Hybrid Necrosis in Wheat-A Genetic System Showing Reduced Capacity to Detoxify Reactive Oxygen Species Leading to Programmed Cell Death

Abstract

Hybrid necrosis in wheat is the premature gradual death of leaves and leaf sheath caused by two complementary genes NeJ and Ne2 when brought together in a hybrid combination. Many promising wheat varieties are carriers of these genes, which limit the parental choice for transfer of desirable traits as the necrotic plants die without

producing seeds. The leaves of Kalyansona x C306 and WL711 x C306 hybrids showed enhanced generation of superoxide radical and H202 than parents before and during progression of necrosis. Higher lipid peroxidation was an early event in hybrid necrosis and was accompanied by a loss in membrane permeability and cell viability. The anti-oxidant defense in necrotic hybrids was not well coordinated culminating in a persistent oxidative stress in the leaf especialiy in the chloroplast. The hybrid necrosis barrier was overcome in some crosses by culturing ears in medium containing antioxidants and F2 seeds have been obtained. Hybrid necrosis is a unique genetic system for studying the molecular mechanism of programmed cell death in plants. The cloning and characterization of Nel and Ne2 may provide a tool having wide applications in agriculture. The review compares hybrid necrosis with other

PCD phenomenon in plants.