BHASKARA REDDY, B.VVENKATARAMANAMMA, K2020-02-242020-02-242019http://krishikosh.egranth.ac.in/handle/1/5810143469D5875The present investigation was undertaken with an aim to study cultural, morphological and genetic variability of Fusarium oxysporum f.sp. ciceris isolates, races identification, evaluation of bioagents (Trichoderma, fluorescent Pseudomonas and Bacillus isolates) against pathogen, molecular characterization of potential antagonists and screening for plant growth promotion characters. In another study, screening of germplasm/genotypes were undertaken to identify resistant lines. Attempts were also made to manage the disease with potential bioagents, fungicides and their integration. A roving survey was conducted during rabi, 2014-15 in six districts of Andhra Pradesh and recorded per cent wilt incidence in the range of 0.2 to 15.5%. Lowest mean wilt incidence of 5.9% was observed in Nellore district and the highest mean wilt incidence of 8.32% was observed in Kadapa district. Other districts such as Anantapuramu, Kurnool, Prakasam and Guntur recorded the mean wilt incidence of 7.28%, 7.77%, 6.6% and 6.74% respectively. A total of 32 Foc isolates were collected from Andhra Pradesh and Telangana. A total of 21 Trichoderma, 12 fluorescent Pseudomonas and 10 Bacillus isolates were collected from soil samples of chickpea rhizosphere. xviii Cultural characters like mycelial colour, margin, texture and pigmentation were studied for all Foc isolates. Morphological characters like size of micro conidia, macro conidia and chlamydospores were measured under microscope. Mean length of macro conidia was in the range of 15.02 µm (Foc-19) to 28.72 µm (Foc-9), and mean width was in the range of 2.72 µm (Foc-3) to 5.10 µm (Foc-28). The mean micro conidia length varies from 7.1 µm (Foc-11) to 11.78 µm (Foc-28) and width varies from 2.51 (Foc-9) µm to 4.3 µm (Foc-17). Chlamydospore diameter was observed in the range of 2.87 µm to 6.15 µm. Maximum sporulation was observed in Foc14 (2.2 × 106/ml) and minimum was observed in Foc-26 (0.2 × 106/ml). Maximum radial growth of 79 mm was observed in Foc-15, Foc-30 at 6 days and minimum radial growth of 39 mm was observed in Foc-12. There was no distinct correlation for cultural and morphological characters of Foc isolates, except for three isolates (Foc-6, Foc-12 and Foc-17). These isolates have white mycelium, cream colour pigmentation, slow radial growth and highly pathogenic (100% wilt incidence). In addition, Foc-6 and Foc-12 have sectors on the reverse side of the colonies on PDA plates. The differences among isolates for all these characters might be due to the genetic differences because all of them were cultured under same laboratory conditions. Twenty primers were used for RAPD analysis of 26 selected Foc isolates and only 16 primers amplified the DNA. Nine primers such as P8, K2, K4, K5, K6, K7, P17, OPX-10 and OPX-13 had given 100% polymorphic bands. PIC values varied from 0.16 (P21 primer) to 0.49 (K4 primer). Maximum number of bands (253) were produced by the P2 primer. UPGMA cluster analysis based on RAPD profiles separated the 26 Foc isolates into three major clusters. The cluster I comprised of eight isolates, cluster II consists of nine Foc isolates and cluster III has seven isolates. Similarity matrix among the 26 isolates indicated that maximum genetic similarity between Foc-27 and Foc-28 with 80.3%. Some of these isolates possess similar cultural characters and virulence pattern and the RAPD technique could differentiated them. Among 20 isolates studied for identification of races, 17 isolates were categorized into race-1 based on resistant reaction on CPS-1, BG-212 and GPF-2. Two isolates such as Foc-3 and Foc-32 exhibited resistant reaction on Chaffa and Annegiri besides CPS-1 and C-104 were categorized as race-6. One isolate (Foc-19) recorded 0% wilt incidence on differential lines except JG-62 (10% incidence) and Chaffa (6.66%) which is a new reaction. The primer pairs SCAR 1F/SCAR 2R and SCAR 2F/SCAR 1R were successfully validated the DNA fragment size of 700 bp in Foc-12. All the 21 Trichoderma isolates were tested for their antagonistic potential against F. oxysporum f.sp. ciceris and recorded inhibition percentage in the range of 10.3 to 48.44%. Maximum percentage of inhibition (48.44) was xix observed in the isolate Tr-20, followed by Tr-6 (45.74%) and Tr-1 (44.02) and Tr-10 (37.52). Ten isolates of Bacillus were evaluated against Foc and recorded inhibition percentage in the range of 5.46 (Bacillus-2) to 74.36 (Bacillus-7). Among 12 Pseudomonas isolates evaluated against the pathogen the isolate CRP-6 was recorded highest inhibition percentage of 58.32, followed by the isolate CRP-8 (56.90%). Clear inhibition zones were observed in dual culture of pathogen with Bacillus (Bacillus-3, 4, 5, 6 and 8) and Pseudomonas (CRP-6 and CRP-8). It might be due to the antifungal substances and/or cell wall degrading enzymes released by the bacteria into the culture medium. From the results of dual culture, four Trichoderma isolates (Tr-1, Tr-6, Tr-10 and Tr-20) two fluorescent Pseudomonas isolates (CRP-6 and CRP-8) and two Bacillus (Bacillus-5 and Bacillus-7) isolates were selected to study plant growth promotion characters. Four potential Trichoderma isolates produced IAA, HCN, chitinases and cellulases and none of them was able to solubilize phosphates. Among the potential bacterial isolates only one isolate (CRP-8) produced IAA, one isolate (Bacillus-5) solubilize phosphates and all of them were produced HCN and chitinases were not detected in bacterial isolates and only two isolates produced cellulases. These potential Trichoderma isolates were identified as T. asperellum based on 18S rDNA sequencing. Two potential Bacillus isolates were identified as Bacillus cereus strains and one potential Pseudomonas isolate was identified as Pseudomonas flourescens based on 16S rDNA sequencing. Eighty five germ plasm lines/advanced genotypes were screened for two rabi seasons i.e., 2014-15 and 2015-16 in wilt sick plot. Pooled data for both the years indicated that 7 entries (ICC-294, ICC-6279, ICC-14669, NBeG-3, NBeG-47, NBeG-119 and NBeG-49) were recorded as resistant and 6 entries were moderately resistant. Among thirteen entries screened (selected in field screening) for three virulent isolates in green house, five entries such as NBeG-3, ICC-14669, NBeG-49, ICC-6279 and ICC-294 recorded 0% incidence. Among the six fungicides evaluated against F. oxysporum f.sp. ciceris the treatments T1 (carbendazim 12% + mancozeb 63%) and T2 (carbendazim 25% + mancozeb 50%) recorded 100% inhibition of pathogen growth, followed by T3 (carbendazim 50%) and T4 (Vitavax power) that inhibited the pathogen growth to the extent of 98.03% and 81.6% respectively. Four potential Trichoderma isolates were tested at 0.2%, 0.15% and 0.1% for compatibility with effective fungicides (carbendazim 12% + mancozeb 63%, carbendazim 25% + mancozeb 50% and carbendazim 50%) and found that none of the fungicides were compatible. Vitavax power (carboxin 35% + thiram 35%) was found moderate compatible with Tr-1, Tr-6 and Tr-20 at 0.1%. xx Vitavax power was tested for compatibility studies with four potential bacterial antagonists i.e., CRP-6, CRP-8, Bacillus-5 and Bacillus7 and found only CRP-6 and CRP-8 antagonists were compatible. Trichoderma isolates Tr-1, Tr-6 and Tr-20 were studied for compatibility with two potential Pseudomonas isolates (CRP-6 and CRP-8) and found that only one isolate Tr-6 was found compatible. The Trichoderma isolate (Tr-6) and Pseudomonas isolate (CRP-8) was selected for field experiments. Seed treatment with reduced dosage (0.1%) was followed for field experiments that have integrated treatments. Among the different treatments imposed, T6 (Seed treatment with Vitavax power @ 1 g/kg, Trichoderma and pseudomonas talc formulation each @ 8 g/kg of seed and soil application of Trichoderma and Pseudomonas multiplied on FYM) recorded higher germination percentage of 91.09, lower wilt incidence of 22.86% and higher yields of 1501 Kg/ha, followed by T4, T9 and T10 treatments.en-USnullThesis