Susceptible Varieties Research Articles

Effect of Different Levels of Sodicity on Soil Enzymes, Soil Microbial Biomass Carbon and Activity of Antioxidant Enzymes in Different Rice Varieties under Semi-arid Conditions

Background: Soil sodicity is a major abiotic stress for crop production in many parts of the world. Soil enzymes have been proposed as potential indicators of soil quality due to their connection to soil biology, ease of measurement and quick responsiveness to changes in soil management. Concerning that how different levels of sodicity affects the activity of soil enzymes, soil MBC and antioxidant enzymes in different rice varieties will promote us to understand the mechanism behind the tolerant varieties and to find out the ways to improve the tolerance mechanism. Methods: A field experiment was conducted at Anbil Dharmalingam Agricultural College and Research Institute, Tiruchirappalli, Tamil Nadu during late samba season. Different rice varieties viz., TRY 1, CO 43, TRY 2, CSR 27, TRY 3 and white ponni (WP) were grown at different levels of Exchangeable Sodium Percentage (ESP) ie., 8, 16, 24, 32, 40 and 48 under field condition. The soil samples were collected at flowering stage and analyzed for urease, alkaline phosphatase (APH), dehydrogenase (DHG) and soil microbial biomass carbon (MBC). The plant samples collected at flowering stage were examined for activity of antioxidant enzymes like catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD). Result: The growth and yield decreases with increasing sodicity levels. The soil enzyme and microbial biomass carbon found to be decreased with increasing ESP levels. The antioxidant enzyme increases with increase in sodicity levels in tolerant varieties and decreases at high ESP levels in susceptible varieties. Overall TRY 3 outperformed under increasing sodicity levels compared to other varieties.

Barley shows reduced Fusarium head blight under drought and modular expression of differentially expressed genes under combined stress.

Plants often face simultaneous abiotic and biotic stress conditions; however, physiological and transcriptional responses under such combined stress conditions are still not fully understood. Spring barley (Hordeum vulgare) is susceptible to Fusarium head blight (FHB), which is strongly affected by weather conditions. We therefore studied the potential influence of drought on FHB severity and plant responses in three varieties of different susceptibility. We found strongly reduced FHB severity in susceptible varieties under drought. The number of differentially expressed genes (DEGs) and strength of transcriptomic regulation reflected the concentrations of physiological stress markers such as abscisic acid or fungal DNA contents. Infection-related gene expression was associated with susceptibility rather than resistance. Weighted gene co-expression network analysis revealed 18 modules of co-expressed genes that reflected the pathogen- or drought-response in the three varieties. A generally infection-related module contained co-expressed genes for defence, programmed cell death, and mycotoxin detoxification, indicating that the diverse genotypes used a similar defence strategy towards FHB, albeit with different degrees of success. Further, DEGs showed co-expression in drought- or genotype-associated modules that correlated with measured phytohormones or the osmolyte proline. The combination of drought stress with infection led to the highest numbers of DEGs and resulted in a modular composition of the single-stress responses rather than a specific transcriptional output.

Genetic diversity and its association with Phytophthora palmivora resistance in Durian (Durio zibethinus) using RAPD markers

Abstract. Numba S. 2023. Genetic diversity and its association with Phytophthora palmivora resistance in Durian (Durio zibethinus) using RAPD markers. Biodiversitas 24: 4542-4548. Durian (Durio zibethinus L.) is a popular tropical fruit that contributes significantly to regional economic value. Root and stem rot disease caused by Phytophthora palmivora has become a serious threat to the growth and development of durian. Indonesia has various local durian varieties that have the potential of resistant to P. palmivora. This study aims to analyze genetic diversity and its association with the resistance of durian to root and stem rot disease caused by P. palmivora using RAPD markers. Ten varieties of durian were compared with those of 2 wild species, namely D. kutejensis (Hassk.) Becc. and Boschia excelsa Korth.. The DNA profile analysis was performed by using 10 RAPD primers. Furthermore, cluster analysis was done using the NTSYS (Numerical Taxonomic and Multivariate Analysis System) ver. 2.0. Observation of the DNA profile (DNA banding pattern) showed that all the primers succeeded in producing amplified DNA fragments. Of the total 78 bands produced, 10 bands were considered monomorphic, while 68 bands (87.20%) were considered polymorphic. The high level of polymorphism causes a low level of similarity between varieties so that not all resistant varieties are grouped in the same cluster. This study found that the 1kb band produced by the OPA-2 primer was a potential gen associated with resistance to P. palmivora. It is suggested to carry out further tests on crosses of resistant and susceptible varieties.

Incidence of Sapota Seed Borer <i>Trymalitis margarias</i> Meyrick and its Management

A study on the incidence and management of sapota seed borer Trymalitis margarias Meyrick was conducted from 2019 to 2020 in Mudigere. The varietal screening experiment revealed that PKM-1 was the least susceptible variety with 4.58% fruit damage followed by DSH-1 (9.79%) while Kalipatti was found to be highly susceptible (18.76%). The highest parasitisation by the larval parasitoid, Bracon sp. was seen in Kalipatti i.e., 28.13% while the least was observed in PKM-1 (7.29%). Among the insecticides screened against T. margarias from two sprays, profenophos 50EC (0.13 larvae/ fruit and 9.72% fruit damage) and novaluron 10EC (0.19 larvae/ fruit and 13.43% fruit damage) performed very well over standard check deltamethrin 2.8EC (0.3 larvae/ fruit and 22.22% fruit damage) in minimizing the infestation. Further, the highest fruit yield and the cost-benefit ratios were documented in novaluron 10EC (7.37 t/ ha and 1: 2.96).

Genetic response of hybrid maize line to downy mildew caused by Peronosclerospora spp. infection

Maize is the second staple food commodity in Indonesia. Apart from being the main source of carbohydrates and protein, the production of maize continues to increase along with the escalation of population growth and animal feed requirements in the last few years. The potential to increase the national production of maize is still feasible because of the yield gap between the potential yields of new superior varieties and the level of yields obtained by farmers. The yield gap caused by biotic stress in maize is mainly caused by pathogens such as downy mildew due to Peronosclerospora spp. Downy mildew distribution is sporadic that can infect a wide area. In Indonesia, it spreads widely and significantly reduces yields in the areas of maize production centres in East Java, Central Java, South Sulawesi, North Sulawesi, Gorontalo, Lampung, and Sumatera. These obstacles can be overcome by integrated pest and disease control technology. One strategy is to discover downy mildew-resistant varieties that can be combined with other control treatments. The phenomenon of resistance to downy mildew infection of several hybrid maize strains began to be detected in the vegetative growth phase, with symptoms beginning at 14 days after planting (DAP), increasing with plant age, and reaching its peak after 28-35 DAP and then the symptoms will gradually disappear until no infection after 42 HST. This study analyses the resistant maize varieties from 2020 to 2022. The data showed the susceptible comparison variety (Anoman) was infected with 88.94% to 100%. In 2020, BMD73 showed a resistant reaction to Philippinensis species, other strains were classified as susceptible in P. maydis except BMD 76. All strains showed highly susceptible and susceptible reactions. In 2021, in P. philippinensis all strains FCP10-FCP16 showed a resistant reaction, but line FCP10-FCP16 had a resistance response that was classified as moderately resistant to P. maydis. The incidence of genetic response in 2022, except BMD86, strains BMD81-BMD85 were classified as resistant, as well as in the P. maydis endemic area all strains showed the same reaction.

Molecular-genetic machanisms of resistance to broomrape in sunflower

Sunflower broomrape (Orobanche cumana Wallr.) is an obligate parasitic plant that specifically infects sunflower and can cause significant yield losses. In this regard, obtaining sunflower varieties resistant to broomrape is an important task for agriculture. Sunflower breeding for resistance to broomrape was initiated in the beginning of the 20th century in USSR. However, the production of new resistant sunflower varieties was accompanied by the emergence of new virulent broomrape races that overcame the effect of resistance genes. For a number of sunflower genetic loci that determine resistance to broomrape, the location on the genetic map was determined, but only for some of them probable candidate genes were identified and the possible molecular mechanism of their action was described. In addition, transcriptomic data have recently been obtained for broomrape-resistant and susceptible sunflower varieties, which also makes it possible to get closer to understanding the molecular basis of resistance formation. This review focuses on molecular genetic mechanisms of sunflower resistance to broomrape, identified on the basis of genetic mapping of resistance loci, determination of probable candidate genes, as well as available transcriptomic data.

English

Narrow brown leaf spot disease of rice caused by fungus Cercospora oryzae Miyake emerged as potential threat to rice crop in previous few years worldwide and can cause more than 40% yield loss. The disease symptoms were noted on various commercially important rice varieties in the rice growing districts of Punjab province of Pakistan. Hence, the studies were planned to assess the effects of Propiconazole fungicide application timings and different rice varieties on the severity of narrow brown leaf spot (NBLS) disease of rice to develop an accurate management strategy for the disease. The Propiconazole fungicide was tested at three various growth phases (early booting, late booting, and soft dough) of four rice varieties against the percent severity of the NBLS disease The experiments were designed under strip-plot (crisscross) design with four replications at research area of Plant Pathology Department, University of Agriculture Faisalabad. Analysis of variance has demonstrated that the main and interactive effects of fungicide applications and rice varieties were found significant. The main effects of years were found non-significant but their interactions with fungicide application timings and rice varieties were significant. Fungicide applications at soft dough and late booting phases of rice variety B-515 were found least effective to reduce the disease severity, respectively. Fungicide application at early booting of rice variety PK-1121 was found most effective by reducing the maximum percent diseases severity (47.25%) compared to control. It is concluded that, to minimize hazardous effects of chemicals on the environment by practicing multiple sprays at inappropriate growth phases of rice crop, fungicides must be applied during the early and late booting phases of rice varieties on mildly resistance, susceptible and highly susceptible rice varieties to reduce NBLS disease severity and to enhance the rice production and quality

Integration of Soybean (Glycine max) Resistance Levels to Sclerotinia Stem Rot into Predictive Sclerotinia sclerotiorum Apothecial Models.

Sclerotinia stem rot (SSR) is a major disease of soybean across the Upper Midwest region of the United States. Management of this disease has relied on fungicide applications, but due to the environmental conditions necessary for SSR to develop, many of these applications are unnecessary. To mitigate this, predictive models have been developed using localized weather data for predicting the formation of Sclerotinia sclerotiorum apothecia, the inoculum source of SSR, and these models were integrated into a decision support system called Sporecaster. However, these models do not account for the soybean resistance levels to SSR. In this study, fungicide trials were performed across seven site-years in Wisconsin between 2020 and 2022 examining fungicide applications applied at one of three action thresholds (low, moderate, and high) following Sporecaster recommendations in combination with four soybean varieties representing three SSR resistance levels (susceptible, moderately resistant, and resistant). From these trials, the low and moderate action thresholds resulted in similarly low disease severity index (DIX) levels comparable to the standard across all varieties. However, the low action threshold was most accurate for predicting SSR development in the susceptible variety, and the high action threshold was most accurate for predicting SSR development for the three resistant varieties. Both the susceptible soybean and a moderately resistant line yielded similarly high results. Additionally, the use of all fungicide applications led to similar partial profits at grain sale prices of either $0.44 or $0.55 kg-1. Overall, this study uncovered relationships between soybean resistance levels to SSR and Sporecaster, allowing for improved recommendations for fungicide applications.

Effects of anti-herbivore resistance on sensory characteristics and ripening of strawberry

Plant resistance to agricultural pests is a fundamental element of sustainable crop protection. However, concerns have been raised that strategies to increase resistance may involve phytochemicals that impact fruit ripening and the sensorial perception of the fruit. Here, we experimentally tested for these putative resistance effects by contrasting susceptible varieties of strawberry (Fragaria vesca) with varieties that were either constitutively resistant to pest insects or with resistance induced with jasmonic acid (JA). GC-MS analysis identified 11 volatile compounds, including alcohols, aldehydes, lactone, terpenoids, and esters, which showed higher concentrations in fruits from resistant/induced plants. Fruits from induced plants ripened faster in the field. In sensory analyses, using a trained analytical panel, some variation between the sensory profiles of the strawberry varieties was detected, but we found no systematic correlations between sensory attributes and the level of plant resistance/induction in the varieties. These results suggest that increased plant resistance comes with positive effects of early ripening, while not strongly affecting the overall sensory experience.

Loss of a Premature Stop Codon in the Rice Wall-Associated Kinase 91 (WAK91) Gene Is a Candidate for Improving Leaf Sheath Blight Disease Resistance.

Leaf sheath blight disease (SB) of rice caused by the soil-borne fungus Rhizoctonia solani results in 10-30% global yield loss annually and can reach 50% under severe outbreaks. Many disease resistance genes and receptor-like kinases (RLKs) are recruited early on by the host plant to respond to pathogens. Wall-associated receptor kinases (WAKs), a subfamily of receptor-like kinases, have been shown to play a role in fungal defense. The rice gene WAK91 (OsWAK91), co-located in the major SB resistance QTL region on chromosome 9, was identified by us as a candidate in defense against rice sheath blight. An SNP mutation T/C in the WAK91 gene was identified in the susceptible rice variety Cocodrie (CCDR) and the resistant line MCR010277 (MCR). The consequence of the resistant allele C is a stop codon loss, resulting in an open reading frame with extra 62 amino acid carrying a longer protein kinase domain and additional phosphorylation sites. Our genotype and phenotype analysis of the parents CCDR and MCR and the top 20 individuals of the double haploid SB population strongly correlate with the SNP. The susceptible allele T is present in the japonica subspecies and most tropical and temperate japonica lines. Multiple US commercial rice varieties with a japonica background carry the susceptible allele and are known for SB susceptibility. This discovery opens the possibility of introducing resistance alleles into high-yielding commercial varieties to reduce yield losses incurred by the sheath blight disease.

Immunological assessment of winter barley cultivars against leaf net blotch

Immunological assessment of winter barley varieties sown in the south of Russia in relation to leaf net blotch infestation for further use in agricultural production has been carried out. Barley net blotch is dominant in the pathologic complex of barley diseases worldwide. The pathophysiological processes of infection development depend on the type of resistance of the variety. Net blotch on resistant varieties is noted as small dark rounded spots. Infection often occurs as a result of mechanical damage to the leaf plate. The symptoms of net blotch disease on a susceptible variety have a characteristic reticulate pattern with pronounced necrosis and extensive chlorosis. One of the main ways to protect crops from the disease is the cultivation of resistant varieties. The study was conducted during the growing seasons of 2020–2022 on artificial infectious background in the sprouting phase phase of the vegetation experiment and in the adult plant on the natural infectious background in field conditions. 10 varieties of winter barley of domestic and foreign selection were selected. Immunological assessment in the sprouting phase revealed two varieties resistant to leaf net blotch, score: Vivat (1.7) and Kvant (1.6); the varieties Artel (3.8), Fox-1 (2.3) of domestic selection and Carioca (2.7) of foreign selection showed moderate resistance. Field moderate resistance was detected in four winter barley varieties, %: Vivat (18.3), Kvant (26.6), Marusya (19.9), Fox-1 (24.9). Immunological assessment of barley varieties recommended for sowing in the south of Russia is one of the main components in the strategy of increasing the efficiency of plant protection measures and improving the ecological component of crops.

Comparative analysis of salicylic acid levels and gene expression in resistant, tolerant, and susceptible cassava varieties following whitefly-mediated SLCMV infection

Sri Lankan cassava mosaic virus (SLCMV), the primary pathogen responsible for cassava mosaic disease in cassava plantations, is transmitted via infected cutting stems and the whitefly vector, Bemisia tabaci. To obtain better insights into the defense mechanism of cassava against SLCMV, whiteflies were used to induce SLCMV infection for activating the salicylic acid (SA) signaling pathway, which triggers the innate immune system. The study aimed to investigate the specific interactions between viruliferous whiteflies and SA accumulation in resistant (C33), tolerant (Kasetsart 50; KU50), and susceptible (Rayong 11) cassava cultivars by infecting with SLCMV. Leaf samples were collected at various time points, from 1 to 7 days after inoculation (dai). The SA levels were quantified by gas chromatography–mass spectrometry and validated by quantitative reverse transcription polymerase chain reaction. The SA levels increased in KU50 and C33 plants at 2 and 3 dai, respectively, but remained undetected in Rayong11 plants. The expression of PR-9e, PR-7f5, SPS1, SYP121, Hsf8, and HSP90 increased in infected C33 plants at 4 dai, whereas that of KU50 plants decreased immediately at 2 dai, and that of Rayong11 plants increased at 1 dai but gradually decreased thereafter. These findings strongly indicate that SA plays a crucial role in regulating antiviral defense mechanisms, especially in SLCMV-resistant plants. Altogether, the findings provide valuable insights into the mechanisms underlying the activation of SA-mediated anti-SLCMV defense pathways, and the resistance, tolerance, and susceptibility of cassava, which can aid future breeding programs aimed at enhancing SLCMV resistance.

Reaction of Maize Genotypes against Fall Armyworm, Spodoptera frugiperda (Smith) in Madhya Pradesh, India

Aims: To identify the less susceptible varieties, allowing for targeted pest management strategies, reduced pesticide use, increased resilience to pest outbreaks, and long-term sustainable pest control solutions.
 Study Design: Randomized Block Design.
 Place and Duration of Study: Research Farm, College of Agriculture, Gwalior (Rajmata Vijayaraje Scindia Krishi Vishwa Vidyalaya, Gwalior) during two consecutive years i.e., Kharif, 2021-22 and Kharif 2022-23.
 Methodology: In the experiment, twelve different varieties were sown on 17th July 2021 and 17th July 2022 during both the consecutive years respectively. Observations on the number of fall armyworm, Spodoptera frugiperda larvae and plant damage per cent were recorded from randomly selected ten plants at weekly intervals. Observations for FAW was also be recorded with visual scoring method. A numerical scale (0-9), also known as the Davis scale, was used to evaluate leaf damage.
 Results: The result of both the year indicated that not all varieties were found to be completely resistant to fall armyworm. For the purpose of interpreting the results, all the varieties were categorized for their reaction based on average data of both the years (Kharif 2021 and Kharif 2022) of mean larval population, mean plant damage percent, and leaf damage scoring. Based on statistical categorization, it was determined that the varieties NWMH-2002 and JM 218 exhibited lower susceptibility. On the other hand, the varieties Dkc-9141, Maize 3845, PAC 740, Yashoda gold, PM 303, Maize Ranker, Maize 5402, and Maize 3046 were classified as moderately susceptible. Lastly, Sona 5101 and M-909 were identified as highly susceptible varieties.
 Conclusions: It concluded that the varieties NWMH-2002 and JM 218 exhibited lower susceptibility against fall armyworm.

Farmer knowledge, management practices and occurrence of tomato root knot nematodes in Kenya

Root-knot nematodes (RKNs) (Meloidogyne spp.) is a major constraint to tomato (Solanum lycopersicum L.) production in sub-Saharan Africa; yet there is low adoption of recommended nematode control measures in regions like east Africa due to inadequate farmer knowledge about the pest and associated diseases. The objective of this study was to assess farmers’ knowledge status, and intensity of damage of root-knot nematodes and their management practices in Kenya. A survey was conducted in Kenya, during February to August 2021; using a semi-structured questionnaire administered to 282 randomly selected household heads of actively growing tomato farmers, at two elevations in three counties. Most farmers (98.9%) could not identify the disease precisely. They mostly attributed its symptoms to moisture stress and nutrient deûciencies. Most farmers (63%) practiced mono-cropping; while only 4.3% of farmers amended soils with manure. Respondents preferred growing RKN susceptible tomato varieties, mainly Rio-Grande, Cal J, Onyx and Kilele FI. A total of 92% expressed willingness to shift to RKNs resistant varieties, if recommended varieties match their desirable characteristics. Majority of the respondents lacked knowledge on nematode characteristics and its associated disease control. A total of 37.9% of the respondents did not use control measures against the RKNs. There was high disease incidence, severity and galling index in the surveyed areas.

Advances in understanding the mechanism of resistance to anthracnose and induced defence response in tea plants.

The tea plant (Camellia sinensis) is susceptible to anthracnose disease that causes considerable crop loss and affects the yield and quality of tea. Multiple Colletotrichum spp. are the causative agents of this disease, which spreads quickly in warm and humid climates. During plant-pathogen interactions, resistant cultivars defend themselves against the hemibiotrophic pathogen by activating defence signalling pathways, whereas the pathogen suppresses plant defences in susceptible varieties. Various fungicides have been used to control this disease on susceptible plants, but these fungicide residues are dangerous to human health and cause fungicide resistance in pathogens. The problem-solving approaches to date are the development of resistant cultivars and ecofriendly biocontrol strategies to achieve sustainable tea cultivation and production. Understanding the infection stages of Colletotrichum, tea plant resistance mechanisms, and induced plant defence against Colletotrichum is essential to support sustainable disease management practices in the field. This review therefore summarizes the current knowledge of the identified causative agent of tea plant anthracnose, the infection strategies and pathogenicity of C. gloeosporioides, anthracnose disease resistance mechanisms, and the caffeine-induced defence response against Colletotrichum infection. The information reported in this review will advance our understanding of host-pathogen interactions and eventually help us to develop new disease control strategies.

Physiological and Gene Expression Analysis of Herbaceous Peony Resistance to Alternaria tenuissima Infection

Leaf spot disease caused by Alternaria pathogens seriously threatens peony production. The physiological mechanism of peony resistance to the pathogen is little reported. This study aimed to reveal the defensive mechanism of peonies in response to the pathogen Alternaria tenuissima. The disease-resistant (R) variety ‘Zi Fengyu’ and susceptible (S) variety ‘Heihai Botao’ were employed, and some parameters in the leaves were analyzed after inoculation with A. tenuissima, mainly including the hypersensitive response (HR), activity of defensive enzymes, and expression of disease-resistance genes. The results showed that compared with the responses in the S genotype, HR occurred more rapidly in the R genotype. Meanwhile, the activity of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase) and other two defense enzymes (polyphenol oxidase and phenylalanine ammonia-lyase) increased more significantly, and the expression of pathogenesis-related (PR) genes (PlPR1, PlPR2, PlPR4B, PlPR5, and PlPR10) and two WRKY genes (PlWRKY13 and PlWRKY65) was more strongly induced. These responses collectively contributed to the disease resistance of the R genotype. These findings provided a theoretical basis for understanding the intrinsic mechanism of peony resistance to Alternaria leaf spot disease and breeding the disease-resistant peony varieties using a molecular approach.

First report of Fusarium poae Causing Fusarium head Blight of Wheat in India.

Wheat is one of major cereal crops with paramount importance that is cultivated across the globe. Fusarium head blight (FHB) is a catastrophic disease of wheat which has recently risen to prominence due to its direct impact on the quality and quantity of wheat on a global scale. During a field survey conducted in Rabi 2021-22, wheat spikes showing characteristic symptoms of head blight were observed in northern parts of the Karnataka, India, in the districts Bagalkote, Belagavi and Dharwad. The infected spikelets from the heads with symptoms of infection were washed well in distilled water and surface sterilized using 1% sodium hypochlorite solution. They were further washed using sterilized distilled water to remove the traces of sodium hypochlorite. These spikelets were then transferred to sterile potato dextrose agar (PDA) plates under aseptic conditions. The plates were incubated at a temperature of 27±1°C for ten days to obtain good fungal growth. The fungus produced white to orangish pink, dense mycelia and hyaline septate hyphae. Macroconidia were sickle-shaped measuring 35.7 to 52.6 x 3.2 to 5.1 µm, dorsoventrally curved with an elongated basal cell ending in a prominent long foot; the apical cell was also elongated, tapered, slightly curved. Spores had 3 to 4 cells and formed on monophialide. Microconidia and chlamydospores were present only in a few isolates. Fungal genomic DNA was extracted from all the established isolates using CTAB (Cetyl-trimethyl ammonium bromide) method (Murray and Thompson, 1980). The ITS region of r-DNA and translation elongation factor-1 alpha (TEF-1α) genes of the ten isolates were amplified using ITS1/ITS4 primer pair (White et al. 1990) and the species-specific EF1F/EF1R primer pair (O'Donnell et al., 1998) respectively, to detect and distinguish within Fusarium species. The results exhibited 95% similarity with Fusarium poae with GenBank Accession No. XMO44849482.1. which was previously reported as a causal agent of Fusarium head blight of wheat in Georgia, USA. The TEF1-α sequences were deposited in the GenBank and the accession numbers from OP716756 to OP716765 were obtained. For the pathogenicity test, spore suspension containing a load of 108 conidia ml-1 was prepared from ten days old Fusarium poae culture and sprayed on the healthy wheat heads of the susceptible variety UAS-304 during anthesis stage by using hand atomizer. Control plants were sprayed in a similar manner with sterile distilled water. In order to enhance disease development and increase the accuracy of the evaluation, humidity was maintained for 72 hours post-inoculation period by covering each spike with a plastic bag and misting at least once daily. The characteristic head blight symptoms were observed in the inoculated wheat spikes. No symptoms were noticed in the water-treated control. The plants initially showed bleaching in single spikelet after seven days of inoculation, which eventually spread to the entire spike. After fourteen days of inoculation, the spikes showed blighted appearance with pinkish or orangish mass of mycelia grown on the affected region. The pathogen was further reisolated from the infected plants and examined under the microscope. The similar morphological features as that of the originally inoculated pathogen was observed, hence fulfilling Koch's postulates. To our knowledge, this is the first report of Fusarium poae causing head blight of wheat in India. Keeping the current climate change scenario in view, the plausibility of this pathogen causing a major havoc in the near future must not be ignored, considering the fact that it has a wide host range and highly evolving nature. The ubiquity of the Fusarium head blight recently in northern parts of Karnataka urges the need to conduct further studies on the variability, distribution and management of the pathogen.

Variation in Susceptibility to Downy Mildew Infection in Spanish Minority Vine Varieties.

Downy mildew is one of the most destructive diseases affecting grapevines (Vitis vinifera L.). Caused by the oomycete Plasmopara viticola (Berk. and Curt.) Berl. and de Toni, it can appear anywhere where vines are cultivated. It is habitually controlled by the application of phytosanitary agents (copper-based or systemic) at different stages of the vine growth cycle. This, however, is costly, can lead to reduced yields, has a considerable environmental impact, and its overuse close to harvest can cause fermentation problems. All grapevines are susceptible to this disease, although the degree of susceptibility differs between varieties. Market demands and European legislation on viticulture and the use of phytosanitary agents (art. 14 of Directive 128/2009/EC) now make it important to know the sensitivity of all available varieties, including minority varieties. Such knowledge allows for a more appropriate use of phytosanitary agents, fosters the commercial use of these varieties and thus increases the offer of wines associated with different terroirs, and helps identify material for use in crop improvement programmes via crossing or genetic transformation, etc. Over 2020-2021, the susceptibility to P. viticola of 63 minority vine varieties from different regions of Spain was examined in the laboratory using the leaf disc technique. Some 87% of these varieties were highly susceptible and 11% moderately susceptible; just 2% showed low susceptibility. The least susceptible of all was the variety Morate (Madrid, IMIDRA). Those showing intermediate susceptibility included the varieties Sanguina (Castilla la Mancha, IVICAM), Planta Mula (Comunidad Valenciana, ITVE), Rayada Melonera (Madrid, IMIDRA), Zamarrica (Galicia, EVEGA), Cariñena Roja (Cataluña, INCAVI), Mandrègue (Aragón, DGA) and Bastardo Blanco (Extremadura, CICYTEX). The highly susceptible varieties could be differentiated into three subgroups depending on sporulation severity and density.

Identification of Novel QTLs for BPH Tolerance in Rice Using Resistant Donor BM 71

Rice is the most widely grown crop in the world, feeding half of the world’s population. Brown plant hopper (BPH) is a considerable risk to rice fields carrying 20-90% yield losses. Hopper burn can be effectively managed by the recognition and use of BPH genes. Marker based genetic analysis of 136 RILcollected from a high yielding susceptible variety, MTU 3626 and BM 71, a BPH donor developed at RARS, identified 3 minor novel QTLs viz; qmbph2.1,qmbph4.1 and qmbph12.1 on chromosomes 2, 4 and 12 and two other QTLson chromosome 5 and 7, namelyqmbph5.1 and qmbph7.1. The phenotyping of RIL’s revealed that ten RIL’s (2711 – 31, 2711 – 37, 2711 – 50, 2711 – 69, 2711 – 84, 2711 – 88, 2711 – 94, 2711 – 100, 2711 – 168 and 2711 – 191) recorded yields comparable to checks, Swarna and Pushyami along with BPH score similar to donor. The BPH resistance lines recognised will be further evaluated, and the confirmed lines can be employed in rice breeding programs.

Stem rust severity and AUDPC values of different wheat varieties in response to Puccinia graminis f. sp tritici

Wheat is the important cereal and is highest produced grain in the world after corn and rice. It is the second most important crop in India next to rice. Like several crops, wheat is also prone to diseases. Among various diseases, wheat stem rust is the main biotic constraint to wheat production and it is important to understand and analyze the disease in terms of pathological responses. Out of six cultivars tested, three wheat varieties showed a resistance response, while the other three varieties showed a susceptible response against stem rust of wheat. Disease severity and area under disease progressive curve (AUDPC) data of three susceptible varieties revealed that the highest AUDPC value (1785.93) was recorded in A-9-30-1 which showed the most susceptible response followed by Agra Local (1762.93) and Kharachia (1645.90). There was no development of stem rust symptoms on three varieties viz., GDW 1255, GW 496 and GW 451.