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Chili peppers (Capsicum annuum L.) are an economically important crop worldwide. Pepper yellow leaf curl Thailand virus (PepYLCTHV), a Begomovirus causing yellow leaf mosaic disease of chili pepper, has been reported to incur 95% economic loss under epiphytotic conditions. Thirty-one chili genotypes were screened for resistance to PepYLCTHV disease through inoculation using 10–15 viruliferous whiteflies per plant. We purified two resistant lines (PEP6 and PEP12) through four generations of selfing and selection. At 28 days after inoculations, two chili genotypes (PEP6 and PEP12) had low disease severity and percentage of disease incidence (DI) compared to four susceptible checks, viz., Yodsonkeam80, Homsupan, Huareau12, and Pong Charian, which had a disease severity score of 5 with 100% DI. Thirty initial plants of PEP6 showed an average disease severity of 3.64 with 69.33% DI, and PEP12 showed an average disease severity of 3.83 with 77.67% DI. From these populations, we selected nine highly resistant plant of PEP6 and seven plants of PEP12 having a disease severity of 0 through pure-line selection for four selfing generations. The ratio of resistance (R) to susceptibility (S) consequently decreased. In PEP6, the ratio decreased from 1R:2S to 1R:1S, while in PEP12 the ratio decreased from 1R:3S to 1R:1S. These lines have potential for release as resistant lines for improving chili pepper resistance to PepYLCTHV and for developing makers associated with the resistant trait. [ABSTRACT FROM AUTHOR]

Sesame Fusarium wilt (SFW), caused by Fusarium oxysporum f. sp. sesami (Fos), is one of the most devastating diseases affecting sesame cultivation. Deciphering the genetic control of SFW resistance is pivotal for effective disease management in sesame. An inheritance study on a cross between the highly resistant variety Yuzhi 11 and the highly susceptible accession Sp1 using a Fos pathogenicity group 1 isolate indicated that resistance was conferred by a single dominant allele. The target locus was located in a 1.24 Mb interval on chromosome 3 using a combination of cross-population association mapping and bulked segregant analysis. Fine genetic mapping further narrowed the interval between 21,350 and 21,401 kb. The locus Sindi_0812400 was identified as the SFW resistance gene and officially designated SiRLK1. This gene encodes a specific malectin/receptor-like protein kinase with three putative tandem kinase domains and is considered a kinase fusion protein. Sequence analysis revealed that a high proportion (49.44%) of variants within the locus was located within the kinase domain III, and several of which were evidently associated with the diversity in SFW response, indicating the critical role of kinase domain III in expression of disease resistance. These findings provide valuable information for further functional analysis of SFW resistance genes and marker-assisted resistance breeding in sesame.

Wheat powdery mildew is a fungal disorder caused by Blumeria graminis f. sp. tritici (Bgt) and is a severe and significant threat to the yield and quality of its host. The most practical and environmentally friendly approach to controlling this disease is through resistance gene identification to develop resistant varieties. Wild germplasm relatives of wheat are a valuable reservoir of genes contributing to resistance against powdery mildew. In our study, we identified the Aegilops tauschii germplasm "KU-2013", exhibiting seedling resistance to Bgt isolate E09 following hexaploidization. Genetic analysis and chromosomal localization of the powdery mildew resistance gene in doubled haploid (DH) KU-2013 indicated that the disease resistance gene in DHKU-2013 is governed by a dominant gene situated in 5DS, tentatively named PmKu-2013. Following the analysis of PmKu-2013 relative to the genes at the Pm2 locus, it was inferred that PmKu-2013 represented a distinct novel gene separate from Pm2. Using molecular marker analysis, PmKu-2013 was found to be ultimately mapped between the sdau5DS5-3 and sdau5DS6-1 markers, with genetic distances of 0.6 cM and 1.3 cM, respectively. Using markers tightly linked to PmKu-2013, the genotypes of core wheat varieties from various regions were identified, laying the foundation for the transfer and utilization of PmKu-2013 in molecular-assisted selection (MAS) for breeding. [ABSTRACT FROM AUTHOR]

Chili peppers (Capsicum annuum L.) are an economically important crop worldwide. Pepper yellow leaf curl Thailand virus (PepYLCTHV), a Begomovirus causing yellow leaf mosaic disease of chili pepper, has been reported to incur 95% economic loss under epiphytotic conditions. Thirty-one chili genotypes were screened for resistance to PepYLCTHV disease through inoculation using 10–15 viruliferous whiteflies per plant. We purified two resistant lines (PEP6 and PEP12) through four generations of selfing and selection. At 28 days after inoculations, two chili genotypes (PEP6 and PEP12) had low disease severity and percentage of disease incidence (DI) compared to four susceptible checks, viz., Yodsonkeam80, Homsupan, Huareau12, and Pong Charian, which had a disease severity score of 5 with 100% DI. Thirty initial plants of PEP6 showed an average disease severity of 3.64 with 69.33% DI, and PEP12 showed an average disease severity of 3.83 with 77.67% DI. From these populations, we selected nine highly resistant plant of PEP6 and seven plants of PEP12 having a disease severity of 0 through pure-line selection for four selfing generations. The ratio of resistance (R) to susceptibility (S) consequently decreased. In PEP6, the ratio decreased from 1R:2S to 1R:1S, while in PEP12 the ratio decreased from 1R:3S to 1R:1S. These lines have potential for release as resistant lines for improving chili pepper resistance to PepYLCTHV and for developing makers associated with the resistant trait.

Wheat powdery mildew is a fungal disorder caused by Blumeria graminis f. sp. tritici (Bgt) and is a severe and significant threat to the yield and quality of its host. The most practical and environmentally friendly approach to controlling this disease is through resistance gene identification to develop resistant varieties. Wild germplasm relatives of wheat are a valuable reservoir of genes contributing to resistance against powdery mildew. In our study, we identified the Aegilops tauschii germplasm “KU-2013”, exhibiting seedling resistance to Bgt isolate E09 following hexaploidization. Genetic analysis and chromosomal localization of the powdery mildew resistance gene in doubled haploid (DH) KU-2013 indicated that the disease resistance gene in DHKU-2013 is governed by a dominant gene situated in 5DS, tentatively named PmKu-2013. Following the analysis of PmKu-2013 relative to the genes at the Pm2 locus, it was inferred that PmKu-2013 represented a distinct novel gene separate from Pm2. Using molecular marker analysis, PmKu-2013 was found to be ultimately mapped between the sdau5DS5-3 and sdau5DS6-1 markers, with genetic distances of 0.6 cM and 1.3 cM, respectively. Using markers tightly linked to PmKu-2013, the genotypes of core wheat varieties from various regions were identified, laying the foundation for the transfer and utilization of PmKu-2013 in molecular-assisted selection (MAS) for breeding.

The cucurbit powdery mildew (CPM) caused by different fungal species is a major concern for cucurbit crops around the world. In Argentina CPM constitutes the most common and damaging disease for cucurbits, especially for squash crops (Cucurbita moschata). The present study displays initial insights into the knowledge of the disease in western Argentina, including the determination of the prevalent species causing CPM, as well as the evaluation of the resistance of squash cultivars and breeding lines. Fungal colonies were isolated from samples collected in Mendoza province, Argentina. A field trial was also performed to assess the resistance of five squash accessions, including commercial cultivars and breeding lines. The severity of CPM was analyzed and epidemiological models were built based on empirical data. The morphological determinations and analysis with specific molecular markers confirmed Podosphaera xanthi as the prevalent causal agent of CPM in Mendoza. The results od the field trial showed differences in the resistance trait among the squash accessions. The advanced breeding line BL717/1 showed promising results as source of CPM resistance for the future development of open pollinated resistant cultivars, a crucial tool for an integrative control of the disease.

Genetic diversity is vital for the survival of any population. If humans were all the same, a single strain of a nasty flu virus, like COVID-19, could wipe us all out! In plants, genetic diversity plays a similar role. The variation in the type and number of resistance gene(s) between individuals can cause the difference between surviving a disease or not. Studies on genetic diversity will lead to the identification of novel disease-resistance genes. Canola (Brassica napus L.) is an economically and nutritionally important oilseed worldwide. Several serious diseases, including blackleg, clubroot, sclerotinia stem rot, and verticillium stripe, threaten canola production in Canada and worldwide. Traditional methods are not enough for effective control of these diseases. Therefore, the ideal approach is to optimize and utilize the resistance genes found in different B. napus cultivars. With the advent of next-generation sequencing and the development of genomics and molecular genetics techniques, it is now possible to rapidly identify and apply resistance genes. This paper reviews current information about disease-resistance genes identified in B. napus cultivars, mapping and cloning, their importance, role and function, and their association with plant disease resistance and application in resistance breeding. The feasibility of using current resistance sources in Canadian cultivars for developing new disease-resistant cultivars is also discussed. Sustainability of a farm and an agricultural system could be maintained by breeding for disease resistance, including the resistant varieties and incorporating other integrated pest management strategies along with it. [ABSTRACT FROM AUTHOR]

Simple Summary: Plants, unlike animals, do not have defender cells or an adaptive immune system. Instead, plants rely on each cell's innate immunity and systemic signals emitted from infection sites. On the other hand, not all plants, even within the same species, are genetically identical, and their genetic backgrounds determine how well they respond to stress factors. Through evolution, plants have acquired various defense mechanisms that play important roles in the never-ending fight between plants and pathogens. Genetic variation in relation to plant disease resistance can thus be contextualized to provide new insights into these defense mechanisms and evolutionary processes that lead to resistance to pathogens. By focusing on genetic variations and mutational events linked with plant–pathogen interactions, the paper explores how genome compartments facilitate plant and pathogen evolutionary processes. Phytopathologists are actively researching the molecular basis of plant–pathogen interactions. The mechanisms of responses to pathogens have been studied extensively in model crop plant species and natural populations. Today, with the rapid expansion of genomic technologies such as DNA sequencing, transcriptomics, proteomics, and metabolomics, as well as the development of new methods and protocols, data analysis, and bioinformatics, it is now possible to assess the role of genetic variation in plant–microbe interactions and to understand the underlying molecular mechanisms of plant defense and microbe pathogenicity with ever-greater resolution and accuracy. Genetic variation is an important force in evolution that enables organisms to survive in stressful environments. Moreover, understanding the role of genetic variation and mutational events is essential for crop breeders to produce improved cultivars. This review focuses on genetic variations and mutational events associated with plant–pathogen interactions and discusses how these genome compartments enhance plants' and pathogens' evolutionary processes. [ABSTRACT FROM AUTHOR]

Aflatoxin contamination is common in several crops, including maize, in warm agricultural areas. For over 40 years, there have been many efforts to develop maize germplasm with resistance to aflatoxin contamination produced by Aspergillus flavus Link:Fr. In Mexico, there are native maize landraces (MLRs) with superior resistance to both aflatoxin contamination and kernel rot by A. flavus. Resistance mechanisms for some MLRs have been characterized. We investigated whether MLRs vary in susceptibility to multiple members of several aflatoxin-producing species and if resistance is affected by length of the infection period. Results indicate significant differences (P < 0.05) in abilities to produce aflatoxin within and among aflatoxin-producing fungi in two MLRs during two infection periods. There were also significant (P < 0.05) differences among several MLRs and a commercial hybrid control to both aflatoxin accumulation and kernel rot in laboratory assays over a 25-day period. The current results suggest breeding for aflatoxin resistance in maize should include several variables. To be broadly useful, commercially acceptable resistant maize germplasm must be resistant to diverse aflatoxin-producing species over time frames and under conditions the maize is exposed to both in the field and during storage. [ABSTRACT FROM AUTHOR]

Twenty-three wheat genotypes were evaluated for stripe and leaf rusts, caused by Puccinia striiformis f. sp. tritici and Puccinia triticina f. sp. tritici, respectively, at seedling and adult stages under greenhouses and field conditions during the 2019/2020 and 2020/2021 growing seasons. The race analysis revealed that 250E254 and TTTST races for stripe and leaf rusts, respectively were the most aggressive. Eight wheat genotypes (Misr-3, Misr-4, Giza-171, Gemmeiza-12, Lr34/Yr18, Lr37/Yr17, Lr46/Yr29, and Lr67/Yr46) were resistant to stripe and leaf rusts at seedling and adult stages. This result was confirmed by identifying the resistance genes: Lr34/Yr18, Lr37/Yr17, Lr46/Yr29, and Lr67/Yr46 in these genotypes showing their role in the resistance. Sids-14 and Shandweel-1 genotypes were susceptible to stripe and leaf rusts. Twelve crosses between the two new susceptible wheat genotypes and the three slow rusting genes (Lr34/Yr18, Lr37/Yr17, and Lr67/Yr46) were conducted. The frequency distribution of disease severity (%) in F2 plants of the twelve crosses was ranged from 0 to 80%. Resistant F2 plants were selected and the resistance genes were detected. This study is important for introducing new active resistance genes into the breeding programs and preserving diversity among recently released wheat genotypes. [ABSTRACT FROM AUTHOR]

Keywords: breeding for resistance; durability of resistance; pathogen populations; resistance location; integrated management; yield; quality; wheat EN breeding for resistance durability of resistance pathogen populations resistance location integrated management yield quality wheat N.PAG N.PAG 5 04/10/21 20210330 NES 210330 Introduction to Wheat Diseases Agriculture in 2050 will need to produce about 50% more food because of the increase in the world population and the change in diets (FAO, [5]). Furthermore, 79 genes and more than 200 QTL were found for leaf rust and 82 genes and 140 QTL for stripe rust in the seedling and adult stages, respectively. Changes of races and virulence genes in Puccinia striiformis f. sp. tritici, the wheat stripe rust pathogen, in the United States from 1968 to 2009. Fabre et al. reported that some crop mechanisms and the expression of specific genes are needed to stimulate this disease, reviewing recent findings on the existence of wheat susceptibility factors, the role of phytohormones on its development and the role of the effectors such as DON in the susceptibility. [Extracted from the article]

Phytopathologists are actively researching the molecular basis of plant–pathogen interactions. The mechanisms of responses to pathogens have been studied extensively in model crop plant species and natural populations. Today, with the rapid expansion of genomic technologies such as DNA sequencing, transcriptomics, proteomics, and metabolomics, as well as the development of new methods and protocols, data analysis, and bioinformatics, it is now possible to assess the role of genetic variation in plant–microbe interactions and to understand the underlying molecular mechanisms of plant defense and microbe pathogenicity with ever-greater resolution and accuracy. Genetic variation is an important force in evolution that enables organisms to survive in stressful environments. Moreover, understanding the role of genetic variation and mutational events is essential for crop breeders to produce improved cultivars. This review focuses on genetic variations and mutational events associated with plant–pathogen interactions and discusses how these genome compartments enhance plants’ and pathogens’ evolutionary processes.

Common bacterial blight (CBB) caused by Xanthomonas axonopodis pv. phaseoli and X. axonopodis pv. phaseoli var. fuscans is one of the major biotic constraints limiting common bean (Phaseolus vulgaris L.) production and productivity in Ethiopia. The objective of this study was to identify new sources of CBB resistance from a diverse panel of genotypes to develop CBB‐resistant common bean varieties. One hundred and ten diverse accessions were evaluated for CBB resistance at three hotspot sites (Melkassa, Arsi Negelle and Mieso) for two seasons (2017 and 2018) in Ethiopia. Data on mean disease severity on leaf (SL) and mean disease severity on pod (SP), the area under disease progress curve (AUDPC), number of pods per plant (PP), number of seeds per pod (SPP) and grain yield (GY) were collected. Data were subjected to standard analysis of variance and principal component analysis. The genotype × site interaction (G × E) had significant (p <.05) effect on all assessed traits. This indicated the presence of marked variation among tested genotypes in CBB resistance across the testing sites. Genotypes including SEC21, SEC23, SMC21, VAX6, SEC12, SEC25, SMC22, VAX5, SEC20, SEC22, SEC24, SEC26, SMC16 SMC24, VAX6, SEC25, SEC21, SEC23 and SMC21 exhibited lower values of SL, SP and AUDPC which are useful genetic resources for future CBB resistance breeding programmes. Nasir provided a grain yield of 3.45 ton/ha followed by VAX1 (2.86 ton/ha) and Hawassa Dume (2.83 ton/ha). Further, CBB‐resistant and high yielding genotypes had the higher PPP and SPP making them ideal candidates for common bean breeding in Ethiopia or similar agro‐ecologies emphasizing CBB resistance and enhanced agronomic traits. [ABSTRACT FROM AUTHOR]

Maize is a staple for billions across the globe. However, in tropical and sub-tropical regions, maize is frequently contaminated with aflatoxins by Aspergillus section Flavi fungi. There is an ongoing search for sources of aflatoxin resistance in maize to reduce continuous exposures of human populations to those dangerous mycotoxins. Large variability in susceptibility to aflatoxin contamination exists within maize germplasm. In Mexico, several maize landrace (MLR) accessions possess superior resistance to both Aspergillus infection and aflatoxin contamination but their mechanisms of resistance have not been reported. Influences of kernel integrity on resistance of four resistant and four susceptible MLR accessions were evaluated in laboratory assays. Wounds significantly (P < 0.05) increased susceptibility to aflatoxin contamination even when kernel viability was unaffected. Treatments supporting greater A. flavus reproduction did not (P > 0.05) proportionally support higher aflatoxin accumulation suggesting differential influences by some resistance factors between sporulation and aflatoxin biosynthesis. Physical barriers (i.e., wax and cuticle) prevented both aflatoxin accumulation and A. flavus sporulation in a highly resistant MLR accession. In addition, influence of temperature on aflatoxin contamination was evaluated in both viable and non-viable kernels of a resistant and a susceptible MLR accession, and a commercial hybrid. Both temperature and living embryo status influenced (P < 0.05) resistance to both aflatoxin accumulation and A. flavus sporulation. Lower sporulation on MLR accessions suggests their utilization would result in reduced speed of propagation and associated epidemic increases in disease both in the field and throughout storage. Results from the current study should encourage researchers across the globe to exploit the large potential that MLRs offer to breed for aflatoxin resistant maize. Furthermore, the studies provide support to the importance of resistance based on the living host and maintaining living status to reducing episodes of post-harvest contamination.

Maize is a staple for billions across the globe. However, in tropical and sub-tropical regions, maize is frequently contaminated with aflatoxins by Aspergillus section Flavi fungi. There is an ongoing search for sources of aflatoxin resistance in maize to reduce continuous exposures of human populations to those dangerous mycotoxins. Large variability in susceptibility to aflatoxin contamination exists within maize germplasm. In Mexico, several maize landrace (MLR) accessions possess superior resistance to both Aspergillus infection and aflatoxin contamination but their mechanisms of resistance have not been reported. Influences of kernel integrity on resistance of four resistant and four susceptible MLR accessions were evaluated in laboratory assays. Wounds significantly (P < 0.05) increased susceptibility to aflatoxin contamination even when kernel viability was unaffected. Treatments supporting greater A. flavus reproduction did not (P > 0.05) proportionally support higher aflatoxin accumulation suggesting differential influences by some resistance factors between sporulation and aflatoxin biosynthesis. Physical barriers (i.e., wax and cuticle) prevented both aflatoxin accumulation and A. flavus sporulation in a highly resistant MLR accession. In addition, influence of temperature on aflatoxin contamination was evaluated in both viable and non-viable kernels of a resistant and a susceptible MLR accession, and a commercial hybrid. Both temperature and living embryo status influenced (P < 0.05) resistance to both aflatoxin accumulation and A. flavus sporulation. Lower sporulation on MLR accessions suggests their utilization would result in reduced speed of propagation and associated epidemic increases in disease both in the field and throughout storage. Results from the current study should encourage researchers across the globe to exploit the large potential that MLRs offer to breed for aflatoxin resistant maize. Furthermore, the studies provide support to the importance of resistance based on the living host and maintaining living status to reducing episodes of post-harvest contamination. [ABSTRACT FROM AUTHOR]

Twenty-three wheat genotypes were evaluated for stripe and leaf rusts, caused by Puccinia striiformis f. sp. tritici and Puccinia triticina f. sp. tritici, respectively, at seedling and adult stages under greenhouses and field conditions during the 2019/2020 and 2020/2021 growing seasons. The race analysis revealed that 250E254 and TTTST races for stripe and leaf rusts, respectively were the most aggressive. Eight wheat genotypes (Misr-3, Misr-4, Giza-171, Gemmeiza-12, Lr34/Yr18, Lr37/Yr17, Lr46/Yr29, and Lr67/Yr46) were resistant to stripe and leaf rusts at seedling and adult stages. This result was confirmed by identifying the resistance genes: Lr34/Yr18, Lr37/Yr17, Lr46/Yr29, and Lr67/Yr46 in these genotypes showing their role in the resistance. Sids-14 and Shandweel-1 genotypes were susceptible to stripe and leaf rusts. Twelve crosses between the two new susceptible wheat genotypes and the three slow rusting genes (Lr34/Yr18, Lr37/Yr17, and Lr67/Yr46) were conducted. The frequency distribution of disease severity (%) in F2 plants of the twelve crosses was ranged from 0 to 80%. Resistant F2 plants were selected and the resistance genes were detected. This study is important for introducing new active resistance genes into the breeding programs and preserving diversity among recently released wheat genotypes.

Verticillium wilt of olive (VWO), caused by the soil-borne pathogen Verticillium dahliae, is considered one of the most important diseases affecting this tree crop. One of the best VWO management measures is the use of tolerant cultivars. Remarkably, no information is available about olive functional traits and their potential relationship with tolerance to V. dahliae. Twenty-five selected functional traits (for leaf, stem, root and whole plant) were evaluated in six olive varieties differing in their VWO tolerance level to identify possible links between this phenotype and functional traits’ variation. High intervarietal diversity was found among cultivars and several functional traits were related with VWO tolerance. Tolerant varieties showed higher leaf area, dry matter content (leaf, stem and plant) and mass fraction for stems, but lower for leaves. Significant differences were also detected for root functional traits, tolerant cultivars displaying larger fine root diameter and lignin content but smaller specific length and area of thick and fine roots. Correlations were found among functional traits both within varieties and between levels of tolerance/susceptibility to VWO. Associations were observed between biomass allocation, dry matter content and VWO tolerance. The most relevant difference between tolerant and susceptible cultivars was related to root system architecture.

Breeding for resistance to forest pests and pathogens is emerging as a promising tool for minimising the impact of the increasing biotic threats that our forests are experiencing as a consequence of global change. Efficient phenotyping protocols of resistance are urgently needed. Here we present the results of two experiments aimed to determine whether the variation in resistance to the pine weevil Hylobius abietis, a harmful pest of European conifers, can be inferred by nondestructive bioassays using excised plant material collected in forest genetic trials. Weevil damage and amount of nonvolatile resin induced by weevil feeding were assessed in young trees and in branches of adult trees using several phenotyping procedures (bioassays using either living trees, excised plant material and cut stem twigs) on four pine species (Pinus pinaster, P. radiata, P. sylvestris and P. pinea). Half of the plants were previously induced with methyl jasmonate (MJ), a treatment that is known to affect resistance to the pine weevil. In Experiment 1, living and excised plants showed parallel results: MJ treatment significantly reduced weevil damage, and saplings responded to weevil damage locally increasing the nonvolatile resin (NVR) in the stems proportionally to the damage suffered. This response was, however, slightly lower in excised than in living saplings. On the contrary, patterns of weevil feeding on stem twigs completely departed from those observed in living and excised seedlings. Moreover, cut stem twigs were unable to respond to weevil feeding increasing NVR according to the weevil damage. In Experiment 2, assessment of weevil damage on excised branches explained around 50% of variation in damage on living branches. This relationship became much more pronounced (R2 = 0.81) when explored at the mean treatment level; branch manipulation did not alter the patterns of variation in resistance across pine species or MJ treatments. Irrespective of the assessment procedure, MJ consistently decreased weevil damage in all pine species, with larger reduction in weevil damage in stone and maritime pine than in radiata and Scots pine. Radiata pine was the most resistant while Scots pine was the most susceptible to the pine weevil. Overall, results suggest that using excised plant material is an operative alternative for phenotyping weevil resistance whenever care is taken to maintain the functionality of the excised plant material. This will allow taking advantage of multiple available conifer genetic trials to deepen the ecological genetics of resistance to the pine weevil and to screen for resistance without compromising the long‐term utility of those genetic trials. [ABSTRACT FROM AUTHOR]

Maize is arguably the most widely grown crop in the world, but it is often associated with one of its major insect pests, the European corn borer (ECB). The damage caused by this species to maize production is generally variable, but in many cases it is economically significant. This review paper provides an overview of the research findings on the natural plant defence mechanisms against ECB larvae published till now. What is resistance and how it is achieved, what is the chemical response of maize plants to insect feeding and how tolerance can be increased. A short introduction in breeding for resistance and a discussion if the mentioned traits can be used in conventional breeding in order to create maize hybrids less affected by ECB are given. [ABSTRACT FROM AUTHOR]

In breeding programs, understanding the potential of parents should be a way to spend significantly less time and costs to obtain new cultivars. For this, the objective of this study was to estimate the general and specific combining ability of parents aiming common bean breeding for resistance to Fusarium wilt (FW) based on disease severity and reduction in plant growth. Eight common bean genotypes were crossed in a 3 x 5 partial diallel mating scheme to obtain F1 hybrids. The parents and their 15 F1 hybrids were evaluated for severity of Fusarium wilt, area under the disease progress curve, percentage of plant height reduction and plant shoot fresh weight reduction and grain yield. The resistance of common bean to FW is controlled by a few dominant genes. The reduction in plant growth is controlled by a different set of genes that can increase the selection efficiency of parents for common bean breeding.

The evolution of cocoa farming was quickly confronted with the development of pests and diseases. These sanitary constraints have shaped the geographical distribution of production over the centuries. Current climate change adds an additional constraint to the plant health constraints, making the future of cocoa farming more uncertain. Climate change is not only affecting the areas where cocoa is grown for physiological reasons, particularly in relation to changes in water regimes, but also affects the distribution of pests and diseases affecting this crop. These different points are discussed in the light of the trajectories observed in the different cocoa-growing areas. The breeding programs of cocoa trees for sustainable resistance to plant health constraints and climate change are therefore particularly important challenges for cocoa farming, with the other management practices of plantations.

Verticillium (Verticillium dahliae Kleb.) wilt is one of the most devastating diseases affecting olive (Olea europaea L. subsp. europaea var. europaea) cultivation. Its effective control strongly relies on integrated management strategies. Olive cultivation systems are experiencing important changes (e.g., high-density orchards, etc.) aiming at improving productivity. The impact of these changes on soil biology and the incidence/severity of olive pests and diseases has not yet been sufficiently evaluated. A comprehensive understanding of the biology of the pathogen and its populations, the epidemiological factors contributing to exacerbating the disease, the underlying mechanisms of tolerance/resistance, and the involvement of the olive-associated microbiota in the tree’s health is needed. This knowledge will be instrumental to developing more effective control measures to confront the disease in regions where the pathogen is present, or to exclude it from V. dahliae-free areas. This review compiles the most recent advances achieved to understand the olive–V. dahliae interaction as well as measures to control the disease. Aspects such as the molecular basis of the host–pathogen interaction, the identification of new biocontrol agents, the implementation of “-omics” approaches to unravel the basis of disease tolerance, and the utilization of remote sensing technology for the early detection of pathogen attacks are highlighted.

Fusarium head blight (FHB) and the accumulation of deoxynivalenol (DON) mycotoxin induced by Fusarium graminearum and other Fusarium fungi cause serious problems for oat production in the Nordic region (Scandinavia, Fennoscandia). Besides toxin accumulation, FHB causes reduction in grain yield and in germination capacity. Here, genomic approaches for accelerating breeding efforts against FHB and DON accumulation were studied. Resistance-related traits included DON content, F. graminearum DNA (relative to oat DNA) content (qFUSG) measured with real-time quantitative polymerase chain reaction (PCR), Fusarium-infected kernels (FIKs) and germination capacity (GC). Plant germplasm used in the study consisted of mostly breeding lines, and additionally, a few cultivars and exotic accessions. Genome-wide association study (GWAS) and genomic prediction, enabling genomic selection (GS) on the resistance-related and collected agronomic traits, were performed. Considerable genetic correlations between resistance-related traits were observed: DON content had a positive correlation (0.60) with qFUSG and a negative correlation (−0.63) with germination capacity. With the material in hand, we were not able to find any significant associations between markers and resistance-related traits. On the other hand, in genomic prediction, some resistance-related traits showed favorable accuracy in fivefold cross-validation (GC = 0.57). Genomic prediction is a promising method and genomic estimated breeding values (GEBVs) generated for germination capacity are applicable in oat breeding programs.

Five winter wheat cultivars, differing in resistance to Septoria tritici blotch (STB), were spray inoculated under field conditions for two years and at two locations with nine Mycosphaerella graminicola isolates and a mixture of isolates that were obtained from different regions of the Czech Republic. Main aims of this study were (i) to compare isolate, host cultivar and environmental effects on five traits indicative of STB severity and (ii) to analyse pathogen aggressiveness and host-pathogen relations for improving evaluation of cultivar resistance. ANOVA showed in all traits, except the reduction in 1000 grain weight, significant isolate effects. However, the effects of isolate and genotype by isolate interactions were much lower (2.3-4%) than cultivar (19.1-53.7%) and environmental (11.9-58.6%) effects. Cultivar resistance to the disease limited much the loss in grain weight per spike to a halve, from 34.7% in the susceptible Bakfis to 17.3% in the resistant Arina. Visual scoring of symptoms in the middle and at the end of disease development (performed on the 1-9 scale), reflecting the disease progress and infected leaf area, showed the highest cultivar effect (54%) and could be recommended for evaluation of cultivar resistance in breeding practice. All examined traits were significantly interrelated, but significant differences between all the five cultivars were only detected after examination of the % coverage of flag leaves with lesions bearing pycnidia. Resistance in the cultivar Arina was detected by all isolates and the isolate mixture. In spite of significant differences in classification of resistances in the cultivars Bohemia and Mulan after inoculation with one isolate (1081), specific interactions between cultivars and isolates collected in this Central European region are rare. The study leads to a conclusion that investigation into stability of STB resistance across a wide range of environments is more valuable for breeding purposes than the study of cultivar response to different isolates. Combination of important isolate properties in a mixture of isolates is stressed as well.

The pod borer [ Helicoverpa armigera Hubner (Lepidoptera: Noctuidae)] is responsible for causing up to 90% damage in chickpea due to its regular occurrence from the vegetative growth to the pod formation stage. In order to manage this problem, growers are tempted to increase the amounts of pesticides, but indiscriminate or injudicious use of pesticides has resulted in residues in the food chain, pesticide resistance, and pest resurgence, in addition to causing harm to non-targeted beneficial organisms and the environment. Here, we reviewed the sustainable approaches to reduce the incidence of pod borer and achieve sustainability in chickpea production systems through the adoption of an integrated approach involving host plant resistance, good agronomic practices, and judicious use of chemical and biological methods. We found that the following major points have been reported to reduce the survival and damage of pod borer: (1) use of resistant varieties (the cheapest and the best method of pod borer management); (2) implementing a number of good agronomic practices, such as early sowing with optimum planting density and fertilizer levels, including inter/trap crops (coriander, mustard, linseed, sunflower, sorghum, and marigold) and installing animated bird perches and T-perches at 2 m distance of predatory zones; and (3) monitoring pod borer through pheromone traps (which is also necessary to understand the major factors influencing pest population and to make the pest control program more effective). Integrating all of these approaches with biological control has shown some encouraging results for sustainable pod borer management and has resulted in high chickpea yields. This review highlights examples of successful management approaches from past studies that were implemented in experimental and farmers' fields. These approaches can be explored as reproducible practices for managing the pest in locations with similar H. armigera concerns. We conclude that an integrated approach is most effective for long-term sustainable management programs. [ABSTRACT FROM AUTHOR]

Field host resistance against the white leaf spot pathogen Pseudocercosporella capsellae was determined across one hundred and seventeen Brassica napus, eleven B. juncea, four B. rapa, five B. oleracea, eight B. fruticulosa and one B. carinata genotypes. Of the one hundred and seventeen B. napus, there were seven lines of B. napus containing weedy crucifer introgression, sixteen lines with B. carinata introgression, fifty six lines of synthetic B. napus from B. juncea into B. carinata and B. rapa into B. oleracea, while remaining B. napus were commercial varieties from Australia. There was wide and significant ( P < 0.001) variation across the test genotypes in terms of relative disease development assessed either as % leaves diseased index (%LDI), values ranging from 0 to 68, or % leaves collapsed index (%LCI), with values ranging from 0 to 38. B. rapa subsp. oleifera ATC 95966 Bo was the most resistant genotype to white leaf spot disease (%LDI = 0, %LCI = 0). Very high resistance was observed in all five B. oleracea genotypes (%LDI < 13, %LCI ≤ 10) and of these B. oleracea var. gongylodes Tronchuda with %LDI = 1.0 and %LCI = 2.5 and B. oleracea var. sabellica Kailan with %LDI = 2.4 and %LCI = 2.0 were the most resistant. Eight B. fruticulosa genotypes showed high resistance with %LDI < 15 and ≤ 10 %LCI. While eight out of twelve B. juncea varieties were highly susceptible, there was a range in %LDI of 5-58 and %LCI of 10-30 and with both Montara and VT 535 G showing best resistance of this species. Amongst B. napus genotypes, more than ten of the Australian commercial cultivars demonstrated comparatively higher resistance to white leaf spot disease than the most resistant genotypes with weedy introgression or synthetic B. napus, with commercial cultivars Oscar and Stubby considered to be highly resistant. These resistances offer unique opportunities both for direct deployment where white leaf spot is severe and for oilseed and vegetable Brassica spp. breeding programs to develop commercial cultivars with effective resistance. [ABSTRACT FROM AUTHOR]

The response of four winter wheat cultivars, differing in resistance to Fusarium head blight (FHB), to spray inoculation with four selected Fusarium graminearum isolates, mixture of these isolates and frequently used F. culmorum isolate B was studied in five field and glasshouse experiments during 2008-2010. Analyses of variance showed highly significant main and interaction effects of cultivar, inoculum source and environment (year-trial) on all five examined traits indicative of disease severity, yield loss and accumulation of mycotoxins. The relations between traits were not evidently influenced by the used isolate. Resistance of host genotypes and environmental conditions accounted for a greater proportion of the total variation (8-36%) than the inoculation source (isolate) that substantially influenced the accumulation of the mycotoxin deoxynivalenol (12%), but expressed relatively low effects on symptom scores, percentage of fusarium damaged kernels and reductions of yield components (2-4%). Two-way and three-way interactions accounted for 25-40% of variation in the examined traits, which indicates great importance of multi-environment tests, using different Fusarium isolates for inoculation. Separate inoculation with F. graminearum isolates, differing in aggressiveness, did not appear to be more advantageous than their use in mixture that showed medium or below-average aggressiveness in all traits. The application of an isolate mixture could be recommended as a "less costly" alternative to inoculation with single isolates in trials repeated in different years and/or locations. It was indicated by these experiments that especially the detection of resistance/moderate resistance to FHB could be facilitated by the use of a carefully selected mixture of isolates. However, the application of aggressive isolates (isolate B of F. culmorum in these experiments) appeared to be beneficial to eliminate FHB susceptible materials in the breeding process.

Tomato germplasm accessions; FLA456-4, FLA591-15, H24, CLN2443A, CLN2443B, CLN2443C, TLB111, TLB182-1, TLB111-F6-4-1, TLB130-F6-3-1 and TLB134-F6-8-1 from the Asian Vegetable Research Development Center (AVRDC), Taiwan, were screened for resistance to the Tomato Yellow Leaf Curl Virus, Thailand isolate (TYLCTHV-[2]). The accessions expressing the resistant genotype were then crossed to the TYLCV-susceptible female parent, Seedathip3 (SD3), to produce F1 hybrids. Tomato parents and their F1 progenies were inoculated with TYLCTHV-[2] at 3 weeks of seedling age using viruliferous whitefly (Bemisia tabaci) as the inoculation vector. Disease response of the seedling was rated according to the incidence and severity of the development of yellowing and curling symptoms. The presence of TYLCTHV-[2] in the inoculated plants was confirmed by Enzyme-Linked Immunosorbent Assay (ELISA). AVRDC tomato parental lines: H24, FLA591-15 and FLA456-4 expressed mild or no symptoms after one month inoculation. Progeny of crosses between the AVRDC donor parental lines and susceptible Thai cultivars showed intermediate tolerance to TYLCTHV-[2] infection. This indicated that resistance was incompletely dominant.

In breeding programs, understanding the potential of parents should be a way to spend significantly less time and costs to obtain new cultivars. For this, the objective of this study was to estimate the general and specific combining ability of parents aiming common bean breeding for resistance to Fusarium wilt (FW) based on disease severity and reduction in plant growth. Eight common bean genotypes were crossed in a 3 x 5 partial diallel mating scheme to obtain F1 hybrids. The parents and their 15 F1 hybrids were evaluated for severity of Fusarium wilt, area under the disease progress curve, percentage of plant height reduction and plant shoot fresh weight reduction and grain yield. The resistance of common bean to FW is controlled by a few dominant genes. The reduction in plant growth is controlled by a different set of genes that can increase the selection efficiency of parents for common bean breeding. [ABSTRACT FROM AUTHOR]

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Five winter wheat cultivars, differing in resistance to Septoria tritici blotch (STB), were spray inoculated under field conditions for two years and at two locations with nine Mycosphaerella graminicola isolates and a mixture of isolates that were obtained from different regions of the Czech Republic. Main aims of this study were (i) to compare isolate, host cultivar and environmental effects on five traits indicative of STB severity and (ii) to analyse pathogen aggressiveness and host-pathogen relations for improving evaluation of cultivar resistance. ANOVA showed in all traits, except the reduction in 1000 grain weight, significant isolate effects. However, the effects of isolate and genotype by isolate interactions were much lower (2.3-4%) than cultivar (19.1-53.7%) and environ- mental (11.9-58.6%) effects. Cultivar resistance to the disease limited much the loss in grain weight per spike to a halve, from 34.7% in the susceptible Bakfis to 17.3% in the resistant Arina. Visual scoring of symptoms in the middle and at the end of disease development (performed on the 1-9 scale), reflecting the disease progress and infected leaf area, showed the highest cultivar effect (54%) and could be recommended for evaluation of cultivar resistance in breeding practice. All examined traits were significantly interrelated, but significant differences between all the five cultivars were only detected after examination of the % coverage of flag leaves with lesions bearing pycnidia. Resistance in the cultivar Arina was detected by all isolates and the isolate mixture. In spite of significant differences in classification of resistances in the cultivars Bohemia and Mulan after inoculation with one isolate (1081), specific interactions between cultivars and isolates collected in this Central European region are rare. The study leads to a conclusion that investigation into stability of STB resistance across a wide range of environments is more valuable for breeding purposes than the study of cultivar response to different isolates. Combination of important isolate properties in a mixture of isolates is stressed as well [ABSTRACT FROM AUTHOR]

Developing verticillium wilt resistant genotypes is currently a major objective in olive breeding. In this study, 6017 genotypes derived from 48 crosses obtained by open pollination and crosses between olive cultivars, wild olive genotypes and other Olea species and Olea europaea subspecies were individually evaluated for verticillium wilt resistance. More than 800 genotypes were identified as resistant to the disease based on the absence of symptoms. High genetic variability and wide segregation in resistance were observed. The inheritance of resistance was studied, and the best parents and crosses to breed resistant genotypes were identified. According to the results, verticillium wilt resistance in olive appears to be a quantitative trait. The results obtained by comparing the level of resistance between different crosses as well as by estimating heritability suggest that it is possible to breed for verticillium wilt resistance in olive. [ABSTRACT FROM AUTHOR]

White mold is a severe disease of common bean worldwide. Partial resistance occurs in the primary and secondary gene pools. Factors essential for identifying high levels of resistance that is effective throughout the growing season are not known. Our objectives were to determine which factors are most essential for identifying high levels of resistance including: (i) pathogen isolates screened, (ii) inoculations/plant, (iii) evaluation dates, (iv) area under disease progress curve (AUDPC), and (v) the SCAR markers linked with WM2.2, WM6.1, WM7.1, WM7.3, and WM8.3 resistance QTL. Thirty-one genotypes were inoculated one to three times/plant with ARS12D and ND710 isolates in the greenhouse in Idaho, and CO467 and NY133 in Colorado. Evaluations were made from 7 to 35 days post-inoculation. Disease severity and AUDPC increased until 21 days in Colorado and 35 days in Idaho. Correlations were positive among isolates at each evaluation date. The presence or absence of white mold resistance QTL was not indicative of resistance response. 'Othello' was susceptible to all isolates with one inoculation, and VC13-5 was resistant to three isolates and intermediate to ND710 after three inoculations per plant; both of these genotypes lacked the five resistance QTL. SE155-9 with WM2.2, WM7.1, and WM8.3 QTL was resistant to CO467 and NY133. However, SE152-6 with the same QTL was resistant and possessed lower AUDPC values to all isolates after three inoculations. Thus, screening with four isolates, three inoculations/plant, and disease evaluations delayed until 21 days or longer helped identify genotypes with high levels of broad-spectrum resistance. [ABSTRACT FROM AUTHOR]

The oil palm is badly affected by basal stem rot (BSR) disease in Southeast Asia. BSR disease is caused by the fungus Ganoderma boninense, which is a major threat to oil palm compared with other Ganoderma spp. Molecular markers associated with BSR disease will accelerate the identification process of resistant breeding materials in screening of plants for tolerance to the disease at the nursery stage. In this study, 58 simple sequence repeat markers were utilized with three progeny types, namely, KA4G1, KA4G8, and KA14G8, to perform a comparative molecular mapping for association with BSR. A total of 319 alleles were identified with an average of 5.51 alleles per locus. Five markers, mEgCIR0793:180, mEgCIR0894:200, mEgCIR03295:210, mEgCIR3737:146 and mEgCIR3785:299 were found to be associated with Ganoderma disease with P values of 0.018, 0.033, 0.037, 0.034 and 0.037, respectively, in single progeny analysis. However, in pooled data (KA4G1, KA4G8 and KA14G8), only two alleles, mEgCIR0804:213 ( P value = 0.001) and mEgCIR3292:183 ( P value = 0.001), were found to be associated with Ganoderma disease. These analyses confirmed that progeny type KA4G1 was tolerant, whereas the other two were susceptible progeny types. These markers and KA4 progeny will be useful in future works on BSR disease resistance in oil palm. [ABSTRACT FROM AUTHOR]

Rhizomania, one of the most devastating diseases in sugar beet production, is caused by Beet necrotic yellow vein virus ( BNYVV) and transmitted by Polymyxa betae. Previously, disease control was possible by cultivation of sugar beet hybrids carrying a major resistance gene Rz1, which restricts virus accumulation in taproots and suppresses symptom development. Over the last few years, BNYVV strains with four RNA components have arisen, which are able to overcome Rz1-mediated resistance. All strains described so far possess an A67V amino acid exchange within the RNA3-encoded P25 pathogenicity factor. In this study, BNYVV was isolated from Rz1 plants, collected in the United Kingdom, the Netherlands and Germany, displaying patches of strong rhizomania symptoms. Sequencing of the coat protein and P25 gene of three isolates showed 100% nucleotide sequence identity and detected AYPR as the P25 tetrad amino acid composition. The ability of this strain to accumulate to higher levels in young plants of Rz1 resistant but not in Rz1 + Rz2 resistant genotypes was initially demonstrated in a greenhouse assay in natural field soil from the Netherlands. This strain was loaded into a virus-free P. betae population and compared to reference strains. The AYPR strain retained its resistance-breaking ability in the Rz1 genotypes and displayed replication at a higher rate compared to the Rz1-resistance-breaking P type. The strain origin is unclear and it remains speculative whether the occurrence at different geographic locations is the result of independent selection or displacement of infested soil. [ABSTRACT FROM AUTHOR]