Weeds are among the major constraints to any crop production system, reducing productivity and profitability. Herbicides are among the most effective methods to control weeds, and reliance on herbicides for weed control has increased significantly with the advent of herbicide-resistant crops. Unfortunately, over-reliance on herbicides leads to environmental-health issues and herbicide-resistant weeds, causing human health and ecological concerns. Crop diversification can help manage weeds sustainably in major crop production systems. It acts as an organizing principle under which technological innovations and ecological insights can be combined to manage weeds sustainably. Diversified cropping can be defined as the conscious inclusion of functional biodiversity at temporal and/or spatial levels to improve the productivity and stability of ecosystem services. Crop diversification helps to reduce weed density by negatively impacting weed seed germination and weed growth. Additionally, diversified farming systems are more resilient to climate change than monoculture systems and provide better crop yield. However, there are a few challenges to adopting a diversified cropping system, ranging from technology innovations, government policies, farm-level decisions, climate change, and market conditions. In this review, we discuss how crop diversification supports sustainable weed management, the challenges associated with it, and the future of weed management with respect to the diversification concept.

Rice (Oryza sativa L.) is a vital crop for achieving global food security. Unfortunately, weeds are the major yield-constraining factor in rice production systems worldwide. Development of rice with higher competitive ability than weeds will help achieve sustainable weed management, as robust rice cultivars will have a competitive advantage over weeds. As wild relatives are often explored by plant breeders in crop improvement programs, greenhouse studies were conducted to evaluate weed-suppressive potential of 54 weedy rice accessions (weedy relatives of cultivated rice) against barnyardgrass (Echinochloa crus-galli) and Amazon sprangletop (Leptochloa panicoides). Three allelopathic rice cultivars (PI312777, PI338046, and Rondo), and two commercial rice cultivars (CL163 and REX) were included as a positive and negative control, respectively. Among all the test accessions of weedy rice, B2 suppressed the growth of E. crus-galli by 52%, whereas accession B81 suppressed L. panicoides growth by 61%. Accession B81 caused greater than 50% growth inhibition of both E. crus-galli and L. panicoides. Thus, B2 and B81 were identified as the most weed-suppressive weedy rice accessions. Weed-suppressive potential in weedy rice was associated morphologically with hull type and awn length. Weed-suppressive weedy rice accessions identified from this study can be used as a source of raw genetic material in rice improvement programs. Future research should focus on identifying the underlying mechanism for a high weed-suppressive potential of specific weedy rice accessions.

Zucchini Yellow Mosaic Virus (ZYMV) is an aphid-transmitted potyvirus that causes severe yield losses in squash (Cucurbita moschata) production worldwide. Development of resistant cultivars using traditional breeding approaches relies on rigorous and resource-intensive phenotypic assays. QTL-seq, a whole genome re-sequencing based bulked segregant analysis, is a powerful tool for mapping quantitative trait loci (QTL) in crop plants. In the current study, the QTL-seq approach was used to identify genetic loci associated with ZYMV resistance in an F₂ population (n = 174) derived from a cross between Nigerian Local (resistant) and Butterbush (susceptible). Whole genome re-sequencing of the parents and bulks of resistant and susceptible F₂ progeny revealed a mapping rate between 94.04% and 98.76%, and a final effective mapping depth ranging from 81.77 to 101.73 across samples. QTL-seq analysis identified four QTLs significantly (p < 0.05) associated with ZYMV resistance on chromosome 2 (QtlZYMV-C02), 4 (QtlZYMV-C04), 8 (QtlZYMV-C08) and 20 (QtlZYMV-C20). Seven markers within the QTL intervals were tested for association with ZYMV resistance in the entire F₂ population. For QtlZYMV-C08, one single nucleotide polymorphism (SNP) marker (KASP-6) was found to be significantly (p < 0.05) associated with ZYMV resistance, while two SNPs (KASP-1 and KASP-3) and an indel (Indel-2) marker were linked to resistance within QtlZYMV-C20. KASP-3 and KASP-6 are non-synonymous SNPs leading to amino acid substitutions in candidate disease resistant gene homologs on chromosomes 20 (CmoCh20G003040.1) and 8 (CmoCh08G007140.1), respectively. Identification of QTL and SNP markers associated with ZYMV resistance will facilitate marker-assisted selection for ZYMV resistance in squash.

Rice is a staple food for more than 3.5 billion people worldwide, with Asia producing almost 90% of the global rice yield. In the US, rice is primarily produced in four regions: Arkansas Grand Prairie, Mississippi Delta, Gulf Coast, and Sacramento Valley of California. Arkansas currently accounts for more than 50% of the rice produced in the US. As global temperatures continue to rise and fluctuate, crop-breeding programs must continue to evolve. Unfortunately, sudden submergence due to climate change and unpredictable flash flooding can cause yield reduction up to 100% and affect 20 million ha of agricultural farmlands. Similarly, it has been demonstrated that temperatures higher than 34°C can cause spikelet infertility resulting in up to 60% reduction in yield. One major drawback to developing abiotic stress-tolerant rice is the loss of critical traits such as vegetative vigor, spikelet fertility, and grain quality, which are essential in increasing economic return for farmers. To replace traits lost in past breeding endeavors, weedy rice (WR) has been proposed as a source for novel trait discovery to improve rice breeding programs. Therefore, the goal of this study was to screen and identify heat- and submergence-tolerant WR accessions. A WR mini germplasm consisting of seedlings at the 3–4 leaf stage was exposed to heat (38°C) and complete submergence for 21 days. After each treatment, height was recorded every 7 days for 28 days, and biomass was collected 28 days after treatment. The average height reduction across all accessions was 19 and 21% at 14 and 28 days after treatment (DAT) for the heat-stress treatment. The average height reduction across all accessions was 25 and 33% for the complete submergence stress. The average biomass reduction across all accessions was 18 and 21% for heat and complete submergence stress, respectively. Morphologically, at 28 DAT, 28% of the surviving WR accessions in the heat-stress treatment with <20% height reduction were straw-colored hull types without awns. Under complete submergence stress, 33% of the surviving WR accessions were blackhull types without awns. These specific biotypes may play a role in the increased resilience of WR populations to heat or submergence stress. The results presented in this paper will highlight elite WR accessions that can survive the effects of climate change.

Pumpkin (Cucurbita pepo) seeds are nutritious and valued as a source of vegetable oil, protein, healthy fatty acids, and minerals. Pumpkin seeds that are naturally devoid of the seedcoat (hull-less) are preferred by the industry as they eliminate the need for de-hulling prior to use. A single recessive gene, designated as n or h, controls the hull-less seed trait in pumpkin. Visual selection for the trait is easy, however, it is resource intensive when applied to large breeding populations. High throughput genotyping assays can aid in the identification of suitable individuals in segregating populations through marker-assisted selection. In the current study, the QTL-seq approach was used to identify genetic loci, SNP markers and candidate genes associated with the hull-less trait in a segregating F₂ population (n = 143) derived from a cross between Kakai (hull-less) × Table Gold Acorn (hulled). The segregation of the hull-less trait in the F₂ population fit a 3:1 ratio (p < 0.05). QTL-seq analysis detected a single QTL on chromosome 12 (Qtlhull-less-C12) which was significantly associated with the hull-less trait in C. pepo. Twenty-eight SNPs were genotyped in the population, two among which (Ch12_3412046 and Ch12_3417142) were significantly associated (p < 0.05) with the hull-less trait in cultivars and accessions of diverse genetic background. Several candidate genes fall within the Qtlhull-less-C12 interval, among them is the No Apical meristem (NAC) domain-containing protein and a Fiber Protein fb11 gene involved in lignin accumulation and cell wall deposition across plant species, respectively. The findings of this study will facilitate the marker-assisted selection for the hull-less seed trait in pumpkin and further our understanding of the functional mechanisms underlying the trait across cucurbit crops.

Weedy rice (Oryzaspp.) is one of the most competitive weeds in rice (Oryza sativaL.) production. Rapid growth, high tillering, enhanced ability to uptake fertilizers, asynchronous maturation, seed shattering, and high seedbank longevity makeOryzaspp. more competitive than cultivated rice and highly persistent.Oryzaspp. may be a source of useful traits for crop improvement such as herbicide tolerance. Greenhouse studies were conducted to evaluate the response of 54Oryzaspp. accessions collected between 2008 and 2009 from Arkansas to glyphosate, glufosinate, and flumioxazin applied at field rates. Rice cultivars ‘CL163’ and ‘REX’ were included for comparison. Accessions B20, B2, and S11 and B49, B51, and S59 showed reduced sensitivity to glyphosate and flumioxazin, respectively. These accessions had less than 40% injury 5 wk after treatment (WAT). Rice cultivars (CL163 and REX) were sensitive to both glyphosate and flumioxazin, with more than 95% plant mortality at 5 WAT. On average, blackhull accessions were more tolerant to glyphosate and flumioxazin than strawhull accessions. Dose–response analysis of B20, B2, and S11 confirmed 3- to 8-fold higher tolerance of these accessions to glyphosate. AllOryzaspp. and cultivated rice were not affected by glufosinate applied at 874 g ai ha⁻¹(1X) and were controlled 100% by 1,311 g ai ha⁻¹(1.5X).Oryzaspp. lines with reduced sensitivity to glyphosate and flumioxazin will be studied further for use in rice crop improvement.