Yield of Syn-1 synthetic varieties of tropical onion resulting from openpollinated Brazilian populations

Due to technological limitations for the development of onion hybrids, first-cycle synthetic varieties (Syn1-SV) could be an alternative to partially explore heterotic vigor. The growing areas of onion hybrids in Brazilare mainly defined by bulb yield and uniformity. From this perspective, the present study aimed to developtropical onion Syn1-SV and estimate mid-parent heterosis (Hm), heterobeltiosis (Hp), and standard heterosis(Hs) as an alternative to hybrid development. Six Syn1-SVs, eight open-pollinated (OP) populations, and onecommercial hybrid were evaluated in a randomized block design with three replications, in two semesters, forthe commercial bulb yield (CBY) and days to bulb harvest (DBH). Significant differences were observed fortreatments (T), semesters (S) and the T*S interaction for both variables (p-value<0.05). The OPs ‘Alfa SF RT’ inthe first semester and ‘IPA11’ in the second semester were the most precocious treatments. The highest CBYwas estimated in the commercial hybrid (105.8 t ha-1) and in ‘Alfa SF RT’ (45.5 t ha-1) in the first and secondsemesters, respectively. Three Syn1-SVs showed positive Hm values, ranging from 2.0% to 6.3% for CBY. ThreeSyn1-SV showed positive Hp values in the first semester, ranging from 3.0% to 5.2%, for CBY. Only the Syn1-SV ‘AlfaSF RT’ × ‘BRS Alfa São Francisco’ (48.9 t ha-1) showed positive Hs values, surpassing by a small value the controlOP population ‘IPA11’ (48.0 t ha-1), indicating the potential of Syn1-SV as an option for onion hybrids.