Estimating genetic gains in sorghum [Sorghum bicolor (L.) Moench] is necessary to assess whether the current rates of improvement will meet future production demands. The current study was conducted to determine the rate of genetic gain in yield and associated traits over the commercial hybrid era using sorghum germplasm from the Texas A&M sorghum breeding program and a US sorghum seed company. From the Texas A&M AgriLife program, 60 hybrids that represented a 50‐yr span of hybrid breeding were grown and evaluated in five environments across Texas in 2016. In a separate set of trials, 14 commercial hybrids representing a similar timespan were evaluated in three Texas environments in 2016. In both programs, grain sorghum yields increased 0.008 t ha−1 annually over their respective timespans. Traits that increased over time included yield potential per plant, heterosis, test weight, panicle size, and grain number per panicle, whereas leaf angle, days to maturity, plant height, and yield stability demonstrated little to no change. Overall, ∼60% of total yield gains in US sorghum production are attributed to genetic improvement through sorghum breeding. Compared with other major US field crops, the rate of genetic gain in sorghum has been slower, presumably due to a combination of factors, which include continually shifting production environments, changing priorities in traits, reduced research investments (compared with other crops), and less‐than‐optimized heterotic groups.

No abstract

No abstract

Our study was conducted to determine agronomic optimum seeding rates (AOSR) for irrigated maize under a range of agroecological conditions in Texas. Environmental factors that affect irrigated maize production vary considerably across Texas. This variability imposes region-specific limitations on statewide maize seeding rate recommendations. Our research examined the efficiency of varying seeding rates on irrigated maize grain yields in five USEPA Level IV Ecoregions that comprise most of the irrigated maize-producing area of Texas. The selected sites span a distance of 1200 km from south to north Texas and elevations from 20 to 1218 m above mean sea level. We conducted the study over three growing seasons from 2005 through 2007 in two Level IV Ecoregions of the High Plains of North Texas (N), one in the East Central Plains (E), one in the Southern Plains and one in Western Gulf Coastal Plains of South Texas (S). We observed that maximum grain yields and AOSR to achieve maximum maize grain yields vary considerably among ecoregions. In South Texas, we observed grain yield response rates of 125-129, 151 kg 1000 seeds À1 in E and 163-199 kg 1000 seeds À1 in N. We show that growing season average daily minimum air temperature (T MIN ) explains most of this variation (r 2 = 0.98, P-value < 0.01) and conclude that seeding rate efficiency is concomitant to T MIN . Maximum grain yields (GY MAX ) determined with seeding rate response analysis also varied among ecoregions and with T MIN from south to north Texas, from a low of 8.3 Mg ha À1 in S to a high of 18.4 Mg ha À1 in N (r 2 = 0.59, P-value < 0.01). We conclude that development of agronomic management models by Level IV Ecoregions of Texas combined with site-specific T MIN climatological data serve as a valid template for delivering robust and agroecozonespecific irrigated maize seeding rate recommendations in Texas.

No abstract