Ecological and evolutionary drivers of phenotypic and genetic variation in the European crabapple [Malus sylvestris (L.) Mill.], a wild relative of the cultivated apple.

BACKGROUND AND AIMS: Studying the relationship between phenotypic and genetic variation in populations distributed across environmental gradients can help us to understand the ecological and evolutionary processes involved in population divergence. We investigated the patterns of genetic and phenotypic diversity in the European crabapple, Malus sylvestris, a wild relative of the cultivated apple (Malus domestica) that occurs naturally across Europe in areas subjected to different climatic conditions, to test for divergence among populations. METHODS: Growth rates and traits related to carbon uptake in seedlings collected across Europe were measured in controlled conditions and associated with the genetic status of the seedlings, which was assessed using 13 microsatellite loci and the Bayesian clustering method. Isolation-by-distance, isolation-by-climate and isolation-by-adaptation patterns, which can explain genetic and phenotypic differentiation among M. sylvestris populations, were also tested. KEY RESULTS: A total of 11.6 % of seedlings were introgressed by M. domestica, indicating that crop-wild gene flow is ongoing in Europe. The remaining seedlings (88.4 %) belonged to seven M. sylvestris populations. Significant phenotypic trait variation among M. sylvestris populations was observed. We did not observe significant isolation by adaptation; however, the significant association between genetic variation and the climate during the Last Glacial Maximum suggests that there has been local adaptation of M. sylvestris to past climates. CONCLUSIONS: This study provides insight into the phenotypic and genetic differentiation among populations of a wild relative of the cultivated apple. This might help us to make better use of its diversity and provide options for mitigating the impact of climate change on the cultivated apple through breeding.

Modifications to a Vitis Shoot Tip Cryopreservation Procedure: Effect of Shoot Tip Size and Use of Cryoplates.

BACKGROUND: Cryopreservation has been considered a preferred method for the long-term storage of plant germplasm, especially to efficiently conserve and maintain the genetic integrity of genebank materials. Droplet-vitrification (DV) procedures have been developed to cryopreserve Vitis shoot tips from in vitro-grown plants. OBJECTIVE: This research focused on optimizing shoot tip sizes for DV and the feasibility of using cryo-plates for Vitis cryopreservation. MATERIALS AND METHODS: Uniform shoot tips were obtained from nodal sections cultured from in vitro-grown stock plants of Vitis aestivalis and Vitis jacquemontii (PI 135726). Shoot tips were precultured for 3 days on medium containing 0.3 M sucrose, salicylic acid, glutathione (reduced form), and ascorbic acid. They were cryopreserved using either DV on aluminum foil strips or by placement in calcium alginate gel in the wells of aluminium cryo-plates (V cryo-plate method). Shoot tips were then treated with loading solution followed by PVS2 treatment prior to liquid nitrogen (LN) exposure. Shoot tips were warmed in unloading solution and placed on recovery medium. The effect of extraction or non-extraction of the cryopreserved shoot tips from alginate beads was also tested. RESULTS: The highest regrowth levels of cryopreserved shoot tips were obtained using 1 mm shoot tips and a PVS2 exposure for 90 min at 0°C with the DV method on aluminum foil strips or by using 30 min of PVS2 at 22°C using V cryo-plates. CONCLUSION: Shoot tip size is an important factor in the cryopreservability of Vitis shoot tips; 1 mm shoot tips were the most successful for the DV cryopreservation method that was tested. In addition, the V cryo-plate cryopreservation technique described herein can be easily executed and results in high regrowth levels (≥70%) with quality plants obtained from cryo-exposed shoot tips, making it a practical and promising Vitis cryopreservation methodology.

Successful Cryopreservation of Vitis Shoot Tips: Novel Pre-treatment Combinations Applied to Nine Species.

BACKGROUND: Secure back-up of Vitis genetic resource collections requires cryopreservation methods that give long-term survival of clonal germplasm having diverse genetic backgrounds. OBJECTIVE: This work sought to increase survival of Vitis shoot tips exposed to liquid nitrogen using combinations of pretreatments and cryoprotection procedures. The new procedure should give high survival of shoot tips from a wide range of Vitis species. MATERIALS AND METHODS: In vitro plants from nine Vitis species were used as source material for nodal sections. Shoot tips were then excised from nodal sections that were grown on medium containing benzyladenine, salicylic acid, glutathione, and ascorbic acid. The shoot tips were treated with loading solution, and then half-strength PVS2 for 30 minutes, prior to full-strength PVS2 treatments for between 60 and 90 minutes prior to liquid nitrogen (LN) exposure. RESULTS: Shoot tip regrowth levels were highest 90 minutes in PVS2+LN and ranged from 24-43% and averaged 35±2% across the nine Vitis species. CONCLUSION: The pretreatment, cryopreservation, and recovery methods yielded successful regrowth for multiple Vitis species using a droplet-vitrification procedure.

Cryopreservation of dormant buds from diverse Fraxinus species.

Ash (Fraxinus) is an economically important tree genus in the landscape industry, as well as a key component of North American forests, especially in the North Central United States and adjacent regions in Canada. In recent years, the Emerald Ash Borer beetle (Agrilus planipennis) has significantly threatened the survival of native North American Fraxinus species. A dormant-bud cryopreservation technique has been developed as a method to conserve specific clones of ash. Dormant buds of three ash species were successfully cryopreserved when desiccated on their stem sections to 30 percent moisture content (w/v) and then cooled at rates of either -1 degree C per h or -5 degree C per day to either -30 or -35 degree C before immersion in liquid nitrogen vapor (LNV). Stem sections were removed from LNV, warmed, and rehydrated, and their buds grafted onto rootstocks to evaluate survival. Recovery percentages ranged from 34 to 100 percent after LNV exposure and were dependent upon accession and cooling rate. The cryopreservation methods proposed herein can complement seed-collection efforts aimed at conserving diversity, supplementing ex situ genebank and botanic-garden collections.

High viability of dormant Malus buds after 10 years of storage in liquid nitrogen vapour.

Three hundred and sixty two Malus accessions from the Canadian Clonal Genebank of Plant Gene Resources of Canada were cryopreserved as dormant buds at the USDA-ARS National Center for Genetic Resources Preservation in 1996. According to grafting data collected on 165 of these accessions in 1999, 80 percent of the accessions had at least 40 percent viability. A subsample of these accessions was processed for cryopreservation by either adjusting the moisture content of the budwood sections containing dormant buds to 32 or 37 percent moisture (fresh weight basis) or by not drying the budwood sections (46 percent moisture fresh weight basis) prior to cooling. Budwood sections were then slow-cooled at 1 degree C per hour to -3 degree C, held for 24 h at -30 degree C and then rapidly transferred to the vapour phase of liquid nitrogen. Cryopreserved buds from 13 accessions that were dried using the various techniques were warmed and grafted in both 1999 and 2006 to determine viability. Overall, bud viability was high at both storage times. At the 10 year time point, some accessions had higher bud growth when they were desiccated prior to slow-cooling when compared to those that were not.

Photoperiod shift effects on yield characteristics of rice.

Edible yield must be maximized for each crop species selected for inclusion in the Controlled Ecological Life-Support System (CELSS) proposed by NASA to support long-term manned space missions. In a greenhouse study aimed at increasing biomass partitioning to rice (Oryza sativa L.) grain, plants of the high yielding semi-dwarf rice cultivar Ai-Nan-Tsao were started in pots under 8-h photoperiods at a density of 212 plants m-2. After different periods of time under 8-h photoperiods, pots were switched to continuous light for the remainder of the cropping cycle. Continuous light did not delay time to first panicle emergence (60 d) or time to harvest (83 d). There was a positive correlation between the length of continuous light treatments and nongrain biomass. Grain yield (1.6 +/- 0.2 g plant-1) did not increase in continuous light. Yield-efficiency rate (grain weight per length of cropping cycle, canopy volume, and weight of nongrain shoot biomass) was used to compare treatments. Small Ai-Nan-Tsao rice canopies grown under 8-h photoperiods were more efficient producers of grain than canopies grown under continuous light for a portion of the rice cropping cycle.