CHARACTERIZATION AND SEED YIELD OF FEMALE PARENTS OF SINGLE AND THREE-WAY SORGHUM HYBRIDS

As a consequence of the recent registration of parental B and R lines of sorghum [Sorghum bicolor (L.)] Moench] adapted to the Highlands of Mexico, it is necessary to develop the corresponding technology for hybrid seed production; that is the objective of this study. In Montecillo, Mexico, in the year 2015, four A-lines and 10 non-isogenic A x B crosses (female parents of single crosses and three-way hybrids, respectively) were characterized morphologically and phenologically. Hybrid seed yield (HSY) was evaluated under 4:2, 8:2, 12:2 and 16:2 female to male row ratios. Line R19 was the common male. The phenological and morphological traits were compared by Student t test; HSY was evaluated in a complete-randomized-blocks design with two replications. Days to flowering and daily and total pollen production were recorded in the male parent. In 2016, the seed yield of three Alines under two plant densities (96,000 and 48,000 female plants/ha) was evaluated in the 8:2 ratio using the same pollinator. The four male-sterile lines were similar in their days to flowering (between 111 and 114 d) and plant height (average of 101 cm). The A1 line has long panicles (25.7 cm) and longest flowering period (12.4 d); the A2 line has the highest seed yield/panicle (38.2 g) while the AS line has the lowest one (21.0 g). The A9 line showed the shortest flowering period (8.7 d), thicker stems (2.03 cm) and lower number of seeds/ panicle (888). The high production of pollen of the male parent allowed to pollinate the female plants even in the 16:2 ratio. The agronomic traits of the A x B non-isogenic direct and inverse crosses were similar, but their seed yield was greater than the line yield. Mean seed yields (2.0 t ha(-1)) may be obtained in ratios of up to 16:2 with R19 as the pollinator.