Screening of South Indian Culinary Melon (Cucumis melo subsp. agrestis var. acidulus) Accessions for Downy Mildew Disease under Natural Epiphytotic Condition

Culinary melon also known as non dessert cucumber (Cucumis melo subsp. agrestis var. acidulus) belongs to the family Cucurbitaceae. It is widely cultivated in Southern parts of Indian subcontinent. It is mainly utilized for preparation of lentil soup, sambar, dosa, palya and chutney. 70 accessions were collected from six South Indian states namely Karnataka, Kerala, Andhra Pradesh, Tamil Nadu, Telangana and Goa. The accessions were evaluated for incidence of downy mildew resistance during Kharif 2018 under natural condition. The percent disease index (PDI) for downy mildew ranged from 3.70 to 48.64%. 10 accessions showed resistance to downy mildew. Among them, accession MS21 showed resistance with average least PDI of 3.70 followed by MS 6 (6.54). 50 accessions were found to be moderately resistant with average PDI ranging from 20 to 39.80. 12 accessions were found susceptible with PDI ranging from 41 to 49. None of the accession was found highly susceptible to the disease. The resistant accessions can be utilized as donor parents for resistant breeding in the improvement of culinary melon as well as melon group of vegetables.

Screening of fungicides and plant extracts for controlling blight disease of Tagetes spp.

A field experiment was conducted in the Botanical research garden, Department of Botany, University of Dhaka during 2015, 2016 and 2017 to evaluate the efficacy of two fungicides and two plant extracts against blight disease of Tagetes erecta L. and T. patula L. Both the fungicides Bavistin 50 WP and Tilt 250 EC and leaf extracts of Azadirachta indica A. Juss. and Citrus medica L. showed effective management of the disease over the untreated check. However, among the treatments, Bavistin 50 WP and Tilt 250 EC at 100 ppm concentration and A. indica and C. medica L. at 10% concentration were found significantly superior in controlling percent disease index and increasing number of healthy flowers. The number of healthy flowers was highest per plant, 17.13 in T. erecta in 2017 and 25.00 in T. patula in the year 2016. J. Asiat. Soc. Bangladesh, Sci. 47(1): 79-89, June 2021

Evaluation of Essential Oils against Early Blight (Alternaria solani) of Tomato

The fungicidal effect of some essential oils viz., Neem, Eucalyptus, Pongamia, Lemongrass, Thyme and Clove were evaluated against Alternaria solani causing early blight of tomato resulting in severe yield loss. All essential oil treatments showed the significantly varied antifungal activity against the pathogen. Among the in-vitro screened essential oils percent growth inhibition of pathogen was higher in Thyme oil (80%) and it was followed by Clove oil and Eucalyptus oil. Plant biometric observations viz., seed germination (84%) and seedling vigor (1747) was maximum with lower percent disease index (13%) was recorded in Thyme oil treated seeds and seedlings of tomato cultivar PKM 1.

Performance Evaluation of Farmers’ Onion Varieties against Purple Blotch Disease

Aims: To evaluate the performance of farmers’ onion varieties against purple blotch disease at different locations and to correlate Percent Disease Index with yield attributing and other important traits. Study Design: Randomized Block Design, Field demonstration. Place and Duration of Study: National Innovation Foundation- India Gandhinagar Gujarat, Repoli and Palghar research stations of Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli Maharashtra during October 2017 to April 2019. Methodology: Two farmers’ onion varieties Sona-40 and Sandip were characterized and tested for their response against purple blotch disease under field condition in comparison with location-specific check varieties. Percent Disease Index of purple blotch was observed, compared and correlated with important traits viz. the plant height, leaves per plant, bulb diameter, maturity period, bulb weight, bulb yield and keeping quality. In Maharashtra areas, the study was conducted under Repoli and Palghar conditions during winter (Rabi) 2017, whereas at Gandhinagar Gujarat, it was undertaken in winter (Rabi) 2017 and 2018. Results: The farmers’ onion cultivars Sandip and Sona-40 were found to be tolerant to the purple blotch disease at all the locations. In Maharashtra and Gujarat, the average Percent Disease Index (PDI) in Sona-40 (12.1%, 12.2%) and Sandip (10.75%, 14.64%) was found significantly lower as compared to the checks respectively. The present studies also confirmed that onion bulb’s yield, weight and keeping quality were significantly correlated with the purple blotch disease. Conclusion: This study exhibited that the farmers’ onion varieties may perform better against disease infestation such as purple blotch disease. It also confirmed that the response of the onion varieties against purple blotch may vary in different locations. It is shown that the bulb weight, yield and shelf life of bulbs are significantly affected by purple blotch disease.

Temperature Drives Contrasting Alternaria Leaf Spot Epidemic Development in Canola and Mustard Rape from Alternaria japonica and A. brassicae

Recent surveys of canola (Brassica napus) crops across southern Australia highlighted that Alternaria leaf spot on canola is not solely caused by Alternaria brassicae but that other Alternaria spp. are also involved, including A. japonica. Studies were undertaken into the effects of different temperatures (14 and 10°C [day and night] or 22 and 17°C [day and night]) on development of Alternaria leaf spot caused by A. japonica as compared with A. brassicae in cotyledons (embryonic leaves) and true leaves (first leaves) of canola (B. napus ‘Thunder TT’) and mustard rape (B. juncea ‘Dune’). Both pathogens expressed less disease at lower temperatures of 14 and 10°C with percent disease index (%DI) of 19.1 for A. japonica and 41.8 for A. brassicae, but expressed significantly more disease at higher temperatures of 22 and 17°C with %DI of 80.8 and 88.2 for the same pathogens, respectively. At 14 and 10°C, mustard rape cotyledons showed less disease (percent cotyledons disease index [%CDI] = 18.1) from A. japonica but showed more disease (%CDI = 75.0) from A. brassicae. However, at 22 and 17°C, cotyledons and true leaves of both canola and mustard rape showed significantly more disease and varied in expressing the disease severity to the two pathogens; true leaves of mustard rape showed less disease (percent true leaf disease index [%TDI] = 48.4) from A. japonica but showed more disease (%TDI = 92.0) from A. brassicae. At 22 and 17°C, cotyledons of canola expressed more disease from A. japonica (%CDI = 99.1) than from A. brassicae (%CDI = 70.7). At the lower temperature, both host species showed the least disease, with mean %DI of 27.3 and 33.5 for canola and mustard rape, respectively, as compared with the higher temperatures, where there was a greater DI, with %DI values of 87.9 and 81.2 for these same host species, respectively. We believe that these are the first studies to highlight the critical role played by temperature for A. japonica as compared with A. brassicae in Alternaria leaf spot disease development and severity. These findings explain how temperature affects Alternaria leaf spot severity caused by A. japonica as compared with A. brassicae on different foliage components of canola and mustard rape.

Management of Leaf Blight Disease Caused by Alternaria polianthi in Tuberose

Tuberose is an ornamental crop which is growing under tropical and sub-tropical areas. Recently, the incidence of leaf blight disease caused by Alternaria polianthi a fungal disease of tuberose is considered as a severe problem causing growth reduction and yield loss triggered by high temperature and humidity. Hence an investigation was carried out in farmer fields at Tumnakatti, Ranebennurtq in Karnataka, to study the bio-efficacy of different fungicides against leaf blight of tuberose. There were six chemicals viz., Tebuconazole 250 EC @ 0.1%, Difenconazole – 25% EC @ 0.1%, Propinoconazole 25% EC @ 0.1%, Hexaconazole 2% SC @ 0.1%, Mancozeb75 WP @ 0.25%, Chlorothalonil 75 WP @ 0.2%, were evaluated in tuberose cultivar Prajwal during kharif 2016 and 2017. Among the different fungicides, four sprays taken with Tebuconazole @ 0.1% at 15 days interval starting from onset of disease proved to be the most effective treatment and resulted in lowest percent disease index, PDI (10.80). Maximum yield and number of flower stalks per square meter area were recorded in Tebuconazole @ 0.1% (50.90). Tebuconazole @ 0.1% could be used for management of leaf blight and increase the yield of tuberose.

Variability Studies in Melon (Cucumis melo.L) F2 Population of Kashi Madhu x COHB38 for Powdery Mildew Resistance

The present investigation was carried at College of Horticulture, Bengaluru. Evaluation of melon F2 population (Kashi Madhu X COHB38) was conducted during rabi 2016 for resistance to powdery mildew disease under natural field condition. Percent Disease Index (PDI) and AUDPC (Area Under Disease Progress Curve) value was calculated to assess the reaction of F2 (Kashi Madhu X COHB38) segregating population of melon along with the parents (COHB38 and Kashi Madhu) and F1. Based on PDI for powdery mildew disease, 152 F2 plants were classified into different categories. Twenty five F2s were resistant (0-25% PDI), 27 were moderately resistant (25.1-40% PDI), 88 were susceptible (40.1-60% PDI) and 12 F2s were highly susceptible (>60% PDI). Among 152 F2 plants, F2 -34 was found to be highly resistant with zero PDI and zero AUDPC value (no disease) followed by F2- 46 and 92 with PDI of 13.89 % and 16.11 % and 46.94 and 55.00 AUDPC value, respectively. The PDI of the disease showed a continuous distribution from highly resistant to highly susceptible phenotypes, without showing any typical segregation pattern. Int. J. Appl. Sci. Biotechnol. Vol 7(4): 407-413

Effect of Planting Time on Sheath Blight Disease of Rice in Bangladesh

Sheath blight (ShB) caused by Rhizoctonia solani is one of the major disease of rice (Oryza sativa L.) in Bangladesh. Effect of planting time on ShB disease of BRRI dhan49 was observed at the experimental plots of Bangladesh Rice Research Institute, Gazipur. Two field experiments were conducted to develop management strategy for controlling ShB during T. Aman 2010-11 seasons. Four planting dates viz. 15 July, 30 July, 15 August and 30 August were imposed to record the effect of planting time on incidence and severity of ShB disease on BRRI dhan49. Significant differences on the Relative Lesion Height (RLH) among the treatments were observed during both 2010 and 2011 seasons. For both the seasons, the highest RLH was recorded in plots transplanted on 15 August (62.1% in 2010 and 61.2% in 2011) because of the remaining high temperature, rainfall and humidity and the lowest in plots transplanted on 30 July (19.4% for both). Similarly, the maximum severity score was recorded in 15 August transplanting (7) and the minimum in 30 July (1) respectively. Percent disease index (PDI) was also varied significantly among the treatments for both the seasons. During both the years, the maximum PDI was recorded in 15 August (76.5 and 75.2% respectively) and the minimum in 30 July transplanting (20.4 and 20.1 respectively). However, the highest number of filled grains panicle-1 was counted in 30 July (151), followed by15 July transplanting (145) during 2010. But, it was the highest in 30 July (141), followed by 15 August transplanting (136) during 2011. Again for both the seasons, the lowest filled grains panicle-1 was recorded in 30 August transplanting (116 and 127). Similarly for both the years, the maximum grain yield was observed in 30 July (6.29 and 5.82 t ha-1 respectively), followed by 15 July (5.67 and 5.17 t ha-1) and the lowest in 30 August transplanting (3.80 and 4.27 t ha-1 respectively). However, 1000 grain weight was 20 g in each date of transplanting during both the seasons. Finally, Integrated Disease Management (IDM) packages need to be developed by using appropriate planting time, cultural practices and fungicides to control ShB disease of rice. Bangladesh Rice j. 2018, 22(2): 55-62

The Assessment of Early Blight Resistance in Different Variety of Solanum tuberosum and Biological Management of Early Blight

The early blight is a common disease in Potato caused by Alternaria species. The present work focused on two aspects, first one is to evaluate the antagonistic effect of isolated bacterial and fungal species from potato fields of Depalpur, Sanwar and Indore tehsils of Indore district of Madhya Pradesh and other side we have screened the resistant variety against Alternaria species for selected potato fields of Indore district. Isolated Bacterial and fungal species were evaluated against Alternaria species by dual culture technique. Data was collected on radial growth and inhibition of growth. For the screening of the resistant variety against Alternaria species for selected potato fields of Indore district, field visits were conducted and evaluated the morphological observation time to time. We have found all studied species of Trichoderma retarded the growth of A. solani but T. harzianum most strongly suppressed the growth of Alternaria solani and in terms of bacterial species promising antagonists were reported as Pseudomonas fluorescens, Bacillus subtilis. The Percent disease index (PDI) caused by Alternaria species in Potato plants were evaluated in Kufri Chipsona-1, Kufri Chipsona-2, Kufri Jawahar, Kufri Surya in different villages of Indore districts, We reported high Percent disease index in Kufri Chipsona-1 and Kufri Surya followed by Kufri Chipsona-2 but it was recorded lower in Kufri Jawahar. Keywords: Solanum tuberosum, Kufri Chipsona-1, Kufri Chipsona-2, Kufri Jawahar, Kufri Surya, Early blight resistance

Diversity in Alternaria brassicae (Berk.) Sacc. isolates and characterization of host response in different oilseed Brassica species

Alternaria brassicae (Berk.) Sacc., a necrotrophic fungus devastating oilseed Brassica crops in India, causes up to 47% reduction in seed yield. So the study is conducting to develop the knowledge about the variability of A. brassicae in terms of cultural, morphological, pathogenic characters and their effects on different Brassica species of rapeseed mustard, for minimizing the losses caused by A. brassicae and help to stabilize the rapeseed mustard production. In variability study, all the isolates showed cultural, morphological variability. Average conidial length was maximum in isolate Ab2 (21.7μ) followed by Ab4 (20.7μ) and minimum in Ab8 (15.6μ). Septation in conidia, both horizontal and vertical also showed variation in different isolates. Finally it was revealed that smallest size of conidia in isolates Ab8 and longest size of conidia in isolates Ab4 were observed. On solid medium, maximum sporulation was observed in Ab7 followed while minimum sporulation recorded in Ab8. On liquid medium, maximum sporulation was observed in Ab7 while minimum sporulation recorded in Ab8. All the isolates showed the variability in qualitative characters i.e. spot colour, presence or absence of central point, concentric rings and yellow halo and as well as in quantitative characters i.e. incubation period and Percent Disease Index.