V.B. Patel

Arbuscular-mycorrhizal fungi alleviate transplantation shock in micropropagated grapevine (Vitis vinifera L.)

Summary The effects of root inoculation with seven different arbuscular-mycorrhizal fungi (AMF) (Acaulospora laevis, A. scorbiculata, Entrophospora colombiana, Gigaspora gigantea, Glomus manihotis, Scutellospora heterograma) and a commercial mixed inoculum (consisting of Glomus moessae, G. manihotis and Gigaspora gigantea) on tissue culture-derived grapevine plantlets were studied during the hardening stage, under glasshouse conditions. Sixty days after inoculation, the percentages of plantlet survival, vine lengths, plant fresh and dry weights, leaf areas, photosynthetic rates, total chlorophyll contents, proline concentrations, nitrate reductase activities and nutrient status were determined. AMF-treated plantlets were superior to control plantlets for all parameters measured. Ex vitro survival rates of micropropagated grapevine plantlets were almost doubled as a result of AMF-inoculation. Correlations were calculated between the extent of root colonisation by AMF and the different parameters.Among the physiological and growth parameters, the highest positive correlation (r = 0.852) was noted for photosynthetic rate, followed by leaf area (r = 0.839). Among the biochemical parameters, the highest correlation was with proline content (r = 0.979) followed by nitrate reductase activity (r = 0.865). For nutrient status, the maximum correlation was between with AMF-colonisation and Zn (r = 0.880), followed by P (r = 0.835). With respect to the different parameters studied, A. laevis, G. manihotis and the mixed inoculum were identified as the most effective inocula. Our results indicated that AMF-colonisation could be an efficient technique to reduce the shock of transplantation for in vitro-raised grapevine plantlets for commercial use.

Effect of high density planting systems on physiological and biochemical status of rejuvenated mango plants of cv. Amrapali

Mango trees grown under high density planting systems show a gradual decline in yield after 11–12 years due to overcrowding of canopies. To find out the effect of high density planting systems on physio-biochemical parameters of mango, an experiment was conducted on an old senile, rejuvenated high density cv. Amrapali orchard over two consecutive years. High density planting systems showed significant effect on physiological, biochemical and nutritional parameters of plants. Among the different planting systems, plants under cluster planting system recorded the highest leaf area (156.68 cm2), transpiration rate (3.77 m mol−1 m−2s−1); and N (1.28%) P (0.20%) and K (0.54%) contents. The maximum leaf relative water content (87.63%) was noted in plants under square planting system, while, the photosynthetic rate (8.36 μmol CO2 m−2 s−1) was highest in hedge-row planting system. The stomatal conductance (0.17 μmol CO2 m−2 s−1) was the highest in plants under double-hedge row planting system. The highest internal carbon concentration was recorded in paired planting system, while the maximum chlorophyll ‘a’ (1.50 mg g−1), chlorophyll ‘b’ (0.65 mg mg g−1) and total chlorophyll (2.02 mg g−1) contents were found in plants under square planting system. The highest total phenolics (53.09 mg g−1) content was recorded under paired planting system. The micronutrient contents in plants, viz. Cu, Zn, Fe and Mn also differed among different planting systems.

Synergistic interaction of arbuscular mycorrhizal fungi and mycorrhiza helper bacteria improving antioxidant activities in Troyer citrange and Cleopatra mandarin under low moisture stress

A glasshouse experiment was conducted to investigate the influence of arbuscular mycorrhizal fungi (AMF) and mycorrhiza helper bacteria (MHB) on growth, osmotic adjustment, and antioxidant activities in Troyer citrange and Cleopatra mandarin in pot culture under well-watered (WW) and water stress (WS) conditions. After 270 days of inoculation with microbial culture(s), half of the seedlings of each genotype were subjected to water stress and the other half were WW for 20 days. During the moisture stress mycorrhizal root colonization showed a durative reduction. No mycorrhizal colonization was observed in the roots of non-AM seedlings. Troyer citrange and Cleopatra mandarin recorded significantly highest root colonization just before imposing differential water treatment (83.34 and 80.00%, respectively) and after 20 days of differential water treatment (66.67 and 62.50%, respectively) under WS and (87.50 and 83.33%, respectively) under WW, when dually inoculated with Glomus intraradices and PSB. Glomus intraradices in association with PSB or Azospirillum accumulated higher concentration of osmolytes like total phenols, proline and total soluble sugars and antioxidant metabolites (carotenoids and ascorbic acid) in leaves of citrus seedlings under WS.