DEVELOPMENT OF MICROBIAL INOCULANTS FOR DROUGHT STRESS MITIGATION AND THEIR IMPACT ON GROUNDNUT CROP (Arachis hypogaea L.)
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Date
2021-09-01
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Acharya N.G. Ranga Agricultural University, Guntur
Abstract
Groundnut is an important oilseed crop suitable for tropical regions of the world. Generally, tropical areas are much prone to drought, which severely affects food production. India, a subtropical country produces groundnut on a large scale and occupies first in the area and second in terms of production. However, India’s groundnut production is anticipated to decline by 29 % due to inadequate rainfall, which demands advanced technological interventions in terms of sustainability. Keeping in view the future requirements and present needs this study was framed to develop bacterial inoculants for the drought prone areas of groundnut. A total of fifty one bacterial inoculants were isolated from drought prone areas viz., Anantapur (Mandals of Anantapur, Kambadur, Gummagatta and Vidapanikal) and Prakasam Districts (Mandals of Chirala, Chinaganjam, Kothapatnam and Vetapalem) of Andhra Pradesh, India.
Out of 51, efficient bacterial isolates nine were nitrogen fixing bacteria (Rhizobium sp.) five were phosphate solubilizing bacteria (PSB), six were potassium releasing bacteria (KRB) and the remaining 31 isolates are drought mitigating bacteria. Among these, a total of 14 efficient bacterial isolates were screened under in vitro by plant growth promoting and biochemical traits. Further these were screened with 16S rRNA gene sequencing and identified as PCMS-1 (Rhizobium sp. having 99.36 % identity), AGVS (Caballeronia zhejiangensis strain ND-B having 100.00 % identity), PCKS-3 (Burkholderia dolosa strain LMG 18943 having 99.79 % identity) and PCKS-5 (Bacillus sp. 7B-635 having 99.46 % identity) finally which were used to formulate an efficient microbial consortium and inoculated to the host crop under pot culture conditions.
In the pot culture experiment, germination percentage (91.00 %), number of branches (9 plant-1), shoot length (22.27 cm plant-1), root length (13.63 cm plant-1), number of nodules (45 plant-1), nodule dry weight (142.68 g plant-1) and number of pods (7 plant-1) were significantly higher in T3 (PCMS-1+AGVS+PCKS-3+PCKS-5) when compared to the other treatments in pot culture conditions. Significantly highest plant biomass (17.76 g plant-1) was found in T1 (PCMS-1+AGVS+PCKS-3), highest chlorophyll content (1.97 mg g-1) and RWC (88.80 %) was observed in
T4 (PCMS-1+AGVS+PCKS-3+PVAS+PCKS-5), T3 had highest chlorophyll stability index (96 %) and bacterial population (7.72 Log CFU g-1 soil).
Further, pot and field trials were conducted with the selected drought mitigating bacterial consortium (PCMS-1+AGVS+PCKS-3+PCKS-5) in combination with different treatments of moisture levels and fertilizer doses.
Relative water content was highest (99.54 %) in T8 (6 Irrigations+75% RDF+MC). Conversely, the highest H2O2 content (9.60 μmol g-1), proline (204.0 μg g-1) and peroxidase activity (62.28 units min-1 g-1) were observed in T1 (2 Irrigations+50% RDF+MC). Organic carbon found highest (0.47 %) in T8 at 90 DAS. Highest chlorophyll content (3.18 mg ml-1), nitrogen (198 kg ha-1), phosphorus (70.04 kg ha-1), potassium (398 kg ha-1) and per cent K (1.91 %) were observed in T8.
Rhizobium sp. (5.91 Log CFU g-1 soil), total bacteria (8.89 Log CFU g-1 soil) and fungal population (5.55 Log CFU g-1 soil) were observed in T8 at 60 DAS. Conversely, the highest KRB (4.80 Log CFU g-1 soil) and DMB (5.88 Log CFU g-1 soil) population were observed in T8 at 90 DAS. Actinomycetes (6.73 Log CFU g-1 soil) and PSB (5.88 Log CFU g-1 soil) population was recorded highly in T12 (8 Irrigations+100% RDF+MC) at 90 DAS. Highest dehydrogenase (33.09 μg TPF g-1 day-1), alkaline phosphatase activity (65.10 μg pNP g-1 h-1) and total aggregate formation (98.36) were observed at 60 DAS in T8.
Microbial biomass carbon decreased after 90 days and found highest in T8 (352.56 μg C g-1) than other treatments. Similarly, microbial biomass nitrogen was highest in T8 (31.21 μg N g-1). Nodule number (295 plant-1) was found highest in T9 (6 Irrigations+100% RDF+MC) correspondingly nodule dry weight (271 mg plant-1) was also obtained highest. Contrastingly, maximum plant biomass (11592 kg ha-1), shoot (51.67 cm plant-1) and root length (20.54 cm plant-1) found higher with the 8 irrigations. Yield parameters like pod yield (3427 kg ha-1) and kernel yield (2633 kg ha-1), 100 kernel weight (63.30 plant-1) and oil content (47.30 %) were attained highest with six irrigations, 75 per cent recommended dose of fertilizers and microbial consortium under field conditions.
The present investigation proved that the application of microbial consortium comprising (Rhizobium sp., Caballeronia zhejiangensis strain ND-B, Burkholderia dolosa strain LMG 18943 and Bacillus sp. 7B-635) is an efficient inoculants in mitigating drought. This was evidenced by improvement in groundnut yield as three per cent with 25 per cent reduction in chemical fertilizer, six irrigations and with microbial consortia when compared to the treatment which does not apply microbial consortia though it received eight irrigations with 100 per cent recommended dose of fertilizer. Thus the drought mitigating bacterial inoculants are highly recommended to use reduced chemical fertilizer dosage with minimum number of irrigations and have considerable benefits to the farming community of drought prone areas.
Description
DEVELOPMENT OF MICROBIAL INOCULANTS FOR DROUGHT STRESS MITIGATION AND THEIR IMPACT ON GROUNDNUT CROP (Arachis hypogaea L.)