Climate change is affecting all regions of the world with different climates, and the scale of damage is increasing due to the occurrence of various natural disasters. In particular, maize production is highly affected by abnormal climate events such as heat waves and droughts. Increasing temperatures can accelerate growth and shorten the growing season, potentially reducing productivity. Additionally, enhanced temperatures during the ripening period can accelerate the process, reducing crop yields. In addition, drought stress due to water deficit can greatly affect seedling formation, early plant growth, photosynthesis, reproductive growth, and yield, so proper water management is critical to maize growth. Maize, in particular, is tall and broad-leaved, so extreme drought stress at planting can cause leaves to curl and stunt growth. It is important to understand that severe drought can have a detrimental effect on the growth and reproduction of maize. In addition, high temperatures caused by drought stress can inhibit the induction of flowering in male flowers and cause factors that interfere with pollen development. It is therefore important to increase the productivity of all food crops, including maize, while maintaining them in the face of persistent drought caused by climate change. This requires a strategy to develop genetically modified crops and drought-tolerant maize that can effectively respond to climate change. The aim of this paper is to investigate the effects of climate change and drought tolerance on maize growth. We also reviewed molecular breeding techniques to develop drought-tolerant maize varieties in response to climate change.

Wheat starch is one of the most important components in wheat grain and is extensively used as the main source in bread, noodles, and cookies. The wheat endosperm is composed of about 70% starch, so differences in the quality and quantity of starch affect the flour processing characteristics. Investigations on starch composition, structure, morphology, molecular markers, and transformations are providing new and efficient techniques that can improve the quality of bread wheat. Additionally, wheat starch composition and quality are varied due to genetics and environmental factors. Starch is more sensitive to heat and drought stress compared to storage proteins. These stresses also have a great influence on the grain filling period and anthesis, and, consequently, a negative effect on starch synthesis. Sucrose metabolizing and starch synthesis enzymes are suppressed under heat and drought stress during the grain filling period. Therefore, it is important to illustrate starch and sucrose mechanisms during plant responses in the grain filling period. In recent years, most of these quality traits have been investigated through genetic modification studies. This is an attractive approach to improve functional properties in wheat starch. The new information collected from hybrid and transgenic plants is expected to help develop novel starch for understanding wheat starch biosynthesis and commercial use. Wheat transformation research using plant genetic engineering technology is the main purpose of continuously controlling and analyzing the properties of wheat starch. The aim of this paper is to review the structure, biosynthesis mechanism, quality, and response to heat and drought stress of wheat starch. Additionally, molecular markers and transformation studies are reviewed to elucidate starch quality in wheat.

Few studies have reported on the flowering time mechanism of tropical maize under short-day conditions. Drought, another important factor that affects flowering time, has been reported to delay the silking date in tropical maize. However, due to the lack of genetic information related to flowering in maize, the mechanism by which drought delays flowering is unclear. To further understand this process, we analyzed drought-responsive genes using RNA sequencing and identified genes related to flowering time, including contigs from de novo assembly. The results revealed changes in the expression of flowering-time genes, including INDETERMINATE1 (ID1), Heading date 3a (Hd3a), CONSTANS-like genes, and ZEA MAYS CENTRORADIALES8 (ZCN8), which are known to be crucial factors in flowering. In particular, Hd3a, CONZ1, and ZCN8, which have been reported to accelerate flowering under short-day conditions, were downregulated by drought stress. Changes in gene expression appear to play an important role in changes in flowering time under drought. These expression profiles will help to further understand the flowering-time genes of tropical maize and the delayed flowering time resulting from drought.

Downy mildew (DM) is a major disease of maize that causes significant yield loss in subtropical and tropical regions around the world. A variety of DM strains have been reported, and the resistance to them is polygenically controlled. In this study, we analyzed the quantitative trait loci (QTLs) involved in resistance to Peronosclerospora sorghi (sorghum DM), P. maydis (Java DM), and Sclerophthora macrospora (crazy top DM) using a recombinant inbred line (RIL) from a cross between B73 (susceptible) and Ki11 (resistant), and the candidate genes for P. sorghi, P. maydis, and S. macrospora resistance were discovered. The linkage map was constructed with 234 simple sequence repeat (SSR) and restriction fragment length polymorphism (RFLP) markers, which was identified seven QTLs (chromosomes 2, 3, 6, and 9) for three DM strains. The major QTL, located on chromosome 2, consists of 12.95% of phenotypic variation explained (PVE) and a logarithm of odds (LOD) score of 14.12. Sixty-two candidate genes for P. sorghi, P. maydis, and S. macrospora resistance were obtained between the flanked markers in the QTL regions. The relative expression level of candidate genes was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) using resistant (CML228, Ki3, and Ki11) and susceptible (B73 and CML270) genotypes. For the 62 candidate genes, 15 genes were upregulated in resistant genotypes. Among these, three (GRMZM2G028643, GRMZM2G128315, and GRMZM2G330907) and AC210003.2_FG004 were annotated as leucine-rich repeat (LRR) and peroxidase (POX) genes, respectively. These candidate genes in the QTL regions provide valuable information for further studies related to P. sorghi, P. maydis, and S. macrospora resistance.

Premise of the study: Positional cloning in combination with phenotyping is a general approach to identify disease‐resistance gene candidates in plants; however, it requires several time‐consuming steps including population or fine mapping. Therefore, in the present study, we suggest a new combined strategy to improve the identification of disease‐resistance gene candidates.Methods and Results: Downy mildew (DM)–resistant maize was selected from five cultivars using a spreader row technique. Positional cloning and bioinformatics tools were used to identify the DM‐resistance quantitative trait locus marker (bnlg1702) and 47 protein‐coding gene annotations. Eventually, five DM‐resistance gene candidates, including bZIP34, Bak1, and Ppr, were identified by quantitative reverse‐transcription PCR (RT‐PCR) without fine mapping of the bnlg1702 locus.Conclusions: The combined protocol with the spreader row technique, quantitative trait locus positional cloning, and quantitative RT‐PCR was effective for identifying DM‐resistance candidate genes. This cloning approach may be applied to other whole‐genome‐sequenced crops or resistance to other diseases.