新中国果树科学研究70年——荔枝

Fruit scientific research in New China in the past 70 years:Litchi

荔枝是典型亚热带果树,我国有悠久的栽培历史,2018年荔枝面积为551 746 hm^2,新中国成立70年以来增长了82.7倍,产量约3 028 100 t,增长了175.4倍,且产期从4月下旬到9月底共达5个月。几代科技人员为之作出了巨大努力。已建立国家(广州)荔枝果树种质资源圃,收集保存荔枝种质400多份,培育新品种38个,优异品种通过区域性试验得到推广应用。近十年来创制了杂交苗数十万株。1980年代研发了螺旋环剥控梢、促花和保果技术,初步克服了荔枝适龄树不开花结果问题;近年则在主要性状分子鉴定、成花与坐果生物学、土壤与植物营养、病虫害、贮藏保鲜、加工和机械化等方面均取得重要研究进展,尤其是明确提出了荔枝花芽分化"阶段性划分"和具假种皮果实发育"球皮对球胆效应"的假说,为花果发育调控提供了坚实的理论支撑,基本解决"成花难和坐果难"问题。已明确,荔枝果皮中大量存在的漆酶,是一种定位于液泡的酚氧化酶,可催化果皮中的表儿茶素与其低聚物花色素苷等氧化聚合形成褐色产物,从而引起果皮褐变。荔枝被列入国家现代农业产业技术体系支持作物,目前有岗站专家29名,团队成员120多人,覆盖示范县55个,带动技术推广骨干165人。展望未来,要重点加快种业科技创新、优质丰产绿色高效生产技术创新和大数据与人工智能等新技术的研究与应用。

Litchi is a typical subtropical fruit tree. China has a long history of litchi cultivation,with planting area of 551 746 hm^2 in 2018,82.7-fold times that of 70 years ago,and production of about 3 028 100 t,an increase of 175.4-fold times. The production season lasts for 5 months from late April to the end of September. Most of the litchi trees were planted from mid 1980 s. More than 400 accessions have been collected and conserved in the National Litchi Germplasm Pool at Guangzhou. Thirty-eight new varieties have been selected and registered,and some of them have been widely expanded via regional trial planting. Hundred thousands of seedlings from cross breeding have been achieved. In order to increase flowering and fruit set the technique of spiral girdling on trunks and large branches during late fall and early spring was created,which has been very helpful to early bearing of the young litchi trees. As the coming of the new centery,lots of critical research progresses in molecular identification of important characters,biology in shoot growth,flower induction and fruit-set,soil and plant nutrition,pests and disease management,post-harvest physiology,processing,and mechanization have been achieved. Specificly,the hypothesis of phasic changes in floral differentiation,and"the skin versus blader effect"in the arillate fruit development were proposed. The process of litchi flower differentiation is composed of four visible stages: hardening of autumnal shoots before the first cold front in the early winter,floral induction under low temperatures,floral evocation(emergence of floral primordia,that is,"white millet") as temperatures ascending in the early spring,and floral development under mild temperatures. The relationship between arils and skin of lychee fruit was investigated,and then"skin growth before arils"of lychee fruit was expounded. Cell division in the peel was found to occur mainly before flowering,and the cell numbers determined the fruit size.Water and solutes fastly entering the fruit,when skins fully expanded,may cause fruit cracking. Stable flowering,good fruit-set and large fruit sizes are potentially achieved with application of the major key technologies. It has been made clear that a large amount of laccases in the peel,is a phenoloxase located in vacuoles,which catalyzed epicatechin-mediated anthocyanin degradation and caused browning of the litchi pericarp. Research progress in soil and plant nutrition,plant protection,post harvest physiology,processing and mechanization are also commented. Litchi has been one of the crops granted from the China Agriculture Research System(CARS) since 2008. The litchi CARS subsystem is composed of 29 research scientists and 120 group members,covering 55 counties and 165 technicians. Looking into the future,we should focus on the research of breeding strategy,technology innovation in high-quality,productive,and green and efficient production,more adoption of new technologies including big data and artificial intelligence in litchi crop.