Mycorrhization as an aid for biohardening of in vitro raised grape (Vitis vinifera L.) plantlets

Tissue culture has paved way for the rapid clonal multiplication in different horticultural plants. However, large-scale mortality of plantlets raised through this technique occur during acclimatization phase (Stage-IV), i.e. glasshouse hardening and later at field transfer. To ameliorate this problem in grape, an attempt was made to use different arbuscular mycorrhizal (AM) strains, which could be inoculated to the roots of such plants to avoid the fungal attack especially those causing rots. Thirty-day-old, in vitro rooted plants of grape cv. Pusa Urvashi and Pusa Navrang were subjected to root colonization with five arbuscular mycorrhizal fungal (AMF) strains viz. Glomus mossae, G. manihotis, G. deserticola, Gigaspora gigantia and Acaulospora laevis along with an un-inoculated control. Mycorrhizal plantlets showed improved vegetative growth, high shoot and root fresh and dry weight, leaf area, chlorophyll, sugars and phenol contents. Respiration rates were significantly reduced while photosynthetic rates were enhanced upto two times in AMF treated plants. The foliar tissues in treated plants showed improved nutrient contents especially for the P, Mg, Zn and Mn. Among the AM strains, G. mossae showed good (42.5%) root colonization for Pusa Urvashi, while G. manihotis was most responsive for Pusa Navrang. Though some of the strains did not give good colonization but drastically reduced the microbial attack. High plantlet survival was noted for the mycorrhizal plants after glasshouse and field transfer