A major limiting factor for high productivity of maize (Zea mays L.) in dense planting is light penetration through the canopy. Plant architecture with a narrower leaf angle (LA) and an optimum leaf orientation value (LOV) is desirable to increase light capture for photosynthesis and production per unit area. However, the genetic control of the plant architecture traits remains poorly understood in maize. In this study, QTL for LA, LOV, and related traits were mapped using a set of 229 F(2:3) families derived from the cross between compact and expanded inbred lines, evaluated in three environments. Twenty-five QTL were detected in total. Three of the QTL explained 37.4% and five of the QTL explained 53.9% of the phenotypic variance for LA and LOV, respectively. Two key genome regions controlling leaf angle and leaf orientation were identified. qLA1 and qLOV1 at nearest marker umc2226 on chromosome 1.02 accounted for 20.4 and 23.2% of the phenotypic variance, respectively; qLA5 and qLOV5 at nearest bnlg1287 on chromosome 5 accounted for 9.7 and 9.8% of the phenotypic variance, respectively. These QTL could provide useful information for marker-assisted selection in improving performance of plant architecture with regard to leaf angle and orientation.

Breeders have been successful in increasing crop performance by exploiting genetic diversity over time. However, the reported annual yield increases are not sufficient in view of rapid human population growth and global environmental changes. Exotic germplasm possesses high levels of genetic diversity for valuable traits. However, only a small fraction of naturally occurring genetic diversity is utilized. Moreover, the yield gap between elite and exotic germplasm widens, which increases the effort needed to use exotic germplasm and to identify beneficial alleles and for their introgression. The advent of high-throughput genotyping and phenotyping technologies together with emerging biotechnologies provide new opportunities to explore exotic genetic variation. This review will summarize potential challenges for utilization of exotic germplasm and provide solutions.

Photoperiod sensitivity is an important consideration in maize cultivation. Flowering time is affected by photoperiod and sensitivity to it limits the potential for successful exchange of germplasm across different latitudes. For resolving the genetic basis of photoperiod sensitivity in maize, a set of 207 recombinant inbred lines derived from a temperate and tropical inbred line cross was evaluated for 2 years in a long-day and short-day environment. Genetic linkage maps were constructed using 237 SSR markers with a total length 1,974.3 cM, and an average space between two makers of 8.33 cM. Twenty-nine QTL were detected for the five measured photoperiod sensitivity traits using composite interval mapping and multiple interval mapping. QTL for flowering time, plant height and leaf number, under long-day conditions, were found clustered on chromosome 10, while QTL for short-day conditions resided on chromosome 3. The QTL in the bin 10.04 region of chromosome 10 were detected associated with photoperiod sensitivity and related traits during long days. These results indicated that this region might contain an important photoperiod sensitivity element.