The Steber Lab is part of the Wheat Health, Genetics, and Quality Research Unit, United States Department of Agriculture, Agricultural Research Service, and is housed in and affiliated with the Department of Crop and Soil Sciences, at Washington State University in Pullman, Washington. The lab is also affiliated with the Molecular Plant Sciences Program at Washington State University. The principal investigator is Camille Steber, and the lab was started in 1998. This USDA research unit originally included Orville Vogel and Robert E. Allen who were internationally recognized for the first introgression of the gibberellin A (GA)-insensitive Rht (Reduced height) genes that gave rise to the green revolution.
The overall objective is to help farmers to succeed financially by producing a more resilient and high-quality crops. The approach is to elucidate the mechanisms controlling plant responses to the environment and to apply this knowledge to wheat improvement. The research goal is to improve wheat genetic resistance to the weather-induced problems of preharvest sprouting, Late Maturity Alpha-Amylase (LMA), and the resulting high grain alpha-amylase enzyme levels. Dr. Steber is a molecular geneticist with expertise in seed biology, gibberellin A (GA) and abscisic acid (ABA) hormone signaling, preharvest sprouting, and LMA research.
The problem is that an excess of the enzyme alpha-amylase can causes financial losses for farmers when their grain is discounted, for millers when an undetected problem can damage equipment or their reputation, and for bakers when damaged product must be disposed of. Problems with excess alpha-amylase enzyme levels in wheat grain are detected in the wheat industry using the Hagberg-Perten Falling Number (FN) method or using the EnviroLogix Inc TotalTarget for Sprout Damage dipstick assay. Lower falling numbers (FN) values are associated with elevated grain alpha-amylase, and farmers receive severe discounts for FN below 300 seconds. Falling number testing of grain from WSU variety testing from 2013 to 2023 was used to generate knowledge about which cultivars have higher or lower risk. These data are still posted on this website. FN testing is now being performed in the laboratory of Dr. Alison Thompson. New and past data will be shared through the WSU Small Grains website.
It is important to understand alpha-amylase regulation because alpha-amylase is needed in the right time, place, and quantity to produce high quality wheat and wheat products. Alpha-amylase is needed during grain/seed germination at planting to mobilize starch as fuel for seedling growth and emergence. Some alpha-amylase is needed to help bread rise, but too much results in bread with sticky crumb and gums up slicing machines. It is also needed for good wheat and barley malting quality. However, starch digestion by alpha-amylase in dough leads to poor end-use quality such as fallen cakes and sticky noodles. Thus, high mature grain amylase is undesirable at the time of sale.
Excessively high grain alpha-amylase is caused by preharvest sprouting (PHS) and late maturity alpha-amylase (LMA). Preharvest sprouting is the germination of mature cereal grain on the mother plant when it is rained on before harvest. Developing wheat and barley grain induce LMA in response to cold temperature stress during the soft dough stage of grain maturation. PHS tolerance results mainly from grain dormancy, whereas mechanisms of LMA tolerance are poorly understood. The plant hormone GA stimulates germination and alpha-amylase expression during germination, whereas ABA induces seed dormancy during development, and inhibits germination and alpha-amylase. Increased ABA or decreased GA sensitivity should increase seed dormancy and reduce PHS.
Ongoing research aims to understand the genes and environmental conditions resulting in elevated mature grain alpha-amylase. This should help us develop genetic strategies to obtain efficient alpha-amylase expression at the right time in the wheat life cycle. On-going research aims to: 1) identify QTL/alleles that can provide tolerance to both LMA and PHS; 2) genes/alleles that can prevent preharvest sprouting without undermining seedling emergence, yield, or malting quality; 3) determine environmental conditions, biochemical and hormonal mechanisms governing cereal grain dormancy, germination, and alpha-amylase expression; and 4) translate knowledge about these mechanisms to prevent preharvest sprouting and LMA in wheat and barley through molecular marker development.