Effect of VAM and foliar application of nutrients on root morphology
Among the tested treatments, there was a significant difference in root morphology in all the treated plots at 30 DAS. Total root length (206 cm), surface area (241cm
2), average diameter (1.11 mm), root volume (1.37 cm
3), number of tips plant
-1 (3700),number of forks plant
-1 (3218) and crossings (79.2) were significantly increased with 150% recommended dose of VAM + foliar application of 0.5% urea + 0.5% ZnSO
4 + 1% FeSO
4 at 25 and 45 DAS (T
13) followed by 125% recommended dose of VAM + foliar application of 0.5% urea + 0.5% ZnSO
4 + 1% FeSO4 at 25 and 45 DAS (T
12). Least values of root morphology was observed in control plot (T
1). Similar trend was observed at 50 DAS. Effect of different doses of soil applied VAM on rice root morphology by using winRHIZO root image analyser was showed in (Fig 1, 1a and 2). This might be due to the symbiosis between host plant roots and fungal hyphae which resulted in a well developed root system, increases water and nutrient uptake and leads to an increase the plant growth
(Basu et al., 2018; Begum et al., 2019; Beura et al., 2020; Iqbal et al., 2021).The increased solubilisation of phosphorous by VAM fungi and availability to rice plants resulted in increased root proliferation.
VAM colonization
Highest percentage of (87.3) VAM colonization was observed in the plot treated with 150% of recommended dose of VAM. The lowest percentage was observed in control plot (16.7). The number of vesicle, arbuscule and hyphal colonization was higher in 150% recommended dose of VAM applied plot compared to the other two doses of soil applied VAM fungi (Fig 3). Microscopic view of root colonized with VAM and without VAM infection was showed in Fig 4. There is no negative effect of foliar application of nutrients on VAM colonization where as VAM colonization was strongly influenced by the higher dose of VAM application of 150% (75 kg ha
-1). The highest root colonization might be due to more spore germination in rice roots. Application of VAM fungi had a positive effect on VAM colonization percentage, extraradical hyphal density (EHD), growth and yield of rice crops under non - flooded conditions as compared to flooding and shading conditions
(Wangiyana et al., 2006 ;
Mitra et al., 2021; Wang et al., 2021).
Photosynthetic pigments
The photosynthetic pigments such as chlorophyll a, chlorophyll b and carotenoids significantly increased on 30 and 50 DAS. Plot which received 150% of recommended dose of VAM + foliar application of 0.5% urea + 0.5% ZnSO
4 + 1% FeSO
4 at 25 and 45 DAS (T
13) recorded significantly higher photosynthetic pigments followed by T
12 except carotenoids. The carotenoids comparable with T
12 on both stages of crop. The lowest photosynthetic pigments observed in control (T
1) (Fig 5, 5a). Similarly, combined application of Zn and VAM fungi significantly increased the leaf chlorophyll content and growth of the rice (
Mohmoud et al., 2022). Foliar nutrient application increased carbohydrate concentration in plants, resulting in increased biochemical activities and chlorophyll and carotenoid concentrations
(Singh et al., 2014; Mahmoodi et al., 2020; Parvin et al., 2020). Increased enzymatic activity such as phosphoenolpyruvate carboxylase (PEPC) and rubisco by VAM fungi, as well as increased auxin metabolism in plants as a result of foliar nutrient application, may result in an increased photosynthetic.
Growth parameters
At 30 DAS plant height (33.1 cm), leaf area index (0.49) shoot weight (0.143 g), root dry weight (0.22 g) and total dry weight (0.36 g) was significantly higher in treatment received 150% of recommended dose of VAM + foliar application of 0.5% urea + 0.5% ZnSO
4 + 1% FeSO
4 at 25 and 45 DAS (T
13) at 30 DAS. This was comparable with T
12 with leaf area index of 0.47. Lowest plant height, leaf area index, shoot weight and root dry weight were observed in control plot (T
1) (Table 2).
At 50 DAS plant height (41.8 cm), leaf area index (2.0) shoot weight ( 2.15 g), root dry weight ( 1.74 g) and total dry weight (4.01 g) significantly increased with 150% of recommended dose of VAM + foliar application of 0.5% urea + 0.5% ZnSO
4 + 1% FeSO
4 at 25 and 45 DAS (T
13). However plant height was comparable with T
12. Lowest plant height, Leaf Area Index, shoot and root dry weight was observed in control plot. Effect of different doses of soil applied VAM fungi on growth of rice showed in Fig 6. The positive effect on plant growth parameters might be due to VAM fungi and foliar application of nutrients to enhance nutrient availability for crop growth and development. Similar findings were observed by
Mostafa et al., 2019; Lahijan et al., 2020;
Hussain et al., 2021; Mohammad Hashim et al., 2021; Patel et al., 2022; Mahmoud Soltani et al., 2022.
Yield attributes and yield
The yield attributes
viz., number of filled grains panicle
-1 (164), grain yield (3702 kg ha
-1), straw yield (4608kg ha
-1) and harvest index were influenced by different dose of soil application of VAM with foliar application of Urea, Iron (Fe) and Zinc (Zn) (Fig 7 and 7a). All these parameters were higher values with 150% of recommended dose of VAM + foliar application of 0.5% urea + 0.5% ZnSO
4 + 1% FeSO
4 at 25 and 45 DAS (T
13). However straw yield and harvest index was on pair with T
12. The present study reported that VAM fungal colonization increased the transport of macro and micronutrients at the different growth stage of the crop which increased the rice yield. These results are in confirmation with the results of
Khan et al., 2022; Aziez et al., 2022.
Correlation analysis
Correlation analysis was carried out for total VAM colonization percentage, growth and yield of the aerobic rice. Results showed that all growth and yield parameters observed were highly positively correlated with total VAM colonization percentage (Fig 8 and 9).