Maize Genomics and Genetics 2025, Vol.16, No.3, 119-128 http://cropscipublisher.com/index.php/mgg 120 studies have also found that heat shock proteins (HSPs) and heat shock factors (HSFs) play an important role in the heat resistance mechanism of corn, and transgenic technology has also provided a new direction for the construction of high-temperature tolerant corn (Xue et al., 2024). It can be seen that strengthening corn heat-resistant breeding is an effective way to cope with global warming. By integrating genetic resources and advanced breeding technologies, the construction of high-yield, stable-yield and high-temperature resistant corn varieties will provide strong support for the sustainable development of agriculture in the future. Therefore, breeding heat-resistant corn is a key measure to ensure sustained yields, improve resource utilization efficiency, and cope with future climate change. Breeding heat-resistant varieties can help reduce irrigation needs and improve yield stability in high temperature environments. However, in current breeding practices, many important traits related to heat resistance are not included in selection indicators. The main reason is that the measurement process of such "secondary traits" is complex, costly, and dependent on precision equipment. Therefore, it is urgent to explore cost-effective and easy-to-operate phenotypic identification methods. At the same time, combined with advanced genomic technology, the breeding process of new "climate-adaptive" varieties can be accelerated. 2 Current Status of Fresh Corn 2.1 Current status of research on heat-resistant breeding of fresh corn With the increasing trend of global warming, high temperature stress has become an important limiting factor affecting the yield and quality of fresh corn. Fresh corn (including glutinous corn and sweet corn) is extremely sensitive to high temperature, especially during the flowering and pollination period and the grain filling period, which is prone to problems such as decreased pollen vitality, blocked pollination and poor grain development, which seriously affect the quality of commodities and economic benefits (Park et al., 2024). Therefore, heat-resistant breeding has become an important direction for the current breeding of fresh corn. The current research progress of heat-resistant breeding of fresh corn is mainly focused on phenotypic screening and the establishment of an evaluation index system. The traditional heat resistance evaluation method mainly relies on field trials, which are comprehensively evaluated by indicators such as flowering duration, silking interval, fruiting rate, and leaf burn index. However, it is greatly affected by environmental variation, and has high labor intensity and a long cycle. Some studies have tried to introduce high-throughput phenotyping technologies, such as image recognition and sensor monitoring, to improve screening efficiency and accuracy. In-depth research is also needed on genetic resource mining and germplasm innovation. In recent years, researchers have begun to pay attention to the mining of heat-resistant genes in local varieties, wild species and tropical germplasm resources, and to improve germplasm by combining molecular marker-assisted selection (MAS) with conventional breeding. Some excellent gene loci (such as genes related to heat shock proteins and heat shock transcription factors) have been gradually identified, providing a theoretical basis for genetic improvement of heat resistance (Saluci et al., 2024). At the same time, molecular breeding techniques such as genomic selection (GS), genome-wide association analysis (GWAS), and QTL positioning have also been gradually introduced into fresh corn breeding. These methods help to reveal the genetic mechanism of heat resistance traits and shorten the breeding cycle. For example, researchers have located multiple SNP loci related to heat resistance through the GWAS method and conducted candidate gene verification studies (Longmei et al., 2021). It can be seen that the breeding of heat resistance in fresh corn not only focuses on stress resistance, but also must take into account commodity traits such as yield, taste, and flavor. Therefore, breeders need to balance the synergistic improvement of various traits in multi-target selection, and improve breeding efficiency and selection accuracy through multi-trait index selection models. High temperature stress often interacts with other environmental factors such as drought and humidity. In recent years, some studies have attempted to construct a multi-environment breeding model that considers genotype×environment interaction (G×E) to improve the accuracy of heat resistance trait prediction (Jarquín et al., 2014).
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