In vitro viability and germination of Carya illinoinensis under different storage conditions

Authors: Wang, Xinwang; WU, YUELIANG - Shenyang Agricultural University; LOMBARDINI, LEO - Texas A&M University

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2020
Publication Date: 9/17/2020
Publication URL: https://handle.nal.usda.gov/10113/7135246
Citation: Wang, X., Wu, Y., Lombardini, L. 2020. In vitro viability and germination of Carya illinoinensis under different storage conditions. Scientia Horticulturae. 275:109662. https://doi.org/10.1016/j.scienta.2020.109662.
DOI: https://doi.org/10.1016/j.scienta.2020.109662

Interpretive Summary: Pecan is a monoecious tree where male and female flowers exist separately on the same tree. There are two types of flowering pecan trees: individual trees whose catkins shed pollen before pistillate flower receptivity are "protandrous" or type I, and individual trees whose female flowers reach receptivity before pollen shed are "protogynous" or type II. Pecan trees are heterodichogamous, with mixed periods of bloom enabling cross pollination and out-crossing. For controlled-cross breeding, breeders need to collect pollen from male flowers, which are likely from a distant orchard, and pollinate to female flowers in order to make controlled crosses to develop new varieties. As other plants, pecan pollen has its viability, which has not been completely tested among the current cultivars. This study presents a complete test for pollen activities during different storage conditions and will provide useful information of short-term storage of pollen source for breeders in pecan breeding programs.

Technical Abstract: Pecan (Carya illinoinensis) is a crossing-pollinated nut tree with male and female flowering separately and mature at different times. This dichogamy pattern requires appropriate pollen storage strategy making hybridization successful in a pecan breeding program. In this study, we first used pecan cultivar 'Pawnee' pollen to optimize germination media on the basis of four published formulas. Consequently, an agar-solidified medium containing 15g sucrose, 0.005g boric acid, and 0.075g calcium nitrate per 100 ml at pH = 7 was optimal to the pecan pollen germination. Pollen of 15 pecan cultivars or breeding lines, including seven protandrous and eight protogynous genotypes, were collected and examined for germination rates on the optimized medium in order to determine germination variation among genotypes. 'Pawnee' pollen was investigated for germination pattern at four storage temperatures with different time intervals. As a result, pollen germination rates varied among cultivars and this variation was related to the pollen maturity status when collected. 'Pawnee' pollen retains viability when stored at -20°C for six weeks (58.5% germination rate) or 4°C for four weeks (57.5%), and still maintains 51.8% viability when stored at -80°C for one year. These results provide useful information for a cross breeding program and mapping population development in pecan.