Joe FLeetwood Hennen (1928–2024)

Dr. Joe F. Hennen was born January 6th, 1928 in Sherman, Texas. He first became seriously interested in plant taxonomy in undergraduate courses taught by the late Dr. Lloyd Shinners at Southern Methodist University (SMU) in Dallas, Texas. After receiving a B.S. from SMU in 1950, he did graduate work in plant pathology and taxonomy of rust fungi in the Arthur Fungarium (PUR) at Purdue University, West Lafayette, Indiana. He received his M.S. in 1952 and Ph.D. in 1954 working with George B. Cummins.

The taxonomy of vascular plants and that of rust fungi was a combination especially interesting to Hennen. From 1954 to 1958, Hennen worked at South Dakota State University as a plant pathologist of cereal crops. This experience impressed upon him the concept that the geographic centers of genetic diversity for crop plants often coincide with the centers of taxonomic diversity of their obligate parasites. Similarly, the intricacies of coevolution of rust fungi with their hosts have long been an area of speculation and research for a multitude of rust taxonomists and plant pathologists.

From 1958 to 1968, Hennen taught a wide range of undergraduate botany courses at Indiana State University. He returned to Purdue University as a Professor of Botany and Plant Pathology and Curator of the PUR in 1968. Upon Cummins's retirement in 1970, Hennen became Director of the PUR the following year.

The most important contributions by Hennen were his fieldwork and collections from several regions of the United States, Central America, and especially Mexico and Brazil, with a focus on the taxonomy of Neotropical rust fungi. In 1995 Hennen retired from Purdue University and moved to Texas, where he became a Resident Research Associate at the Botanical Research Institute of Texas in Fort Worth. Hennen remains in contact with the Purdue Herbaria staff, having visited post-retirement and advised graduate student research conducted in the Aime Lab.

Hennen remained in contact as a consultant to Director Aime until his passing on March 4, 2024 at the age of 96.

International Specialist in Rust Fungi

Originally prepared for the Mycological Society of America Inoculum June 2024

Following in the line of rust specialists at Purdue University, Joe Hennen lived well into his nineties studying rust fungi until his recent passing at 96. Borne in Sherman, Texas, he started his career at Southern Methodist University, studying plant taxonomy with Dr. Lloyd Shinners, receiving his B.S. in 1950. He returned to Texas when he retired from Purdue in 1995 and, with his supportive wife Mary, who was also knowledgeable in rust fungi, continued his research at the Botanical Research Institute of Texas in Fort Worth, Texas. In between he spent most of his time at Purdue University, West Lafayette, Indiana, where he received his M.S. in 1952 and Ph.D. in 1954 studying with George B. Cummins, who lived to be 102. After serving as a plant pathologist of cereal crops at South Dakota State University from 1954–1958 and teaching undergraduate botany at Indiana State University from 1958–1968, he returned to Purdue as a Professor of Botany and Plant Pathology in 1968. Soon he was promoted to Director of the Purdue Herbarium, a position he held from 1971–1995.

As Director of the Purdue Herbarium he organized this vast collection of rust fungi contributing his own meticulously documented specimens. Each specimen has extensive notes and drawings making them incredibly valuable to future scientists and often saving the specimen from destruction. This resource now serves as the center of research on the phylogeny of rust fungi and determination of the coevolution of rust fungi with their hosts carried on by his successor Dr. M. Catherine Aime.

Research by Hennen centered on the study of rust fungi now Pucciniales at first in the United States but later throughout the world especially in Mexico, Central and South America. He published widely with many collaborators training the next generation of rust specialists. Following his predecessors J.A. Arthur, who wrote the only account of all rust fungi of the United States (Arthur 1934), and Cummins, who published comprehensive books on rust fungi of grasses and composites, Hennen’s early research emphasized fungi on grasses in the western United States. Hennen & Ono (1978) published on the first and only rust known to infect a member of the palm family (Arecaceae).

Gradually his focus shifted to tropical regions including Hawaii (Hennen & Hodges 1981) and Mexico (Hennen et al. 1972; Hennen & Cummins 1973), then moving south to Argentina (Hernandez & Hennen 2002) and Brazil (de Carvalho & Hennen 2019; Hennen et al. 1982), always collaborating with local mycologists. Starting in about 1975, Hennen stimulated an increase in interest in the rust fungi in Brazil. He was always concentrating on his work on fungi planning comprehensive projects taking his associates collecting, observing symptoms present in the plants, bringing his magnifying hand lens close to the symptoms and, if there was a high probability that it was rust, he would show a gleam in his clear eyes, inviting anyone nearby to also observe, offering his knowledge for anyone who wanted to learn. This collaboration culminated in the two major outputs, first, the on-line Hennen et al. 2005, and finally the recently published Illustrated Genera of Rust Fungi of Brazil (de Carvalho & Hennen, 2023)

In addition to his dedication to the rust fungi, Joe was a family man married to Mary M. Winkler Hennen and had their son, Philip (image left). Mary accompanied him on collecting trips and published with him. Joe often had a merry twinkle in his eye and was friendly and supportive to all with a willingness to collaborate and train others in the study of rust fungi.

Authors: Amy Rossman, Anibal de Carvalho Jr., Phil Hennen.