Introduction

Niger is an important minor oilseed crop cultivated in India and constitutes about 3% of oilseed production. Niger seed contains 35 to 45% oil, 20% protein and 12% soluble sugars. Both seed and oil are edible with no anti nutrient character and consumed by rural and tribal people. It is grown in both  marginal and sub marginal lands with negligible inputs under rainfed conditions (Ranganatha et al., 2009) with high degree of tolerance to insect pests, diseases and by grazing animals (Ranganatha et al., 2014). Niger, being an important oil seed crop is found to be affected by many pest and diseases which causes huge damage to the crop. Niger crop suffers from many fungal diseases like leaf blight, root rot, damping-off, rust, wilt, charcoal rot, powdery mildew, leaf spot, galls and bacterial diseases namely wilt, blight and spot diseases. Further, the accidental rain at flowering stage enhances the Alternaria and Cercospora leaf spot incidence and results in the poor seed set and seed yield. The yield losses was more due to Cercospora leaf spot and Alternaria leaf blight (Kansara and Sabalpara, 2015 and 2016: Sandipan et al., 2014a, 2014c and 2018). Hence, mapping the extent of disease severity in different niger growing areas would enable us to locate the hot spots of disease severity and to evolve appropriate disease management strategies to mitigate the loss caused by disease in the respective localities by the cultivation of resistant varieties with suitable chemical management practices (Jagtap et al., 2014, Kansara and Sabalpara, 2015 and 2016, Sandipan et al., 2014a). An effective programme of disease management including breeding for disease resistance, currently studies pertaining to the use of fungicides, botanicals in management of these diseases are highly emphasized (Rajpurohit et al., 2005; Rajpurohit, 2011, Gupta, 2017, and Gupta et al.,2018). But this management is not ecofriendly and safe. So there is a need to screen and develop the disease resistant varieties. Some of resistant varieties were identified (Hegde, 2005 and Rajpurohit et al., 2005 and Kansara, 2014), which helps in disease management and thereby increases the productivity. Cursory perusal of literature revealed that, research work on screening of germplasm against Alternaria leaf blight is limited. Hence, an effort was made to screen lines against Alternaria leaf blight (Table 1).

Table 1: Alternaria leaf spot disease scoring in niger

Materials and Methods

A field experiment was conducted at College of Agriculture, Raichur, UAS, Raichur (North-Eastern dry zone (Zone-2) of Karnataka, 16° 15´N latitude and 77° 20´E longitude at an elevation of 389 meters above mean sea level) to identify the sources of resistance to leaf blight in niger. Totally 200 germplasm lines supplied by Project Coordinating Unit, AICRP on Sesame and Niger, Jabalpur were screened for resistance during Kharif 2013 under natural epiphytotic conditions.

Each test lines were sown in a single row of 4 m length with a spacing of 30×10 cm² with three replications in randomised block design. In each replication 10 plants were randomly selected and the intensity of leaf blight caused by Alternaria spp., was recorded after 30^th and 60^th day of planting by using 0-5 scale. Among 200 germplasm lines sown, 189 lines were germinated and used for evaluation. In addition to the disease screening, the data on days to 50% flowering, plant height (cm), number of primary branches per plant, number of capitula per plant and the seed yield was recorded. The main emphasis was given on the screening of germplasm against the disease and their yield parameter.

Results and Discussion

The data on morphological, seed yield and yield attributing traits was subjected to descriptive statistics analysis in SPSS 23 software. Highest plant height was recorded by the genotype JN 122 (165.5 cm) and lowest was by EC 158672 (33.5 cm). The number of primary branches per plant was less (4.0) in the genotypes, 5-1, NSS 5427, JGP 50, KOMKEMP, NSS 5433, JN 32, JN 28 and JN 142, but the branches number was more in the genotypes UNS 9. Highest number of capsules (165) was recorded by ONS 133 and lowest by JN 20 (17.2). The seed yield data ranged from 0.5 g to 34 g (Table 2). Among the genotypes, KEC 6 recorded maximum yield of 34 g followed by JN 144 (26.5 g), JN 132 (26 g), PHW 5004-2 (25.5 g), N 122 (21 g) and JN recorded 20 g. The remaining germplasm recorded the yield less than 20 g/line. Similarly Getinet and Wold (2006) characterised 241 niger germplasm collections from different parts of Ethiopia and evaluated. Sreedhar (2003) reported the variability studies in niger. Genetic variability studies was carried out in niger germplasm and studied the yield and yield attributing characters (Vinod and Rajani, 2016, Baghel et al., 2018 and Suvarna et al., 2019).

Table 2: Mean data of morphological and seed yield and yield attributing characters and disease scoring of niger germplasm during kharif 2013

Table 2: Continue...

Table 2: Continue...

The most simple and effective and economical method in the management of disease is utilisation of resistant cultivars. Resistant cultivars conserve natural resources and reduce the cost, time and energy when compared to the other methods of disease management. In the present study, 198 germplasm lines were screened for their reaction to leaf blight disease. The disease reaction of different germplasm lines was recorded. The germplasm lines showed varied degrees of reaction for the disease. It was observed that the germplasm showed immune to moderately resistant reaction with disease score varying between 0 to 2 (Table 2). Hence, the germplasm lines screened were showed immune to moderately resistant and the results were in accordance with the results reported by AICRP centers of Niger for the same set of lines scored in their location. (Annonymous, 2013).

Among 189 evaluated lines, 32 lines namely KEC 6, JN-10, RCR 23, RCR 238, RCR 2090, RCR 328, cherol No.1 etc., were immune and scored 0 grade, whereas 100 lines showed resistant reaction with disease score of 1 grade (JN 144, JN 132, PHW 5004-2, N-122, JN 94, JN 21, JN 20, BMD 69 etc.). The remaining 57 germplasm lines (COMB 2, UNS 9, BMD 66, No.14-B, PCU 183, JN 107, JN 77, etc.) were moderately resistant and scored 2 grade by showing 11-25% disease incidence. None of the genotypes were susceptible. For further confirmation, the disease screening should be carried out under artificial epiphytotic conditions. The results were on accordance with the work carried out by the different centres of AICRP on Niger and they were also identified resistant lines against Alternaria leaf bight (Anonymous, 2011, and 2013). Sandipan et al. (2014) observed significant differences in resistance to all the diseases in the elite material tested under natural condition and the disease score of Alternaria and Cercospora varied between 1 to 3 grade, respectively. Some of resistant varieties were identified like JNC-6, 1GP-76, Deomali, GA-11, ONS-8 (Hegde, 2005 and Rajpurohitet al., 2005). Kansara (2014), screened 16 genotypes of niger against the leaf spot disease under natural condition, PCU-197 showed resistant reaction while 671/1, NB-76-14, 645/1, IGP- 76, CWA-1, JLN-13, 233/1 and SVT-801 exhibited moderately resistant reaction. The six genotypes viz., NRS-96-1, NRS-99- 1, 207/1, IGPN-2004-1, RCR – 317, DHRN-1 and GN-1 exhibited moderately susceptible reaction against Alternaria blight of niger. The above results were also identical to findings of Prashant et al. (2014b), they screened 3 IVT and six AVT elite entries of niger against Alternaria blight diseases. Out of 19 elite materials, none were shown resistant reaction, where as IVT-13-7, IVT-13-8 and IVT-13-1 lines showed moderately resistant and all the AVT screened lines were moderately resistant to Alternaria blight of niger.

Conclusion

Niger is an important minor oilseed crop in Karnataka, India and cultivated as a mixed crop. Though it is tolerant to diseases, under favourable weather conditions disease may causes severe losses. Hence, there is a need to identify the resistant sources by screening of niger germplasm for location wise under hot spot conditions. In the present study, some of the genotypes viz., KEC-6, RCR 23, RCR 238, RCR 290, RCR 328, PCU 211, KEC 8, KEC 15, PCU 206, PCU 197, PCU 200, PCU 194, 5-70, 18-64, 89-25, 5-4, 5-1,5-64, CH 7, CHEROL No. 1, IGD 272, Phule 4, NA 48, NA 47, CH 11, CH 32, EC 158672, JN 9, JN 10 AND JN 13 recorded immune reaction and some genotypes viz., KEC 6, JN 144, JN 132, PHW 5004-2, N 122 and JN 10 showed resistant reaction with high yield. Hence, breeding for disease resistance needs the identifying the resistance source through screening and also helps in developing high yielding disease resistant genotypes against Altenaria blight.

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