Fruit Ripening and Quality

Unraveling the interactions between transcriptional regulators of ripening to improve tomato fruit quality.
We are working to provide a better understanding of the genetic factors controlling tomato ripening in order enhance breeding for fruit quality and extended shelf life.

Depicting the intersection between strawberry shelf life and postharvest quality.
We are identifying strawberry loci controlling fruit shelf life and postharvest quality in order to test the feasibility of using genomic prediction to assist breeding for these attributes. This study is a collaboration with Prof. Steven Knapp and the UCD Strawberry Breeding Program. The long-term goal of this study is to develop strawberry varieties that meet the standards for mass-production and shipping to long-distance markets and additionally have improved flavor.

Characterizing pistachio hull, shell, and kernel development as a function of degree-day accumulation and source-sink relationships.
We are studying the development and maturity of pistachio nuts to generate phenological and physiological data for efficient orchard management and pest control. The physiological basis of shell split and hull ripening in pistachio is not well understood, although these processes influence the susceptibility to insect damage and the quality of the nuts. We are particularly interested in how heat accumulation and various management practices can differently influence the growth of the whole nut or just the kernel, and how they impact hull maturity, ripening, and deterioration.

Fruit-Pathogen Interactions

Characterizing the infection strategies of postharvest fungal pathogens.
We are studying how fungal pathogens infect fruit and cause decay under postharvest conditions. Most of these fungi display necrotrophic lifestyles, which are not as well-studied as other types of plant pathogens, even though they cause significant crop losses. We have recently published a research article on how three of these pathogens, Botrytis cinerea, Fusarium acuminatum, and Rhizopus stolonifer, adjust their infection strategies in response to the ripening stage of tomato fruit.

Investigating the ripening-associated increase in tomato fruit susceptibility to fungal pathogens.
We are interested in host genetic and regulatory factors that control fruit susceptibility to fungal disease. We are currently working on a comprehensive transcriptomic study that integrates mutant and gene-edited lines to investigate the critical impacts of ripening on susceptibility. In addition, we have initiated a study on the role of DNA methylation in the context of fruit susceptibility.

Developing early detection methods for Botrytis cinerea (gray mold) in strawberries.
We are developing a sensitive, consistent platform for the early, non-destructive detection and identification of B. cinerea in strawberries under commercial storage. The high perishability of strawberries is linked to their high susceptibility to fungal decay, mainly caused by this pathogen.

Depicting the interaction between nectarine and Monilinia laxa (brown rot).
We have collaborated with the Institute for Food and Agricultural Research and Technology (IRTA) in Catalonia, Spain to identify mechanisms of susceptibility and resistance of nectarines against brown rot, which is a relevant postharvest disease of stone fruit worldwide.

Fruit Cell Wall Dynamics

Improving tomato texture by modulating fruit cell wall disassembly.
In collaboration with Prof. Graham Seymour at the University of Nottingham, we have demonstrated that the enzyme pectate lyase (PL) is the main contributor to fruit softening in tomatoes. We are expanding this work by developing higher-order knockout mutants of PL and other cell wall modifying enzymes specific for fruit ripening. We will evaluate these lines for modifications in fruit cell ultrastructure and biochemical composition, texture traits, shelf-life, susceptibility to fungal decay, and quality attributes. This project will deepen the understanding of mechanisms controlling tomato fruit firmness.

Characterizing the processing quality of tomato commercial lines.
Developing tomato lines that produce high consistency paste would reduce the amount of tomato fruit needed to reach a determinate level of quality in a processed product resulting in increased crop efficiency and profitability. Among multiple factors, the biochemical composition and changes in the fruit pectin have a profound effect on the final consistency of the tomato paste. In this project, we will determine key molecular, biochemical, and physicochemical factors related to pectin that impact the consistency of tomato products.

Identifying cell wall factors affecting the firmness of raspberries during postharvest storage.
We are evaluating changes in gene expression and activity of key cell wall degrading enzymes during cold storage of three raspberry accessions. We are also determining changes in the composition of soluble pectins that could explain the differences in firmness and shelf-life among the accessions.