WHEAT CULTIVAR SUSCEPTIBILITY TO GRAIN DAMAGE BY THE NEW-ZEALAND WHEAT BUG, NYSIUS-HUTTONI, AND CULTIVAR SUSCEPTIBILITY TO THE EFFECTS OF BUG PROTEINASE ON BAITING QUALITY

Immature wheat grain in New Zealand is attacked sporadically by the na tive insect (bug), Nysius huttoni. This 'bug-damaged wheat' contains a bug salivary proteinase, and bread made from this wheat has a charact eristically poor loaf volume and texture. Historical baking data sugge st variations in wheat cultivar susceptibility to bug damage. This sug gestion was tested in two trials (1992/1993 and 1993/1994) on immature wheat using nine or seven New Zealand cultivars and breeding lines en closed together in nylon mesh cages with and without N. huttoni. Visib le damage, bug-proteinase levels, electrophoretic protein patterns, an d baking properties of the grain were analysed. Both trials showed tha t susceptibility to bug damage was significantly different amongst cul tivars and breeding lines. The ranking of cultivar susceptibility was the same for the two trials, except for cv. Arawa, which was one of th e most susceptible cultivars in the first trial, bur one of the least susceptible in the second trial. Cultivars Domino and Oroua consistent ly showed less susceptibility to bug attack. The breeding line WW378 a nd the cultivar Otane were the most susceptible to bug attack. The hig h quality bread wheats (Otane, Oroua, Domino and Batten) were less sus ceptible to the effects of bug proteinase in baking than the poor baki ng quality wheats (Karamu, WW378, ASPS9927 and ASPS9928). Batten was s ignificantly less susceptible than any other cultivar in test baking. There was no relationship between bug-damage susceptibility and grain characters such as colour, hardness and texture, or head characters su ch as shape, awns and waxiness. (C) 1998 Academic Press Limited.