Percent Disease Index Research Articles

Evaluation of phenotypic, physiological and biochemical attributes connected with resistance in tomato against Alternaria solani

Early blight (EB) disease caused by fungus Alternaria solani is one of the world's most catastrophic Solanum lycopersicum L. diseases. This study was aimed to check the response of 29 different tomato genotypes toward EB disease with the help of phenotypic (percent disease index and growth inhibition index), physiological (total chlorophyll content and carotenoids) and biochemical attributes [total protein content (TPC), total phenolics (TP) and activities of catalase (CAT), peroxidase (POX), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL)] at 30 and 60 DAI (days after inoculation). The experiment consisted of all 29 inoculated and uninoculated genotypes of tomato which were placed in greenhouse. The results obtained from investigated parameters grouped eight genotypes as resistant, seven as moderately resistant, six as moderately susceptible and eight as susceptible to the infection of the pathogen. Moreover, from the findings of physiological and biochemical attributes in the grouped genotypes, possible resistance mechanisms activated in the host were also predicted. Activation of defense responses was revealed by elevated biochemical attributes in all inoculated genotypes and changes were more obvious in resistant and moderately resistant tomato genotypes due to the least reduction of health markers. Among antioxidant enzymes, CAT contributed maximum to resistance, as the enzyme activity was highest in resistant genotypes.

Induced defense responses against Rhizoctonia solani in rice seedling by a novel antifungalmycin N2 from Streptomyces sp. N2

Antifungalmycin N2 (3-methyl-3,5-amino-4-vinyl-2-pyrone, C6H7O2N), was a novel and broad-spectrum antifungal metabolite produced by Streptomyces sp. N2. In the present work, antifungalmycin N2 was evaluated its induction of resistance against Rhizoctonia solani in rice seedling by measuring the defense-related physiological and biochemical parameters, such as the production of reactive oxygen species (ROS), the enzymatic activities involved in antioxidant systems (superoxide dismutase, SOD; catalase, CAT; peroxidase, POD), phenolics metabolism (phenylalanine ammonia-lyase, PAL; polyphenol oxidase, PPO), and pathogenesis-related proteins (β-1,3-glucanase and chitinase). It was found that the percentage disease index (PDI) of the R. solani-inoculated rice reduced from 65.21% to 26.02% when treated with 5.77 μg/ml antifungalmycin N2. Further results showed that the rice seedling could trigger its defense responses to R. solani infection by sharply accelerating the accumulation of ROS such as ·O2¬ and H2O2. But when the R. solani-inoculated rice was treated with antifungalmycin N2, the antioxidant SOD, CAT, and POD were significantly induced during the whole period of post inoculation (24–96 h), and consequently resulted in a sharp decline of ·O2¬ and H2O2 in rice seedlings. Compared with the R. solani-inoculated rice, the enzymatic activities of PPO, PAL, β-1,3-glucanase, and chitinase were significantly enhanced in the rice treated with antifungalmycin N2 plus R. solani. In conclusion, the above results suggested that antifungalmycin N2 could induce the resistance against R. solani in rice seedling by stimulating a series of defense responses, which would provide a comprehensive insight into the biocontrol function beyond its direct antagonistic activity against plant fungal pathogens.

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.

Correlation studies of sunflower Alternaria leaf blight with weather parameters

To assess the impact of weather conditions on the progress of Alternaria leaf blight in two cultivars KBHS-44and Morden of sunflower, an experiment was conducted during kharif 2013-14 and 2014-15. It was recorded that per cent disease index (PDI) was positively correlated with relative humidity during morning (RH1), relative humidity during evening (RH2), and with crop age for two cultivars. These correlations were found to be significant under protected and unprotected conditions. PDI was negatively correlated with temperature maximum significantly and also with rainy days, sunshine hours and wind velocity. But the effect of temperature minimum was not significant.

Screening for Alternaria leaf blight disease in breeding lines of sunflower (Helianthus annuus L.)

Several pathogens attack sunflower crop and among them sunflower leaf blight disease caused by Alternariahelianthi is major one in kharif season infecting from seedling to seed filling stage. The screening of 75 sunflower breeding lines revealed that PM6, PM160, PM26, PM163 recorded resistant reaction with PDI (percent disease index) of 4%, 3.3%, 3.1% and 7% respectively. These breeding lines can be used as resistant source in developing resistant hybrids for Alternaria leaf blight after confirming the resistance in artificial epiphytotic conditions.

Genetic association studies for oil yield in F3 generation of sunflower (Helianthus annuus L.) for the cross COSF7B x 302 B

Eleven progenies of F3 generation of sunflower were selected for the character association study to assess therelationship among oil yield and its components. Observations were recorded on fourteen traits viz., days to firstflowering, days to maturity, plant height, head diameter, powdery mildew percentage disease index, 100 seed weight, volume weight, seed yield, seed shape, seed colour, stripes on the margin, stripes between the margin, seed yield/plant, oil content and oil yield. Character association analysis revealed strong positive association of oil yield/plant with head diameter, 100-seed weight, seed yield and oil content. Hence, synchronized selection of these characters would contribute for the improvement of the oil yield/plant.

<i>In-Vivo</i> Management of Purple Blotch of Onion Caused by <i>Alternaria porri</i> (Ellis) Cif. through Fungicides

An experiment was carried out to study the outcome of environmental factors (Temperature, Relative Humidity, Rainfall) and management of the purple blotch disease of onion using five treatments (Rovral + Ridoil gold with 3,4,5,6 sprays and control). The Taherpuri variety was used during the 2015-2016 cropping seasons at BARI, Gazipur, Bangladesh. In the experiment, the purple blotch disease surfaced at the end of January 2016 and was severe in late February to March (PDI 76.12%) due to temperature and RH above 24°C and 95%, respectively. As for the chemical control, the PDI for the treatments ranged from 50.66% to 83.33%. Significantly higher stem height was recorded by T4 (68.06 cm), where six sprays of Rovral + Ridomil were applied. The minimum stem height was recorded in T5 (59.23 cm). The maximum stem number per hill was recorded in T4 (2.30) numerically but differed significantly with T5 (2.00), where fungicides were not applied. The maximum lesion area was measured in T5 (25.26 mm2). Regarding PDI (Percent disease index), there was a significant difference among the treatments. The PDI value on purple blotch of onion ranged from 34.00 to 83.33. The lowest PDI was assessed in T4 (34.00). Statistical analysis revealed that a significant decrease of PDI on purple blotch was recorded under treatments of T1, T2, T3, and T4 (39.20%, 45.60%, 49.59%, and 59.19%) on controlling the disease and giving the optimum yield but all of them significantly differed with T5 (83.33%) where no fungicides were sprayed.

Survey on black spot of papaya in major papaya growing areas of Southern Karnataka

Papaya is affected by several diseases like, foot rot, anthracnose, powdery mildew, black spot, brown spot, papaya ring spot, mosaic and leaf curl diseases. Among them black spot disease caused by Asperisporium caricae is emerging as an important one in limiting papaya prodiction. A random survey was conducted during September to November months of 2018 in Southern Karnataka for the severity of black spot of papaya caused by Asperisporium caricae. Among the different districts surveyed viz., Mandya, Ramanagar, Mysore, Hassan and Chamrajnagar, the per cent disease index (PDI) was ranged from 7.86-38.00 per cent on leaves and 0.00-24.97 per cent on fruits. Highest PDI was recorded in Ramanagar district at Kanakapura taluk on leaves 35 per cent and on fruits 22 per cent. Lowest PDI was recorded in Chamrajnagara district at Yelandur taluk on leaves 7.86 per cent and on fruits 0.71 per cent.

Evaluation of bio-efficacy and phytotoxicity of BAS 751 01 F SC against early blight disease of tomato

Early blight disease in tomato is destructive in nature and reduces fruit yield. Fungicides were used to control early blight disease but still early blight disease occurs. Hence, for in search of good alternative fungicide to control early blight disease, field experiment on efficacy of BAS 751 01 F SC against early blight disease was conducted in kharif season of 2017-18 and 2018-19. There were 7 treatments with six fungicides and control. Observations on per cent disease index (PDI), fruit yield and phytotoxicity of fungicides on tomato were recorded. In both 2017-18 and 2018-19, BAS 751 01 F SC with a.i.(g) of 200 @ 500 ml or g/ 500 – 750 litres of water was found superior in reducing disease severity (22.12 % mean PDI) over other fungicides used. In 2017-18 and 2018-19, BAS 751 01 F SC with a.i.(g) of 200 @ 500 ml or g/ 500 – 750 litres of water treated plants produced higher yield of tomato fruits (19.41 t/ha, 19.80 t/ha) over other fungicides. BAS 751 01 F SC with a.i.(g) of 200 @ 500 ml or g/ 500 – 750 litres of water were not toxic to tomato plant in kharif season of 2017-18 and 2018-19. The results concluded that use of BAS 751 01 F SC with a.i.(g) of 200 @ 500 ml or g/ 500 – 750 litres of water resulted in reducing disease severity and improved yield.

Efficacy of Mineral oil with Fungicides in Management of Sigatoka Leaf Spot of Banana

Field experiments were carried out in the village Thondamandhurai to evaluate the efficacy of Propiconazole 0.1 per cent with mineral oil and second spray of carbendazim 0.05 per cent with mineral oil 1.0 per cent against Sigatoka leaf spot in Banana with farmers practices of applying carbendazim alone in two sprays. The findings revealed that mineral oil with fungicide was effective and significantly superior over farmer’s practice in reducing the Sigatoka leaf spot. The results revealed that the significant minimum leaf spot PDI (14.36) was observed in treated field during harvesting stage and pooled Percent Disease Index (PDI) of all months was 15.01. The maximum yield (45.8 t/ha) and BCR (1:1.91) was obtained in treated field.

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

A study on preventive effects of Lawsonia inermis L. bioformulations against leaf spot disease of maize

Abstract Leaf spot disease caused by Curvularia lunata is one of the major constraints affecting the cultivation of maize in India. Recently, it has been reported that the severity of curvularia leaf spot was prevalent in moderate to severe intensities and cause extensive damage to the crop thus lowering the yields. In the present study, in vivo preventive effect of Lawsonia inermis Linn. bioformulation on curvularia leaf spot disease of maize has been studied. All the experiments were conducted in pots. Percent disease index (PDI), percent efficacy of disease control (PEDC), chlorophyll contents, total carotenoids, and others various growth characteristics like plant height, number of leaves per plant, total carbohydrate and protein content were recorded. Percent seed germination was also observed for seeds treated with all formulations. A significant control of leaf spot disease was recorded with bioformulations treatment T3 [seeds were treated with partially purified acetone extract (4 ml): 100% clove bud oil cake (4 ml): 100% cow dung (2 ml)], T4 [seeds were treated with partially purified acetone extract (3 ml): 100% clove bud oil cake (4 ml): 100% cow dung (3 ml)], T2 [seeds were treated with 100% alcoholic crude extract (2 ml): 100% clove bud oil cake (6 ml): 100% cow dung (2 ml)] and T1 [seeds were treated with 100% alcoholic crude extract (4 ml): 100% clove bud oil cake (4 ml): 100% cow dung (2 ml)] as compared to other bioformulation treatments and its PDI and PEDC were recorded 9.10%, 10.00%, 17.50%, 19.00% and 89.47%, 88.43%, 79.76%, 78.03%, respectively. Results showed that treatment with bioformulation treatment T3, notably increased plant height, number of leaves per plant, chlorophyll, carotenoids, and total soluble sugar content followed by formulations number T4, T2, and T1. However, total soluble protein content was observed to be less in T3 as compared to control. This study suggests that these bioformulations could be essential towards sustainable agricultural science deprived of harming the ecosystem. The synthesized bioformulations have enormous potential to be commercially explored for agriculture use.

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

Screening Rice Germplasm against Sheath Blight Disease of Rice and its Integrated Management in Bangladesh

Fifty-seven rice germplasm collected from BRRI Genebank were screened against sheath blight (ShB) by artificial inoculation in field and laboratory conditions in T. Aman 2012. Significant differences on relation to lesion height (RLH) among the germplasm were observed, where the highest (83%) was recorded in susceptible check, BR11 and the lowest (8.33%) was in Orgoja. Severity score of ShB was recorded maximum (9) in Dudhsail, Basi, Chaula mari, Holdemota, Calendamota, Semmua, Kotijira, Halisail, Horakani, Kalisura, Ashfuli, Huglapata and BR11 as highly susceptible to ShB, whereas it was minimum (1) in Orgoja. Gopal ghosh was observed as moderately tolerant with 27.33% RLH and severity score 3, while Kala binni, Khazur chari, Binni, Kalagora, Patjait and Dorkumur found moderately tolerant with severity score 5. In detached sheath inoculation method in test tube, most of the germplasms found highly susceptible, except Orgoja as resistant and Gopal ghosh as moderately tolerant. However, Orgoja showed resistance in both field inoculation and detached sheath inoculation methods. But, Dorkumur was found moderately tolerant in field and highly susceptible in detached sheath inoculation in laboratory. The experiment of Integrated Disease Management (IDM) packages was conducted in the farmer’s field with BR11 at Fulpur, Mymensingh during T. Aman 2013. The IDM practices of rice ShB resulted profound effect. Relative lesion height, percent disease index, tiller infection and hill infection were maximum (68%, 69%, 86% and 79% respectively) in T6 (control) and minimum in T1 [FDR (removal of floating debris) + 30 July transplanting + Potash (K) fertilizer (202 g decimal-1) + Top dressing of urea (247 kg ha-1) in four equal splits at 15 days interval + single spray of fungicides of Azoxystrobin 10% (0.17 kg ha-1) + Tebuconazole 90% (500 ml ha-1)]. Moreover, the highest number of panicles per m2, filled grains per panicle and grains yield were recorded in T1 (160, 150 and 6.25 t ha-1 respectively) and the minimum in T6 (227, 120 and 3.6 t ha-1 respectively). Therefore, the best IDM package was T1 for its effective control of ShB disease as well as yield maximization of rice. Finally, Orgoja could be used in resistance breeding for varietal improvement and the IDM package of T1 need to be recommended to prescribe in the farmer’s field after simulation in different AEZs and seasons with different varieties of Bangladesh.
 Bangladesh Rice j. 2018, 22(2): 1-12

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

Breeding chili pepper for simultaneous improvement in dry fruit yield, fruit quality and leaf curl virus disease tolerance

ABSTRACT Enhanced productivity in dry chili pepper (Capsicum annuum L.), and improvement of fruit quality for industrial use in the export market, is a goal of plant breeders worldwide. Genotypes having a broad genetic background, and phenotypic diversity, were chosen as parents and crossed in a 6 × 6 diallel fashion without reciprocals to produce 15 F1 pepper hybrids to determine the mode of gene action, the extent of heterosis and dominance effect, and to estimate combining ability for quantitative traits. The predictability ratio exhibited a desired response for non-additive gene action in controlling expression of most traits including dry fruit yield per plant, but not for fruit length, fruit diameter, and capsaicin content which were controlled by additive and non-additive gene action, and dry fruit weight, percent disease index (PDI) of leaf curl virus controlled by additive gene effect. The maximum heterobeltiosis, in the desired direction, was for dry fruit yield per plant followed by a number of fruit per plant, fruit β-carotene content, PDI of chili leaf curl virus, and American Spice Trade Association (ASTA) color value. The good combiners cvs. Srinagar, Beldanga and BCCH Sel-4 were identified based on general combining ability effects and average performance. Hybrids ‘BCC-30 × G-4ʹand ‘BCCH Sel-4 × Beldanga’ were considered promising for value-added products and export based on average values, heterosis manifested, and relevance of specific combining ability effects. Testing is required to verify responses under field conditions. Promising hybrids could also be exploited in segregating generations to identify pure lines with desirable traits. Commercially exploitable chili hybrids tolerant to leaf curl virus disease could be developed with involvement of a single parent tolerant to this disease. Correlation indicated that selecting high yielding genotypes could have more contents of capsaicin, β-carotene, and ASTA color value in dry chili fruit. The outcome of the study for improved quality and productivity of dry chili will enable India and neighboring dry chili producing countries (China, Pakistan and Bangladesh) to increase exports of chilies and chili products, effectively meeting the competition from South American and African countries.

Polymer coating for higher pesticide use efficiency, seed yield and quality in onion (Allium cepa)

Onion (Allium cepa) seed crop is infected with several pest and diseases which reduce the seed yield and quality. The present study explores the feasibility of using polymer as an efficient delivery system for seed-protectant chemicals during onion seed production. Polymer coating prolonged the release of pesticides. After 30 DAP, 557% and 1087% higher retention of fungicide and insecticide was observed in polymer coated bulbs over traditional method of bulb treatment. Onion bulb coating with polymer and 0.15 % fipronil + 0.25 % (carbendazim + mancozeb) showed significantly higher values for seed yield attributes, viz. productive scapes/plant (5.56), lower percent lodged scapes (21.16), seed yield/ plant (21.15 g) and seed quality attributes in comparison to control and traditional method of bulb treatment. Lowest percent disease index (36.39) was recorded in treatment- polymer coating + 0.15 % fipronil + 0.25 % (carbendazim + mancozeb) and lowest number of thrips/plant (5.14) was recorded in bulbs coated with polymer + 0.15 % fipronil + 500 ppm streptocyclin. Treating of onion bulbs with polymer is beneficial in increasing the efficacy of the applied pesticides, reducing the incidence of pest and diseases and enhancing seed yield and quality.

Heterotic expression of okra hybrids for tolerance to enation leaf curl virus

ABSTRACTOkra (Abelmoschus esculentus L. Moench) production in the tropics is threatened by heavy incidence of enation leaf curl virus (ELCV) causing crop loss when infection is at the early growth stages. A high yielding okra hybrid with acceptable tolerance to ELCV disease is needed. In this investigation, six diverse cultivated genotypes were crossed in half diallel fashion to study the extent of heterosis, mode of gene action, combining ability effects, and dominance effects of 14 yield component traits including disease severity of ELCV. Predominance of nonadditive gene action occurred in the control for all characters studied except for percent disease index of ELCV which was conditioned by both additive and nonadditive gene action. Partial, to overdominance, effects were involved in inheritance of fruit yield and most of horticultural traits studied. Two parents ‘2014/OKYV RES-5ʹ and ‘2014/OKYV RES-10ʹ were identified as most promising donors for future breeding. Heterosis for fruit yield per plant was manifested through node at first flowering, plant height, fruit length, number of fruit per plant, nodes on the main stem, and seed per fruit. Two promising hybrids ‘2014/OKYV RES-5 × 2014/OKYV RES-10ʹ and ‘2014/OKYV RES-5 × BCO-1ʹ were identified based on average values, heterosis manifested, and relevance of specific combining ability effects, and these hybrids could be commercialized in okra growing zones in the tropics after critical testing.

Microscopic and ultrastructural studies of grape cultivars (Vitis vinifera L.) with variable susceptibilities to anthracnose

The present studies were conducted to decipher structural traits of grape varieties associated with resistance to anthracnose. Vines of grape varieties viz., Perlette, Pusa Navrang, Beauty Seedless, Flame Seedless and H 516 (Punjab MACS Purple) grown at the Research Farm of Department of Fruit Science, Punjab Agricultural University, Ludhiana were screened for resistance and susceptibility to anthracnose. The variety H 516 having Percent disease index (PDI) 1.66 was categorised as resistant to anthracnose, whereas Perlette was rated as susceptible with PDI of 73.00. The stomatal length, width and stomatal index were significantly high in the most susceptible variety Perlette as compared to the rest of the varieties. Transverse section of leaves of H 516 indicated presence of highly compact spongy mesophyll and trichomes conferring resistance.

Genetic control of enation leaf curl virus disease tolerance in cultivated species of okra

ABSTRACTOkra enation leaf curl virus (ELCV) disease is an emerging threat to okra (Abelmoschus esculentus L. Moench.) cultivation in the tropics. Identifying and utilizing tolerant germplasm, and understanding the genetic control of ELCV disease tolerance, is necessary to develop an effective breeding strategy. Six generations of the crosses: Tolerant × Tolerant and Tolerant × Susceptible, were utilized to study the genetic basis of ELCV disease tolerance. The pattern of segregation of 2 tolerant parents indicated a single dominant gene, along with some minor factors, governed ELCV disease susceptibility in tolerant parents. The segregation pattern for ELCV disease in the F2 generation of 2 Tolerant × Susceptible crosses indicated existence of 2 genes with duplicate recessive epistasis. Non-additive gene action and duplicate epistasis were the most predominant types of gene effects controlling days to 1st appearance of ELCV disease and percent disease index of ELCV traits. For improvement of these traits, selection should be in later segregating generations, and intermating among selected segregates be followed by 1 or 2 generations of selfing to break the undesirable linkage and allow accumulation of favorable alleles.