Despite much effort, little exotic germplasm has been introduced in temperate maize breeding programs. Tropical and subtropical maize germplasm from CIMMYT is the most genetically diverse in the world and should be useful in widening the genetic base of temperate maize germplasm. Extracting the most suitable material from exotic germplasm is a tough challenge for plant breeding programs. This study aimed to determine the optimal number of testers to screen a maize line derived from tropical and subtropical CIMMYT germplasm. For this purpose, four temperate maize testers (MO17, B73, K47/3, and K18) and nine lines from CIMMYT were crossed. The 36 crosses along with two hybrid checks were assessed in a randomized complete block design with three replications at four maize growing regions in Iran. The GGE biplot procedure and methodology proposed by Fan et al. (2010) were used to analyze the results indicating a possibility of direct use of 2, 3, 4, and 9 CIMMYT lines to improve grain yield in temperate environments. Temperate maize testers B73 and K47/3, which belong to the Reid Yellow Dent heterotic group, were very efficient in selecting superior tropical and subtropical CIMMYT germplasm, whereas testers MO17 and K18 from the Lancaster Sure Crop heterotic group were fairly good and weak, respectively. Actually just one temperate tester could select most, if not all, of the top exotic tropical and subtropical lines, and a second tester would provide backup.

尽管付出了很大的努力，温带玉米育种计划却很少引入外来种质。CIMMYT的热带和亚热带玉米种质是世界上遗传多样性最丰富的品种，应有助于拓宽温带玉米种质的遗传基础。从外来种质中提取最合适的材料是植物育种计划的一项艰巨挑战。这项研究旨在确定筛选来自热带和亚热带CIMMYT种质的玉米品系的最佳测试员数量。为此，越过了四个温带玉米测试仪（MO17，B73，K47 / 3和K18）和来自CIMMYT的9条品系。在伊朗的四个玉米种植区，采用随机完整区组设计对36个杂交和两个杂交检查进行了评估，并进行了三次重复。Fan等人提出的GGE双线图程序和方法。（2010年）被用来分析结果，表明有可能直接使用2、3、4和9个CIMMYT品系来改善温带环境下的谷物产量。温带玉米测试员B73和K47 / 3（属于里德·黄登特杂种优势组）在选择优良的热带和亚热带CIMMYT种质方面非常有效，而兰开斯特Sure Crop杂种优势组的测试员MO17和K18分别相当好和很弱。 。实际上，只有一个温带测试仪可以选择大多数（如果不是全部）顶级的热带和亚热带热带气候带，而第二个测试仪可以提供支持。温带玉米测试员B73和K47 / 3（属于里德·黄登特杂种优势组）在选择优良的热带和亚热带CIMMYT种质方面非常有效，而兰开斯特Sure Crop杂种优势组的测试员MO17和K18分别相当好和很弱。 。实际上，只有一个温带测试仪可以选择大多数（如果不是全部）顶级的热带和亚热带热带气候带，而第二个测试仪可以提供支持。温带玉米测试员B73和K47 / 3（属于里德·黄登特杂种优势组）在选择优良的热带和亚热带CIMMYT种质方面非常有效，而兰开斯特Sure Crop杂种优势组的测试员MO17和K18分别相当好和很弱。 。实际上，只有一个温带测试仪可以选择大多数（如果不是全部）顶级的热带和亚热带热带气候带，而第二个测试仪可以提供支持。