Evaluation of abiotic stress tolerance of genetically modified potatoes (Solanum tuberosum cv. Desiree)

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Abiotic stresses such as drought and extremes of temperature commonly reduce both yield and quality of potato. This study investigated the potential to use gene transfer technology to enhance the tolerance of potato to commonly encountered abiotic stresses. Agrobacterium mediated transformation was used to create lines of potato (cv. Desiree) that over-expressed either a wheat mitochondrial Mn superoxide dismutase (SOD3:1), dehydrin 4 (DHN 4) isolated from barley, a cold-inducible transcriptional factor DREB/CBF1 isolated from canola or ROB5, a stress inducible gene isolated from bromegrass that encodes for a heat stable LEA group 3-like protein. The transgenes were under the control of either a constitutive 35S promoter or a stress-induced Arabidopsis COR78 promoter. Yield potential of the transformed lines was evaluated under drought stress conditions in a greenhouse trial and under non-irrigated conditions in field trials conducted over 4 years in Saskatoon, Saskatchewan. In the years when the field trials experienced significant drought stress (2001, 2003 and 2006) many of the transformed lines produced higher yields than the control. However, under relatively cooler, wetter conditions (2005 cropping season) yields of most transformed lines were equivalent or inferior to the non-transformed parental line. Under non-stressed conditions, transformations utilizing the stress-induced COR78 promoter were higher yielding than transformations based on the constitutive 35S promoter. Combining the ROB5, DHN or SOD3.1 transgenes with the COR78 promoter all showed significant potential to enhance yields under moisture stress. All of the transgenes appeared to enhance the heat stress tolerance (44°C) of whole plants or excised leaves, with lines transformed with SOD3.1 showing the greatest effect. In low temperature stress trials conducted under controlled environment conditions and in the field, lines over-expressing SOD3:1 showed an enhanced capacity to grow at sub-optimal temperatures (10°C), while lines transformed with SOD3.1 or ROB5 had greater tolerance of freezing temperatures than the parental line. These results are encouraging as even a small degree of enhancement of stress tolerance has the potential to produce significant economic benefits in high value/stress sensitive crops such as potato.