Improving in vitro mineral nutrition for diverse pear germplasm

Abstract

Mineral nutrition in the media used for growth of in vitro plants is often difficult to optimize due to complex chemical interactions of required nutrients. The response of plant tissue to standard growth media varies widely due to the genetic diversity of the plant species studied. This study was designed as the initial step in determining the optimal mineral nutrient requirements for micropropagation of shoot tips from a collection of genetically diverse pear germplasm. Five mineral nutrient factors were defined from Murashige and Skoog salts: NH4NO3, KNO3 ,m esos (CaCl 2·2H20- KH2PO4-MgSO4), micronutrients (B, Cu, Co, I, Mn, Mo, and Zn), and Fe-EDTA. Each factor was varied over a range of concentrations. Treatment combinations were selected using response surface methods. Five pears in three species (Pyrus communis 'Horner 51, '' Old Home×Farmingdale 87, '' Winter Nelis,' Pyrus dimorphophylla ,a ndPyrus ussuriensis 'Hang Pa Li') were grown on each treatment combination, responses were measured, and each response was analyzed by analysis of variance. The analyses resulted in the identification of the following factors with the single largest effects on plant response: shoot quality (mesos), leaf spotting/necrosis (mesos), leaf size (mesos), leaf color (mesos, NH4NO3, and KNO3), shoot number (NH4NO3 and Fe), nodes (NH4NO3 and KNO3), and shoot length (mesos and Fe). Factors with the largest effects (mesos and Fe) were similar among the genotypes. This approach was very successful for defining the appropriate types and con- centrations of mineral nutrients for micropropagation of diverse pear genotypes.