Mitigating water stress in summer rice using beneficial root endophytic fungus Piriformospora indica

Abstract

The study entitled ‘Mitigating water stress in summer rice using beneficial root endophytic fungus Piriformospora indica’ was undertaken at College of Agriculture, Vellayani during 2019 - 2021. The objective of the study was to assess the performance of P. indica colonized rice under different levels of moisture stress during summer. The field experiment was laid out in randomized block design with 2 x 3 x 2 treatments, replicated thrice in the low land paddy fields during February to May 2021, using variety Prathyasa. The treatments included colonizing with P. indica [p1- P. indica colonized rice and p2- non-colonized rice(control)], three irrigation intervals[i1- 30 mm CPE (cumulative pan evaporation), i2- 35 mm CPE and i3- 40mm CPE] and two irrigation depths(d1- to a depth of 1.5 cm and d2- to a depth of 3 cm). P. indica colonized/ non-colonized rice seedlings raised in trays were transplanted at 14 days after sowing at 15 cm x 10 cm and uniformly irrigated till 10 days after transplanting (DAT). The crop was raised as per the KAU package of practices recommendation for short duration rice (KAU, 2016). The results of the study revealed that colonization and irrigation to 3 cm depth improved the growth and growth attributes viz., plant height, tiller number m-2 , leaf area index and dry matter production of summer rice. Colonization with P.indica significantly influenced the number of tillers m-2 with 10.64, 16 and 15.69 per cent increase in tiller production at 30, 45 and 60 DAT respectively, compared to non-colonized plants. Colonized plants irrigated at 30 mm CPE to a depth of 3 cm evinced the maximum leaf area index (4.54) at 60 DAT and dry matter production (4559.26 kg ha-1 ) at harvest. Yield attributes and yield of rice were significantly affected by P. indica colonization, irrigation interval and depth of irrigation. Superior number of productive tillers m-2 (222.84), filled grains per panicle (81.11) and the lowest sterility percentage (13.37) were recorded with colonization. Colonized plants irrigated at 30 mm CPE to a depth of 3 cm produced significantly superior productive tillers m-2 (275.00), filled grains per panicle (111.33) and the lowest sterility percentage (8.80). Among second order interactions, p1i1d2 produced significantly superior grain yield (2698.56 kg ha-1 ) and straw yield (2848.13kg ha-1 ). P. indica colonization, irrigation interval and depth of irrigation had significant effect on root parameters of rice at all stages of observation. P. indica colonized plants showed significantly superior rooting depth at all stages. Colonized rice plants irrigated at 35 mm CPE 157 to a depth of 3 cm revealed superior rooting depth viz., 19.4, 29.86 and 30.00 cm and average root length of 23.36, 34.87 and 36.20 cm at 30, 60 DAT and harvest respectively. Significantly superior root volume and root dry weight at 30, 45, 60 DAT and harvest respectively were recorded in colonized plants irrigated at 30 mm CPE to a depth of 3 cm. Among the physiological parameters studied, proline content declined in the order of decreasing CPE, 40 mm >35 mm > 30 mm. P. indica colonized plants irrigated at 40 mm CPE to a depth of 1.5 cm produced significantly greater proline (115.33 and 106.00 μmole g-1 at panicle initiation and flowering respectively). Colonized rice plants at 30 mm CPE to a depth of 3 cm observed the maximum relative leaf water content, cell membrane stability and chlorophyll stability index at panicle initiation and flowering respectively. P x I x D remained significant with the highest water use efficiency (WUE) of 3.47 kg ha-1mm-1 for P. indica colonized plants irrigated at 30 mm CPE to a depth of 3 cm. P. indica, irrigation interval and depth of irrigation could significantly influence the available nitrogen, phosphorus and potassium status of soil after experiment. Colonized plants irrigated at 40 mm CPE to a depth of 1.5 cm resulted in significantly superior available phosphorus (179.93 kg ha-1 ). Considering the economics, P. indica colonized plants irrigated at 30 mm CPE to a depth of 3 cm brought about the highest gross income (₹ 88951 ha-1 ), net income (₹ 30351 ha-1 ) and B: C ratio (1.51). Based on the above findings, it could be inferred that rice plants colonized with P. indica significantly enhanced the growth and yield attributes, root biomass, nutrient uptake and WUE, irrespective of interval and depth of irrigation.Yield and WUE of P. indica colonized plants subjected to severe stress, were observed to be equivalent to those of non-colonized plants under moderate stress. Colonization resulted in saving of 30 mm water or 3 irrigations and could help rice to combat drought stress by enhanced root biomass, nutrient uptake and water use efficiency during summer.