Certain Physiological and Chemical Indicators Drive the Yield and Quality of Cladode Mucilage in Three Fodder Nopal Morphotypes (<i>Opuntia</i> spp.) Under Different Soil Water Content Conditions

Nopal cladode mucilage is a product of great importance in fodder, agri-food, industry, and health areas. This study aimed to evaluate the effect of three soil moisture contents on some physiological and chemical variables associated with the mucilage yield and quality of three morphotypes of fodder nopal (<i>Opuntia</i> spp.). A randomized block experimental design in a split–split plot arrangement with three replicates was used. The large plots represented the following soil moisture contents (SMC): optimum soil moisture content (OSMC) from 22 to 27%; suboptimum soil moisture content (SSMC) from 16 to 21%; and deficient soil moisture content (DSMC) from 10 to 15%. The subplots consisted of three cactus pear genotypes identified by the following IDs: C-CH, -C-NA, and C-HE. The relative water content (RWC) was significantly higher in the C-HE morphotype across each soil moisture content, and the lowest value was recorded in C-NA with OSMC; -C-CH had the lowest values in SSMC and DSMC, with 71.3% and 44.3%, respectively. There were slight variations in chlorophyll with SSMC; the C-NA and C-CH morphotypes had significantly higher chlorophyll contents, with values of 10.3 mg g⁻¹ 100 FW of chlorophyll <i>a.</i> and 5.87 mg 100 g⁻¹ FW of chlorophyll <i>b</i>. The C-CH morphotype had the best mucilage yield, with 800 mL kg⁻¹ FW and 712.6 mL kg⁻¹ FW in OSMC and SSMC, respectively; DSMC showed the lowest yield at 552.3 mL kg⁻¹ FW. The quality of cladode mucilage by treatment did not vary by soil moisture content or among nopal morphotypes. Additionally, there was a positive correlation among the relative water content and the chlorophyll <i>a</i>, <i>b</i>, and total chlorophyll contents with the yield of the nopal cladode mucilage, but not with the ash content or total solids as variables of mucilage quality vs. yield.