SEED COAT PUNCTURE RESISTANCE IN CEREAL AND OILSEED CULTIVARS—A POSSIBLE SOURCE OF SUSCEPTIBILITY TO INSECT DAMAGE IN STORED GRAINS

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Abstract
Seed coat puncture resistance of 42 cultivars of common [Triticum aestivum L.] and durum wheat [T. durum Desf.] oats [Avena sativa L.], barley [Hordeum distichum L.] and rapeseed [ Brassica napus L. and B. campestris L.] were measured by puncture tests believed to approximate seed penetration by weevils [rice weevil, granary weevil and maize weevil (Sitophilus spp.)] infesting stored grain. All 7 spp. of crops, several cultivars and germ and endosperm parts of the seed within the same cultivar varied significantly (P .ltoreq. 0.05) in puncture resistance of seeds when moisture contents were in equilibrium at 0% and 70% RH [relative humidity]. Dry durum wheat (cv. Wakooma) showed the highest puncture resistance, moist rapeseed (cv. Torch) the lowest. The mean puncture resistance of the endosperm coat of moist crop cultivars ranged from 2074-2456 g for common wheat; 3316-4131 g for durum wheat; 1145-1404 g for oats; 1321-1861 g for barley and 184-222 g for rapeseed. Differences in seed coat strength suggest that it is one source governing susceptibility to insect damage of stored grain. The drier the seed, the greater the difficulty for an insect to penetrate the seed coat.