How Does the Addition of Biostimulants Affect the Growth, Yield, and Quality Parameters of the Snap Bean (Phaseolus vulgaris L.)? How Is This Reflected in Its Nutritional Value?

Recently, the use of biostimulants as natural and eco-friendly fertilizers has received increasing attention because of their efficiency in terms of improving crops’ qualitative and quantitative parameters, i.e., growth, yield, and chemical composition. We studied the effect of four biostimulants—humic acid (20 g/L), vermicompost tea (15 mL/L), moringa leaf extract (1:30 v/v), and yeast extract (5 g/L), with tap water as a control treatment—on the qualitative and quantitative characteristics of snap beans. The experiment was designed using a complete randomized block with triplicates. The results showed a significant improvement in treated plant performance (growth and yield), chlorophyll, and chemical composition compared to untreated plants. Using moringa leaf extract increased the plant height, number of leaves and branches/plant, and fresh and dry weight. Additionally, the diameter of the treated plant stems and the quality of the crop and pods were also significantly higher than those of plants treated with vermicompost or humic acid extract. It is also noted that the profile of amino acids was improved using all tested biostimulants. This leads to the conclusion that the addition of moringa leaf extract and vermicompost tea not only positively affects the qualitative and quantitative properties of snap bean but is also reflected in its nutritional value as a plant-based food.

Loss of pod strings in common bean is associated with gene duplication, retrotransposon insertion, and overexpression of PvIND

Regulation of fruit development has been central in the evolution and domestication of flowering plants. In common bean (Phaseolus vulgaris L.), a major global staple crop, the two main economic categories are distinguished by differences in fiber deposition in pods: a)dry beans with fibrous and stringy pods; and b) stringless snap/green beans withreduced fiber deposition, but which frequently revert to the ancestral stringy state. To better understand control of this important trait, we first characterized developmental patterns of gene expression in four phenotypically diverse varieties. Then, using isogenic stringless/revertant pairs of six snap bean varieties, we identified strong overexpression of the common bean ortholog of INDEHISCENT (PvIND) in non-stringy types compared to their string-producing counterparts. Microscopy of these pairs indicates that PvIND overexpression is associated with overspecification of weak dehiscence zone cells throughout the entire pod vascular sheath. No differences in PvIND DNA methylation were correlated with pod string phenotype. Sequencing of a 500 kb region surrounding PvIND in the stringless snap bean cultivar Hystyle revealed that PvIND had been duplicated into two tandem repeats, and that a Ty1-copia retrotransposon was inserted between these tandem repeats, possibly driving PvIND overexpression. Further sequencing of stringless/revertant isogenic pairs and diverse materials indicated that these sequence features had been uniformly lost in revertant types and were strongly predictive of pod phenotype, supporting their role in PvIND overexpression and pod string phenotype.

Seasonal Abundance and Spatial Pattern of Distribution of Liriomyza trifolii (Diptera: Agromyzidae) and Its Parasitoid on Bean and Squash in South Florida

American serpentine leafminer, Liriomyza trifolii, is a polyphagous insect pest that feeds on a wide range of vegetable and ornamental plants around the world. To develop an effective IPM program, information on the seasonal field distribution and population dynamics of leafminer and its parasitoids is very important. Therefore, seasonal abundances and spatial distributions of, L. trifolii on snap bean and squash were studied during four crop growing periods between 2013 to 2015 in Homestead, Florida. The mean numbers of mines, larvae, pupae, emerged adults, and parasitoids on snap bean were highest at 2 weeks after planting during all four growing periods. Whereas, the mean numbers of mines, larvae, pupae, emerged adults, and parasitoids on squash were highest at 3 weeks after planting during all four growing periods. L. trifolii distributions tended to be aggregated on snap bean at 2 weeks after planting during most of growing periods but had uniform distributions on squash at 2 weeks after planting during most of growing periods. Similar results were seen on the distribution of leafminer parasitoids on both bean and squash.

Comparative Study between Traditional and Nano Calcium Phosphate Fertilizers on Growth and Production of Snap Bean (Phaseolus vulgaris L.) Plants

Recently, nanofertilizers are being tested as a new technology, either for soil or foliar applications, to improve food production and with a reduced environmental impact. Nano calcium phosphate (NCaP) was successfully synthesized, characterized and applied in this study. A pot experiment was carried out in two successive seasons in 2016 and 2017 on (Phaseolus vulgaris L.) plants to obtain the best phosphorus treatments. The results were applied in a field experiment during the 2018–2019 season. Single superphosphate (SSP) at 30 and 60 kg P2O5 fed−1 and NCaP at 10%, 20% and 30% from the recommended dose were applied to the soil. Foliar application involved both monoammonium phosphate (MAP) at one rate of 2.5 g L−1 and NCaP at 5% and 10% from the MAP rate. The results of all experiments showed that NCaP significantly increased the shoot and root dry weights, the nutrient content in the shoot and root, the yield components, the nutrient concentration and crude protein percentage in pods of the snap bean plants compared with traditional P. The greatest increase was obtained from a 20% NCaP soil application in combination with a 5% NCaP foliar application. The present study recommends using NCaP as an alternative source of P to mitigate the negative effects of traditional sources.

Associated SNPs, Heritabilities, Trait Correlations, and Genomic Breeding Values for Resistance in Snap Beans (Phaseolus vulgaris L.) to Root Rot Caused by Fusarium solani (Mart.) f. sp. phaseoli (Burkholder)

Root rot is a major constraint to snap bean (Phaseolus vulgaris) production in the United States and around the world. Genetic resistance is needed to effectively control root rot disease because cultural control methods are ineffective, and the pathogen will be present at the end of one season of production on previously clean land. A diversity panel of 149 snap bean pure lines was evaluated for resistance to Fusarium root rot in Oregon. Morphological traits potentially associated with root rot resistance, such as aboveground biomass, adventitious roots, taproot diameter, basal root diameter, deepest root angle, shallowest root angle, root angle average, root angle difference, and root angle geometric mean were evaluated and correlated to disease severity. A genome wide association study (GWAS) using the Fixed and random model Circulating Probability Unification (FarmCPU) statistical method, identified five associated single nucleotide polymorphisms (SNPs) for disease severity and two SNPs for biomass. The SNPs were found on Pv03, Pv07, Pv08, Pv10, and Pv11. One candidate gene for disease reaction near a SNP on Pv03 codes for a peroxidase, and two candidates associated with biomass SNPs were a 2-alkenal reductase gene cluster on Pv10 and a Pentatricopeptide repeat domain on Pv11. Bean lines utilized in the study were ranked by genomic estimated breeding values (GEBV) for disease severity, biomass, and the root architecture traits, and the observed and predicted values had high to moderate correlations. Cross validation of genomic predictions showed slightly lower correlational accuracy. Bean lines with the highest GEBV were among the most resistant, but did not necessarily rank at the very top numerically. This study provides information on the relationship of root architecture traits to root rot disease reaction. Snap bean lines with genetic merit for genomic selection were identified and may be utilized in future breeding efforts.

Shrub legume green manure intercropped with maize preceding organic snap bean cultivation

ABSTRACT This study aimed to evaluate strategies for growing pigeon pea and tephrosia intercropped with maize in different spatial arrangements for green manure in organic snap bean farming in succession. The experimental design was a randomized block, in a 2x3 + 1 factorial scheme, corresponding to the two species and the cropping system (monocropping; intercropping with sowing in the same row or between rows). The treatments consisted of pigeon pea and tephrosia monocropping, pigeon pea or tephrosia intercropped with maize in the same planting furrow, pigeon pea or tephrosia intercropped with maize between rows, and maize monocropping (control). After cutting the pre-crops, snap beans were sown. The authors verified that the introduction of shrub leguminous plants in intercropping did not interfere with the phytotechnical characteristics of maize. The tephrosia monocropping and the intercropping of this species with maize, regardless of sowing location, provided, respectively, the highest productivities of pods and dry beans of snap beans, compared with pigeon pea pre-cropping.

Comparing the Fungicide Sensitivity of Sclerotinia sclerotiorum Using Mycelial Growth and Ascospore Germination Assays

The infection of the floral tissues of snap bean and other crops by Sclerotinia sclerotiorum, the causative agent of white mold, is by ascospores. Irrespective of the fungicide mode of action being evaluated, in vitro fungicide sensitivity tests are conducted almost exclusively using mycelial growth assays. This is likely due to difficulties and time involved in sclerotial conditioning required to produce apothecia and ascospores. The objective of this research was to compare estimates of fungicide sensitivity between mycelial growth and ascospore germination assays for S. sclerotiorum. Sensitivity assays were conducted using serial doses of three fungicides commonly used to control white mold: boscalid, fluazinam, and thiophanate-methyl. A total of 27 isolates were evaluated in replicated trials conducted for each fungicide and assay type. The effective concentration to reduce mycelial growth or ascospore germination by 50% (EC50) was estimated for each isolate, fungicide, assay type, and trial. The median EC50 values obtained from ascospore germination assays were 52.7, 10.0, and 2.7 times higher than those estimated from the mycelial growth for boscalid, fluazinam, and thiophanate-methyl, respectively. No significant correlation was found between EC50 values estimated by the two methods. These findings highlight differences that may be important in evaluating the sensitivity of S. sclerotiorum given the fungicide mode of action and how they will be used in the field.