DOI: https://doi.org/10.15368/theses.2020.99
Available at: https://digitalcommons.calpoly.edu/theses/2549
Date of Award
3-2020
Degree Name
MS in Agriculture - Crop Science
Department/Program
Horticulture and Crop Science
College
College of Agriculture, Food, and Environmental Sciences
Advisor
Lauren Garner
Advisor Department
Horticulture and Crop Science
Advisor College
College of Agriculture, Food, and Environmental Sciences
Abstract
‘Wonderful’ pomegranate flowering and fruiting habits are not well understood. Characterizing any relationship between flowering habit and fruit size and quality could lead to effective cultural practices for producing high-value fruit. Five mature ‘Wonderful’ pomegranate trees were monitored every 5-14 days throughout the 2015 growing season. Newly emerged flowers were tagged and characterized with respect to sex (determined by ovary shape and style length at anthesis), clustering habit, age of wood on which floral buds were borne, and direction of wood growth. More than 1,100 hermaphroditic flowers were identified and ovary/fruit diameter was recorded throughout the season. In addition to tagging 1,800 staminate flowers at anthesis, approximately 14,000 abscised staminate flowers were collected and used to estimate total flower number and the ratio of hermaphroditic (fruit producing) to staminate flowers. Trees were strip picked at harvest. Fruit weight, maximum hemispheric diameter and exocarp color were recorded. Arils (seeds with a fleshy seed coat) were removed and weighed; aril number was estimated from the weight of 100 arils, and aril titratable acidity and total soluble solids were measured. The age of wood on which flowers were borne was a significant predictor of flower sexual condition. One-year-old wood produced the highest number of flowers (70% of total) with the smallest proportion of hermaphroditic flowers (5%) for any age of wood. Two-year-old wood produced fewer flowers (19% of total) with 10% hermaphroditic flowers. Wood that was greater than two years old produced 10% of total flowers and 20% were hermaphroditic. Overall, 93% of the flowers were staminate. Despite the low proportion of hermaphroditic flowers produced on one-year-old wood, 57% of marketable sized fruit were produced on one-year-old wood. There were three distinct bloom periods, the first lasting approximately 6 weeks. Bloom time was highly predictive of fruit quality. Late-blooming flowers produced low-quality fruit that were smaller in diameter with fewer arils and poor exocarp color. Such fruit accounted for approximately 13% of total fruit weight. Location within the canopy influenced fruit diameter significantly. Flowering rarely occurred in the typically “closed” interior of the canopy and flowers in the northwest tree quadrant were less likely to be early blooming or hermaphroditic than flowers in other quadrants. The results suggest that development of cultural methods that limit excessive production of staminate flowers reduce late-season flowering and/or fruit production and/or increase light exposure to fruiting wood could increase the production of high-value fruit for ‘Wonderful’ pomegranate.