Germination trials at The Berry Botanic Garden yielded no germination of apparently good seed. Seeds were either cold stratified or not, and then subjected to either constant 68F (20C) or alternating 50F/68F (10C/20C) temperatures. Further research is needed to determine optimum germination requirements (BBG File). If no success is achieved, seed viability tests should be conducted.

Determination of genetic diversity through isozyme analysis. Samples from 11 populations around the lake were analyzed to determine the genetic diversity within and between sites. The results show extremely limited variation. Eight of the eleven populations were identical for the 23 loci examined (all homozygous). The remaining three populations were nearly identical. They were nearly homozygous except for one or two loci, which were variable. The results indicate very low levels of gene flow and suggest that most plants around the lake may be a single clone (NFGEL 2000)

Seed germination was found to be stimulated by in vitro germination in the presence of cytokinin (Pence 2006). In vitro propagation and cryopreservation protocols were also developed for this species at CREW.

Seed germination was found to be stimulated by in vitro germination in the presence of cytokinin (Pence 2006). In vitro propagation and cryopreservation protocols were also developed for this species at CREW.

Based on an September 2020 extract of the California Plant Rescue Database, California Botanic Garden holds 5 accessions of Rorippa subumbellata in orthodox seed collection. There are as many as 110740 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

Based on an September 2020 extract of the California Plant Rescue Database, Rae Selling Berry Seed Bank & Plant Conservation Program holds 3 accessions of Rorippa subumbellata in orthodox seed collection. There are as many as 2689 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

Based on an August 2020 extract of the California Plant Rescue Database, Rae Selling Berry Seed Bank & Plant Conservation Program has collected 3 seed accessions of Rorippa subumbellata from 3 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 3 maternal plants

Seed germination was found to be stimulated by in vitro germination in the presence of cytokinin (Pence 2006).  In vitro propagation and cryopreservation protocols were also developed for this species at CREW.

Tahoe yellow-cress is known from approximately 44-63 occurrences. There are many historical occurrences. The species occupies a very narrow habitat band within the shore zone of Lake Tahoe, California and Nevada. The habitat experiences heavy recreational use at most sites, and is regularly subject to major contractions caused by maintenance of artificially high water levels in Lake Tahoe, with resulting further concentration of beach impacts in the habitat remaining exposed. Only the two largest occurrences (and about 20-35% of the total sub-EOs) remain active during prolonged periods of high water. Portions of the lakeside habitat have been developed for casinos (on the Nevada side of the lake) and for other tourism-related facilities, and many other portions are in heavily visited parklands.

Habitat destruction (beach houses, boat ramps, recreation, etc) (Reynolds 1988). Soil/sand disturbance (CA Dept. of Parks and Recreation 1991). Rising lake levels (Reynolds 1988). Grazing (Ferreira 1986).

There are approximately 42 different sites around the lake where Rorippa subumbellata has been found at some point since surveys began in 1979. Many may have been extirpated, and populations seem to come and go depending on the conditions (California State Lands Commission 1998). In 1999, 14 sites were observed: 5 on private property, 9 on federal land. The number and size of populations fluctuates with changing lake levels (USFWS 2000).

Determination of genetic diversity through isozyme analysis. Samples from 11 populations around the lake were analyzed to determine the genetic diversity within and between sites. The results show extremely limited variation. Eight of the eleven populations were identical for the 23 loci examined (all homozygous). The remaining three populations were nearly identical. They were nearly homozygous except for one or two loci, which were variable. The results indicate very low levels of gene flow and suggest that most plants around the lake may be a single clone (NFGEL 2000) Germination trials at The Berry Botanic Garden yielded no germination of apparently good seed. Seeds were either cold stratified or not, and then subjected to either constant 68F (20C) or alternating 50F/68F (10C/20C) temperatures. Further research is needed to determine optimum germination requirements (BBG File). If no success is achieved, seed viability tests should be conducted. Ongoing biological studies by the Tahoe-Baikal Institute. Student interns have studied human disturbances, monitored populations, and observed the pollinators of Rorippa subumbellata.

Sites managed by the US Forest Service and California State Parks are monitored regularly and are fenced to reduce or eliminate recreational disturbances (USFWS 2000). Three sites on U.S. Forest Service land were planted with 500 seedlings each in 1988. Populations were surveyed in 1990 and again in 1993. There was an overall survival rate of 12 to 43% (California State Lands Commission 1998). In 1999, the Tahoe-Baikal Institute directed a study to monitor all populations of the Tahoe Yellowcress. They designed a protocol that could be followed to monitor the plant from year to year. They also recommended future management strategies that may contribute to the conservation of the Tahoe yellowcress in the basin. A draft Conservation Strategy is being written and should be finalized and distributed in the spring of 2002 (Gross, pers. comm.) Seeds from three sites are stored at The Berry Botanic Garden.

Fence populations (Ferreira 1986). Investigate possible mycorrhizal associations and other vegetation relationships. Maintain and protect populations, especially the three largest, which contain different alleles than the smaller populations (NFGEL 2000). Determine how long dormant plants can survive inundation by lake water. Determine the dominant method of site colonization. Is it by seed, re-sprouting roots, or deposition of plant material (i.e. fragments) Determine success of reproduction. Study the longevity and viability of seeds. Study pollination and reproductive biology. Determine patterns of gene flow. If worse comes to worst, manipulate lake levels in order to create more suitable habitat and promote establishment. Study the biological and ecological reasons for this species' rarity, including: population structure and dynamics, life history, and environmental requirements (California State Lands Commission 1998).

Determine germination requirements. Determine if seeds can effectively be stored for long periods of time. Collect and store seeds from populations around the lake, especially from populations that contain unique genes. Determine effective propagation and re-introduction methods.