Cotton is widely cultivated in temperate regions across the world and is often constrained by a short planting window that is bookended by low, suboptimal temperatures. With the growing interest in early season planting, improvements in the cold germination ability of cotton will be necessary to ensure the production stability of early planted crops. The importance of saturation levels of membrane and storage lipids in enhancing cold tolerance in plants, as well as improving cold germination ability in seeds have been widely researched in a range of plant species. While studies have shown that higher levels of unsaturated lipids can enhance cold germination ability and reduce seedling injury in other crops, similar efforts have been fairly limited in cotton. This review looks at the functional properties of membrane and storage lipids, and their role in membrane stability and reorganization during the early stages of germination. Additionally, the importance of storage lipid composition as an energy source to the growing embryo is described in the context of cellular energetics (i.e., fatty acid catabolism). Finally, perspectives in improving the cold germination of upland cotton by manipulating the fatty acid composition of both membrane and storage lipid content of seeds are presented.

Silverleaf nightshade (Solanum elaeagnifolium Cav.) is an invasive species that has successfully spread outside its native range to become a noxious weed in 21 states in the United States and 42 countries worldwide. The successful establishment of S. elaeagnifolium outside its native habitat indicates its innate ability to adapt to a multitude of environments. Phenotypic plasticity and/or genetic adaptation have been identified as key mechanisms underlying the adaptive success of invasive species. Whereas phenotypic plasticity allows a species to buffer changes in the environment by altering its phenotypic attributes within the short term, genetic adaptation is responsible for the longer-term adaptability of plants to heterogeneous environments and is dependent on the amount of genetic variation present in the species. In this study, we screened DNA markers that are specific to tomato (Solanum lycopersicum L.) and Solanum lycopersicoides Dunal for their interspecific transferability to S. elaeagnifolium and determined the applicability of the transferable DNA markers in assessing the extent of genetic variation in populations from Lubbock, Littlefield, and Blackwell, TX. Of the 187 markers screened, 78 successfully amplified targets in S. elaeagnifolium, indicating the evolutionary conservation of marker loci across S. lycopersicum, S. lycopersicoides, and S. elaeagnifolium, despite their genetic divergence millions of years ago. Genotyping of S. elaeagnifolium populations using 50 DNA markers that consistently amplified clear bands in more than 60% of the plants identified nine polymorphic markers with 0.014 to 0.621 polymorphism information content. Genetic diversity analysis by DNA marker profiling established genetic variation among populations and within individuals of different populations. Unweighted paired group method with arithmetic mean analysis grouped the plants into six clusters that are generally defined by selection pressures unique to each collection site. Results of the study indicate the capacity of S. elaeagnifolium for genetic differentiation in response to variable selection pressures within the same geographic region.

Cotton is a tropical/subtropical crop and is innately susceptible to cold. Using an approach that integrates morphological, biochemical, and transcriptome analyses, the study aimed to understand the molecular underpinnings of phenotypic adjustments in cotton seedlings under cold stress. Exposure of six cotton accessions to 15°C during the seedling stage significantly reduced chlorophyll content, stomatal conductance, plant height, and biomass, but increased malondialdehyde and proline production. Comparative transcriptome profiling of the cold-sensitive accession SA 3781 grown under low and normal temperatures showed the upregulation of genes related to the production of reactive oxygen species (ROS) under cold stress. Despite a similar upregulation of genes encoding metabolites that can scavenge ROS and provide osmoprotection for the cell, the stressed plants still exhibited oxidative stress in terms of lipid peroxidation. This may be due in part to the upregulation of abscisic acid synthesis genes and downregulation of chlorophyll synthesis genes effecting lower stomatal conductance and chlorophyll contents, respectively. Additionally, stomatal closure which is required to avoid the cooling effect and dehydration under cold conditions may have contributed in reducing the net photosynthetic rates in plants exposed to low temperature. These findings provide an insight into the expression of key genes regulating the phenotypic changes observed in cotton in response to cold stress.

Solanum lycopersicoides is a wild nightshade relative of tomato with known resistance to a wide range of pests and pathogens, as well as tolerance to cold, drought and salt stress. To effectively utilize S. lycopersicoides as a genetic resource in breeding for tomato improvement, the underlying basis of observable traits in the species needs to be understood. Molecular markers are important tools that can unlock the genetic underpinnings of phenotypic variation in wild crop relatives. Unfortunately, DNA markers that are specific to S. lycopersicoides are limited in number, distribution and polymorphism rate. In this study, we developed a suite of S. lycopersicoides-specific SSR and indel markers by sequencing, building and analyzing a draft assembly of the wild nightshade genome. Mapping of a total of 1.45 Gb of S. lycopersicoides contigs against the tomato reference genome assembled a moderate number of contiguous reads into longer scaffolds. Interrogation of the obtained draft yielded SSR information for more than 55,000 loci in S. lycopersicoides for which more than 35,000 primers pairs were designed. Additionally, indel markers were developed based on sequence alignments between S. lycopersicoides and tomato. Synthesis and experimental validation of 345 primer sets resulted in the amplification of single and multilocus targets in S. lycopersicoides and polymorphic loci between S. lycopersicoides and tomato. Cross-species amplification of the 345 markers in tomato, eggplant, silverleaf nightshade and pepper resulted in varying degrees of transferability that ranged from 55 to 83%. The markers reported in this study significantly expands the genetic marker resource for S. lycopersicoides, as well as for related Solanum spp. for applications in genetics and breeding studies.

Key message Alien introgressions that were captured in the genome of diploid plants segregating from progenies of monosomic alien addition lines of S. lycopersicoides confer novel phenotypes with commercial and agronomic value in tomato breeding. Abstract Solanum lycopersicoides is a wild relative of tomato with a natural adaptation to a wide array of biotic and abiotic challenges. In this study, we identified and characterized diploid plants segregating from the progenies of monosomic alien addition lines (MAALs) of S. lycopersicoides to establish their potential as donors in breeding for target trait improvement in tomato. Molecular genotyping identified 28 of 38 MAAL progenies having the complete chromosome complement of the cultivated tomato parent and limited chromosome introgressions from the wild S. lycopersicoides parent. Analysis of SSR and indel marker profiles identified 34 unique alien introgressions in the 28 MAAL-derived introgression lines (MDILs) in the genetic background of tomato. Conserved patterns of alien introgressions were detected among sibs of MDILs 2, 3, 4 and 8. Across MDILs, a degree of preferential transmission of specific chromosome segments was also observed. Morphologically, the MDILs closely resembled the cultivated tomato more than S. lycopersicoides. The appearance of novel phenotypes in the MDILs that are lacking in the cultivated parent or the source MAALs indicates the capture of novel genetic variation by the diploid introgression lines that can add commercial and agronomic value to tomato. In particular, screening of representative MDILs for drought tolerance at the vegetative stage identified MDIL 2 and MDIL 11III as drought tolerant based on visual scoring. A regulated increase in stomatal conductance of MDIL 2 under drought stress indicates better water use efficiency that allowed it to survive for 7 days under 0% moisture level.