herbivores, though its production is affected by soil salinity. This work aimed to evaluate the development of cactus pear clones subjected to salt stress as a measure of their salinity tolerance. The experimental design was a randomized block with 6 replications. Twenty genotypes of cactus pear were used from the Active Germplasm Bank, with variability in resistance to carmine cochineal [Dactylopius opuntiae (Cockerell)] as this insect species destroys many stands of cactus on farms. One cladode was planted per pot containing 12 kg of sandy soil. Water with a salinity of 3.6 dS/m was applied at 14-day intervals. The clones were scored at 28-day intervals for degree of damage to cladodes (1‒5) and were harvested when they reached a score of 5, showing 100% damage (chlorosis and dehydration) to the whole plant. The Liso Forrageiro clone took 419 days to reach Score 5, indicating its greater tolerance to salinity. Highest dry matter yields were achieved by Orelha de Elefante Mexicana and Orelha de Elefante Africana clones with 51.5 and 50.8 g/plant, respectively, while Liso Forrageiro yielded only 36.1 g/plant, despite having similar surface area and weight of roots to these 2 clones. Further studies in the field involving these better-performing clones seem warranted to determine how the pot trial results are repeated in the field, especially in areas where carmine cochineal insect is prevalent.