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ARS Home » Plains Area » College Station, Texas » Southern Plains Agricultural Research Center » Crop Germplasm Research » Research » Research Project #442069

Research Project: Studies of Fruit-bud Differentiation for Pecan Breeding Selections

Location: Crop Germplasm Research

Project Number: 3091-21000-046-003-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Jun 1, 2022
End Date: May 31, 2025

This agreement is to investigate the phenology of both male and female flower differentiation in protandrous and protogynous pecans for breeding selection. In pecans the timing of primordium initiation and differentiation were different between male and female flowers. Floral initiation refers to the onset of flower development, where the buds of a plant become identifiable to form; floral bud differentiation is the step after initiation that is the further formation of floral primordium. In pecans, staminate inflorescence is initiated and differentiated in the previous spring, a full year before anthesis. In contrast to male flowers, the initiation of pistillate inflorescences occurs in the previous summer, but their differentiation does not begin until the spring just before bloom for that production year. Return bloom in the spring includes both male and female flower quality and quantity which translates into nut quality and quantity during the fall harvest. However, the study on the anatomical structure of pecan's male and female flower primordium is very limited. The information on the mechanism of return bloom is lacking. In this project we will compare the flower differentiation process of the different genotypes to provide a tool for selecting cultivars with a better return bloom characteristic.

Both terminal and 1st lateral buds will be sampled from 32 cultivars every three days from February 24th until bud break. Buds will be fixed in FAA (70% ethanol: acetic acid: formalin, 16:1:1 by vol.) at room temperature for subsequent histological analyses. Samples are dehydrated in an alcohol series (i.e. 70%, 80%, 85%, 90%, 95% and 100%), embedded in paraffin and then sectioned at 10µm thickness by using microtome. Flatted and dried wax slides are stained with 1% safranin in 70% ethanol for 6 hours followed by counterstaining of 0.5% fast green for 30 seconds. Paraffin sections will be made and the slices will be observed by Olympus BX51 Microscope with DP70 Digital Camera System.