Comparative evaluation of biotization for hardening of tissue culture (TC) Banana cv. Nendran

Abstract

The study entitled “Comparative evaluation of biotization for hardening of tissue culture (TC) banana cv. Nendran” was carried out at RARS, Pilicode and College of Agriculture Padannakkad during 2023 to 2024 to study identification of ideal stage of biotization and comparative evaluation of biotization agents in hardening of TC banana cv. Nendran.The study comprised four experiments: in vitro culture, primary hardening, secondary hardening, and combined evaluation of biotization agents during hardening. The in vitro rooting stage experiment carried out in completely randomised design with four treatments and five replications. The treatments were T1 (Piriformospora indica along with rooting medium), T2 (Phosphate Solubilizing Bacteria (PSB) along with rooting medium), T3 (Pseudomonas fluorescens (PF) along with rooting medium), and T4 (Control: rooting medium). Among these, T1 significantly enhanced early root initiation, shoot proliferation, and overall rooting efficiency. Plantlets treated with P. indica (T1) during in vitro rooting showed superior performance during primary hardening, achieving the highest survival rate (93.33%) and enhanced growth traits: plant height (10.33 cm), pseudostem girth (2.47 cm), leaf length (5.23 cm), leaf width (1.93 cm), leaf area (15.39 cm2 ), number of primary roots (2.67), root length (2.80 cm), number of secondary roots (18.33), shoot dry weight (0.02 g), chlorophyll content (0.56 mg g-1) and relative growth rate (0.044 mg g-1 d-1). Lower proline content (1.04 µmol g⁻¹ FW) indicated reduced stress, and improved uptake of N, P, and K and micronutrients confirmed its role in nutrient acquisition. During secondary hardening, both T1 (P. indica) and T3 (Pseudomonas fluorescens) showed 100% survival, but T1 outperformed T3 in all growth parameters, including plant height (13.17 cm), pseudostem girth (2.33 cm), leaf length (8.80 cm), leaf width (2.67 cm), number of leaves (5.33), leaf area (59.93 cm2), number of primary roots (3.67), root length (10.47 cm), number of secondary roots (75), root fresh weight (0.44 g), shoot fresh weight (1.52 g), shoot dry weight (0.10 g) and relative growth rate (0.037 mg g-1 d-1). T1 also exhibited the lowest proline content (0.71 µmol g⁻¹ FW), suggesting better stress tolerance. The primary hardening experiment carried out in completely randomised design with eight treatments and three replications. The treatments were T1 (P. indica), T2 (PSB), T3 (PF), T4 (PF + PSB), T5 (PF + P. indica), T6 (PSB + P. indica), T7 (PF + PSB + P. indica) and T8 (control). Biotization with P. indica (T1) produced the highest survival rate (100%) and demonstrated superior plant growth, including significant increases in plant height (5.70 cm), leaf length (6.97 cm), leaf width (2.33 cm), leaf area (12.48 cm2), root length (5.97 cm) root fresh weight (0.62 g), chlorophyll content (0.47 mg g-1), relative growth rate (0.047 mg g-1 d-1), macronutrient and micronutrient uptake (N, P, K, Fe and Cu). Proline accumulation (1.25 µ mol. g-1 FW) was lower in T1, suggesting improved stress tolerance. The secondary hardening experiment carried out in completely randomised design with eight treatments and three replications. The treatments were T1 (P. indica), T2 (PSB), T3 (PF), T4 (PF + PSB), T5 (PF + P. indica), T6 (PSB + P. indica), T7 (PF + PSB + P. indica) and T8 (control). During this experiment, T7 showed excellent results, with improved growth metrics such as plant height (15.20 cm), leaf length (8.90 cm), number of leaves (5.67), leaf area (45.88 cm2), root length (12.07 cm), number of secondary roots (111.67 ), root fresh weight (0.65 g), chlorophyll content (0.46 mg g 1), shoot fresh weight (1.20 g), shoot dry weight (0.08 g), macronutrient and micronutrient uptake (N, Fe, Cu, Zn). Combined evaluation study was laid out in completely randomised design with 11 treatments and two replications. The treatments were T1 (P. indica during in vitro and primary hardening), T2 (P. indica during in vitro and primary and secondary hardening), T3 (PSB during in vitro and primary hardening ), T4 (PSB during in vitro and primary and secondary hardening), T5 (PF during in vitro and primary hardening), T6 (PF during in vitro and primary and secondary hardening), T7 (PF during in vitro + PSB during primary and secondary hardening), T8 (PF during in vitro + P. indica during primary and secondary hardening), T9 (PSB during in vitro + P. indica during primary and secondary hardening ), T10 (PF during in vitro + PSB + P. indica during primary and secondary hardening) and T11 (Control). T2 exhibited superior growth and stress tolerance compared to other treatments. This was evidenced by enhanced plant height (14.83 cm), leaf length (9.40 cm), leaf width (3.13 cm), number of leaves (6.00), leaf area (69.29 cm²), number of primary roots (5.67), secondary roots (86.67), root fresh weight (0.72 g), shoot dry weight (0.11 g), chlorophyll concentration (0.26 mg g⁻¹), and relative growth rate (0.04 mg g⁻¹ d⁻¹). Notably, lower proline accumulation (0.81 µmol g⁻¹ FW) indicated reduced abiotic stress. T2 also showed much increased nutrient uptake, primarily of Phosphorus (0.50%), Potassium (0.07%), Iron (225.24 ppm), Copper (26.95 ppm), Manganese (135.33 ppm), Zinc (43.87 ppm), and Boron (18.61 ppm).