IDENTIFICATION OF PLANT PARASITIC NEMATODES IN TRIPLOID AND TETRAPLOID BANANAS IN BRAZIL

ABSTRACT Nematodes are important pathogens in banana plants, and the lack of resistant genotypes is the biggest challenge of the banana breeding programs. Little is known on the behavior of banana triploids and tetraploids developed by Embrapa regarding parasitism by plant-parasitic nematodes in field conditions. Embrapa Mandioca e Fruticultura experimental areas, naturally infested in five Brazilian states (Embrapa Acre - Acre, Embrapa Semiárido - Pernambuco, Embrapa Cerrados - Distrito Federal, Palmital - São Paulo and Epagri - Santa Catarina) were evaluated for the distribution and population levels of plant-parasitic nematodes in commercial cultivars and triploid and tetraploid genotypes in the final breeding stage. The root-knot nematodes (Meloidogyne spp.) were the most frequent in roots (40 - 100%) and soil (85.71 - 100%), with a detectable number of juveniles (J2) varying between genotypes (4 - 148 J2.250g-1 roots, and 1 - 110 J2.100 cm-3soil). Four esterase phenotypes were characterized: M. incognita (Est I1 = Rm: 1.0), M. javanica (Est J3 = Rm: 1.0; 1.25 and 1.40 and Est J2 = Rm: 1.0 and 1.40) and M. arenaria (Est A2 = Rm: 1.20 and 1.35), M. javanica (Est J3) was predominant. Meloidogyne javanica and M. incognita were predominant, however mixed infestations between species were found. The occurrence of Meloidogyne spp. was: M. javanica (68.26%), M. incognita (64.73%) and M. arenaria (16.81%). Helicotylenchus multicinctus and Rotylenchulus reniformis was the second most frequent group. Radopholus similis, Scutellonema sp., Criconemoides sp. and Helicotylenchus sp. presented themselves in low frequency and population levels in banana plants.

摘要
线虫是香蕉植株的重要病原物，而抗病基因型的匮乏是当前香蕉育种项目面临的最大挑战。目前学界对巴西农牧业研究公司木薯与果树研究所（Embrapa Mandioca e Fruticultura）培育的三倍体与四倍体香蕉材料在田间条件下抵御植物寄生线虫（plant-parasitic nematodes）寄生的行为特征尚缺乏深入了解。
研究团队选取了巴西5个州的自然侵染试验田，分别为巴西农牧业研究公司阿克雷州试验站（Embrapa Acre - Acre）、巴西农牧业研究公司半干旱农业研究所（Embrapa Semiárido - Pernambuco）、巴西农牧业研究公司塞拉多研究所（Embrapa Cerrados - Distrito Federal）、帕尔米塔尔试验点（Palmital - São Paulo）以及圣卡塔琳娜州农业研究公司（Epagri - Santa Catarina）试验点，对商业化栽培品种以及育种最终阶段的三倍体、四倍体材料中植物寄生线虫的分布与种群水平开展了系统评估。
根结线虫属（Meloidogyne spp.）是根系（检出率40%~100%）与土壤（检出率85.71%~100%）中最常见的类群，其可检测的二龄幼虫（J2）数量因宿主材料不同存在显著差异：根系中为4~148条·250g⁻¹，土壤中为1~110条·100cm⁻³。
研究共鉴定出4种酯酶表型（esterase phenotypes），分别对应南方根结线虫（Meloidogyne incognita，Est I1 = Rm: 1.0）、爪哇根结线虫（Meloidogyne javanica，Est J3 = Rm: 1.0、1.25与1.40；Est J2 = Rm: 1.0与1.40）以及花生根结线虫（Meloidogyne arenaria，Est A2 = Rm: 1.20与1.35），其中爪哇根结线虫（Est J3）为试验田中占比最高的优势类群。
研究同时发现，爪哇根结线虫与南方根结线虫为主要优势种，但也存在多个根结线虫物种混合侵染的情况。根结线虫属（Meloidogyne spp.）的物种检出占比分别为：爪哇根结线虫68.26%、南方根结线虫64.73%以及花生根结线虫16.81%。
多带螺旋线虫（Helicotylenchus multicinctus）与肾形肾状线虫（Rotylenchulus reniformis）为第二常见的线虫类群。相似穿孔线虫（Radopholus similis）、盾小环线虫属（Scutellonema sp.）、环根结线虫属（Criconemoides sp.）以及螺旋线虫属（Helicotylenchus sp.）在香蕉植株中的检出频率与种群水平均较低。