Physiological and molecular basis of alternate bearing in perennial fruit crops

In perennial fruit crops, reproductive success and productivity are principally governed by the core event, regular flowering. However, this feature bearing can be influenced by different factors viz. environmental conditions, germplasm, rootstocks, and cultural operations. The phenomenon of irregular bearing is more dominant in perennial fruit crops. In order to ensure regular and quality fruit production it is therefore, imperative to regulate the flowering phenology. The comparative studies conducted by the researchers for understanding the physiological and molecular aspects associated with regular and irregular bearing phenomenon in perennial fruit crops are helpful to understand the crux of flowering, discover the regulatory factors for regularity in bearing. Further, differential gene expression studies allow the identification of key genes related with the regular bearing feature. The identified candidate genes in this regard could be harnessed for selection of desirable parents, hybrids in early nursery stage, thus facilitating the plant breeders through precision breeding approaches. This paper reviews the current understanding of the physiological and molecular basis associated with the flowering phenology along with the impact of different factors on alternate bearing in perennial fruit crops.