Physiological responses of wheat to cereal cyst nematode infection: A growth stage analysis

Abstract

Heterodera avenae infection imposes severe physiological stress on wheat (Triticum aestivum cv. WH 1105), with chlorophyll b emerging as the most vulnerable pigment (41.02% mean reduction). Screenhouse experiments revealed biphasic pigment dynamics: chlorophylls a/b, carotenoids, and total chlorophyll increased during 30-60 days after sowing (DAS) but declined sharply at 90 DAS, with nematode inoculation exacerbating losses (peak 50.00% for chlorophyll b). Gas exchange parameters peaked in disruption at 60 DAS: photosynthetic rate declined by 38.17%, transpiration by 47.39%, and stomatal conductance by 42.85%, triggering a 0.77°C leaf temperature increase due to impaired evaporative cooling. This 60 DAS physiological crisis aligned precisely with the energy-intensive egg-laying phase of nematode reproduction. Chlorophyll fluorescence (Fv/Fm) showed maximal impairment (10.46%) at 90 DAS. The cascade of stress responses—prioritizing degradation of light-harvesting complexes (evidenced by elevated chlorophyll a/b ratio) and stomatal dysfunction—culminated in 40.61% biomass reduction. These findings identify chlorophyll b sensitivity as an early stress biomarker and establish 60 DAS as a critical window for intervention. Mitigation strategies targeting pre-60 DAS nematode control are essential to preserve photosynthetic function during reproductive feeding.