Germination response and viability of Orobanche crenata Forsk. seeds subjected to temperature treatment

Abstract

Orobanche crenata is a chlorophyll-lacking holoparasite that subsists on the roots of plants, inflicting severe damage to legume crops (broad bean, pea, lentil, vetch, grass pea, chickpea) in the Mediterranean and Middle East regions. Laboratory studies were conducted to determine the effects of high temperatures [20˚C (control), 38˚C, 40˚C, 42˚C, or 44 0.5˚C] on seed germination of O. crenata in relation to different duration of temperature treatments (12 or 24 h), seed age (57 or 94 months), and root extracts (Vicia faba major cv. 45 NS and V. faba minor cv. Sikelia). The seed viability response to temperature (20–100˚C) in relation to 2 seed ages (57 or 93 months) was also investigated. The increase in temperature exposure of seed from 20˚C to 30˚C, 40˚C, 42˚C, and 44˚C determined a significantly progressive reduction in the germination percentage, which was 21, 13, 6, 0, and 0%, respectively. This reduction in germination was due mainly to an increase in the secondary dormancy, since viability of the same seed, checked by tetrazolium test, ranged between 60% and 99%. Seed viability linearly decreased with increasing seed exposure temperature until reaching zero at 80˚C.