Genomics of Pineapple Disease-Resistance Genes

Abstract

Pineapple is a major tropical fruit crop with high nutritious values. It possesses crassulacean acid metabolism (CAM) photosynthesis and can survive in harsh and arid environment. But it is susceptible to various diseases, thus the quality and yield can be negatively affected. The major pineapple diseases include fusariosis, pink disease, and mealybug wilt disease. The diseases are sporadically distributed geographically, and the severity of diseases is different according to the latitude or weather. Some wild pineapples are resistant to the diseases, which may result from greater genetic diversity. Several pineapple cultivars are also resistant to certain disease and the disease resistance can be additive or quantitative. For instance, a pineapple cultivar selected from crossing between the pineapple cv. Primavera (PRI) and the cv. Smooth Cayenne (SC), “Vitoria”, is resistant to fusariosis, while PRI and SC are susceptible to fusariosis. Transgenic approaches also facilitate disease resistance in pineapple by transforming polyphenol oxidase (PPO) or chitinases. Transgenic expression of PPO gene displayed increased resistance for blackheart, and transgenic plants with chitinases expressed enhanced resistance against fungal pathogen. Nucleotide-binding site (NBS) gene family is the largest class of disease-resistance (R) genes. From the draft genome of pineapple, 177 NBS resistance genes have been identified. The identification and classification of NBS genes in pineapple provide a valuable genomic resource and improve the understanding of pineapple R genes, which further facilitates the development of pineapple disease-resistant cultivars.