The rising demand for popcorn necessitates improving the popping quality with higher yield of popcorn cultivars. Towards this direction several Quantitative Traits Loci (QTLs) for popping traits have been identified. However, identification of accurate and consistent QTLs across different genetic backgrounds and environments is necessary to effectively utilize the identified QTLs in marker-assisted breeding. In the current study, 99 QTLs related to popping traits reported in 8 different studies were assembled and projected on the reference map "Genetic 2005" using BioMercator v4.2 to identify metaQTLs with consistent QTLs. Total ten metaQTLs were identified on chromosome 1 (7 metaQTLs) and 6 (3 metaQTLs) with physical distance ranging between 0.43 and 12.75 Mb, respectively. Four identified metaQTLs, viz., mQTL1_1, mQTL1_5, mQTL1_7 and mQTL6_2 harboured 5–8 QTL clusters with moderately high R² value. The clustered QTLs were from two or more experiments. Based on the expression pattern in endosperm and pericarp tissues, a total of 229 genes were selected. Nineteen of these genes are involved in carbohydrate metabolism. Of the 19 genes specifically involved in carbohydrate metabolism, 11 of them were in these regions, implying the importance of these clustered QTLs. MetaQTL1_1 at bin location 1.01 coincided with the reported QTLs related to various agronomic traits like stalk diameter, tassel length, leaf area and plant height. The identified metaQTLs can be further explored for fine mapping and candidate gene identification, which can be validated by loss or gain of function. Identified metaQTLs can be used for introgression of popping traits towards enhancing the popping ability.

Fostering a culture of continuous improvement through regular monitoring of genetic trends in breeding pipelines is essential to improve efficiency and increase accountability. This is the first global study to estimate genetic trends across the International Maize and Wheat Improvement Center (CIMMYT) tropical maize breeding pipelines in eastern and southern Africa (ESA), South Asia, and Latin America over the past decade. Data from a total of 4152 advanced breeding trials and 34,813 entries, conducted at 1331 locations in 28 countries globally, were used for this study. Genetic trends for grain yield reached up to 138 kg ha⁻¹ yr⁻¹ in ESA, 118 kg ha⁻¹ yr⁻¹ South Asia and 143 kg ha⁻¹ yr⁻¹ in Latin America. Genetic trend was, in part, related to the extent of deployment of new breeding tools in each pipeline, strength of an extensive phenotyping network, and funding stability. Over the past decade, CIMMYT’s breeding pipelines have significantly evolved, incorporating new tools/technologies to increase selection accuracy and intensity, while reducing cycle time. The first pipeline, Eastern Africa Product Profile 1a (EA-PP1a), to implement marker-assisted forward-breeding for resistance to key diseases, coupled with rapid-cycle genomic selection for drought, recorded a genetic trend of 2.46% per year highlighting the potential for deploying new tools/technologies to increase genetic gain.

Heterosis has been widely exploited in plants and animals, and also revolutionized agriculture by improving important agronomic traits. However, the molecular mechanism is still remaining elusive. Though different classical models, viz., dominance, overdominance and epistasis still holds true, the recent studies on epigenomics, transcriptomic, proteomic, metabolomics and circadian model have provided new insights. Multigene models have been proposed as the basis of complementation of allelic and gene expression variation, which is a major probable contributor to heterosis. The evolving epigenetic and genomic field put forward the role of interaction of alleles from different parental genomes in reprogramming the genes involved in stress tolerance, fitness and growth of hybrids. In the majority of the studies, transcriptomic, proteomic and metabolomic studies have found many complex regulatory network changes in genetic, epigenetic, regulatory and biochemical levels and only a few patterns could be established. Thus, heterosis is the outcome of the series of interactions in the genomes. Furthermore, epigenetic modifications of the circadian clock genes and their reciprocal regulators were reported to regulate the expression of downstream genes and pathways leading to more product accumulation in hybrids. Moreover, the majority of the epigenetic studies are limited to Arabidopsis thaliana and Zea mays, however, such studies on different crops may further bring more insights on the role of epigenetic mechanisms in determining heterosis. Further, none of the models is capable to explain heterosis alone which reflects the limitations of the individual model. The present review critically assesses different theories from different fields and also unravels the existing rapid methods to exploit them.