Rising temperature extremes during critical reproductive periods threaten the yield of major grain and fruit crops. Flowering plant reproduction depends on the ability of pollen grains to generate a pollen tube, which elongates through the pistil to deliver sperm cells to female gametes for double fertilization. We used tomato as a model fruit crop to determine how high temperature affects the pollen tube growth phase, taking advantage of cultivars noted for fruit production in exceptionally hot growing seasons. We found that exposure to high temperature solely during the pollen tube growth phase limits fruit biomass and seed set more significantly in thermosensitive cultivars than in thermotolerant cultivars. Importantly, we found that pollen tubes from the thermotolerant Tamaulipas cultivar have enhanced growth in vivo and in vitro under high temperature. Analysis of the pollen tube transcriptome’s response to high temperature allowed us to define two response modes (enhanced induction of stress responses and higher basal levels of growth pathways repressed by heat stress) associated with reproductive thermotolerance. Importantly, we define key components of the pollen tube stress response, identifying enhanced reactive oxygen species (ROS) homeostasis and pollen tube callose synthesis and deposition as important components of reproductive thermotolerance in Tamaulipas. Our work identifies the pollen tube growth phase as a viable target to enhance reproductive thermotolerance and delineates key pathways that are altered in crop varieties capable of fruiting under high-temperature conditions.

Farmland abandonment represents a significant issue globally, and in arid environments reclaiming ecosystems is challenging. In the Sonoran Desert, much irrigated farmland has been abandoned since 1950. Our objective was to compare changes in vegetative (canopy) cover and species over a 26-year period on abandoned farmland and unfarmed controls in southcentral Arizona (precipitation <300 mm/year). We evaluated time since abandonment and precipitation effects on these variables between 1976 and 2003 with point frame methods on eight farmland sites using stepwise multiple regression. Results suggest antecedent precipitation (AP) is more important than time since abandonment in explaining cover changes. On 26 abandoned sites, we used non-parametric ANOVA to show that vegetative cover (point frame and line intercept methods) declined by about 43% from 1977 to 2023, which was greater than on non-farmed controls. Few farmlands had cover and species composition like reference communities in 2003. Paired farmland-control sites exhibited similar vegetation in 1977 and 2003 suggesting local factors (e.g., soil chemistry, roadways) may have overwhelmed that of farming. Uninterrupted (natural) surface water flow may predict where revegetation was most successful. Our research indicates that farmland may exist in alternative states, and passive revegetation will not reestablish native Sonoran Desert communities on most abandoned farmland sites.

Crop diversity conservation in situ is an ecosystem service with benefits at household, community, and global scales. These include risk reduction and adaptation to changing physical and sociocultural environments-both important given the accelerating changes in climate, human migration, and the industrialization of agriculture. In situ conservation typically occurs as part of small-scale, traditionally based agriculture and can support cultural identity and values. Although decisions regarding crop diversity occur at the household level, few data detail the household context of in situ crop diversity management. Our research addressed this data gap for maize and Phaseolus bean in Oaxaca, Mexico, a major center of diversity for those crops. We defined diversity as farmer-named varieties and interviewed 400 farming households across eight communities in two contrasting socioecological regions. Our research asked, "In a major center of maize and Phaseolus diversity, what are the demographic, production, and consumption characteristics of the households that are stewarding this diversity?" We describe the context of conservation and its variation within and between communities and regions and significant associations between diversity and various independent variables, including direct maize consumption, region, and marketing of crops. These results provide a benchmark for communities to understand and strengthen their maize and bean systems in ways they value and for scientists to support those communities in dynamically stewarding locally and globally significant diversity.

Synergid cells in the micropylar end of the female gametophyte are required for critical cell-cell signaling interactions between the pollen tube and the ovule that precede double fertilization and seed formation in flowering plants. LORELEI (LRE) encodes a putative GPI-anchored protein that is expressed primarily in the synergid cells, and together with FERONIA, a receptor-like kinase, it controls pollen tube reception by the receptive synergid cell. Still, how LRE expression is controlled in synergid cells remains poorly characterized. We identified candidate cis-regulatory elements enriched in LRE and other synergid cell-expressed genes. One of the candidate motifs ('TAATATCT') in the LRE promoter was an uncharacterized variant of the Evening Element motif that we named as the Short Evening Element-like (SEEL) motif. Deletion or point mutations in the SEEL motif of the LRE promoter resulted in decreased reporter expression in synergid cells, demonstrating that the SEEL motif is important for expression of LRE in synergid cells. Additionally, we found that LRE expression is decreased in the loss of function mutants of REVEILLE (RVE) transcription factors, which are clock genes known to bind the SEEL and other closely related motifs. We propose that RVE transcription factors regulate LRE expression in synergid cells by binding to the SEEL motif in the LRE promoter. Identification of cis-regulatory elements and transcription factors involved in the expression of LRE will serve as a foundation to characterize the gene regulatory networks in synergid cells.

As discussed in chapter 2, food gardening always involves working with change and uncertainty, but how to respond to that change may depend on whether it is in the form of familiar variation or long-term trends. This chapter begins with an overview and some basic concepts about responding to change, and then describe making observations, doing experiments, and organizing how to work together to respond effectively. More detailed discussion about doing formal experiments can be found in Appendix 3A.

This chapter outlines how to manage physical, historical, and social factors when choosing a new garden site, or working with an existing one. This is especially important in situations that are problematic in terms of sunlight, contamination, or tenure, or where large investments, for example in land, improvements, perennial plants, or terracing, are being considered. First, the chapter discusses physical space, including changing sunlight and shadow during the day and year, temperature, air and water flow, and planting patterns. Then, it looks at historical and social contexts, including contamination, access, noise, and security.

Abstract The first section of this chapter describes the ecological approach to managing non-crop organisms in the garden. The second section briefly describes the common types of pests, pathogens and other organisms (including beneficial organisms) found in gardens. Five sections covers five basic management strategies, emphasizing pests and pathogens: managing the garden environment, choosing crop plants, biological control, physical control, and chemical control. For each of these, both concepts to use for optimizing net benefits and avoiding major problems are included, and for the last three, concepts to use when a major problem does develop. Section 9.8 is a guide to diagnosing and managing specific problems, and includes tables and accompanying figures summarizing some key concepts with examples.

Abstract This chapter steps back to see the larger picture of the connection between gardens and what is happening in the communities and environments. It looks at how change in the form of familiar variation is different from change in the form of trends, and then outlines the four major trends affecting food gardens and gardeners: increasing resource scarcity; changing climate; increasing inequity; and the changing character of populations in the global north, using the US as an example.

Most seed saving is relatively easy, and many gardeners already know how to do it. But the key to getting the most out of saving and sharing garden seeds is understanding how these affect diversity and adaptation, and what that means to people and the communities. This chapter focuses on concepts that can make your seed saving and sharing more effective and consistent with your goals and values, and on practical suggestions for using those concepts. The four processes that shape the genetic diversity in garden crops, and all living organisms are discussed. Being aware of these processes gives you a new way to see and manage what's going on in the garden and seed stocks, to keep varieties healthy and vigorous, and retain important characteristics. Two of these processes (mutation and gene flow) usually increase diversity in the garden by adding new alleles; the other two (selection and genetic drift) typically decrease diversity by removing alleles. These processes result in microevolutionary changes in garden crops, that is, changes in frequencies of alleles and of genotypes over time.

Abstract In food gardens, water carries plant nutrients from the roots upward, and carbohydrates from photosynthesis throughout the plant. Water is also a medium for chemical reactions, cools the plant by evaporating from the leaves, and is essential for photosynthesis. The immediate goal of garden water management is to provide plants with enough water to produce a harvest and other benefits for a reasonable investment of time, money, and other resources, and without creating salinity or waterlogging problems. Another important goal of garden water management is strengthening equitable access to good quality water for people, while providing adequate water for food production and natural ecosystems, now and in the future. This chapter looks at some concepts of water-soil-plant relationships that are key to achieving these goals as water becomes scarcer.

Most annual garden crops, and some perennials, can be grown from seed. Vegetative propagation is the other way to start garden crops, especially longer-lived species such as fruit trees, but may also be useful for some annual plants. This chapter focuses on starting garden plants from seeds both directly in the garden and in nursery beds and containers for transplanting into the garden. It also gives a brief introduction to starting plants using vegetative propagation, discussing seed quality, planting, and early seedling care, especially under hot, dry conditions. The chapter also suggests ways to diagnose a few common seed planting problems.

This chapter discusses the following topics: (i) origin and importance of soils; (ii) soil physical properties; (iii) soil and plant nutrition; (iv) nutrient cycles and anthropogenic climate change; (v) managing soil organic matter; (vi) composting; and (vii) soil resources.

Abstract This chapter covers concepts important for assessing the value of existing or planned gardens, and for increasing their benefits. Topics discussed include diet and nutrition, physical activity, psychological and social benefits, environmental benefits and economic benefits.

The accumulation of sodium in soil (saline conditions) negatively affects plant growth and development. The Salt Overly Sensitive (SOS) pathway in Arabidopsis (Arabidopsis thaliana) functions to remove sodium from the cytosol during vegetative development preventing its accumulation to toxic levels. In this pathway, the SOS3 and CALCINEURIN B-LIKE10 (CBL10) calcium sensors interact with the SOS2 protein kinase to activate sodium/proton exchange at the plasma membrane (SOS1) or vacuolar membrane. To determine if the same pathway functions during reproductive development in response to salt, fertility was analyzed in wild type and the SOS pathway mutants grown in saline conditions. In response to salt, CBL10 functions early in reproductive development before fertilization, while SOS1 functions mostly after fertilization when seed development begins. Neither SOS2 nor SOS3 function in reproductive development in response to salt. Loss of CBL10 function resulted in reduced anther dehiscence, shortened stamen filaments, and aborted pollen development. In addition, cbl10 mutant pistils could not sustain the growth of wild-type pollen tubes. These results suggest that CBL10 is critical for reproductive development in the presence of salt and that it functions in different pathways during vegetative and reproductive development.

Johnsongrass (Sorghum halepense) is a striking example of a post-Columbian founder event. This natural experiment within ecological time-scales provides a unique opportunity for understanding patterns of continent-wide genetic diversity following range expansion. Microsatellite markers were used for population genetic analyses including leaf-optimized Neighbor-Joining tree, pairwise FST, mismatch analysis, principle coordinate analysis, Tajima's D, Fu's F and Bayesian clusterings of population structure. Evidence indicates two geographically distant introductions of divergent genotypes, which spread across much of the US in <200 years. Based on geophylogeny, gene flow patterns can be inferred to have involved five phases. Centers of genetic diversity have shifted from two introduction sites separated by ~2000 miles toward the middle of the range, consistent with admixture between genotypes from the respective introductions. Genotyping provides evidence for a 'habitat switch' from agricultural to non-agricultural systems and may contribute to both Johnsongrass ubiquity and aggressiveness. Despite lower and more structured diversity at the invasion front, Johnsongrass continues to advance northward into cooler and drier habitats. Association genetic approaches may permit identification of alleles contributing to the habitat switch or other traits important to weed/invasive management and/or crop improvement.

Agave palmeri Engelmann is a semelparous perennial succulent thought to provide a critical food source for the endangered species, Leptonycteris curasoae Miller. Concern over impacts to existing A. palmeri populations has accelerated interest into reestablishing populations after disturbance. Little is known about its early life history and potential for restoration by seed in its arid habitat. In a greenhouse we measured emergence for 5.5 months across treatments with four variables: simulated precipitation (low: 170mm, average: 285mm, high: 390mm), shade (present, absent), surface mulch (straw, gravel, bare soil), and soil type (sand, sandy loam, loamy sand). The highest emergence was associated with high simulated precipitation (33%), straw mulch (42%), shade (38%), and the loamy soils (mean: 30%). High simulated precipitation on shaded, straw mulched treatments had the highest overall emergence (63%). Lowest emergence involved low simulated precipitation (11%), bare soil (9%), absence of shade (10%), and sandy soil (10%). Low levels of simulated precipitation, combined with unshaded, bare soil treatments-conditions common in heavily disturbed arid environments-had zero seedling emergence. Our results indicate that microsite conditions play a crucial role in the emergence of this species, and manipulation of these conditions may significantly increase emergence, even when water availability is low. This is critical information for land managers attempting to recover populations, as duration and frequency of rainfall are characteristically variable in regions A. palmeri inhabits. Thus, the use of surface mulches and shade may effectively facilitate restoration in large-scale disturbances when unfavorable conditions cannot be controlled.

In flowering plants, meiocytes develop from subepidermal cells in anthers and ovules. The mechanisms that integrate gene-regulatory processes with meiotic programs during reproductive development remain poorly characterized. Here, we show that Arabidopsis thaliana plants deficient in ACTIN-RELATED PROTEIN6 (ARP6), a subunit of the SWR1 ATP-dependent chromatin-remodeling complex, exhibit defects in prophase I of female meiosis. We found that this meiotic defect is likely due to dysregulated expression of meiotic genes, particularly those involved in meiotic recombination, including DMC1 (DISRUPTED MEIOTIC cDNA1). Analysis of DMC1 expression in arp6 mutant plants indicated that ARP6 inhibits expression of DMC1 in the megasporocyte and surrounding nonsporogeneous ovule cells before meiosis. After cells enter meiosis, however, ARP6 activates DMC1 expression specifically in the megasporocyte even as it continues to inhibit DMC1 expression in the nonsporogenous ovule cells. We further show that deposition of the histone variant H2A.Z, mediated by the SWR1 chromatin-remodeling complex at the DMC1 gene body, requires ARP6. Therefore, ARP6 regulates female meiosis by determining the spatial and temporal patterns of gene expression required for proper meiosis during ovule development.

We discuss the process of domesticating wild halophytes to serve as crop plants using seawater irrigation. First steps in this domestication involve determining whether halophyte species exist that may produce significant amounts of a usable product under seawater irrigation and that this is a sustainable agronomic practice. This is followed by development of strategies to improve crop productivity via selecting appropriate species for domestication and then affecting agronomic traits through plant breeding. We demonstrate that halophytes may be productive under seawater irrigation, that this management system may be sustainable, and there are demonstrated pathways toward domestication.

Understanding the distribution of key biotic elements of forest ecosystems is essential in contemporary forest management and in planning to meet future management needs. Habitat distribution (niche) models based on known occurrences provide geographical structure for such management as the environmental factors change. Bark beetles play critical roles in coniferous forest dynamics in western North America. Among these insects, Dendroctonus rhizophagus Thomas and Bright, which occurs in the Sierra Madre Occidental in Mexico, is unique in that it attacks only immature trees ( Pinus spp.) and therefore represents a threat to forest regeneration. We developed current habitat distribution models for D. rhizophagus and its Pinus hosts and projected these to future climate scenarios. Predicted suitable habitat of D. rhizophagus currently covers approximately 119 000 km 2 of which approximately 11% is occupied, and overlap with suitable habitat for all Pinus hosts exceeds 99.5%. Some suitable habitat occurs isolated from known D. rhizophagus occurrences in Mexico and the south‐western U.S.A. Habitat distribution models were projected to four potential climate scenarios for the period 2040–2060 and this predicted the gains and losses of suitable D. rhizophagus habitat throughout the region. Areas of north‐western Mexico maintain large areas of suitable D. rhizophagus and Pinus host habitat in all scenarios. Dispersal to isolated areas of D. rhizophagus habitat appears unlikely. The results of the present study can be used to target D. rhizophagus monitoring and management activities and may serve as a model for the management of other invasive species.