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ARS Home » Pacific West Area » Wapato, Washington » Temperate Tree Fruit and Vegetable Research » Research » Research Project #430796

Research Project: Mechanistic Aspects of Tolerance to In-season Heat Stress for Retention of Postharvest Quality

Location: Temperate Tree Fruit and Vegetable Research

Project Number: 2092-21220-002-04-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Jul 31, 2016
End Date: Jul 30, 2019

This research will continue our efforts to determine the mechanism(s) by which heat stress reduces or totally abolishes resistance to low temperature sweetening (LTS) in cultivars specifically bred to possess this trait. Specific objectives include: (1) Screen advanced LTS-resistant clones from the Northwest Variety Development Program (NWVDP) for tolerance to in-season and postharvest heat stress for retention of LTS-resistant phenotype, (2) Determine the effects of heat stress on cold inducible aspects of carbohydrate metabolism (gene expression, enzyme activity, starch catabolism, sugar buildup) in relation to changes in process quality. (3) Examine the effect of heat stress on phenylpropanoid metabolism.

Tubers will be subjected to heat stress treatments during development in the field and using a heat-priming protocol directly following harvest. Application of heat stress treatments in-season involves manipulating soil and thus tuber temperature during various phases of tuber growth (tuberization, bulking, maturation) with heat cables installed in-furrow at planting. The in-season heat stress studies facilitate assessment of clonal susceptibility/resistance to sugar-related disorders that affect quality (sugar ends, mottling, translucent tissue defect, etc.) directly out of the field and later in storage. The postharvest heat stress protocol offers the opportunity to screen a wider range of LTS-resistant genotypes for heat tolerance under controlled conditions. In addition to conventionally bred clones, the postharvest heat stress studies will involve clones that have been genetically modified to silence genes encoding key enzymes involved in LTS (e.g. starch phosphorylase, amylase, invertase) to deduce their role in heat-induced loss of LTS resistance.