Rice (Oryza sativa L.) and Arabidopsis thaliana (L.) life cycles involve several major phase changes, throughout which MADS-box genes have a variety of functions. MADS-box genes are well recognized for their functions in floral induction and development, and some have multiple functions in apparently unrelated developmental stages. For example, in Arabidopsis, AGL15 and AGL6 play roles in both vegetative development and floral transition. Similarly, in rice, OsMADS1 is involved in flowering time and seed development, and OsMADS26 is expressed not only in the roots, but also in the leaves, shoots, panicles, and seeds. The roles of other MADS-box genes responsible for the regulation of specific traits in both rice and Arabidopsis are also discussed. Several are key components of gene regulatory networks involved in root development under diverse environmental factors such as drought, heat, and salt stress, and are also involved in the shift from vegetative to flowering growth in response to seasonal changes in environmental conditions. Thus, we argue that MADS-box genes are critical elements of gene regulation that underpin diverse gene expression profiles, each of which is linked to a unique developmental stage that occurs during root development and the shift from vegetative to reproductive growth.

This research was carried out to check genetic variability, heritability and genetic advance in 11 F4 bread wheat (Triticum aestivum L.) genotypes (10 F4 lines and one check) in a randomized block design with three replications at the University of Agriculture Peshawar, Pakistan during 2015-16. Data was/were taken on parameters such as days to heading (days), plant height (cm), flag leaf area (cm2), spike length (cm), grain weight spike-1 (g), 1000-grain weight (g), grain yield plant-1 (g), biological yield plant-1 (g)and harvest index (%). The statistically significant difference(s) was/were detected for the investigated traits. The high magnitude of heritability (˃0.62) was noted for all parameters except spike length (0.57) which was moderate. Low expected genetic advance was recorded for days to heading (3.90%) and spike length (8.13%), moderate expected genetic advance was observed for plant height (9.95%), grain weight spike-1 (11.54%) and 1000 grain weight (13.41%), while high expected genetic advance was noted for flag leaf area (24.72%), grain yield plant-1 (20.45%), biological yield plant-1 (23.64%) and harvest index (24%). Grain yield plant-1 was non-significantly and positively correlated with days to heading (rG = 0.19NS and rP = 0.07 NS), plant height (rG = 0.30 NS and rP = 0.26 NS), flag leaf area (rG = 0.25 NS and rP = 0.18 NS), spike length (rG = 0.01 NS and rP = 0.07 NS), grain weight spike-1 (rG = 0.28 NS and rP = 0.22 NS) and 1000-grain weight (rG = 0.02 NS and rP = 0.07 NS) at both genotypic and phenotypic levels. While significantly and positively correlated with biological yield plant-1 (rG = 0.34* and rP = 0.33*) and harvest index (rG = 0.58** and rP = 0.66**) at both genotypic and phenotypic levels. High heritability showed that these traits are under genetic control and single plant selection could be started in F5 generation. The strong correlation of grain yield plant-1 with the mentioned traits showed that grain yield could be indirectly improved by improving these traits.

Heading date (HD) is one of the agronomic traits that influence maturity, regional adaptability, and grain yield. The present study was a follow-up of a previous quantitative trait loci (QTL) mapping study conducted on three populations, which uncovered a total of 62 QTLs associated with 10 agronomic traits. Two of the QTLs for HD on chromosome 7 (qHD7a and qHD7b) had a common flanking marker (RM3670) that may be due to tight linkage, and/or weakness of the statistical method. The objectives of the present study were to map QTLs associated with HD in a set of 76 chromosome segment substitution lines (CSSLs), fine map and validate one of the QTLs (qHD7b) using 2997 BC₅F_2:3 plants, and identify candidate genes using sequencing and expression analysis. Using the CSSLs genotyped with 120 markers and evaluated under two short-day and two long-day growing conditions, we uncovered a total of fourteen QTLs (qHD2a, qHD4a, qHD4b, qHD5a, qHD6a, qHD6b, qHD7b, qHD7c, qHD8a, qHD10a, qHD10b, qHD11a, qHD12a, and qHD12b). However, only qHD6a and qHD7b were consistently detected in all four environments. The phenotypic variance explained by qHD6a and qHD7b varied from 10.1% to 36.1% (mean 23.1%) and from 8.1% to 32.8% (mean 20.5%), respectively. One of the CSSL lines (CSSL52), which harbored a segment from the early heading XieqingzaoB (XQZB) parent at the qHD7b locus, was then used to develop a BC₅F_2:3 population for fine mapping and validation. Using a backcross population evaluated for four seasons under different day lengths and temperatures, the qHD7b interval was delimited to a 912.7-kb region, which is located between RM5436 and RM5499. Sequencing and expression analysis revealed a total of 29 candidate genes, of which Ghd7 (Os07g0261200) is a well-known gene that affects heading date, plant height, and grain yield in rice. The ghd7 mutants generated through CRISPR/Cas9 gene editing exhibited early heading. Taken together, the results from both the previous and present study revealed a consistent QTL for heading date on chromosome 7, which coincided not only with the physical position of a known gene, but also with two major effect QTLs that controlled the stigma exertion rate and the number of spikelets in rice. The results provide contributions to the broader adaptability of marker-assisted breeding to develop high-yield rice varieties.