Variation in Reproductive Characteristics and Seed Production in the USDA Garlic Germplasm Collection

Diverse garlic germplasm has proven to be essential for production of true seed. Yet, fertile accessions in garlic germplasm collections have not been characterized for breeders and researchers, and information on morphological characteristics associated with seed producing plants is very limited. The objective of this study was to evaluate re- productive characteristics and true seed production capacity in the USDA garlic germplasm collection. Most stable traits, such as flower stem appearance, opening ability of spathe, level of difficulty to remove bulbils, tepal color, umbel shape, and the number of flowers per umbel, were similar across populations evaluated. Other characteristics including position of stigma, tepal closure, pollen viability, time of flowering, scape senescence rate, and number of seeds produced by individual plants varied within accession evaluated. Of 47 accessions, 19 produced true seeds (from 48.5 to 1.5 seeds per plant) in the Central Valley of California. Seed production in the germplasm evaluated is adequate to initiate garlic breeding projects. True seed development in garlic (Allium sativum L. and A. longicuspis Regel) has been reported in literature for almost 50 years (Ko- nonkow, 1953). In the past 18 years, several reports on the production of large numbers of seed were published (Etoh, 1986; Etoh et al., 1988; Inaba et al., 1995; Jenderek, 1998; Jenderek and Hannan, 2000; Konvicka, 1984; Pooler and Simon, 1994). In spite of this, seed- producing germplasm is not readily available for garlic breeders and seed producers. Fertile germplasm is of great interest not only to breed- ers, but also to small farm garlic producers interested in developing novel products for niche markets. Garlic florogenesis was de- scribed by Hua et al. (1994) and Kamenetsky and Rabinowitch (2001), but comprehensive description of flower traits and seed production ability is very limited. The USDA National Plant Germplasm System garlic collection is maintained at the Western Regional Plant Introduction Station (WRIPS), Pullman, Wash. Currently, 195 ac- cessions of A. sativum and 10 accessions of A. longicuspis from 27 countries are available for research. A preliminary evaluation of seed production ability of selected accessions in this collection was reported by Jenderek and Hannan (2000), but the variation in flowering and fertility was not described. The objective of this study was to evaluate garlic clones selected from the NPGS collection for seed producing ability, and to identify characteristics that were associated with reproductive capacity.