Yield Loss Research Articles

Toxicity of Bt Protein on Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) Fed With Corn Leaves in Paraguay

The fall armyworm Spodoptera frugiperda is the most destructive pest in corn cultivation in Paraguay with yield losses of 20 to 70%. The adoption of genetically modified crops (GMO) is a valid technique for managing this pest. The objective of this investigation was to evaluate the toxicity among Bt events used locally; determining mortality and important biological parameters. The S. frugiperda population previously collected from the field was raised under laboratory conditions fed with leaves from events MIR162TM (Vip3A19), VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb), PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) and a treatment with non-maize. Bt BR106TM. The mortality of 120 larvae was evaluated for each treatment and the viability until the adult stage of those larvae that managed to survive the different treatments was observed. A high toxicity effect was verified with 100% mortality of neonatal larvae fed with the MIR162TM (Vip3A19) event; as for the other events, 86% and 61% VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb), and PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) respectively; with 13% mortality for the non-Bt control variety BR106TM. The oviposition period, viability and number of eggs laid in adults surviving the PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) and VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb) events were reduced, affecting the fecundity of the surviving insect population.

Toxicity of Bt Protein on Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) Fed With Corn Leaves in Paraguay

The fall armyworm Spodoptera frugiperda is the most destructive pest in corn cultivation in Paraguay with yield losses of 20 to 70%. The adoption of genetically modified crops (GMO) is a valid technique for managing this pest. The objective of this investigation was to evaluate the toxicity among Bt events used locally; determining mortality and important biological parameters. The S. frugiperda population previously collected from the field was raised under laboratory conditions fed with leaves from events MIR162TM (Vip3A19), VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb), PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) and a treatment with non-maize. Bt BR106TM. The mortality of 120 larvae was evaluated for each treatment and the viability until the adult stage of those larvae that managed to survive the different treatments was observed. A high toxicity effect was verified with 100% mortality of neonatal larvae fed with the MIR162TM (Vip3A19) event; as for the other events, 86% and 61% VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb), and PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) respectively; with 13% mortality for the non-Bt control variety BR106TM. The oviposition period, viability and number of eggs laid in adults surviving the PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) and VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb) events were reduced, affecting the fecundity of the surviving insect population.

Short-term residual effects of occasional tillage on crop performance, soil water, and water-use efficiency in a 10-year no-till system under a dry Mediterranean climate

Conservation Agriculture is a farming system based on no mechanical soil disturbance, permanent soil cover, and crop diversification. A study was carried out in an on-farm field trial set up in Meknes (Morocco) under a long-term no-till (NT) system to evaluate the residual effect of one-time occasional tillage (OT) on crop performance, soil water, and water-use efficiency (WUE) one and two years after OT implementation. Shallow and deep options of OT were compared with common NT practices (with crop residue retention and with crop residue removal) for two consecutive seasons of 2021–2022 (year 1) and 2022–2023 (year 2). The four tillage practices were implemented in November 2020. Three crops were studied each year: durum wheat (Triticum durum), faba bean (Vicia faba minor), and chickpea (Cicer arietinum) all grown under NT in both the years and arranged in four crop rotations. Our findings show that grain yield of wheat and chickpea was negatively affected by OT for all years considered. In wheat, there was a grain yield loss of 18 and 20% for shallow and deep OT, respectively compared to NT with crop residue retention. In chickpea, the grain yield loss was as high as 47 and 49% for shallow and deep OT, respectively. Average soil water storage measured at 0–60 cm at sowing was also lower in deep OT (133 mm) compared to NT with crop residue retention (151 mm) for all years and rotations considered. Yet, in wheat year 1, deep OT slightly improved soil water content at 30 cm depth compared to NT treatments. The comparison of WUE between treatments showed that, under NT with crop residue retention, the crops produced more grain and aboveground biomass per mm of water. Wheat/faba bean rotation had a greater grain yield and WUE (all years considered) and overall greater soil water content (year 1), compared to the wheat/chickpea rotation. The results suggest that the effects of OT on crop performance and water productivity in the short term can be adverse. On the other hand, grain yield of wheat can be improved by a judicious choice of legume to be used as a preceding crop.

Appropriate nitrogen supply and intercropping reduce epidemics, the compound disease of faba bean, and yield and economic losses

Appropriate nitrogen supply and intercropping reduce epidemics, the compound disease of faba bean, and yield and economic losses

Field response and genetic variability of elite spring bread wheat (Triticum aestivum L.) genotypes for septoria tritici blotch under natural infection in Northwest Ethiopia

AbstractFungal diseases cause significant yield loss to wheat production. Septoria tritici blotch (STB), caused by the ascomycete fungus Zymoseptoria trtici, is one of the major fungal diseases affecting wheat production worldwide. In Ethiopia, STB is a severe problem that causes significant yield loss in high and mid‐altitude wheat‐growing areas. The use of resistant varieties is one of the sustainable disease management strategies, particularly for resource‐poor farmers in developing countries. Two hundred and fifty bread wheat genotypes were evaluated to identify septoria tritici resistant genotypes and estimate the extent of genetic variability for resistance to STB and other economically important traits using alpha lattice design under natural infestation in two STB hotspot environments. Analysis of variance revealed highly significant differences among genotypes, environment, and genotype × environment interaction for all traits measured. The genetic coefficient of variance was lower than the phenotypic coefficient of variance for all traits studied, and both test environments showed the influence of the environment on trait expression. High and moderate heritability values were observed for the septoria disease severity parameters, indicating that the STB resistance trait was less influenced by the environment. The days to heading and plant height were inversely correlated with disease severity. This suggests that genotypes with tall plant height and long maturity period could be resistant to septoria tritici blotch through escape mechanisms. Four of the genotypes, namely, G‐215, G‐255, G‐257, and G‐258, were found to be resistant across all locations. These and other promising genotypes will be used in future breeding programmes to select or develop high‐yielding and STB‐resistant bread wheat genotypes that can be deployed in septoria tritici blotch‐prone areas. Highly susceptible genotypes will also be used as controls for STB resistance breeding programmes.

Different control of resistance to two Colletotrichum orbiculare pathogenic races 0 and 1 in cucumber (Cucumis sativus L.).

Quantitative trait locus analysis identified independent novel loci in cucumbers responsible for resistance to races 0 and 1 of the anthracnose fungal pathogen Colletotrichum orbiculare. Cucumbers have been reported to be vulnerable to Colletotrichum orbiculare, causing anthracnose disease with significant yield loss under favorable conditions. The deployment of a single recessive Cssgr gene in cucumber breeding for anthracnose resistance was effective until a recent report on high-virulent strains infecting cucumbers in Japan conquering the resistance. QTL mapping was conducted to identify the resistance loci in the cucumber accession Ban Kyuri (G100) against C. orbiculare strains 104-T and CcM-1 of pathogenic races 0 and 1, respectively. A single dominant locus An5 was detected in the disease resistance hotspot on chromosome 5 for resistance to 104-T. Resistance to CcM-1 was governed by three loci with additive effects located on chromosomes 2 (An2) and 1 (An1.1 and An1.2). Molecular markers were developed based on variant calling between the corresponding QTL regions in the de novo assembly of the G100 genome and the publicly available cucumber genomes. Multiple backcrossed populations were deployed to fine-map An5 locus and narrow the region to approximately 222 kbp. Accumulation of An2 and An1.1 alleles displayed an adequate resistance to CcM-1 strain. This study provides functional molecular markers for pyramiding resistance loci that confer sufficient resistance against anthracnose in cucumbers.

Rice Brown Planthopper, Nilaparvata lugens (Stål) Feeding Behaviour in Resistant NAGINA22 Rice Mutants

Background: Rice (Oryza sativa L.), is an important staple food and an excellent source of calories in India. Of the different insect pests attacking rice, brown planthopper, BPH, Nilaparvata lugens (Stål) is an important sucking pest causing upto 100% yield losses. Host plant resistance is the most important method in keeping BPH under control and understanding the underlying mechanisms of resistance is necessary to breed the resistant varieties with desirable characters. Methods: Selected EMS mutant lines of Nagina22 (N22) variety, which were previously mass screened under controlled greenhouse conditions were assessed for their antixenosis mechanism to brown planthopper feeding by measuring probing marks and honeydew excretion area by following standard procedures and statistical analysis was done by using Statistix 8.1 software. Result: Both the brown planthopper nymphs and adults probed more in the resistant mutants compared to the susceptible mutants whereas the BPH adults probed more times (24.4) compared to the nymphs (22.2). The recorded honeydew excretion area by the resistant mutants was lower than that of susceptible mutants. In general, the BPH adults fed more and excreted more honeydew (79.5 mm2) compared to the nymphs (59.0 mm2). The damage score has a negative correlation with the probing marks of adults (-0.207) and nymphs (-0.411); and a positive correlation with honeydew excretion of adults (0.547) and nymphs (0.200). In this study, the EMS N22 mutants resistant to BPH, with a greater number of probing marks and less honeydew excretion area can serve as best donors in the breeding programmes to develop brown planthopper resistant varieties.

Assessing the Effectiveness of Neem oil and Microalgae in the Management of Cowpea (Vigna unguiculata L.) Leaf Spot Caused by Alternaria spp.

The current study aimed to assess the effectiveness of neem oil and microalgae in controlling leaf spot caused by Alternaria spp. in cowpea (Vigna unguiculataL.). The research was conducted during the Zaid season of 2022 at the Central Research Field of the Department of Plant Pathology, SHUATS, Prayagraj, Uttar Pradesh, using a Randomized Block Design with three replications and seven treatments. Analysis of variance (ANOVA) was utilized to draw conclusions from the data. Leaf spot disease caused by Alternaria spp poses a significant threat to cowpea crops, resulting in yield losses and decreased plant vigor. An in vivo study was carried out to evaluate the impact of different concentrations of microalgae combined with neem oil at 1% on plant growth parameters and Disease Intensity (%). The application of microalgae @540 grams in various splits and neem oil @1% was done. Among all the treatments, T4 (Microalgae 48gms @5 DAS 96gms@15,45 DAS + Neem oil @1% showed promising results. Notably, the T4 treatment significantly increased plant height (84.63 cm) and the number of branches(10.83) at60DAS. Moreover, an increased numberof nodules per plant (21.44) was observed at 75 DAS, indicating improved root health and nitrogen fixation. Additionally, the treatment led to longer pod length (34.44 cm) in three pickings, suggesting enhanced yield potential. Furthermore, the combined application of microalgae and neem oil resulted in a significant reduction in disease intensity, with a notable decrease of 24.47% compared to untreated plants and those treated with chemicals (Bavistin). This indicates that the use of microalgae and neem oil together effectively suppressed leaf spot disease caused by Alternaria spp. in cowpea, thereby improving plant health and productivity. In conclusion, these findings underscore the potential use of eco-friendly alternatives like microalgae and neem oil for managing leaf spot disease in cowpea cultivation. Further research in this area is recommended for sustainable agricultural practices.

Deciphering genetic factors contributing to enhanced resistance against Cercospora leaf blight in soybean (Glycine max L.) using GWAS analysis

Cercospora leaf blight (CLB), caused by Cercospora cf. flagellaris, C. kikuchii, and C. cf. sigesbeckiae, is a significant soybean [Glycine max (L.) Merr.] disease in regions with hot and humid conditions causing yield loss in the United States and Canada. There is limited information regarding resistant soybean cultivars, and there have been marginal efforts to identify the genomic regions underlying resistance to CLB. A Genome-Wide Association Study was conducted using a diverse panel of 460 soybean accessions from maturity groups III to VII to identify the genomic regions associated to the CLB disease. These accessions were evaluated for CLB in different regions of the southeastern United States over 3 years. In total, the study identified 99 Single Nucleotide Polymorphism (SNPs) associated with the disease severity and 85 SNPs associated with disease incidence. Across multiple environments, 47 disease severity SNPs and 23 incidence SNPs were common. Candidate genes within 10 kb of these SNPs were involved in biotic and abiotic stress pathways. This information will contribute to the development of resistant soybean germplasm. Further research is warranted to study the effect of pyramiding desirable genomic regions and investigate the role of identified genes in soybean CLB resistance.

Field screening and identification of biochemical indices of pod borer (Helicoverpa armigera) resistance in chickpea mutants

Chickpea pod borer (CPB) (Helicoverpa armigera) is one of the major pests, causing significant yield losses. The objectives were to screen chickpea mutants for pod borer resistance/tolerance under field conditions and identification of biochemical markers of tolerance. Chickpea mutant CM216-A/15 had highest leaf (25 trichomes/mm2) and stem trichome density (17 trichomes/mm2) with least pod damage at Kallur Kot and highest pod weight per plant (22.8 ± 2.6g) at AZRI. Higher total phenolic contents (TPCs) and antioxidant capacity were detected in tolerant mutants, i.e., CM216-A/15 and CM664/15. TPC was positively associated with pod yield and had negative correlation with pod damage. Mutants CM216-A/15, CM664/15, and CM766/15 depicted the highest resilience to CPB, owing to higher hairiness, better antioxidant defense response, and lower levels of hydrolytic enzymes and sugars. Identified biochemical markers like TPC, total oxidant status, superoxide dismutase, and pigments can be used for screening of CPB-tolerant/resistant mutants.

Developing Economic Injury Levels for Thrips (Frankliniella occidentalis) in Idaho Alfalfa Under Controlled Pest Populations

Thrips are a new pest of alfalfa in Eastern Idaho. University of Idaho Extension Educators studied the yield losses associated with this pest in a controlled greenhouse experiment. This data has been used to calculate the economic injury level (EIL) of thrips in alfalfa. The EIL represents the level of insect infestation at which control measures will begin to be economically viable. We calculate that for the 2021 growing season conditions the EIL was approximately 20 thrips per six stems. We also calculated EIL curves that growers and consultants can use as spray costs and hay values change.

Demystifying the wheat (Triticum aestivum) yield penalty due to delay in sowing: Empirical evidence from eastern India

Wheat (Triticum aestivum L.) yield in Indo-Gangetic plain of eastern India is much less than its actual potential. Apart from several yield deterministic factors, late sowing of wheat is one of the major reasons for sub-optimal wheat yield. The persistent yield gap poses a threat to future food security of this region with a vast population that is growing rapidly. In the present research, an attempt was made to quantify and classify the yield losses in wheat due to late sowing which is prevalent in this part of India. On-farm participatory agronomic trial was conducted at 1073 plots in 3 districts of eastern India, 2 from Uttar Pradesh and 1 from the state of Bihar. The trial was conducted during four consecutive winter season from 2016–17 to 2019–20. Following a split-plot design, main plots were categorized based on wheat sowing time and sub-plots were classified depending on the wheat varietal class. A sample survey of randomly selected 629 wheat farmers was conducted in 2017–18 wheat season in these 3 districts. Results from the agronomic trial showed that wheat yield decreased by 58 kg/ha for every one-day delay in sowing. Moreover, the yield of long-duration improved wheat variety (HD-2967) was statistically same (P=0.479) compared to the most preferred short-duration variety (PBW-373) in a very late-sown scenario (late December). Farmers’ survey data reconfirmed that the wheat yield has a very strong negative correlation with the sowing dates, but the yield decline was statistically insignificant until mid-November. Wheat yield in this part of India can be adequately boosted if sowing time of wheat advances and adoption of long-duration improved wheat varieties improves.

Precision mapping and expression analysis of recessive bacterial blight resistance gene xa-45(t) from Oryza glaberrima.

Bacterial blight, caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most devastating diseases of rice leading to huge yield losses in Southeast Asia. The recessive resistance gene xa-45(t) from Oryza glaberrima IRGC102600B, mapped on rice chromosome 8, spans 80Kb with 9 candidate genes on Nipponbare reference genome IRGSP-1.0. The xa-45(t) gene provides durable resistance against all the ten Xanthomonas pathotypes of Northern India, thus aiding in the expansion of recessive bacterial blight resistance gene pool. Punjab Rice PR127, carrying xa-45(t), was released for wider use in breeding programs. This study aims to precisely locate the target gene among the 9 candidates conferring resistance to bacterial blight disease. Sanger sequencing of all nine candidate genes revealed seven SNPs and an Indel between the susceptible parent Pusa 44 and the resistant introgression line IL274. The genotyping with polymorphic markers identified three recombinant breakpoints for LOC_Os08g42370, and LOC_Os08g42400, 15 recombinants for LOC_Os08g423420 and 26 for LOC_Os08g42440 out of 190 individuals. Relative expression analysis across six time intervals (0, 8, 24, 48, 72, and 96h) after bacterial blight infection showed over expression of LOC_Os08g42410-specific transcripts in IL274 compared to Pusa 44, with a significant 4.46-fold increase observed at 72h post-inoculation. The Indel marker at the locus LOC_Os08g42410 was found co-segregating with the phenotype, suggesting its candidacy towards xa-45(t). The transcript abundance assay provides strong evidence for the involvement of LOC_Os08g42410 in the resistance conferred by the bacterial blight gene xa-45(t).

Preharvest Sprouting in Quinoa: A New Screening Method Adapted to Panicles and GWAS Components

The introduction of quinoa into new growing regions and environments is of interest to farmers, consumers, and stakeholders around the world. Many plant breeding programs have already started to adapt quinoa to the environmental and agronomic conditions of their local fields. Formal quinoa breeding efforts in Washington State started in 2010, led by Professor Kevin Murphy out of Washington State University. Preharvest sprouting appeared as the primary obstacle to increased production in the coastal regions of the Pacific Northwest. Preharvest sprouting (PHS) is the undesirable sprouting of seeds that occurs before harvest, is triggered by rain or humid conditions, and is responsible for yield losses and lower nutrition in cereal grains. PHS has been extensively studied in wheat, barley, and rice, but there are limited reports for quinoa, partly because it has only recently emerged as a problem. This study aimed to better understand PHS in quinoa by adapting a PHS screening method commonly used in cereals. This involved carrying out panicle-wetting tests and developing a scoring scale specific for panicles to quantify sprouting. Assessment of the trait was performed in a diversity panel (N = 336), and the resulting phenotypes were used to create PHS tolerance rankings and undertake a GWAS analysis (n = 279). Our findings indicate that PHS occurred at varying degrees across a subset of the quinoa germplasm tested and that it is possible to access PHS tolerance from natural sources. Ultimately, these genotypes can be used as parental lines in future breeding programs aiming to incorporate tolerance to PHS.

A New Dataset and Comparative Study for Aphid Cluster Detection and Segmentation in Sorghum Fields

Aphid infestations are one of the primary causes of extensive damage to wheat and sorghum fields and are one of the most common vectors for plant viruses, resulting in significant agricultural yield losses. To address this problem, farmers often employ the inefficient use of harmful chemical pesticides that have negative health and environmental impacts. As a result, a large amount of pesticide is wasted on areas without significant pest infestation. This brings to attention the urgent need for an intelligent autonomous system that can locate and spray sufficiently large infestations selectively within the complex crop canopies. We have developed a large multi-scale dataset for aphid cluster detection and segmentation, collected from actual sorghum fields and meticulously annotated to include clusters of aphids. Our dataset comprises a total of 54,742 image patches, showcasing a variety of viewpoints, diverse lighting conditions, and multiple scales, highlighting its effectiveness for real-world applications. In this study, we trained and evaluated four real-time semantic segmentation models and three object detection models specifically for aphid cluster segmentation and detection. Considering the balance between accuracy and efficiency, Fast-SCNN delivered the most effective segmentation results, achieving 80.46% mean precision, 81.21% mean recall, and 91.66 frames per second (FPS). For object detection, RT-DETR exhibited the best overall performance with a 61.63% mean average precision (mAP), 92.6% mean recall, and 72.55 on an NVIDIA V100 GPU. Our experiments further indicate that aphid cluster segmentation is more suitable for assessing aphid infestations than using detection models.

Accumulation of Hydrogen Peroxide in Flag Leaves Induces Effective Regeneration of Triticale During Rehydration After Water Stress

AbstractA key element in the effective recovery of plants after drought is slowing down of their senescence accelerated during the drought. Therefore, in this paper the relationships between hydrogen peroxide content and effective recovery during rehydration after water stress were analyzed. The study focused on two DH lines of winter triticale with different regeneration potential, as shown by different numbers of lateral stems with ears, grown during rehydration after water stress. During rehydration, the GZDH27 line grows two to three lateral stems with ears, whereas the GZDH88 line grows a single lateral stem with ear. The two DH lines of winter triticale showed comparable responses to the drought stress but their responses to rehydration after the drought stress were clearly different. Results revealed, that the increased accumulation of hydrogen peroxide, which was induced during the drought, can be maintained during rehydration, thus stimulating plant senescence. In the line GZDH88, rehydration did not slow down drought-induced senescence. This was manifested by higher levels of hydrogen peroxide, accompanied by lower levels of chlorophyll in the flag leaves of GZDH88 plants, as the result of which only one lateral stem was formed during rehydration. However, development of one lateral stems during rehydration in the GZDH88 line allowed for smaller yield loss than in the GZDH77 line, that developed of three lateral stems during rehydration. The efficient production of carbohydrates and their effective allocation into the ears of the lateral stems required considerable energy expenditure in the GZDH27 line. Our results indicate that growing three lateral stems with ears during rehydration does not guarantee limitation of grain yield loss. However, to reach the final conclusion, it is important to evaluate a greater number of triticale genotypes under drought stress and rehydration during various stages of a plants development.

First Report of Xanthomonas perforans Causing Bacterial Spot of Pepper (Capsicum annuum) in North Carolina.

North Carolina (NC) is the fifth largest producer of bell pepper (Capsicum annuum) in the US with an estimated 2,400 acres in production (NASS-USDA, 2022). A survey of bacterial diseases of peppers was initiated in 2020 after numerous bacterial spot outbreaks were reported in NC. Bacterial spot is caused by a complex of four Xanthomonads: X. euvesicatoria, X. vesicatoria, X. perforans, and X. hortorum pv. gardneri (Larrahondo-Rodríguez et al., 2022). If not preemptively managed, bacterial spot can cause up to 40% yield loss (Kousik and Ritchie, 1998). During the 2020 and 2021 growing seasons, 103 yellow mucoid colonies were isolated from plants representing 51 pepper cultivars symptomatic of bacterial spot, i.e., water-soaked leaf lesions that become necrotic spots on leaves and fruits across 22 commercial fields in NC following published methods (Klein-Gordon et al., 2021). All colonies were characterized to species using the qPCR species-specific primers and probes described by Strayer et al. 2016. Of the 103 colonies, 12 isolates tested positive for X. perforans. To confirm qPCR results, a Multi-Locus Sequence Analysis (MLSA) was run using fusA, gapA, gltA, gyrB, and lacF following previously described methods (Almeida et al., 2010) on three representative isolates: AHX61, collected in September 2020 from a field with 20% disease severity in Wake County on cv. Canary Bell; AHX261, collected in July 2021 from a field with 50% disease severity in Sampson County on Jalapeño; and AHX426, collected in August 2021 from a field with 50% disease severity in Dublin County on Jalapeño. All gene sequences were deposited to NCBI (GenBank Accessions: OQ799538-OQ799552) and compared to those from X. euvesicatoria, X. hortorum pv. gardneri, X. perforans, and X. vesicatoria type strains (Almeida et al., 2010). The MLSA showed AHX61, AHX261, and AHX426 cluster with X. perforans ICMP16690T, sharing 99-100% nucleotide similarity. Koch's postulates were performed with the three strains, Xp1484T [ X. perforans type strain, (Wilson 1987)], and water as a negative control. Three 10-week-old bell pepper plants (cv. Early Cal Wonder) were dip-inoculated in 600 mL of a bacterial suspension at an OD600 of 0.3 (~5x108 CFU/mL) and 0.04% Silwet L-77 per strain or water. All 18 plants were individually incubated in a plastic bag for 48 h post-inoculation at 28°C, 80% relative humidity, and 14 h:10 h light-dark cycle in a growth chamber, after which plastic bags were removed. Water-soaking and necrotic spots characteristic of bacterial spot were first observed at six days post-inoculation (dpi). At 14 dpi, symptomatic leaves were removed from treated plants to attempt pathogen re-isolation. Yellow mucoid colonies similar in morphology to those originally inoculated were recovered from all plants and confirmed to be X. perforans through sequencing; no isolates were recovered from water-treated plants. To our knowledge, this is the first time X. perforans is isolated in commercial bell pepper and specialty pepper fields in the state. This is an indication that the Xanthomonas population on peppers in the state is more diverse than previously reported and that pathogen populations will require monitoring for possible species shifts for this crop in NC.

Use of modelling tools to assess climate change impacts on smallholder oil seed yields in South Africa.

Oil seed crops are the second most important field crops after cereals in the agricultural economy globally. The use and demand for oilseed crops such as groundnut, soybean and sunflower have grown significantly, but climate change is expected to alter the agroecological conditions required for oilseed crop production. This study aims to present an approach that utilizes decision-making tools to assess the potential climate change impacts on groundnut, soybean and sunflower yields and the greenhouse gas emissions from the management of the crops. The Decision Support Tool for Agrotechnology Transfer (DSSAT v4.7), a dynamic crop model and the Cool Farm Tool, a GHG calculator, was used to simulate yields and estimate GHG emissions from these crops, respectively. Four representative concentration pathways (RCPs 2.6, 4.5, 6.0, and 8.5), three nitrogen (0, 75, and 150 kg/ha) and phosphorous (0, 30 and 60 P kg/ha) fertilizer rates at three sites in Limpopo, South Africa (Ofcolaco, Syferkuil and Punda Maria) were used in field trials for calibrating the models. The highest yield was achieved by sunflower across all crops, years and sites. Soybean yield is projected to decrease across all sites and scenarios by 2030 and 2050, except at Ofcolaco, where yield increases of at least 15.6% is projected under the RCP 4.5 scenario. Positive climate change impacts are predicted for groundnut at Ofcolaco and Syferkuil by 2030 and 2050, while negative impacts with losses of up to 50% are projected under RCP8.5 by 2050 at Punda Maria. Sunflower yield is projected to decrease across all sites and scenarios by 2030 and 2050. A comparison of the climate change impacts across sites shows that groundnut yield is projected to increase under climate change while notable yield losses are projected for sunflower and soybean. GHG emissions from the management of each crop showed that sunflower and groundnut production had the highest and lowest emissions across all sites respectively. With positive climate change impacts, a reduction of GHG emissions per ton per hectare was projected for groundnuts at Ofcolaco and Syferkuil and for sunflower in Ofcolaco in the future. However, the carbon footprint from groundnut is expected to increase by 40 to 107% in Punda Maria for the period up to 2030 and between 70-250% for 2050, with sunflower following a similar trend. We conclude that climate change will potentially reduce yield for oilseed crops while management will increase emissions. Therefore, in designing adaptation measures, there is a need to consider emission effects to gain a holistic understanding of how both climate change impacts on crops and mitigation efforts could be targeted.

Re-evaluating soil moisture-based drought criteria for rainfed crops in peninsular India

Background: Peninsular India, being completely under the influence of monsoonal climate, suffers crop yield variability due to rainfall distribution-induced soil moisture constraints. Timely and appropriate assessment of this rainfall and soil moisture-induced crop yield variability serves as a key for exemplary relief assistance. Per cent available soil moisture (PASM) is one among several drought declaration indices followed by stakeholders in India for declaration of drought, needs re-evaluation as the existing criteria in unable to capture the yield loss due to ineffective classification of PASM categories. This study attempts to revise the agricultural drought classes by PASM based on relationships established between yield of major rainfed crops of the study region and PASM.Methods: Analysis of yield variability due to PASM was carried out based on long term observations in experiments conducted at five dry farming locations (Akola, Parbhani, Kovilpatti, Ananthapuramu and Bengaluru) of peninsular India. The average yield for each category of PASM was calculated and tabulated for regression analysis. The PASM versus yield in each group was correlated and regression equations were developed if significant positive correlations were established.Results: The range of available soil moisture to obtain at least 50 percent of optimum yield in cereals (maize: 26 and finger millet: 52.9 PASM), pulses (pigeon pea: 37.2 PASM), oilseeds (soybean: 26.8 to 30.5, groundnut: 53.8 to 61.7 PASM) and commercial crops (cotton: 26.3 PASM) was 26–61 percent.Conclusion: The revised PASM-based drought classes (0–50 severe; 51–75 mild and 76–100 no drought) would help in drought declaration and precise identification of drought-hit areas for meaningful relief assistance. However, there is further investigation is needed to include a soil component for further fine-tuning of the criteria.

Bacterial blight: Once a menacing disease of cotton in India, now tamed and fading from research spotlight

AbstractBacterial blight, incited by Xanthomonas citri pv. malvacearum (Xcm), is historically one of the most devastating diseases of cotton globally. In India, the initial documentation of the disease dates back to 1918 and it assumed a great magnitude after 1947, primarily triggered by cultivation of tetraploid cotton, as the earlier cultivated indigenous diploid cotton was naturally resistant to the pathogen, and became widespread during the 1970s. Among 20 races of bacterial blight pathogen documented at global level, Race 18 is the most virulent one and prominent in India. The pathogen inflicts damage at all crop stages, beginning with seedlings. The disease caused regular yield losses of 30%–35% in India and had become a formidable adversary to cotton cultivation in the country; however, over the years its appearance diminished. Much larger gains were apparently achieved when disease was managed with a combination of seed treatment, foliar sprays and bio‐agents. Furthermore, extensive breeding programmes led to development of resistant cultivars, which proved instrumental in managing the disease. The disease exhibited a sharp decline from the beginning of the 21st century and is now no longer a chronic problem in India. This comprehensive review attempts to provide insight into the dynamic nature of bacterial blight threatening cotton cultivation in India during the last century and the underpinning multifaceted research efforts that paved the way for countering the disease. An attempt is made to discuss the qualitative and quantitative studies on genetics of bacterial blight for facilitating the breeding programmes.