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A gap exists between the growth of active germplasm collections and their effective use because of the size of these collections and the limitations of financial resources, skilled labor, and information on the traits of each accession conserved in germplasm banks. To overcome this, the development of core collections (CCs) is of significant importance. In this study, we established the CCs of lima bean ( Phaseolus lunatus ) accessions from the Germplasm Bank of Phaseolus at the Universidade Federal do Piauí based on two selection strategies and performed validation based on nuclear microsatellite (ncSSR) data. Two CCs were established from 395 accessions and characterized by 11 phenotypic traits of the seed. These CCs were defined using proportional and logarithmic sampling strategies, each consisting of 79 accessions. A set of 13 ncSSRs was used to validate and estimate the genetic diversity. The estimates of parameters (means, variances, and amplitudes of variation), kurtosis, skewness, and average variability retention index indicated no differences between the two CCs when compared with the entire collection (EC). However, the comparison between the accessions that did not coincide with the two CCs through ncSSRs showed differences. The logarithmic CC showed higher expected heterozygosity, mean number of alleles, and number of private alleles (0.521, 4.308, and 30, respectively) than those of the proportional CC strategy (0.352, 2.154, and 2, respectively), indicating greater genetic diversity. Thus, the logarithmic CC proved to be more suitable for conservation purposes and should be further examined in the establishment of thematic collections of lima beans.

Lima bean ( Phaseolus lunatus L.) is an essential subsistence crop in Brazil, especially in the northeast, because of its adaptability to diverse environmental conditions and genetic variability. However, achieving high productivity remains challenging due to anthracnose caused by Colletotrichum truncatum . This study aimed to characterize the genetic diversity of Lima bean in Alagoas state and to identify anthracnose-resistant landraces. P. lunatus seeds were collected from local farmers in Alagoas between July 2017 and February 2018. Semi-structured interviews were conducted to examine the characteristics of Lima bean smallholders, focusing on socioeconomic, cultural, and agroecological factors. Genetic characterization of P. lunatus involved phylogenetic analysis of the internal transcribed spacer (ITS) region of ribosomal DNA and morphology analysis based on agronomic descriptors. The interviews confirmed that P. lunatus landraces were cultivated under rustic management conditions in subsistence agriculture. Twenty-seven landraces from twelve municipalities were obtained, representing three morphotypes: Big Lima, Potato, and Sieva, with Potato and Sieva being predominant. Lima bean landraces were classified genetically into Mesoamerican gene pools I and II, with the Big Lima morphotype grouped within the Mesoamerican gene pool II. Additionally, some hybrid landraces were identified. Broad resistance to anthracnose was associated with the Mesoamerican gene pool I, highlighting their importance for genetic improvement initiatives. This is crucial given the varied etiological agents of anthracnose across northeast Brazil.

Plant defenses against herbivores include the emission of specific blends of volatiles, which enable plants to attract natural enemies of herbivores. We characterized a plastidial terpene synthase gene, PlTPS2, from lima bean (Phaseolus lunatus). The recombinant PlTPS2 protein was multifunctional, producing linalool, (E)-nerolidol and (E,E)-geranyllinalool, precursors of (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene [TMTT]. Transgenic Lotus japonicus and Nicotiana tabacum plants, expressing PlTPS2 or its homolog Medicago truncatula TPS3 (MtTPS3), were produced and used for bioassays with herbivorous and predatory mites. Transgenic L. japonicus plants expressing PlTPS2 produced (E,E)-geranyllinalool and TMTT, whereas wild-type plants and transgenic plants expressing MtTPS3 did not. Transgenic N. tabacum expressing PlTPS2 produced (E, E)-geranyllinalool but not TMTT. Moreover, in olfactory assays, the generalist predatory mite Neoseiulus californicus but not the specialist Phytoseiulus persimilis was attracted to uninfested, transgenic L. japonicus plants expressing PlTPS2 over wild-type plants. The specialist P. persimilis was more strongly attracted by the transgenic plants infested with spider mites than by infested wild-type plants. Predator responses to transgenic plant volatile TMTT depend on various background volatiles endogenously produced by the transgenic plants. Therefore, the manipulation of TMTT is an ideal platform for pest control via the attraction of generalist and specialist predators in different manners.

In this study, propolis extract (EPE) and oregano essential oil (OEO), both natural products with different bioactive compounds, were evaluated in vitro and in vivo against Sclerotinia sclerotiorum. This phytopathogen is important worldwide as it can contaminate seeds and infect seedlings of many species. Antifungal susceptibility assays on culture media revealed that EPE and OEO were highly active against this phytopathogen, both individually and combined. EPE showed a fungistatic dose-dependent effect, acting mainly through diffusion, while OEO completely prevented mycelial growth at very low concentrations, with a combination of vapor and diffusion activity. Interestingly, OEO was more effective than EPE, as their minimum inhibitory concentrations were 0.39 μl/mL and 5 μl/mL, respectively. Combinations of EPE and OEO showed, depending on the doses, additive or synergistic antifungal effects. In the in vivo trial, dilutions of EPE and OEO made in sterile distilled water (SDW) were tested through a pathosystem with lima bean seeds and S. sclerotiorum . Seeds soaked in formulations with 40% EPE + 12% OEO + 48% SDW, and 20% EPE + 6% OEO + 74% SDW reduced disease incidence of 40% and 60% respectively, significantly decreased severity, with a minimum phytotoxic effect. This study strengthens previous work showing the antifungal action of EPE and OEO against S. sclerotiorum , and, as a main goal, highlights their potential for the development of biofungicides to protect lima bean seeds.

The locally cultivated creole varieties of Phaseolus lunatus are adapted to specific climatic and environmental conditions. Family farmers and local communities preserve and multiply their seeds over generations, promoting genetic diversity, food and nutritional security, and agricultural sustainability. This species has great geno-phenotypic diversity, which can be harnessed in breeding programs if accurately characterized. We evaluated the phenotypic variations of P. lunatus seeds from 13 varieties in three states (Sergipe, Bahia, and Alagoas) using image analysis. We estimated the weight of 100 seeds using a precision analytical balance and obtained morphometric measurements, including area, maximum diameter, and minimum diameter, using Groundeye (TBit®) imaging equipment and software. We also recorded dominant color and RGB color system descriptors. The morphometric variables underwent variance analysis using the F-test, and the means were clustered using the Scott-Knott test at 5% significance level. The data underwent Pearson Correlation Analysis (t-Student at 5%), were grouped based on dissimilarity using the UPGMA method, and were represented in a dendrogram. We also performed Principal Component Analysis on the evaluated characteristics. The dominant color of the seeds was predominantly orange in nine varieties. Morphometry showed a positive and significant association. The dendrogram revealed two homogeneous and distinct groups, and the first two principal components accounted for 86.80% of the genotypic variation. Therefore, high-resolution images for phenotypic characterization of creole lima bean seeds are a promising non-destructive tool for selection purposes.

The lima bean (Phaseolus lunatus L.) is an important food crop that is cultivated in temperate, arid, and semiarid tropical regions. It is a source of dietary protein for millions of people living in low-income countries. However, the genetic variability available for breeding programs is still poorly understood, which limits its productive potential. Knowledge of landrace germplasm through molecular and agromorphological markers could facilitate future breeding gains. Therefore, we evaluated the genetic variation of agromorphological and molecular markers in a lima bean collection. Twelve quantitative traits and microsatellite markers (SSRs) were used to determine genetic polymorphisms and differentiation among the 26 lima bean accessions. Considerable diversity was observed in traits related to agronomic performance, such as pod width, seed length, and seed width. At the molecular level, the expected mean heterozygosity (He = 0.486) was greater than the observed value (Ho = 0.128), indicating a deficiency of heterozygotes, which is a result of the reproductive system of the species. Although having a mixed system of reproduction, the lima bean is predominantly autogamous. The polymorphic information content (PIC) ranged from 0.04 to 0.67. Loci BM211 and BM156 were highly informative and are indicated for further studies with lima beans. The UFPI accessions 222, 234, 237, 228, 264, 230, and 251 showed the highest levels of similarity, while UFPI 230 and UFPI 276 were genetically distant and complementary in their traits; therefore, they could be used in crosses. Furthermore, the pairs of accessions UFPI 121/UFPI 173, UFPI 274/UFPI 276, and UFPI 271/UFPI 134 were duplicates found in the lima bean germplasm collection. The information generated in this study will play a significant role in future lima bean breeding programs.

Plants simultaneously maintain mutualistic relationships with different partners that are connected through the same host, but do not interact directly. One or more participating mutualists may alter their host's phenotype, resulting in a shift in the host's ecological interactions with all other mutualists involved. Understanding the functional interplay of mutualists associated with the same host remains an important challenge in biology. Here, we show belowground nitrogen-fixing rhizobia on lima bean ( Phaseolus lunatus ) alter their host plant's defensive mutualism with aboveground ants. We induced extrafloral nectar (EFN), an indirect defense acting through ant attraction. We also measured various nutritive and defensive plant traits, biomass, and counted ants on rhizobial and rhizobia-free plants. Rhizobia increased plant protein as well as cyanogenesis, a direct chemical defense against herbivores, but decreased EFN. Ants were significantly more attracted to rhizobia-free plants, and our structural equation model shows a strong link between rhizobia and reduced EFN as well as between EFN and ants: the sole path to ant recruitment. The rhizobia-mediated effects on simultaneously expressed defensive plant traits indicate rhizobia can have significant bottom-up effects on higher trophic levels. Our results show belowground symbionts play a critical and underestimated role in determining aboveground mutualistic interactions.

1 Many plant species respond to herbivory with increased emission of volatile organic compounds (VOCs): these attract carnivorous arthropods and thereby function as an indirect defence mechanism. Whether neighbouring plants can 'eavesdrop' on such airborne cues and tailor their defences accordingly, remains controversial. 2 We used Lima bean plants (Phaseolus lunatus) to investigate whether herbivore-induced VOCs induce another indirect defence strategy, i.e. the secretion of extrafloral nectar (EFN) in conspecific plant neighbours, and whether this enhances the defence status of the receiving plant under natural conditions. 3 EFN secretion was induced by VOCs released from herbivore-damaged bean tendrils as well as by a synthetic VOC mixture resembling the natural one. One constituent of the herbivore-induced blend - the green leaf volatile (3Z)-hex-3-enyl acetate - was sufficient to elicit the defence reaction. 4 A long-term experiment comparing the defensive effect of EFN alone with the VOC-mediated effect (EFN induction plus attraction of plant defenders) suggested that Lima bean benefits from both indirect defences. Repeated treatment of tendrils with either an artificial blend of VOCs or with EFN led to the attraction of a higher cumulative number of predatory and parasitoid insects (i.e. ants and wasps) as well as to less herbivore damage and an increased production of inflorescences and leaves. 5 Our results demonstrate that one indirect defence mechanism can induce another one in conspecific plants, and that Lima bean plants can benefit from this VOC-induced EFN secretion under natural conditions. Both extrafloral nectaries and the capability to release VOCs upon herbivory are present in many plant taxa and airborne signalling may thus represent a common mechanism for regulating the secretion of EFN in plant parts which face an increased risk of herbivory.

Background: This study explores the role of leguminous crops like lima bean in enhancing soil quality and ecosystem stability. Despite existing studies on agronomic aspects, there is a significant research gap on its impact on soil organic matter level, microbial activity, soil health, and nutrient availability. Therefore, this study examines the capacity of lima bean to reactivate soil quality, focusing on its impact on soil organic matter level, microbial activity, soil health, and nutrient availability. Methods: The experimental area was set up in 2023 using three replicates and a randomized block design. Two treatments were used: lima bean-planted plots and control plots with various weeds and without lima bean. Post-harvest soil samples were collected from various agroecological zones and sterilely packed, and physical, chemical, and biological indices were examined. Results: lima bean significantly affected nutrients, enzymes, soil microbial respiration, and other markers. Amylase activity (0.41**) was positively correlated with urease activity (0.73**), while dehydrogenase activity positively correlated with both. Dehydrogenase activity was negatively correlated with total nitrogen (0.66**) and sulfur (0.60**). Lima bean significantly affected soil quality, with all locations showing higher ratings (55–77%) than wild land, except for location D (Ilora). A total of 70% of total nitrogen variation may be attributed to soil quality (r2 = 0.696). Lima bean enhanced soil quality, potentially enhancing productivity and reducing dependence on inorganic nitrogen inputs. Conclusions: The symbiotic relationship between lima bean and nitrogen-fixing bacteria improves nutrient cycling, enhancing agricultural productivity and environmental conservation. Future research should explore the economic viability of integrating lima bean into crop rotations or agroforestry systems for sustainable agricultural practices, providing valuable information for farmers.

1. Plant defence theory predicts trade-offs among defence traits as a result of resource limitation or pleiotropic effects. Although theoretically widely accepted, empirical demonstrations of such trade-offs are surprisingly scarce and mechanistic explanations are usually lacking. 2. We quantified cyanogenesis (the release of hydrogen cyanide (HCN)) as a direct defence and the emission of volatile organic compounds (VOCs) as an indirect defence against herbivores. To elucidate whether the trade-offs occur at the genetic or phenotypic level we investigated cultivated and wild-type accessions of lima bean (Fabaceae: Phaseolus lunatus L.) and compared different leaf developmental stages. Genetic relationships among the accessions were studied using amplified fragment length polymorphism (AFLP) analysis. 3. Cyanogenesis and the release of VOCs differed significantly among the accessions and were negatively correlated: high cyanogenic accessions released low amounts of VOCs and vice versa. The same remained true for the ontogenetic stages, since primary leaves of all accessions hardly ever produced HCN at all, yet regularly showed high release rates of VOCs. 4. Low and high cyanogenic accessions of lima bean formed distinct clades in an AFLP-based dendrogram, while wild-types and cultivars did not separate. The first pattern indicates that the underlying defensive syndromes are genetically conserved, while the latter is likely to be caused by a multiple origin of cultivated lima beans or an extensive gene flow among cultivated and wild plants. 5. Synthesis. Trade-offs between cynogenesis and VOC release were obvious both between accessions and at the ontogenetic level, and thus cannot be explained by pleiotropy. We contend that allocation restrictions and/or adaptations to different enemy pressures are most likely to explain why lima bean can invest into cyanogenesis or VOCs, but not both.