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Common bean breeding obtained cultivars with high yield and resistance to diseases. We evaluated anthracnose resistance of genotypes from breeding programs where selection was made mainly to increase grain yield. A germplasm collection of 845 lines were assessed with four of the most frequent Colletotrichum lindemuthianum races found in Brazil (65, 73, 81 and 89). In addition to high reaction variability, we identified 633 lines resistant to at least one race. Most resistant lines have a Carioca grain type. The virulence indexes ranged from 51.7% to 63.2% (races 81 and 73) and resistance indexes ranged from 0% (susceptible) to 100% (resistant). This study presents complete characterization about resistance to anthracnose of a wide collection, provides information about cultivars that can be directly introduced in current breeding programs and shows that breeding focused on increasing grain yield has also been successful in selecting resistant genotypes to anthracnose disease. [ABSTRACT FROM AUTHOR]

Cassava brown streak disease (CBSD) threatens cassava production in sub-Saharan Africa despite the availability of resistant varieties. Extreme environmental factors weaken plant defenses, reducing CBSD resistance. This study examined CBSD inheritance in cassava populations, assessed genetic variability, and identified superior sources of resistance using F1, S1, and half-sib offspring populations derived from resistant sources. The offspring underwent field evaluation at two distinct sites from 2019 to 2021, and the symptom-free genotypes were analyzed using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Resistance to CBSD was categorized as most resistant, resistant, most tolerant, or tolerant based on symptoms and virus titers. The findings indicated that the resistance to CBSD is highly influenced by genotypes, F1/S1 types, and environmental conditions. An analysis of combining abilities revealed significant general combining abilities (GCAs) for CBSD, cassava mosaic disease (CMD), and traits associated with yield. The heritability estimates for resistance to CBSD varied between 43.4% and 63.2% for foliar symptoms and 14.6% and 57.9% for root necrosis across locations. The inheritance pattern involved a combination of additive and recessive genes with selfed (S1) populations displaying stronger and more effective resistance to the disease. The cassava brown streak virus (CBSV) was highly prevalent, and the Ugandan cassava brown streak virus (UCBSV) was not prevalent. Four genotypes were highly resistant to CBSD and could be key sources of resistance to this disease. [ABSTRACT FROM AUTHOR]

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Tomato leaf curl virus disease (ToLCD), caused by whitefly transmitted begomo virus is a devastating disease affecting tomatoes worldwide. Twenty seven genotypes (Five breeding lines from World Vegetable Centre, Taiwan, nine commercial hybrids, eight germplasm accessions from NBPGR, one local collection from Idukki and four KAU varieties) were screened for ToLCV resistance under natural field conditions at Thrissur, Kerala during summer 2021. Among the screened genotypes, Ansal was found to be highly resistant, while, Kaustubh, EC 519806, Arka Rakshak and local collection (Idukki) were identified as resistant genotypes. Among the genotypes evaluated, four genotypes were moderately susceptible (AVTO 1726, AVTO 1727, Anagha and Akshaya), twelve were susceptible (AVTO 1707, AVTO 1706, AVTO 0922, Virang, Durg, Abhiraj, EC 528360, EC 620428, EC 521067 B, Manuprabha, Manulekshmi and EC 620486) and six were highly susceptible (Aryaman, Raymond, Pranay, EC 538153, EC 315489 and EC 567305) to ToLCV. The genotypes found to be highly resistant and resistant were found to be resistant to ToLCV even after whitefly mediated artificial inoculation. The resistant and highly resistant genotypes remained asymptomatic, whereas, the susceptible genotypes (Anagha and Manuprabha) exhibited ToLCV symptoms. The genotypes varied significantly with respect to plant height, number of primary branches/plant and days to flowering. Correlation between trichome density, and disease severity showed that glandular trichome density on abaxial and adaxial surfaces of leaf was significantly and negatively correlated with per cent disease incidence and disease severity index. However, the negative correlation between the abaxial glandular trichome density and ToLCV incidence was stronger. The glandular trichome density of the resistant genotypes identified in the field screening was found to be high. Non-glandular trichome density on abaxial and adaxial side of the leaf was significantly and positively correlated with per cent disease incidence and disease severity index. The resistant genotypes identified in the present study can be used for resistance breeding in tomato against ToLCV disease. [ABSTRACT FROM AUTHOR]

Gummy stem blight caused by the fungus Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae), is a devastating disease of watermelon all over the world including India. Several strategies are being explored for the management of this disease. Though cultural and chemical management gives partial relief, the development of resistant cultivar is cost-effective and environment friendly. However, the development of resistant varieties for this disease is constrained by the non-availability of suitable resistant sources. Hence, in the present study, we evaluated a panel of watermelon germplasm for the identification of resistance sources against gummy stem blight. A total of 266 genotypes of watermelon comprising of 260 germplasm collections and six commercial checks were evaluated for the identification of resistance sources under artificial screening and natural epiphytotic conditions. A highly virulent watermelon isolate (MN396362) obtained from the research farm of Division of Vegetable Crops, ICAR-IIHR was used for artificial screening, employing mycelial disc inoculation technique. Host response in terms of symptom expression ranging from necrosis in leaves, stem cankers, rotting of the infected stem to complete wilting and death of plants were observed. Among the genotypes evaluated, IIHR-617, IIHR-82, IIHR-545, BIL-53 and IIHR-556 were found to be resistant. These potential sources of resistance identified shall be of great value in developing gummy stem blight resistant varieties of watermelon. [ABSTRACT FROM AUTHOR]

Race Ug99 of the fungus Puccinia graminis f. sp. tritici that causes stem rust disease on wheat was first detected in Uganda in 1998. 13 races belonging to the Ug99 lineage are now known in 13 countries. In Egypt three races in the Ug99 race group; TTKST, TTKTK and TTKSK were detected. The present study conducted to screening of resistance sources to stem rust Ug99 (TTKSK) in sixty wheat genotypes delivered to Egypt by International Maize and Wheat Improvement Center (CIMMYT) during 2017/2018 and 2018/2019 growing seasons under field conditions. The results revealed that Sources with Sr24, Sr26, a combination genes (Sr2+ Sr24+Sr26) and adult plant resistance genes (APR) exhibited high level of slow rusting resistance and the most effective to the prevalent Ug99 race. While, Sources with the Sr25 gene showed disease severity ranged from moderate resistant-moderately susceptible (MRMS) to susceptible (S). Sources with Srl3, Sr22, Sr42, SrHuw234 displayed MRMS to MSS. On the other hand, sources that carry unknown genes were susceptible (S) to stem rust Ug99 (TTKSK) at the adult plant stage in both seasons. From this study the slow rusting lines achieved with combining non-race specific and race specific genes that is more durable at adult plant resistance, so can used in wheat breeding programme for stem rust resistance. [ABSTRACT FROM AUTHOR]

Background. The efficiency of heterotic breeding is determined by reasonable selection of the lines with the best combining abilities and important breeding traits. It is possible to use the variability potential of the majority of traits when the level of resistance to the main diseases and pests is quite high. The most harmful disease of maize is common or boil smut (caused by Ustilago zeae (Beckm.) Unger). The breeding of resistant lines and hybrids of maize is the most rational, cheap and ecologically safe way to fight the disease. The initial stage of breeding work is the identification of pathogen-resistant forms.Materials and methods. In 2017, 594 accessions of six main Zea mays L. subspecies were studied using a score scale against the natural infectious background at the Kuban Experiment Station of VIR. The weather conditions (downpours and abrupt daily temperature fluctuations) were favorable for severe infection of maize plants with the pathogen.Results and conclusion. No disease symptoms were found in 173 accessions; 162 genotypes were affected only slightly. The greatest number of accessions with resistance to boil smut belonged to subsp. indentata (Sturt.) Zhuk. (69.4% of the total studied accessions), subsp. everta (69.2%) and subsp. semidentata (Sturt.) Zhuk. (66.7%). Accessions of subsp. amylacea (Sturt.) Zhuk. were more susceptible to the pathogen than other maize subspecies. The Russian, European and North American local maize varieties and self-pollinated lines had a low infection rate, while the accessions that came to the VIR collection from Asia and South America showed higher rates. After two years of comprehensive studies, the selected forms can be recommended for the use in breeding for immunity.

Ascochyta blight caused by Ascochyta rabiei (Pass.) Lab. (Telomorph: Didymella rabiei) (Kov.) is one of the most important fungal diseases in chickpea worldwide. Knowledge about pathogen aggressiveness and identification resistance sources to different pathotypes is very useful for proper decisions in breeding programs. In this study, virulence of 32 A. rabiei isolates from different part of Iran were analyzed on seven chickpea differentials and grouped into six races based on 0–9 rating scale and susceptibility/resistant pattern of chickpea differentials. The least and most frequent races were race V and race I, respectively. Race V and VI showed highly virulence on most of differential, while race I showed least aggressiveness. Resistance pattern of 165 chickpea genotypes also were tested against six different A. rabiei races. ANOVA analysis showed high significant difference for isolate, chickpea genotypes and their interactions. Overall chickpea × isolate (race) interactions, 259 resistance responses (disease severity ≤ 4) were identified. Resistance spectra of chickpea genotypes showed more resistance rate to race I (49.70%) and race III (35.15%), while there were no resistance genotypes to race VI. Cluster analysis based on disease severity rate, grouped chickpea genotypes into four distinct clusters. Interactions between isolates or races used in this study, showed the lack of a genotype with complete resistance. Our finding for virulence pattern of A. rabiei and newly identified resistance sources could be considerably important for integration of ascochyta blight resistance genes into chickpea breeding programs and proper decision in future for germplasm conservation and diseases management.

Fungal diseases are considered as main causes of yield loss and increased costs in wheat production. Stem or black rust caused by Puccinia graminis f. sp. tritici (Pgt), is a devastating fungal disease of wheat, worldwide. Identification of new stem rust resistance sources, and the involved genes are required to achieve resistant cultivars and durable resistance as the most efficient control method of wheat stem rust. In order to identify new seedling resistance sources, virulence pattern of eight Pgt isolates was studied on 27 wheat commercial cultivars and elite lines of national breeding programs in a randomized block design with three replications. Furthermore, the rust resistance loci Sr25/Lr19, Sr26, Sr36 and Sr38/Lr37/Yr17 were tracked as effective genes involved in wheat seedling resistance to stem rust using the linked molecular markers. Phenotypic data confirmed acceptable levels of seedling resistance to all tested Pgt races in the wheat lines S-83-4, S-84-14, SEP-49 and SEP-59. Based on the molecular results, Sr25/Lr19 locus was identified in SEP-58 and cultivar Mehregan, while Sr38/Lr37/Yr17 locus was found in the cultivar Sarang, and the lines N-92-10, N-92-12 and M-91-10. Sr26 and Sr36 were not identified in genotypes tested. Frequency of effective resistance genes in new wheat cultivars could be increased using the resistant genotypes identified in this research for stem rust resistance particularly to Ug99 race group and also to Iranian predominant Pgt races, as the donor parent in wheat breeding programs. [ABSTRACT FROM AUTHOR]

Anthracnose is a severe disease of common bean that, under favorable conditions, can cause a 100% yield loss. For effective resistance breeding, the virulence and genetic variability of the causal pathogen, Colletotrichum lindemuthianum, must be understood and the emergence of new races monitored to ensure the development of broad-spectrum, durable resistance. In the present study, 28 isolates of C. lindemuthianum collected in Pernambuco, Brazil, were characterized: i) for their pathogenicity on a differential common bean cultivar set, ii) for their genetic variability, based on the Internally Transcribed Spacer (ITS) region sequences, and iii) for their ability to cause anthracnose on a selection of 20 common bean accessions. The 12 differential cultivars were inoculated with the 28 isolates, identifying 16 races of C. lindemuthianum: 2, 3, 8, 9, 10, 64, 65, 72, 73, 75, 81, 85, 89, 117, 139, and 331. Except for race 81, all were reported for the first time in Pernambuco; this was the first report of race 139 in Brazil and of race 331 in the world. The ITS region sequence of 17 isolates revealed the presence of 27 SNPs, four SNPs in the ITS 1 region, and 23 SNPs in the ITS 2 region. Of the 20 common bean accessions screened for resistance with the 16 isolates of C. lindemuthianum, the Andean accessions 'Praia' and 'Africano 4' were the most resistant. The broad resistance detected in some common bean accessions indicates their utility as potential sources of resistance to C. lindemuthianum, particularly in areas where Mesoamerican beans and Mesoamerican races of the pathogen are predominant. [ABSTRACT FROM AUTHOR]

Marker-assisted selection (MAS) is a tool that is widely applied in tomato resistance breeding. To determine the robustness of some molecular markers commonly used in MAS, extensive screening of 964 tomato lines was performed under a controlled experimental condition. Initially, the application of 36 molecular markers targeting 26 resistance genes (R genes) and 14 major diseases was evaluated. Here, we employed basic molecular biology and bioinformatics techniques for analysis where polymorphism, accuracy and clearness of amplicons constituted the selection criteria of markers. Upon initial analysis, 20 of these markers designated as efficient markers, among which 8 were considered gene-based markers and referred to as perfect markers were selected for detail evaluation. Information extrapolated from PCR result revealed 18 R genes that control 12 diseases were grouped under efficient markers. On the other hand, grouping of breeding lines based on the number of R gene harbored comprehensively revealed 62% of the lines to be void of R gene, while 38% carry different types of R genes. This provides us with an avenue to better understand new sources of resistance in the breeding lines. Conclusively, these efficient markers and their limited PCR condition can be suggested as basis of a diagnostic kit for MAS applications against 12 major tomato diseases and the identified resistant breeding lines could be conserved in order to be propagated as different sources of resistance for the development of new resistant varieties. Therefore, in areas with high vulnerability to diseases, high efficiency combination of the relevant R genes and their pyramiding into commercial tomato varieties are proposed to be implemented as a pragmatic approach. [ABSTRACT FROM AUTHOR]

Powdery mildew infection caused by Blumeria graminis f. sp. tritici and grain yield of 23 spring wheat cultivars were investigated under controlled and natural conditions during two growing seasons (2016/17 and 2017/18). Under controlled greenhouse conditions, seedling infection types of 9 cultivars, Sids-12, Sids-13, Gemmeiza-3, Gemmeiza-10, Sakha-61, Sakha-93, Sakha-94, Giza-160 and Giza-163 revealed susceptibility to the disease, while 14 cultivars, Misr-1, Misr-2, Sids-1, Gemmeiza-1, Gemmeiza-5, Gemmeiza-7, Gemmeiza-9, Gemmeiza-11, Gemmeiza-12, Sakha-8, Sakha-69, Giza-167, Giza-168 and Giza-171 showed resistance during both seasons. In the field, adult plant infections revealed susceptibility of 8 cultivars, Gemmeiza-3, Gemmeiza-5, Gemmeiza-7, Sakha-8, Sakha-61, Sakha-93, Giza-160 and Giza-163, while 7 cultivars, Misr-2, Sids-13, Gemmeiza-11, Gemmeiza-12, Giza-167, Giza-168 and Giza-171 exhibited resistance during both seasons. These last-mentioned 7 cultivars also showed best resistance in seedling infection tests during both seasons. The highest levels of disease severity were recorded with Gemmeiza-3, Sakha-61 and Sakha-94, while the lowest ones were in Giza-167 and Giza-168 as resistant cultivars. Significant losses in grain yield (1000-kernel weight) were recorded with highly susceptible cultivars, reaching 26.68% in Gemmeiza-3, while insignificant loss was recorded with resistant cultivars, 2.06% in Giza-168. A strong positive correlation was observed between % disease severity and % loss in 1000-kernel weight, recording r = 0.9195 in the first season and r = 0.9402 in the second season. In susceptible cultivars, disease was an important yield constraint. Resistant cultivars may be incorporated in breeding programs to prevent yield losses. [ABSTRACT FROM AUTHOR]

The Australian Ascochyta rabiei (Pass.) Labr. (syn. Phoma rabiei) population has low genotypic diversity with only one mating type detected to date, potentially precluding substantial evolution through recombination. However, a large diversity in aggressiveness exists. In an effort to better understand the risk from selective adaptation to currently used resistance sources and chemical control strategies, the population was examined in detail. For this, a total of 598 isolates were quasi-hierarchically sampled between 2013 and 2015 across all major Australian chickpea growing regions and commonly grown host genotypes. Although a large number of haplotypes were identified (66) through short sequence repeat (SSR) genotyping, overall low gene diversity (Hexp = 0.066) and genotypic diversity (D = 0.57) was detected. Almost 70% of the isolates assessed were of a single dominant haplotype (ARH01). Disease screening on a differential host set, including three commonly deployed resistance sources, revealed distinct aggressiveness among the isolates, with 17% of all isolates identified as highly aggressive. Almost 75% of these were of the ARH01 haplotype. A similar pattern was observed at the host level, with 46% of all isolates collected from the commonly grown host genotype Genesis090 (classified as “resistant” during the term of collection) identified as highly aggressive. Of these, 63% belonged to the ARH01 haplotype. In conclusion, the ARH01 haplotype represents a significant risk to the Australian chickpea industry, being not only widely adapted to the diverse agro-geographical environments of the Australian chickpea growing regions, but also containing a disproportionately large number of aggressive isolates, indicating fitness to survive and replicate on the best resistance sources in the Australian germplasm.

Two major impediments to profitable maize,Zea maysL., production in the southern United States are from feeding by fall armyworm,Spodoptera frugiperda(J.E. Smith), and losses from the production and accumulation of aflatoxin in maize grain. A diallel cross was produced by making all possible crosses among five germplasm lines developed as sources of resistance to fall armyworm leaf feeding and five lines developed as sources of resistance to aflatoxin accumulation. For resistance to both leaf feeding and aflatoxin accumulation, general combining ability (GCA) was a significant source of variation. Specific combining ability (SCA) was significant for fall armyworm feeding only. Estimates of GCA effects for reduced aflatoxin accumulation were significant for Mp715 and Mp719, two lines selected for resistance to aflatoxin accumulation. The GCA effects for reduced fall armyworm damage were significant for all five lines selected for fall armyworm resistance: Mp707, Mp708, Mp713, Mp714, and Mp716. [ABSTRACT FROM PUBLISHER]

Nematodes are among the most important agents affecting potato crops. Heavy infestations by Globodera rostochiensis and G. pallida can cause significant yield losses and limit the choice of potato cultivars that can be grown effectively (Oerke, 2006). Breeding of new potato cultivar resistant to G. rostochiensis and G. pallida is a long-term process. It is preceded by screening of potato breeding lines for resistance in repeated biotests, which seems to be the most effective and safest method of protection. Evaluation of nematode resistance is an important element of characterization of breeding lines and new cultivars. Resistance to Globodera spp. is evaluated in biological tests. The use of DNA markers for detecting nematode resistance genes may be an alternative approach to phenotypic evaluation of resistance degree of potato plants (Jena and Mackill, 2008). The goal of this report is focused on a description of resistance assessment procedure of breeding lines and varieties of potato to PCN and on comparison of biological and molecular methods of resistance evaluation. Presented information is addressed to both breeders and Polish inspection services. [ABSTRACT FROM AUTHOR]

Powdery mildew (PM) is a devastating disease of many legume species, including common bean. In this work, we assessed the responses of 108 dry and snap bean accessions to PM, and characterised the genetic control of the resistance in three bean genotypes. Resistance tests under controlled conditions led to the identification of 11 dry bean accessions with total resistance. However, no snap bean accessions showed total resistance, although two cultivars showed mixed phenotypes including seedlings with total resistance. The inheritance of resistance was analysed in three F2:3 populations involving the resistant bean genotypes BelNeb, G19833 and BGE003161. In the three populations, the segregation for PM resistance fit the expected ratio for one dominant gene. The resistance loci were mapped to the beginning of the linkage group Pv04. The physical positions of the flanking markers indicated that the three resistance genes were located between the physical positions 0 and 1.09 Mb. This work provides new PM-resistance sources and markers linked to resistance genes, which will be very useful in common bean breeding programs focussed on protecting bean crops against this disease. [ABSTRACT FROM AUTHOR]

The Australian Ascochyta rabiei (Pass.) Labr. (syn. Phoma rabiei) population has low genotypic diversity with only one mating type detected to date, potentially precluding substantial evolution through recombination. However, a large diversity in aggressiveness exists. In an effort to better understand the risk from selective adaptation to currently used resistance sources and chemical control strategies, the population was examined in detail. For this, a total of 598 isolates were quasi-hierarchically sampled between 2013 and 2015 across all major Australian chickpea growing regions and commonly grown host genotypes. Although a large number of haplotypes were identified (66) through short sequence repeat (SSR) genotyping, overall low gene diversity (Hexp D 0.066) and genotypic diversity (D = 0.57) was detected. Almost 70% of the isolates assessed were of a single dominant haplotype (ARH01). Disease screening on a differential host set, including three commonly deployed resistance sources, revealed distinct aggressiveness among the isolates, with 17% of all isolates identified as highly aggressive. Almost 75% of these were of the ARH01 haplotype. A similar pattern was observed at the host level, with 46% of all isolates collected from the commonly grown host genotype Genesis090 (classified as “resistant” during the term of collection) identified as highly aggressive. Of these, 63% belonged to the ARH01 haplotype. In conclusion, the ARH01 haplotype represents a significant risk to the Australian chickpea industry, being not only widely adapted to the diverse agro-geographical environments of the Australian chickpea growing regions, but also containing a disproportionately large number of aggressive isolates, indicating fitness to survive and replicate on the best resistance sources in the Australian germplasm. [ABSTRACT FROM AUTHOR]

In this contribution actual results of the Czech national ring tests of disease resistance in wheat are presented that are performed at 3-5 locations each year. Special attention was paid to possibilities of increasing resistance to rusts, powdery mildew, Fusarium head blight and brown leaf spot diseases. New sources of resistance to the above-mentioned diseases were detected and described. Achievements and prospects of wheat breeding for resistance to these diseases, as well as to other important diseases and pests (common and dwarf bunt, eyespot and stem base diseases, barley yellow dwarf virus, orange wheat blossom midge) are discussed.

The reaction of winter and spring wheat to infection with barley yellow dwarf virus (BYDV-PAV) was evaluated in three-year small-plot field trials on 71 wheat varieties registered in the Czech Republic and at two locations for two years on 63 selected potential sources of resistance. Disease symptoms (VSS) were visually recorded using a 0-9 scale and the percent reduction of grain weight per spike (GWS-R) was measured on twenty plants per plot. The evaluation showed that among the registered varieties of winter and spring wheat no variety had a high resistance to BYDV (with VSS lower than 3.5). GWS-R ranged between 24% and 60%. Higher variability in VSS was detected for the registered varieties of spring wheat compared to winter wheat. Among the registered varieties of winter wheat, Saskia, Rialto, Meritto, Rexia, and Svitava, as well as the spring wheat Leguan, received the best long-term evaluations. The highest level of resistance was detected for the PSR 3628 line (a hybrid of wheat and couch-grass), but in connection with a low agronomic value. The WKL91-138 line of spring wheat and some varieties (lines) with the detected moderate level of resistance, in particular, could offer good prospects for use in breeding. The presence of the Bdv2 gene was expressed only in the reduction of virus content on the 11th day after inoculation. Nevertheless, genotypes carrying this gene were evaluated in field trials as susceptible or very susceptible to infection with the Czech PAV isolate. Similarly, the presence of the Bdv1 gene detected with the help of WMS130 marker was no assurance of an increased level of resistance to BYDV. Hybridological analyses of crosses with the WKL91-138 line showed a polygenic nature of inheritance. Thus, the marker-assisted selection does not obviously promise success without a focus on detecting a larger number of QTLs.

Ascochyta blights are major diseases of many legumes and an emerging disease in many areas in which common bean ( Phaseolus vulgaris L.) is grown. Ascochyta blight symptoms in bean can be caused by three fungus species. We investigated the species that caused ascochyta blight symptoms in bean crops from northern Spain using species-specific molecular markers and analysis of their nucleotide sequences. Results suggested that the two local isolates analyzed may correspond to the specie Phoma exigua var. diversispora. The variation in the reaction of common bean germplasm against a local isolate was also investigated in controlled conditions and was scored using a 1-9 severity scale. A total of 200 accessions from a core collection, 89 breeding lines and 11 accessions of Phaseolus coccineus L. were screened to identify potential sources of resistance. Most Phaseolus coccineus accessions showed higher levels of resistance (score < 5) while most Phaseolus vulgaris accessions and breeding lines had low levels (score > 5). However, five breeding lines and 17 accessions exhibited moderate resistance after five resistance tests, with variation in the response of seedlings within accessions. Thus, five lines were obtained by self-pollination from each of the 17 selected accessions. Evaluation of these lines revealed significant variation within lines derived from two accessions and allowed verification of the high level of resistance in lines derived from three accessions. Finally, the lines with higher levels of resistance identified in previous evaluations were tested in three additional tests. The lines UI465, BGE04435-22 and BGE04453-4 revealed resistance levels not significantly different from the best Phaseolus coccineus accession included in this study (score < 3.5). The identified resistance sources could be used in the in the short term to increase the level of resistance to ascochyta blight in specific bean genotypes or for development of new resistant genotypes by pyramiding of genes. [ABSTRACT FROM AUTHOR]

Three-way cross hybrids from the Agronomic Institute Campinas (IAC) maizebreeding program were evaluated for tropical rust resistance caused by Physopella zeae, infield conditions. Two experiments of top crosses, derived from crosses between two testers(experimental single-cross hybrids A and B) and IAC and CIMMYT (Centro Internacional deMejoramiento de Maíz y Trigo) lines were carried out. A randomized complete-block designwas used, with three replications, evaluating in each experiment 30 three-way cross hybrids, the respective testers and three commercial checks. Both experiments were cultivated in Guaira,in the north region of São Paulo State, under high natural presence of tropical rust. Theevaluations were performed 30 days after flowering, according to a scale of notes from 1 to 9,corresponding to: 0% to >75% affected leaf area in the adult plant. In TC 1, showed to beresistant (notes from 3,0 to 4,4) 30% of the three-way cross hybrids and 43% was moderatelyresistant (notes from 4,5 to 5,4). In TC 2, this proportion was inverted, that is, 43% of thethree-way cross hybrids showed to be resistant and 33% moderately resistant. The combinedanalyses of variance of the three-way cross hybrids with common lines did not detect significantdifferences, indicating that additive effects predominated for resistance to P. zeae. It was identifiedsome resistant lines which could be utilized to generate synthetics with high resistance to P.zeae, in maize recurrent selection program for tropical rust resistance.

Fusarium wilt (FW), caused by the fungal pathogen Fusarium oxysporum f. sp. vasinfectum (FOV), is a significant economic constraint to cotton production worldwide. The pathogen has a wide geographical distribution, and its biological characteristics have enabled its establishment of eight races in several agro-ecosystems spanning from regions with high precipitation to semi-arid and arid irrigated zones. Management of Fusarium wilt is challenging because of the ability of FOV to persist in production systems through formation of long-lived chlamydospores and through its parasitic and pathogenic associations with cotton and other rotational cops and weeds. The interaction of FOV with nematodes constitutes additional constraints to the management of the disease. Breeding and utilizing FW-resistant cultivars has proven to be the most cost-effective control method. Numerous approaches and methods have been used in screening cotton for resistance to FW. This review provides a background on accumulated knowledge over the past two decades on sources of FW resistance and methods of screening for resistance including inoculation and evaluation protocols in cotton. The review also provides an overview of the biology and management of FOV. [ABSTRACT FROM AUTHOR]

Mungbean yellow mosaic virus (MYMV) is a disastrous pathogen of mungbean. It is widespread in most of southern India and no complete resistance has been identified among its commercial cultivars. Two isolates of MYMV, representing its diversity, were used to assess and characterize the susceptibility reaction of all the three species of Vigna. The seeds were agroinoculated with the virus and the presence of the viral DNA was confirmed after 12 d by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis after which the plants were monitored for the expression of symptoms. All of the 20 accessions of Vigna radiata and ten accessions of Vigna mungo were systemically infected with MYMV, and they all produced typical symptoms. On the other hand, the 24 accessions of Vigna umbellata were found to be resistant to both the isolates. For additional affirmation, three representative accessions of V. radiata and V. mungo and all the accessions of V. umbellata were agroinoculated, and quantitative RT-PCR was performed for the quantitative detection of the MYMV. The mRNA transcripts of MYMV were detected in V. radiata and V. mungo plants but not in the V. umbellata plants. Researching the molecular basis of the resistance in V. umbellate against MYMV might definitely be very constructive for developing resistant varieties of mungbean on a commercial scale. This genetic quality offering resistance to MYMV could also be incorporated into V. radiata/V. mungo by means of interspecific crosses. [ABSTRACT FROM AUTHOR]

In this contribution actual results of the Czech national ring tests of disease resistance in wheat are presented that are performed at 3-5 locations each year. Special attention was paid to possibilities of increasing resistance to rusts, powdery mildew, Fusarium head blight and brown leaf spot diseases. New sources of resistance to the above-mentioned diseases were detected and described. Achievements and prospects of wheat breeding for resistance to these diseases, as well as to other important diseases and pests (common and dwarf bunt, eyespot and stem base diseases, barley yellow dwarf virus, orange wheat blossom midge) are discussed. [ABSTRACT FROM AUTHOR]

Powdery mildew can cause severe yield losses in bean crops. Limited information about resistance sources, and nature and inheritance of resistance are available to bean breeders and plant pathologist. Sources of resistance were searched in seedling tests under controlled conditions in 44 well-known genotypes and in a Spanish germplasm core collection consisting on 201 accessions. A 0-4 scale was used to describe the infection types (IT) observed. Only six out of the 245 evaluated genotypes showed a complete resistance (IT0) without visible symptoms on the leaves: Amanda, Belneb, Cornell 49242, Negro San Luis, Porrillo Sintetico and the local accession BGE003161. Inheritance of resistance was studied in F and F segregating populations. Observed reactions in the five segregating populations fitted to Mendelian ratios with different modes of inheritance. Results revealed that cultivar Porrillo Sintetico carries two dominant and independent resistance genes: one gene conferring complete resistance (IT0), and another gene conferring IT3, characterized by a moderate mycelial development on the leaves. Both genes show a dominant epistatic relationship. Inheritance of response to powdery mildew in cv. Cornell 49242 was similar to cv. Porrillo Sintetico although the correspondence with the genes described in Porrillo Sintetico was not established. Line X2776 carries one dominant gene conferring IT3, and shares this gene with cv. Porrillo Sintetico. In cv. Amanda, two complementary genes appear to be involved in resistance to this fungus. This information will be relevant for the implementation of breeding programs focused on the development of cultivars carrying genetic resistance to powdery mildew. [ABSTRACT FROM AUTHOR]

Co-evolution of wheat and its devastating pathogen Mycosphaerella graminicola (anamorph Septoria tritici) , the causal agent of septoria tritici blotch, a foliar disease of wheat, is suggested to occur in Fertile Crescent as their center of origin and, thus, interaction between pathogen virulence and host resistance is important subject to be addressed. We have investigated resistance spectra of 54 wheat genotypes including a set of differentials carrying known resistance genes and virulence patterns of 14 M. graminicola isolates at seedling stage under controlled environmental conditions. The isolates were collected in Iran from five provinces. Diversity in virulence and aggressiveness was observed among the isolates from four provinces. Isolates collected from Golestan province were virulent to all wheat genotypes from germplasm of Iran, while specific resistances were identified to the isolates from other provinces. Among wheat genotypes, cvs. Chamran, Morvarid and Hirmand had the greatest number of specific resistances as well as partial resistance. Wheat genotypes of the differential set also differed in their reactions to the isolates. Arina, Flame and TE 9111 were specifically resistant to the greatest number of isolates from different provinces. Most isolates were virulent to the other differentials such as cvs. Shafir, Estanzuela federal and Courtot indicating that extensive adaption of virulence to most of the known resistance genes ( Stb) has occurred in these regions. The new sources of resistance to highly virulent isolates from Iran may also be utilized in wheat breeding programs to develop resistant cultivars against pathogen populations in other countries. [ABSTRACT FROM AUTHOR]

Of the 242 groundnut genotypes, tested both in epiphytotic field and laboratory conditions, the genotypes viz., ICGV 90009, ICGV 86699, ICGV 86329, 91177, 91234, ICGV-94252 and TG 26 were found promising both with low incidence of PBND besides longer incubation periods, DFSA, DLSA and IP 50%. Further, significant positive correlation was found between IP 50% vs DLSA, DFSA and final PBND (%) was negatively correlated with IP 50% and DFSA. [ABSTRACT FROM AUTHOR]

Abstract: The host range of eighty isolates of Leptosphaeria maculans obtained from various cruciferous hosts in Western Australia was tested by inoculating onto cotyledons of 13 cruciferous hosts, including six Brassica species and one interspecific line of Brassica. These field isolates produced highly variable responses across the hosts tested. One or more isolates overcame the resistance in each of the tested Brassica species with the B-genome, such as B. juncea, B. nigra and B. carinata and of other species tested, including Raphanus raphanistrum, Crambe abyssinica, Sinapis alba, Eruca vesicaria and Raphanus sativus. None of the isolates tested to date were virulent on Camelina sativa. Of all isolates, 48.8% (and 75% of isolates taken from cultivars containing single dominant gene-based resistance derived from B. rapa ssp. sylvestris) showed high virulence against canola cultivars containing this single dominant gene-based resistance. There was a relationship between host source of isolates with virulence. Results clearly illustrated that extensive levels of variation exist within L. maculans populations in Western Australia such that major gene-based resistance in a range of these hosts could be rapidly overcome by one or more field populations of the pathogen. It is noteworthy that this ability to overcome such resistance in various cruciferous hosts was found to be present in certain isolates in the L. maculans population even prior to exposure of the pathogen to such major gene-based resistance sources in commercial crops. Our results indicated that seeking major gene-based resistance from within cruciferae for B. napus canola breeding, including from taxa which to date have shown resistance to L. maculans when used in the field as rotation, industrial oil or green manure crops, may lead to both breakdown and wastage of these valuable sources of resistance to blackleg disease. [Copyright &y& Elsevier]

Using the results of evaluation of Malus accessions during the last 20 years more than 15 new resistant apple cultivars were selected. The breeding aim was the combination of different kinds of resistance with good fruit quality. The best of these cultivars enclose resistance against Venturia inaequalis, Podosphaera leucotricha, Erwinia amylovora, Pseudomonas syringae, Panonychus ulmi and winterfrost. Different scab resistance sources (Vf, Vr, VA) found among the Malus species are combined in the most recent breeding lines. The new resistant Pillnitz apple cultivars ('Recultivars®') guarantee the possibility to reduce 80% and more of fungicide spraying in fruit growing and are very suitable for ecological and integrated fruit production. Four of these, 'Reanda', 'Rebella', 'Remo' and 'Rewena', are triple resistant to scab, mildew and fire blight and are good donors for breeding multiple resistance. [ABSTRACT FROM AUTHOR]