207 Mycorrhizal Enhancement of the Physiology and Growth of Micropropagated Chile Ancho Pepper (Capsicum annuum L. cv. San Luis) Plantlets during Acclimatization and Post-acclimatization

Abstract

The role of mycorrhiza fungi during acclimatization and post-acclimatization of micropropagated chile ancho plantlets was characterized through physiological and plantlet development changes. Regardless of mycorrhizal colonization, the pepper plantlets had initially low photosynthetic rates and poor growth following transplanting ex vitro. During the first days of acclimatization, water deficits occurred as evidenced by drastic reductions in relative water content. Consequently, transpiration rates and stomatal conductance (gs) declined, confirming that in vitro formed stomata were functional, thus avoiding excessive leaf dehydration and plant death. Mycorrhiza had a positive effect on gas exchange as early as day 7 and 8, as indicated by increasing photosynthesis (A) and gs. Mycorrhizal plantlets had reduced levels of abscisic acid (ABA) during peak stress (6 days after transplanting ex vitro), which corresponded with subsequent increases in gs and A. During acclimatization, A increased in both non-colonized and colonized plantlets, with greater rates observed in mycorrhizal plantlets. During post-acclimatization, mycorrhiza colonized 45% of the roots of pepper plantlets and enhanced plant growth by increasing leaf area, leaf dry mass, and fruit number. Mycorrhiza also enhanced total leaf chlorophyll content, A, and nutrient uptake of pepper plantlets, particularly N, P, and K. Early mycorrhizal colonization produced important benefits, which helped ex vitro transplanted plantlets recover during acclimatization and enhance physiological performance and growth during post-acclimatization.