Development and characterization of wheat-sea wheatgrass (Thinopyrum junceiforme) amphiploids for biotic stress resistance and abiotic stress tolerance.

KEY MESSAGE: Development of a complete wheat-Thinopyrum junceiforme amphiploid facilitated identification of resistance to multiple pests and abiotic stress derived from the wild species and shed new light on its genome composition. Wheat production is facing numerous challenges from biotic and abiotic stresses. Alien gene transfer has been an effective approach for wheat germplasm enhancement. Thinopyrum junceiforme, also known as sea wheatgrass (SWG), is a distant relative of wheat and a relatively untapped source for wheat improvement. In the present study, we developed a complete amphiploid, 13G819, between emmer wheat and SWG for the first time. Analysis of the chromosome constitution of the wheat-SWG amphiploid by multiple-color genomic in situ hybridization indicated that SWG is an allotetraploid with its J1 genome closely related to Th. bessarabicum and Th. elongatum, and its J2 genome was derived from an unknown source. Two SWG-derived perennial wheat lines, 14F3516 and 14F3536, are partial amphiploids and carry 13 SWG chromosomes of mixed J1 and J2 genome composition, suggesting cytological instability. We challenged the amphiploid 13G819 with various abiotic and biotic stress treatments together with its emmer wheat parent. Compared to its emmer wheat parent, the amphiploid showed high tolerance to waterlogging, manganese toxicity and salinity, low nitrogen and possibly to heat as well. The amphiploid 13G819 is also highly resistant to the wheat streak mosaic virus (temperature insensitive) and Fusarium head blight. All three amphiploids had solid stems, which confer resistance to wheat stem sawflies. All these traits make SWG an excellent source for improving wheat resistance to diseases and insects and tolerance to abiotic stress.

Insect infestations, incidence of viral plant diseases, and yield of winter wheat in relation to planting date in the northern Great Plains.

Planting date effects on arthropod infestation and viral plant disease are undocumented for winter wheat, Triticum aestivum L., in South Dakota and the northern Great Plains. Winter wheat was planted over three dates (early, middle, and late; generally from late August to late September) to determine the effect on abundance of insect pests, incidence of plant damage, incidence of viral plant disease, and grain yield. The study was conducted simultaneously at two sites in South Dakota over three consecutive cropping seasons for a total of six site yr. Cereal aphids (Homoptera: Aphididae) were abundant in three site yr. Rhopalosiphum padi (L.), bird cherry-oat aphid, was the most abundant cereal aphid at the Brookings site, whereas Schizaphis graminum (Rondani), greenbug, predominated at Highmore. Aphid-days were greater in early versus late plantings. Aphid abundance in middle plantings depended on aphid species and site, but it usually did not differ from that in early plantings. Incidence of Barley yellow dwarf virus (family Luteoviridae, genus Luteovirus, BYDV) declined with later planting and was correlated with autumnal abundance of cereal aphids. Incidence of BYDV ranged from 24 to 81% among 1999 plantings and was < 8% in other years. Damage to seedling wheat by chewing insects varied for two site-years, with greater incidence in early and middle plantings. Wheat streak mosaic virus, spring infestations of cereal aphids, wheat stem maggot, and grasshoppers were insignificant. Yield at Brookings was negatively correlated with BYDV incidence but not cereal aphid abundance, whereas yield at Highmore was negatively correlated with aphid abundance but not BYDV incidence. Planting on 20 September or later reduced damage from chewing insects and reduced cereal aphid infestations and resulting BYDV incidence.