Maize production in Argentina has increased in recent years, following the global gain (GG) in grain yield (GY). The GG in GY depends on genetic progress (GP), which requires frequent quantification to detect potential plateaus and variations in its contribution to the GG. In this sense, hybrid adoption in Argentina shifted from double- and three-way to single cross (F1) hybrids in the 1990s, thereby increasing the level of heterosis of released hybrids. Since heterosis increase may have had a greater impact on estimates of maize GG than those based on a single cross type, GP based exclusively on F1 hybrids and its contribution to GG could be lower than that including different types of crosses. The main objectives of this work were to (i) analyze grain yield GP, (ii) dissect grain yield GP into the corresponding trends in its physiological determinants and numerical components, and (iii) estimate the relative contribution of GP to GG in the main maize producing region of Argentina for the period marked by significant changes in heterosis level (i.e. from 1960s to 1990s) and the period of massive adoption of F1 hybrids (from 1990s onwards). We used a dataset obtained at the core of the mentioned region (INTA Pergamino; 33°56’S, 60°34’W) from era-decade experiments (ERA) including 24 hybrids released between 1965 and 2016 and grown with no abiotic or biotic restrictions. We quantified GY, its numeric components (KN: kernel number m, KW: individual kernel weight) and its physiological determinants (B: total shoot biomass at maturity, HI: harvest index). A GP of 0.84 % y was computed for GY from 1965 to 1993, and of 0.51 % y thereafter. We also detected genetic progress for KN (0.53 % y) and B (0.26 % y) but not for KW. A GP of 0.66 % y was computed for HI up to 1993, which plateaued thereafter. A 40 % contribution of GP to GG was estimated for the Pergamino site from 1965 to 1993, predominantly driven by changes in heterosis level. The contribution dropped to 32 % from 1993 onwards, when F1 hybrids were massively adopted by the farmers. This contribution was much smaller (e.g. 19 %) in areas less representative of the target population of environments of dominant breeding programs. Our findings underline that the relative contribution of GP to GY improvement at the regional level varies markedly depending upon the period included in the analysis and the environment used for evaluation. The decline observed at less representative locations of the main target population of environments may guide breeders in their decision for developing new programs.

中文翻译：

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玉米育种对粮食产量遗传进展的影响及其对阿根廷全球增产的贡献


近年来，随着全球粮食产量（GY）的增加（GG），阿根廷的玉米产量有所增加。 GY 中的 GG 取决于遗传进展 (GP)，这需要频繁量化以检测其对 GG 贡献的潜在平台和变化。从这个意义上说，阿根廷的杂交品种在 20 世纪 90 年代从双交和三交杂交转向单交 (F1) 杂交，从而提高了已投放的杂交品种的杂种优势水平。由于杂种优势的增加可能比基于单一杂交类型的玉米 GG 估计产生更大的影响，因此仅基于 F1 杂种的 GP 及其对 GG 的贡献可能低于包含不同类型杂交的 GP。这项工作的主要目标是（i）分析谷物产量 GP，（ii）将谷物产量 GP 剖析为其生理决定因素和数值成分的相应趋势，以及（iii）估计 GP 对 GG 的主要贡献阿根廷玉米产区以杂种优势水平显着变化为标志的时期（即从 1960 年代到 1990 年代）和大规模采用 F1 杂交种的时期（从 1990 年代起）。我们使用了在上述区域（INTA Pergamino；南纬 33°56'，西经 60°34'）核心区域通过十年实验 (ERA) 获得的数据集，其中包括 1965 年至 2016 年间释放的 24 个杂交品种，且在没有非生物或生物限制的情况下生长。我们量化了 GY、其数字组成部分（KN：粒数 m，KW：单粒重量）及其生理决定因素（B：成熟时的芽总生物量，HI：收获指数）。计算出 1965 年至 1993 年 GY 的 GP 为 0.84% y，此后为 0.51% y。我们还检测到 KN (0.53 % y) 和 B (0.26 % y) 的遗传进展，但未检测到 KW 的遗传进展。 GP为0。计算结果显示，截至 1993 年，HI 的 y 值为 66%，此后趋于稳定。据估计，从 1965 年到 1993 年，Pergamino 位点的 GP 对 GG 的贡献为 40%，这主要是由杂种优势水平的变化驱动的。从 1993 年起，当 F1 杂交品种被农民大量采用时，这一贡献下降到 32%。在不太能代表优势育种计划环境目标种群的地区，这一贡献要小得多（例如 19%）。我们的研究结果强调，GP 对区域层面 GY 改善的相对贡献存在显着差异，具体取决于分析所包含的时期和评估所使用的环境。在主要目标环境种群的代表性较低的地点观察到的下降可能会指导育种者制定新计划的决定。