Resistance Breeding Programs Research Articles

The Use of Genitors in Biotic Stress Resistant Radish Breeding Program

Turp (Raphanus sativus L.), Brassicaceae (Lahanagiller) familyasının içinde yer alan önemli bir sebzedir. Lahanagil grubu sebze türleri içerisinde kültüre alınan en eski türdür. Turplar şekil ve irilik özellikleri yönünden çok geniş bir genetik vasyasyona sahiptir. Günümüzde turp yetiştiriciliğinde biyotik stres (hastalık ve zararlı etmenleri vb.) faktörleri nedeniyle önemli düzeylerde verim ve kalite kayıpları meydana gelmektedir. Turp yetiştiriciliğinde en yaygın olarak gözlemlenen hastalıklar; beyaz pas, Fusarium solgunluğu, mildiyö ve şalgam mozaik virüsü olarak sıralanabilir. Ayrıca turplar; kök, gövde ve yaprakları ile beslenen lahana kurdu, turp afiti, kök lezyon nematodu gibi birçok zararlının da tehlikesi ve tehdidi altındadır. Genetik kaynaklar, çeşit ıslah çalışmalarının başarıya ulaşmasında en önemli faktörlerden birisi olan fenotipik varyasyonun temelini oluşturmaktadır. Ayrıca halihazırda ticareti yapılan turp çeşitlerinde bulunmayan dayanıklılık genleri, yabani ve farklı alt varyetelerde bulunabilmektedir. Son yıllarda turp bitkisinde mevcut genetik kaynaklardan yararlanılarak hibrit çeşit ıslahı çalışmalarında hastalık ve zararlılara karşı tolerant yeni genotiplerin geliştirilmesi ve tolerantlıkta rol alan mekanizmaların belirlenmesine yönelik çalışmalara daha fazla önem verilmeye başlanmıştır. Bu derlemede turp ıslah programlarında dayanıklılık kaynağı olarak yararlanılan genitörler ve hastalık ve zararlılara karşı tolerant yeni genotiplerin geliştirilmesi konusunda yapılan ıslah çalışmaları derlenmiştir.

Introgression of the Powdery Mildew Resistance Genes Pm60 and Pm60b from Triticum urartu to Common Wheat Using Durum as a 'Bridge'.

Powdery mildew, caused by the fungus Blumeria graminis f. sp. tritici (Bgt), has limited wheat yields in many major wheat-production areas across the world. Introducing resistance genes from wild relatives into cultivated wheat can enrich the genetic resources for disease resistance breeding. The powdery mildew resistance gene Pm60 was first identified in diploid wild wheat Triticum urartu (T. urartu). In this study, we used durum as a ‘bridge’ approach to transfer Pm60 and Pm60b into hexaploid common wheat. Synthetic hexaploid wheat (SHW, AABBAuAu), developed by crossing T. urartu (AuAu) with durum (AABB), was used for crossing and backcrossing with common wheat. The Pm60 alleles were tracked by molecular markers and the resistance to powdery mildew. From BC1F1 backcross populations, eight recombinant types were identified based on five Pm60-flanking markers, which indicated different sizes of the introgressed chromosome segments from T. urartu. Moreover, we have selected two resistance-harboring introgression lines with high self-fertility, which could be easily used in wheat breeding system. Our results showed that the durum was an excellent ‘bridge’ for introducing the target gene from diploid T. urartu into the hexaploid cultivated wheat. Moreover, these introgression lines could be deployed in wheat resistance breeding programs, together with the assistance of the molecular markers for Pm60 alleles.

Genome-wide association analysis of anthracnose resistance in sorghum [Sorghum bicolor (L.) Moench

In warm-humid ago-ecologies of the world, sorghum [Sorghum bicolor (L.) Moench] production is severely affected by anthracnose disease caused by Colletotrichum sublineolum Henn. New sources of anthracnose resistance should be identified to introgress novel genes into susceptible varieties in resistance breeding programs. The objective of this study was to determine genome-wide association of Diversity Arrays Technology Sequencing (DArTseq) based single nucleotide polymorphisms (SNP) markers and anthracnose resistance genes in diverse sorghum populations for resistance breeding. Three hundred sixty-six sorghum populations were assessed for anthracnose resistance in three seasons in western Ethiopia using artificial inoculation. Data on anthracnose severity and the relative area under the disease progress curve were computed. Furthermore, the test populations were genotyped using SNP markers with DArTseq protocol. Population structure analysis and genome-wide association mapping were undertaken based on 11,643 SNPs with <10% missing data. The evaluated population was grouped into eight distinct genetic clusters. A total of eight significant (P < 0.001) marker-trait associations (MTAs) were detected, explaining 4.86-15.9% of the phenotypic variation for anthracnose resistance. Out of which the four markers were above the cutoff point. The significant MTAs in the assessed sorghum population are useful for marker-assisted selection (MAS) in anthracnose resistance breeding programs and for gene and quantitative trait loci (QTL) mapping.

Fungal Species Causing Maize Leaf Blight in Different Agro-Ecologies in India.

Foliar diseases of maize cause severe economic losses in India and around the world. The increasing severity of maize leaf blight (MLB) over the past ten years necessitates rigorous identification and characterization of MLB-causing pathogens from different maize production zones to ensure the success of resistance breeding programs and the selection of appropriate disease management strategies. Although Bipolaris maydis is the primary pathogen causing MLB in India, other related genera such as Curvularia, Drechslera, and Exserohilum, and a taxonomically distant genus, Alternaria, are known to infect maize in other countries. To investigate the diversity of pathogens associated with MLB in India, 350 symptomatic leaf samples were collected between 2016 and 2018, from 20 MLB hotspots in nine states representing six ecological zones where maize is grown in India. Twenty representative fungal isolates causing MLB symptoms were characterized based on cultural, pathogenic, and molecular variability. Internal Transcribed Spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (GADPH) gene sequence-based phylogenies showed that the majority of isolates (13/20) were Bipolaris maydis. There were also two Curvularia papendorfii isolates, and one isolate each of Bipolaris zeicola, Curvularia siddiquii, Curvularia sporobolicola, an unknown Curvularia sp. isolate phylogenetically close to C. graminicola, and an Alternaria sp. isolate. The B. zeicola, the aforesaid four Curvularia species, and the Alternaria sp. are the first reports of these fungi causing MLB in India. Pathogenicity tests on maize plants showed that isolates identified as Curvularia spp. and Alternaria sp. generally caused more severe MLB symptoms than those identified as Bipolaris spp. The diversity of fungi causing MLB, types of lesions, and variation in disease severity by different isolates described in this study provide baseline information for further investigations on MLB disease distribution, diagnosis, and management in India.

Influence of the different pod positions and screening methods on soybean pod shattering

Pod shattering is one of the major soybean constraints in the soybean production centers, particularly in the tropics. The screening for pod shattering resistance of 16 genotypes was carried out using detached and undetached pod methods on the three different pod positions on the stem. The field research was arranged in a randomized block design, during the dry season in Banyuwangi, Indonesia. The shattering evaluation was conducted in the laboratory using the ovendry method. The screening methods to investigate the pod shattering resistance of each genotype consisted of the detached pod (DP), undetached pod (UDP), and undetached whole-stem method (UWS). The result showed that the detached pod method (DP) resulted in a higher average podshattering percentage (15%) than the undetached pod methods (UDP and UWS, 13% and 11%, respectively). Nevertheless, the detached pod and undetached pod methods provide a consistent result for the evaluation of pod shattering resistance, showed by their correlation coefficients (DP and UDP, r = 0.98**; DP and UWS, r = 0.98**, UDP and UWS, r = 0.99**). The detached pod with the oven-dry method was suggested to be used for screening of pod shattering resistance. This method enables to screen genotypes in greater numbers, provides a homogeneous selection pressure and environmental condition. Pods at the upper part of the stem were more resistant to shattering than those pods in the middle part and lower part. The pod length, seed length, seed weight, pod wall weight to the pod weight ratio, and weight of 25 seeds appeared to be the significant indicators for pod shattering resistance. The shattering evaluation resulted in five soybean genotypes (Anj/G100H-28, Anj/G100H-44, Anj/Rjbs-304, Anj/Rjbs-30, and Detap 1) with consistent resistance to pod shattering based on the three methods. These genotypes can be used as donor parents in the breeding program for pod shattering resistance.

The diversity of chili pepper volatile compounds and its relationship to insect pests

Selection activities in plant breeding can be carried out only if there is variation in the plant’s genetic materials. Plant volatile compounds are media for interaction between plants and insects, making them potential to be used as a selection parameter in resistant plant breeding programs against insect pests. This study aimed to determine the diversity of chili pepper (Capsicum spp.) volatile compounds and to explain its relationship to the main insect pests of chili pepper. The research was carried out at IVEGRI’s research station in Lembang, West Java, Indonesia from March to September 2020. The treatment involved 34 chili pepper varieties. The observation parameters included profiles of volatile compounds measured using GC-MS and incidence of main insect pests (thrips, worms, and fruit fly). The results showed that 87 volatile compounds detected, eight of them, i.e. 3,6-Nonadien-1-ol, (E, Z)-,β-Ocimene, trans-β-Ocimene, 3-Allylcyclohexene, 2,4,6-Octatriene, 3,4-dimethyl-, Neo-allo-ocimene, 1-Octanol and 2-Methylanisole showed a high level of diversity among the chili pepper varieties tested. The results of a simple correlation test showed positive and negative correlations between eight volatile compounds and pest incidence, with a range from -6.80 to 0.87. The relationship between these volatiles compounds and pest incidence will be subject to a further discussion.

Characterisation and Pathogenicity of Fusarium Species Associated with Yellowing Disease in Black Pepper (Piper nigrum L.)

Yellowing disease has become one of the main threats to black pepper (Piper nigrum L.) production. This study was conducted to isolate and characterize Fusarium species associated with yellowing disease based on morphological and molecular characteristics, and to evaluate their pathogenicity on black pepper. Fungal isolates were recovered from symptomatic black pepper plants located in major growing areas in Sarawak. Based on morphological characteristics, a total of 73 Fusarium isolates were identified. Genomic DNA sequence analysis of nuclear ribosomal DNA internal transcribed spacer (ITS) and translation elongation factor-1 alpha (EF-1α) had confirmed the identity of the Fusarium isolates. The four identified Fusarium species were F. solani (90.4%), F. oxysporum (5.5%), F. concentricum (2.7%), and F. mangiferae (1.4%). Based on morphological characterisation, F. solani isolates were grouped into two distinct morphotypes, morphotype I and II. Phylogenetic analysis of F. solani has shown a high level of intraspecific variation among the isolates. The two major clades formed were found to correspond to the morphotype grouping. Pathogenicity test showed that all four Fusarium species are pathogenic to black pepper based on disease incidence and severity. This study provides new insights into the Fusarium species associated with yellowing disease in black pepper, and highlights the high genetic variability among the Fusarium isolates. This result calls for a critical revision of the current strategies in disease management, and resistance breeding programs in black pepper.

Mapping and breeding application of the brown planthopper (Nilaparvata lugens)‐resistance genes derived from a durable resistant PTB33 rice variety (Oryza sativa)

AbstractThe brown planthopper (BPH) is a substantial threat to rice production in Asian countries. The variety PTB33 exhibits a high and durable resistance to BPH. Here, three resistance genes from chromosomes 3, 4 and 6 were detected, with LOD scores of 6.2, 5.0 and 4.3, respectively. The gene from chromosome 4 flanked by markers RM5757 and RM6997 was allelic to Bph6. They shared an 89% amino acid similarity. Another gene detected on chromosome 6 was linked with RM598 and was the reported gene Bph3. The gene from chromosome 3, harbouring markers RM5626 and RM6283, was a novel resistance gene. Moreover, by crossing different rice lines with PTB33, 27 backcrossing lines were developed that contained a genetic background of restorers, maintainers, sterile lines and cultivated varieties. These lines displayed resistance to BPH and had a survival rate &gt;50%. Among these, seven lines were highly resistant to BPH and showed agronomic merit traits. Thus, the detected genes and developed BPH resistant lines can significantly contribute to breeding programmes for BPH resistance.

A multiplex polymerase chain reaction for the simultaneous detection of the virus and satellite components associated with cotton leaf curl begomovirus disease complex

Cotton leaf curl disease (CLCuD) is caused by a complex of several whiteflies (Bemisia tabaci Genn.)-transmitted begomovirus species, Cotton leaf curl Multan virus (CLCuMuV), Cotton leaf curl Kokhran virus (CLCuKoV) and Cotton leaf curl Alabad virus (CLCuAlV) by individual of mixed infection, associated with Cotton leaf curl Multan betasatellite (CLCuMB) and several alphasatellites. The disease causes major economic losses in cotton in the Indian subcontinent. For monitoring of epidemiology and development of management strategies of CLCuD, a quick, sensitive and effective method capable of detecting all the begomovirus, betasatellite and alphasatellite components associated with CLCuD is required. With this objective, a multiplex polymerase chain reaction (mPCR) assay was developed for the simultaneous detection of these three viral components associated with CLCuD of cotton. Primers for each component were designed based on the retrieved reference sequences from the GenBank. Each pair of primers, designed for each of the respective component, was evaluated for its sensitivity and specificity in both the component-specific simplex polymerase chain reaction (sPCR) and mPCR assay. This report identified three viral component-specific pairs of primers which, in all combinations, amplified simultaneously the CP gene (780 nts) of the begomovirus, the βC1gene (375 nts) of the betasatellite and the Rep gene (452 nts) of the alphasatellite associated with CLCuD in the mPCR assays. The amplified products specific to each component produced by these assays were identified based on their amplicon sizes, and the identities of the viral components amplified were confirmed by cloning and sequencing the amplicons obtained in the mPCR. The mPCR assay was validated using naturally CLCuD-affected cotton plants of the fields. This assay will be useful for rapid detection of CLCuD-associated begomovirus, betasatellite and alphasatellite DNA in field samples, extensive resistance screening in resistance breeding programme, and also monitoring epidemiology for detection of virus and its components when symptoms are mild or absent in the plant.

Durum Wheat Mediterranean Landraces: A Valuable Source for Resistance to Tan Spot Disease

Tan spot (TS), caused by Pyrenophora tritici-repentis (Ptr), has gained significant importance in Tunisia. In this study, a Mediterranean durum wheat collection of 113 accessions were evaluated under field conditions, during the 2018–2019 cropping season, for resistance to Ptr at Koudia experimental station in Bou Salem (Tunisia). The disease progress curve (AUDPC) was used to screen this collection, and the effect of days to heading (DH) and plant height (PH) were evaluated in relation to TS resistance. No significant correlation of PH with AUDPC was found, yet a significant correlation (r = 0.212, p ≤ 0.05) was established between DH and AUDPC scores, suggesting that DH may have an effect on TS development. Moreover, correlation between seedling and adult reactions was significant (r = 0.695, p ≤ 0.001). Although susceptible accessions clustered separately from resistant accessions, the clustering was independent of the country of origin and the status of improvement of the wheat accessions. In total, 67% and 80% of resistant and moderately resistant accessions, respectively, were landraces, suggesting therefore the possible presence of novel sources of resistance to Ptr in some landraces, which can be used to establish a breeding program for resistance to tan spot disease.

Genotypic and phenotypic dissection of Xanthomonas oryzae pv. oryzae on Indica rice cultivars for bacterial blight resistance

Aim: To evaluate the level of virulence of different Xoo isolates/ pathotypes of Eastern and North-eastern India and to identify the suitable donors in rice cultivars having various R-gene combination against virulent Xoo races of Bacterial Blight disease of rice. Methodology: Thirty six Xoo isolates were collected from different places of Eastern and North-eastern India and genetic diversity/ similarity was examined by genotyping of pathotypes using JEL1/JEL2 markers. The 34 Indica rice cultivars carrying different R-gene combination were selected and grown in net house and inoculated artificially with Xoo inoculants from these races/ isolates bacterial of blight disease. Results: The selected 36 Xoo isolates of Eastern and North-eastern India were grouped into seven different isolates/ races based on their genetic diversity using JEL1/JEL2 markers. Among 34 Indica rice cultivars, three or more R-gene combination (xa5 + xa13 + Xa21 and/or Xa4 + xa5 + xa13 + Xa21) cultivars exhibited highly resistant as compared to cultivars with single and double gene combination cultivars against most of the Xoo isolates/ races. Interpretation: The cultivars may determine different level of resistance due to complementary effect of inheritance of suitable R-gene combination. Identified donors may be used for rice resistance breeding programme for Eastern and North-eastern India.

Screening for okra enation leaf curl disease resistance in wild okra (Abelmoschus moschatus ssp. moschatus) germplasm of India

Okra enation leaf curl disease (OELCuD) caused by Okra enation leaf curl virus (OELCuV) is a whitefly (Bemisia tabaci) transmitted viral disease of okra which deteriorates vegetable quality and reduces yield. The OELCuV was confirmed based on the amplicon of 1.3 Kb of beta satellite (DNA-β) molecule of the virus. Field screening of wild okra (Abelmoschus moschatus ssp. moschatus) accessions was carried out for OELCuD resistance during kharif 2017-19 at experimental Farm of ICAR-National Bureau of Plant Genetic Resources, Pusa, New Delhi. Out of 76 wild okra accessions tested, 10 accessions, viz. EC360586, EC360794, EC360830, EC360900, EC359730, EC359836, EC359870, EC360351, EC361111 and EC361171 showed resistant (R) reaction in kharif 2017, whereas in kharif 2019, only four accessions, viz. EC360794, EC360586, EC360830 and EC361171 exhibited R reaction and remaining six accessions were moderately resistant (MR). In the first year, average percent disease index (PDI) was 14.15 and overall PDI ranged from 3.70 to 52.86. The range of PDI was 4.53-56.40 during the second year with an average PDI value 18.04. Apart from PDI determination, whitefly population was also monitored in both the years mainly showed moderate preference. The prominent four accessions of okra, viz. EC360794, EC360586, EC360830 and EC361171 could be utilized in resistance breeding programmes against OELCuV.

Pathogenic Variability of the Jackfruit-Bronzing Bacterium Pantoea stewartii Subspecies stewartii Infection to Jackfruit Varieties and Its Pivotal Plant Hosts in Malaysia

Infection with Pantoea stewartii subspecies stewartii, which causes jackfruit-bronzing disease, is a huge problem faced by the jackfruit industry in Malaysia. This study was carried out to assess the disease ratings and aggressiveness performance of 28 Pantoea stewartii subspecies stewartii isolated from jackfruit-bronzing diseased jackfruits from four collection areas (Jenderam in Selangor State, Maran and Muadzam Shah in Pahang State, and Ipoh in Perak State) in Peninsular Malaysia, inoculated into jackfruit varieties (Tekam Yellow J33, Hong J34 and Subang Chap Boy J39), the sweetcorn variety, Mas Madu (two-week-old seedlings and nine-week-old seedlings), the cucumber variety, Rocky, and the pineapple variety, MD2. The results revealed that Pantoea stewartii subspecies stewartii produced symptoms upon all inoculations in the pathogenicity testing, thus fulfilling Koch’s postulates, except in the case of J39 and sweetcorn (two-week-old seedlings). No disease symptoms (disease rating 0) were observed in J39 and sweetcorn (two-week-old seedlings) within 14 days post-inoculation (14 dpi). The disease progression (based on disease ratings) proved that the jackfruit variety J39 was the most resistant, whereas J33 and J34 were susceptible to jackfruit-bronzing disease. The disease ratings of the 14-dpi period revealed a variability of disease progression among the 28 bacterial isolates, where the isolate JEN-14 had the fastest and highest disease ratings when inoculated into J33, J34, nine-week-old sweetcorn seedlings, cucumber, and pineapple. Likewise, the AUDPC value, based on disease rating, across the 28 isolates indicated that JEN-14 is the most aggressive and significant of the isolates (J33, J34, nine-week-old sweetcorn seedlings, cucumber, and cucumber pineapple inoculation; p &lt; 0.05). Even though isolates from Jenderam (other than JEN-14) and Maran had better disease ratings and the area under the disease progress curve (AUDPC) values than isolates from Muadzam Shah and Ipoh, no significant differences were found among the isolates (p &lt; 0.05). Based on our findings, we identified the isolate JEN-14 as the best potential candidate to assist in jackfruit-bronzing disease resistance breeding in the future. Last but not least, the methods, disease ratings, and variations of the aggressiveness profiles among the isolates from this study may be beneficial and significant by providing disease-rating references and appropriate screening approaches when selecting the most appropriately aggressive isolates for evaluating the defense response in the disease resistance breeding program.

Identification and Validation of a QTL for Bacterial Leaf Streak Resistance in Rice (Oryza sativa L.) against Thai Xoc Strains.

Rice is one of the most important food crops in the world and is of vital importance to many countries. Various diseases caused by fungi, bacteria and viruses constantly threaten rice plants and cause yield losses. Bacterial leaf streak disease (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is one of the most devastating rice diseases. However, most modern rice varieties are susceptible to BLS. In this study, we applied the QTL-seq approach using an F2 population derived from the cross between IR62266 and Homcholasit (HSC) to rapidly identify the quantitative trait loci (QTL) that confers resistance to BLS caused by a Thai Xoc isolate, SP7-5. The results showed that a single genomic region at the beginning of chromosome 5 was highly associated with resistance to BLS. The gene xa5 was considered a potential candidate gene in this region since most associated single nucleotide polymorphisms (SNPs) were within this gene. A Kompetitive Allele-Specific PCR (KASP) marker was developed based on two consecutive functional SNPs in xa5 and validated in six F2 populations inoculated with another Thai Xoc isolate, 2NY2-2. The phenotypic variance explained by this marker (PVE) ranged from 59.04% to 70.84% in the six populations. These findings indicate that xa5 is a viable candidate gene for BLS resistance and may help in breeding programs for BLS resistance.

Assessment of Resistance to Cereal Cyst Nematode, Stripe Rust, and Powdery Mildew in Wheat-Thinopyrum intermedium Derivatives and Their Chromosome Composition.

Wide hybridization between wheat and wild relatives such as Thinopyrum intermedium is important for broadening genetic diversity and improving disease resistance in wheat. We developed 30 wheat-Th. intermedium derivatives. Here, we report assessments of their resistance to different pathogens including cereal cyst nematode (CCN; Heterodera spp.), Puccinia striiformis f. tritici Erikss. causing stripe rust, and Blumeria graminis f. tritici (DC.) Speer inciting powdery mildew. Under natural field infection, all the wheat-Th. intermedium lines were resistant to at least one of the pathogens, and four lines were resistant to multiple pathogens. Twenty-nine of 30 tested lines exhibited resistance to H. avenae, a dominant CCN species in wheat fields. Twenty-four lines were resistant to H. filipjevi, an emerging threat to wheat production. Tests of phenotypic responses in the naturally infected field nurseries identified six stripe rust-resistant lines and 13 powdery mildew-resistant lines. Mitotic observation demonstrated that these newly developed wheat-Th. intermedium derivatives included not only octoploid but also chromosome addition, substitution, and translocation lines. Chromosome compositions of the four lines resistant to multiple pathogens were analyzed by genomic in situ hybridization and fluorescence in situ hybridization. The octoploid lines Zhong 10-68 and Zhong 10-117 carried both intact Th. intermedium chromosomes and translocated chromosomes. Line Zhong 10-149 had 42 wheat chromosomes and two wheat ditelosomes plus a pair of T3BS·J translocated chromosomes. Line Zhong 10-160 carried 41 wheat chromosomes plus one pair of the J genome chromosomes of Th. intermedium. The multiple disease-resistant wheat-Th. intermedium derivatives, especially lines with chromosome counts close to that of common wheat, provide valuable materials for wheat resistance breeding programs.

Integrated Strategies for Durable Rice Blast Resistance in Sub-Saharan Africa.

Rice is a key food security crop in Africa. The importance of rice has led to increasing country-specific, regional, and multinational efforts to develop germplasm and policy initiatives to boost production for a more food-secure continent. Currently, this critically important cereal crop is predominantly cultivated by small-scale farmers under suboptimal conditions in most parts of sub-Saharan Africa (SSA). Rice blast disease, caused by the fungus Magnaporthe oryzae, represents one of the major biotic constraints to rice production under small-scale farming systems of Africa, and developing durable disease resistance is therefore of critical importance. In this review, we provide an overview of the major advances by a multinational collaborative research effort to enhance sustainable rice production across SSA and how it is affected by advances in regional policy. As part of the multinational effort, we highlight the importance of joint international partnerships in tackling multiple crop production constraints through integrated research and outreach programs. More specifically, we highlight recent progress in establishing international networks for rice blast disease surveillance, farmer engagement, monitoring pathogen virulence spectra, and the establishment of regionally based blast resistance breeding programs. To develop blast-resistant, high yielding rice varieties for Africa, we have established a breeding pipeline that utilizes real-time data of pathogen diversity and virulence spectra, to identify major and minor blast resistance genes for introgression into locally adapted rice cultivars. In addition, the project has developed a package to support sustainable rice production through regular stakeholder engagement, training of agricultural extension officers, and establishment of plant clinics.

Evaluation of Pigeonpea Genotypes against Fusarium Wilt and Sterility Mosaic Disease in Gujarat

Background: Fusarium wilt (FW) and sterility mosaic disease (SMD) are two important biotic constraints to pigeonpea production worldwide that can cause loss up to 100 per cent. Host plant resistance is the most durable and economical way to manage these diseases. Methods: Thirty five pigeonpea genotypes comprises [mid early, mid late, dual and hybrid (mid early) group] were evaluated in a fusarium wilt and sterility-mosaic disease-screening nursery at three location viz., Sardarkrushinagar, Bharuch and Vadodara in Gujarat during kharif season 2015-16, to identify genotypes having resistance to both the diseases. Result: Five genotypes identified in each group of pigeonpea viz; mid early (SKNP1303, SKNP 1021, SKNP 0805, SKNP 0920, SKNP 1004), mid late (SKNP 1233, SKNP 10-34, AAUVT 07-10, AAUVT 09-24, GJP1207) and dual (SKNP-1119, BP 06-33, BP 08-06, BP 10-03, BP 10-04) and in hybrid (mid early) group only one hybrid i.e. SKNPCH 1211 were found combined resistance to Fusarium wilt and SMD ( less than 10% disease). These diverse genotypes that are resistant to Fusarium wilt and SMD may be useful in pigeonpea disease resistance breeding programme while hybrid identified as resistance to both the diseases may be recommended for commercial cultivation.

Virulence of Phytophthora infestans isolates from potato in Spain

The oomycete Phytophthora infestans is responsible for the disease known as late blight in potato and tomato. It is the plant pathogen that has caused the greatest impact on humankind so far and, despite all the studies that have been made, it remains the most important in this crop. In Spain during the last years a greater severity of the disease has been observed in both, potato and tomato, probably due to genetic changes in pathogen populations described recently. The aim of this study was the characterization of the physiological strains of 52 isolates of P. infestans obtained in different potato-growing areas in Spain. For this purpose, inoculations on detached leaves were performed in order to determine compatibility or incompatibility reactions. A total of 17 physiological races were found. The less frequent virulence factors were Avr5 and Avr8. By studying the epidemiology of the pathogen, a specific breeding program for late blight resistance can be implemented.

The Emergence of New Aggressive Leaf Rust Races with the Potential to Supplant the Resistance of Wheat Cultivars.

Simple SummaryThe pathogen that causes wheat leaf rust, Puccinia triticina, possesses numerous aggressive races that can erode the resistant genes in its host. This study presents the recognition of the new physiological races of P. triticina, their distribution, and their resistance genes in wheat cultivars, which are critical for directing and improving wheat breeding programs for resistance to leaf rust. Winds often transport the pathogen’s initial inoculum from one country to another. Our findings trigger an alert to the whole world about developing races capable of supplanting leaf rust resistance.Characterization of the genetic structure and the physiological races of Puccinia triticina is a growing necessity to apply host genetic resistance against wheat leaf rust as a successful control strategy. Herein, we collected and identified about 130 isolates of P. triticina from 16 Egyptian commercial wheat cultivars grown at different locations, over two seasons (2019/2020 and 2020/2021). The 130 isolates of P. triticina were segregated into 17 different physiological races. TTTST and TTTKS were the most common virulent races, whereas TTTST and MTTGT were the most frequent races. The races were classified into three groups, based on their distinct DNA band sizes (150 bp, 200 bp, and 300 bp) after RAPD analysis. The new wheat cultivars (Sakha-94, Sakha-95, and Shandweel-1) infected with the most virulent race (TTTST), Gemmeiza-12, and Misr-3 were resistant to all physiological races. The resistance of these cultivars was mostly due to the presence of Lr19- and Lr28-resistant genes. Our results serve as a warning about emerging aggressive races capable of supplanting resistance to leaf rust, and help in the understanding of the pathotype–cultivar–location association and its role in the susceptibility/resistance of new wheat cultivars to P. triticina.

Defensive responses of Erianthus arundinaceus against sugarcane shoot borer, Chilo infuscatellus (Snellen) (Crambidae: Lepidoptera)

A total of eight field screened Erianthus arundinaceus genotypes against sugarcane shoot borer, Chilo infuscatellus was further screened under laboratory conditions along with a ruling variety Co 86032 for their confirmation of resistance and susceptibility. A significant reduction of C. infuscatellus larval and pupal survival; larval and female pupal weight; adult longevity; fecundity rate (eggs/female) and extended larval and pupal duration was recorded in the genotypes IJ 76 370, IJ 76 364 and IK 76 78, respectively. Biochemical parameters viz., total phenols, poly phenol oxidase and proteinase inhibitors and total proteins were highest in the genotypes IJ 76 370 and IJ 76 364 which indicates the presence of antibiosis mechanism of resistance against C. infuscatellus. The total soluble sugars were significantly lower in all genotypes. The genotypes IJ 76 364 and IK 76 84 fed – C. infuscatellus showed lowest larval total carbohydrate and protein content, respectively. The study identified two elite E. arundinaceus IJ 76 370 and IJ 76 364, that could be used as new genetic stocks for the possible utilization in the future resistant breeding programme against sugarcane shoot borer.