Genetic comparisons of temperature tolerances of a candidate sea vegetable crop, Alaria esculenta

Project Overview

Project Type: Graduate Student
Funds awarded in 2014: $14,992.00
Projected End Date: 12/31/2016
Grant Recipient: University of Maine
Region: Northeast
State: Maine
Graduate Student:
Faculty Advisor:
Susan Brawley
University of Maine

Annual Reports


  • Vegetables: sea vegetables; macroalgae; seaweeds


  • Crop Production: plant breeding and genetics, tissue analysis, aquaculture
  • Education and Training: extension, networking, technical assistance, workshop
  • Farm Business Management: community-supported agriculture
  • Natural Resources/Environment: biodiversity
  • Production Systems: aquaponics, hydroponics, general crop production, nursery development
  • Sustainable Communities: employment opportunities, local and regional food systems, public participation, sustainability measures

    Proposal abstract:

    The development of sea vegetable aquaculture on the Maine coast will produce higher yields of species that are currently wild-harvested. Aquaculturists are especially excited about experimental grow-out demonstrations of the kelp Alaria esculenta (hereafter, Alaria) during 2013-2014 on the Maine coast. This is because Alaria is very similar to Japanese “wakame”; global production value of wakame in 2010 was $450 million (see supplemental reference (1)). Temperature tolerance of candidate sea vegetables needs to be considered as appropriate strains for aquaculture are isolated due to pending climate change; hence, this study investigates temperature tolerance of Alaria, which ranges from Massachusetts to the subarctic. The primary objective is to isolate cultivars with tolerance to the elevated temperatures predicted for the Gulf of Maine in the future, and isolates from Maine and Massachusetts will be used to determine potential regional genetic adaptations. Kelps have two different life history phases; temperature tolerances of microscopic stages (gametophytes) and the large, harvested blade (sporophyte) are equally important. Cultured gametophytes and sporophytes from each region will be exposed to 18°C and 24°C. Growth (measured with ImageJ) and transcriptional studies with RNA-Seq will define temperature tolerance and reveal marker genes for additional, economical identification of temperature-tolerant strains with high growth rates. This work will help to assure that Alaria esculenta is a robust, sustainable addition to sea vegetable aquaculture in Maine and these numerous additional strains will greatly supplement those few currently available for Alaria aquaculture.

    Project objectives from proposal:

     Objectives of this proposal (all funded by the proposed budget): all hypotheses are stated as null hypotheses, and predictions are based on refutation of the null hypotheses.


    Objective 1: Identify temperature-tolerant (TT) seedstock strains of Alaria esculenta gametophytes for Maine sea vegetable aquaculture (SVA). During strain identification, regional differences can be determined.


    Hypothesis A: Gametophytic growth and abundance will not differ between southern and northern sites.


    Prediction A: At high experimental temperatures, more southern zoospores will develop into gametophytes and will grow larger compared to northern TT strains due to historical exposure to warmer waters.


    Objective 2: Identify TT crop strains of Alaria sporophytes that demonstrate rapid growth for Maine SVA, examining regional differences, and determine whether temperature tolerance is heritable.


    Hypothesis B: Sporophyte fertilization success and growth will not differ between southern and northern sites.


    Prediction B: Southern TT strains will have higher fertilization success and grow better at high experimental temperatures than northern TT strains at high experimental temperatures.


    Hypothesis C: Gametophyte temperature tolerance does not determine sporophyte tolerance level (i.e. there is no difference in average growth between experimental temperatures for either TT or TI crosses).


    Prediction C: Crosses of TT gametophytes will produce TT sporophytes and crosses of TI gametophytes will produce TI sporophytes.


    Objective 3: Determine which temperature-responsive genes are associated with temperature tolerance (i.e. examine differences in gene expression).


    Hypothesis D: There is no difference in gene expression between TT gametophytes and TI gametophytes; there is no difference between TT and TI sporophytes.


    Prediction D: TT expression levels for both gametophytes and sporophytes will have upregulated patterns of temperature-responsive genes (i.e. more copies of genes involved in dealing with temperature stress are present in the transcript data).


    Hypothesis E: There is no difference in gene expression between northern and southern sites (in both gametophytes and sporophytes); no ecotypes have evolved in New England populations of Alaria.


    Prediction E: When comparing degree of change between TT and TI transcripts: (i) southern sites will have upregulated patterns of temperature-responsive genes (more copies to deal with stress) or (ii) southern sites will have downregulated patterns (adapted to require fewer copies to deal with stress) when compared to northern sites.


    Objective 4: Promote sea vegetable aquaculture in Maine by attending conferences and forums and working directly with harvesters (see Outreach).

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.