Genetic Improvement of Chinese Jujube for Disease Resistances: Status, Knowledge Gaps and Research Needs

Abstract

Chinese jujube is one of the earliest domesticated fruit trees in the world. This fruit crop is becoming increasingly popular globally for its outstanding adaptability to marginal land and a broad range of climate conditions. There is a growing demand by growers and consumers for new cultivars with improved yields, earliness, resistance to biotic and abiotic stresses and fruit quality attributes. Breeding jujube for disease resistance is still in its infancy despite the consensus that disease is the top-ranking production constraint and growing disease resistant cultivars is the most sustainable and cost-effective approach for diseases management. Major knowledge gaps remain to be filled in the current breeding scheme for enhancing disease resistance. These knowledge gaps include, but are not limited to (1) a lack of understanding of jujube pathogens in terms of their taxonomy, epidemiology and genetic diversity; (2) a lack of standardized screening methods to identify host resistance; (3) a high rate of germplasm mislabeling; and (4) ineffective production of hybrid progenies. Nonetheless, recent progress in utilization of male sterile parents in controlled crosses, coupled with mounting genomic information on both pathogens and jujube, will likely speed up the combination of host resistance with other horticultural traits. This article reviews the status of jujube disease resistance breeding and suggests future research needs for developing disease resistant cultivars of Chinese jujube. Although the review focuses on jujube breeding programs in China, the summarized information should be useful to researchers in the international jujube community as well.

Elevated temperature and drought stress significantly affect fruit quality and activity of anthocyanin-related enzymes in jujube (Ziziphus jujuba Mill. cv. ‘Lingwuchangzao’)

“…It is an ideal crop in arid and semi-arid areas of temperate and subtropical regions, where other fruit trees do not grow well. This feature makes jujube trees an important economic crop and has made important contributions to poverty reduction and afforestation in China [11,13]. The crop has been widely planted in about 50 countries in Asia, Europe, Africa, America and Oceania [13][14][15].…”

“…Fresh dates are usually harvested before they are fully ripe, in order to have the best quality, flavor and a good balance of sugar and acid content. Jujube fruit undergo significant texture and color changes during fruit development and postharvest ripening [16] The flavor and external attractiveness (color) are the most important quality attributes that determine consumer recognition and commercial value [13,17]. High-quality fruit typically have a deep red color, high sugar content and a balanced sugar-to-acid ratio [18,19].…”

“…In semi-arid temperate regions, such as many jujube-producing regions in northwestern China, jujube growers must consider the effects of both water stress and rising temperatures due to global climate change. Different abiotic stresses may affect the primary and secondary metabolism of jujube in different ways, thereby changing their quality attributes, including the flavor, texture and color of the fruit [13,49]. This knowledge will play a key role in enabling us to predict the potential impact of climate change on jujube production in Northwest China.…”

Jujube witches’ broom phytoplasmas inhibit ZjBRC1-mediated abscisic acid metabolism to induce shoot proliferation

“…Since jujube plants could be asymptomatic at the early stage of JWB phytoplasma infection and the distribution of JWB phytoplasmas among different seasons and tissues was uneven, researchers were unable to determine the optimal injection period. Screening of JWB-resistant germplasms [ 5 , 17 ] and cryopreservation-mediated plantlet regeneration [ 18 ] would be effective for JWB disease management and long-term storage of phytoplasma-free jujube plants. Furthermore, in the past several years, information on jujube–JWB phytoplasma interactions has been obtained by multiomics analyses, highlighting some special gene loci and hormone pathways related to defence responses in diseased leaves [ 19–21 ].…”

Effects of Aspergillus niger Infection on the Quality of Jujube and Ochratoxin A Cumulative Effect

“…The jujube is easily infected by fungi such as A. niger , Aspergillus flavus , and Alternaria , and produces mycotoxins during growth and maturation [ 7 , 8 ]. According to the report, there are 38 diseases/disease complexes that infect jujubes during pre-and post-harvest stages [ 9 ]. Moreover, some of these diseases will cause worsening quality, rendering jujubes non-edible.…”