Challenges and Responses to Ongoing and Projected Climate Change for Dryland Cereal Production Systems throughout the World

Can cereal-legume intercrop systems contribute to household nutrition in semi-arid environments: A systematic review and meta-analysis

Introduction

Intercropping cereals with legumes can intensify rainfed cereal monocropping for improved household food and nutritional security. However, there is scant literature confirming the associated nutritional benefits.

Methodology

A systematic review and meta-analysis of nutritional water productivity (NWP) and nutrient contribution (NC) of selected cereal-legume intercrop systems was conducted through literature searches in Scopus, Web of Science and ScienceDirect databases. After the assessment, only nine articles written in English that were field experiments comprising grain cereal and legume intercrop systems were retained. Using the R statistical software (version 3.6.0), paired t-tests were used to determine if differences existed between the intercrop system and the corresponding cereal monocrop for yield (Y), water productivity (WP), NC, and NWP.

Results

The intercropped cereal or legume yield was 10 to 35% lower than that for the corresponding monocrop system. In most instances, intercropping cereals with legumes improved NY, NWP, and NC due to their added nutrients. Substantial improvements were observed for calcium (Ca), where NY, NWP, and NC improved by 658, 82, and 256%, respectively.

Discussion

Results showed that cereal-legume intercrop systems could improve nutrient yield in water-limited environments. Promoting cereal- legume intercrops that feature nutrient-dense legume component crops could contribute toward addressing the SDGs of Zero Hunger (SDG 3), Good Health and Well-3 (SDG 2) and Responsible consumption and production (SDG 12).

Transcriptomic and Physiological Response of Durum Wheat Grain to Short-Term Heat Stress during Early Grain Filling

In a changing climate, extreme weather events such as heatwaves will be more frequent and could affect grain weight and the quality of crops such as wheat, one of the most significant crops in terms of global food security. In this work, we characterized the response of Triticum turgidum L. spp. durum wheat to short-term heat stress (HS) treatment at transcriptomic and physiological levels during early grain filling in glasshouse experiments. We found a significant reduction in grain weight (23.9%) and grain dimensions from HS treatment. Grain quality was also affected, showing a decrease in starch content (20.8%), in addition to increments in grain protein levels (14.6%), with respect to the control condition. Moreover, RNA-seq analysis of durum wheat grains allowed us to identify 1590 differentially expressed genes related to photosynthesis, response to heat, and carbohydrate metabolic process. A gene regulatory network analysis of HS-responsive genes uncovered novel transcription factors (TFs) controlling the expression of genes involved in abiotic stress response and grain quality, such as a member of the DOF family predicted to regulate glycogen and starch biosynthetic processes in response to HS in grains. In summary, our results provide new insights into the extensive transcriptome reprogramming that occurs during short-term HS in durum wheat grains.

Genetic diversity and population structure of a global invader Mayweed chamomile (Anthemis cotula): management implications

Mayweed chamomile (Anthemis cotula) is a globally invasive, troublesome annual weed but knowledge of its genetic diversity, population structure in invaded regions and invasion patterns remains unstudied. Therefore, germplasm from 19 A. cotula populations (sites) from three geographically distinct invaded regions: the Walla Walla Basin (located in southern Washington) and the Palouse (located in both northern Idaho and eastern Washington), Pacific Northwest, USA and Kashmir Valley, India were grown in the greenhouse for DNA extraction and sequencing. A total of 18 829 single-nucleotide polymorphisms were called and filtered for each of 89 samples. Pairwise F ST, Nei's genetic distance, heterozygosity, Wright's inbreeding coefficient (F) and self-fertilization rates were estimated for populations within and among the three regions with a total of 19 populations comprised of 89 individuals. Overall measurements of genetic variation were low but significant among regions, populations and individuals. Despite the weak genetic structure, two main genetic clusters were evident, one comprised of populations from Palouse and Kashmir Valley, the other comprised of populations from the Walla Walla Basin. Significant selfing was observed in populations from the Walla Walla Basin and Palouse but not from Kashmir Valley, indicating that Mayweed chamomile in the Pacific Northwest, USA could persist with low pollinator or pollen donor densities. Although F ST values between the regions indicate Palouse populations are more closely related to Kashmir Valley than to Walla Walla Basin populations, based on Migrate-n analysis, panmixis was the most likely model, suggesting an unrestricted gene flow among all three regions. Our study indicated that Kashmir Valley populations either originated from or shared the origin with the Palouse populations, suggesting human-mediated migration of A. cotula between regions.

Optimizing Traditional Cropping Systems Under Climate Change: A Case of Maize Landraces and Bambara Groundnut

Traditional crop species are reported to be drought-tolerant and nutrient-dense with potential to contribute to sustainable food and nutrition security within marginal production systems under climate change. We hypothesized that intercropping maize landraces (Zea mays L.) with bambara groundnut (Vigna subterranea (L.) Verdc.), together with optimum management strategies, can improve productivity and water use efficiency (WUE) under climate change. Using an ex-ante approach, we assessed climate change impacts and agronomic management options, such as plant ratios, and plant sequences, on yield and WUE of intercropped maize landrace and bambara groundnut. The Agricultural Production Systems sIMulator (APSIM) model was applied over four time periods; namely past (1961-1991), present (1995-2025), mid-century (2030-2060) and late-century (2065-2095), obtained from six GCMs. Across timescales, there were no significant differences with mean annual rainfall, but late century projections of mean annual temperature and reference crop evaporation (ET0) showed average increases of 3.5°C and 155mm, respectively. By late century and relative to the present, the projected changes in yield and WUE were -10 and -15% and 5 and 7% for intercropped bambara groundnut and maize landrace, respectively. Regardless of timescale, increasing plant population improved yield and WUE of intercropped bambara groundnut. Asynchronous planting increased yield and WUE for both maize landrace (5 and 14%) and bambara groundnut (35 and 47%, respectively). Most significant improvements were observed when either crop was planted 2-3 months apart. To reduce yield gaps in intercrop systems, low-cost management options like changing plant populations and sequential cropping can increase yield and WUE under projected climate change. To further increase sustainability, there is a need to expand the research to consider other management strategies such as use of other traditional crop species, fertilization, rainwater harvesting and soil conservation techniques.

Cereal Root Interactions with Soilborne Pathogens—From Trait to Gene and Back

Realizing the yield potential of crop plants in the presence of shifting pathogen populations, soil quality, rainfall, and other agro-environmental variables remains a challenge for growers and breeders worldwide. In this review, we discuss current approaches for combatting the soilborne phytopathogenic nematodes, Pratylenchus and Heterodera of wheat and barley, and Meloidogyne graminicola Golden and Birchfield, 1965 of rice. The necrotrophic fungal pathogens, Rhizoctonia solani Kühn 1858 AG-8 and Fusarium spp. of wheat and barley, also are discussed. These pathogens constitute major causes of yield loss in small-grain cereals of the Pacific Northwest, USA and throughout the world. Current topics include new sources of genetic resistance, molecular leads from whole genome sequencing and genome-wide patterns of hosts, nematode or fungal gene expression during root-pathogen interactions, host-induced gene silencing, and building a molecular toolbox of genes and regulatory sequences for deployment of resistance genes. In conclusion, improvement of wheat, barley, and rice will require multiple approaches.