Plant breeding mainly relies upon creation of variation and thereby selection of suitable variant genotypes. There are plenty of methods to create variation such as hybridization, mutation, somaclonal variations etc. Once such variation is created then it can be released through recombination in which different combination of alleles are received by gametes. Now the question arises do recombination rate is same throughout the chromosomes so that genes/QTLs at any region will have equal chance of recombining with others. In actual situations recombination rate is not same throughout the genome; it varies and show recombination landscapes (RL). Recombination landscapes—the variation in recombination rates along the chromosome.

Recombination is generally biased towards telomeric ends and it is supressed in peri-centromeric regions. Moreover, recombination rates are positively correlated with gene density and it has negative correlation with repetitive elements. Recombination rates are also influenced by three important phenomenon namely interference, crossover assurance and centromere effect1. Additionally, age, sex, genetic background and environment also influence RLs. Recombination landscapes can be changed by overexpressing pro-crossover genes and by knocking out anti-cross over related genes such as RECQ4, FANCM, FIDGETIN-LIKE 1 to target different regions of chromosome. RLs can also be changed by affecting methylation patterns, various mutant genes in maize mop1, zmet2 and met1 in Arabidopsis thaliana resulted in changed RLs2.

Breeding outcomes can be changed by manipulating RLs. Variations in recombination rate genome wide or at specific positions can assist in increasing genetic gain. A study in maize shown that predicted genetic gains doubled by targeted recombination for traits such as yield, moisture and test weight3. In another case, increased recombination assisted in backcross program where linkage drag was reduced due to increased recombination rate targeting both hot and cold recombination spots4.

In conclusion, RLs vary in individuals due to various factors and they can be changed by knock out, overexpression of crossover related genes and by changing methylation patterns. Changes in RL can lead to enhancement of genetic gain and reduction of linkage drag in targeted regions thereby, improving outcomes in breeding.

References 

PAZHAYAM, N. M., TURCOTTE, C. A. AND SEKELSKY, J., 2021, Meiotic crossover patterning. Front. Cell Dev. Biol., 9: 681123. 

EPSTEIN, R., SAJAI, N., ZELKOWSKI, M., ZHOU, A., ROBBINS, K. R. AND PAWLOWSKI, W. P., 2023, Exploring impact of recombination landscapes on breeding outcomes. Proc. Natl. Acad. Sci., 120(14): e2205785119.

 BRANDARIZ, S. P. AND BERNARDO, R., 2019, Predicted genetic gains from targeted recombination in elite biparental maize populations. Plant genome, 12(1): 180062.

 TOURRETTE, E., FALQUE, M. AND MARTIN, O. C., 2021, Enhancing backcross programs through increased recombination. Genet. Sel. Evol., 53(1): 1-13.