Resistance sources to root-knot nematodes Meloidogyne javanica, M. incognita and M. enterolobii in sweet potato

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Abstract

ABSTRACT One of the main obstacles for food production in many developing countries, as in Brazil, is the damage caused by root-knot nematodes, mainly those belonging to the genus Meloidogyne. This study aimed to assess the resistance levels of 44 sweet potato genotypes to M. javanica, M. incognita race 1 and M. enterolobii. These researches were carried out in 2014, under greenhouse conditions in Brasília-DF, Brazil. A completely randomized design with six replicates of one plant/plot/treatment was used. We determined the gall index (GI) and egg mass index (EMI) in the root system of each plant, the number of eggs and juveniles per gram of root with galls and the nematode reproduction factor. M. javanica was less aggressive and reproduced in only 9.09% of the evaluated genotypes; M. incognita race 1 was intermediate (47.73%); whereas M. enterolobii was more aggressive, with a population increase in 79.55% of the genotypes. The genotypes CNPH 1200, CNPH 1219, CNPH 1292, CNPH 1392, CNPH 60 and ‘Coquinho’ were the most resistant to the three species and can be used in breeding programs for multiple resistance to root-knot nematodes.

Translated abstract

RESUMO Um dos principais obstáculos para a produção de alimentos em muitos países em desenvolvimento, como no Brasil, é o dano causado por fitonematoides, principalmente os formadores de galhas, pertencentes ao gênero Meloidogyne. O trabalho teve como objetivo avaliar o nível de resistência de 44 genótipos de batata-doce a M. javanica, M. incognita raça 1 e M. enterolobii. O experimento foi realizado em 2014, em casa de vegetação, em Brasília-DF. Utilizou-se o delineamento inteiramente casualizado, com seis repetições, constituindo-se de uma planta por tratamento. Foi determinado o índice de galhas (GI) e de massas de ovos (EMI) no sistema radicular de cada planta, quantificado o número de ovos e juvenis por grama de raiz e parte da raiz tuberosa com galhas e efetuado o cálculo do fator de reprodução dos nematoides. Verificou-se que M. javanica foi menos agressivo e se reproduziu em apenas 9,09% dos genótipos avaliados. M. incognita raça 1 foi intermediário, com 47,73%; enquanto que M. enterolobii foi mais agressivo, com aumento populacional em 79,55% dos genótipos. Os genótipos CNPH 1200, CNPH 1219, CNPH 1292, CNPH 1392, CNPH 60 e ‘Coquinho’ foram os mais resistentes às três espécies avaliadas, podendo ser utilizados no melhoramento visando à resistência múltipla aos nematoides-das-galhas.

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Most cited references 24

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Meloidogyne enterolobii n. sp. (Meloidogynidae), a Root-knot Nematode Parasitizing Pacara Earpod Tree in China.

B. Yang, J D Eisenback (1983)

Meloidogyne enterolobii n. sp. is described and illustrated from roots of pacara earpod tree, Enterolobium contortisiliquum (Vell.) Morong, on Hainan Island in China. The perineal pattern of the female is usually oval shaped, the striae are fine to coarse, the dorsal arch is moderately high to high and usually rounded, and the phasmids are large. The stylet knobs in females are divided longitudinally by a groove so that each knob appears as two. The mean distance of the excretory pore to the anterior end in the female is 62.9 mum. Males have a large, rounded labial disc that fuses with the medial lips to form a dorso-ventrally elongate head cap. The labial disc is slightly elevated, and the medial lips are crescent shaped. The second-stage juvenile mean body length is 436.6 mum. The lateral lips are large and triangular in face view. The tail is 56.4 mum long and narrow with a broad, bluntly rounded tip. M. enterolobii n. sp reproduces well on E. contortisiliquum and causes severe damage. Other good hosts include cotton, resistant tobacco 'NC 95,' pepper, watermelon, and tomato.

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Strategies for transgenic nematode control in developed and developing world crops.

Howard J. Atkinson, Catherine J Lilley, Peter E. Urwin (2012)

Nematodes cause an estimated $118b annual losses to world crops and they are not readily controlled by pesticides or other control options. For many crops natural resistance genes are unavailable to plant breeders or progress by this approach is slow. Transgenic plants can provide nematode resistance for such crops. Two approaches have been field trialled that control a wide range of nematodes by either limiting use of their dietary protein uptake from the crop or by preventing root invasion without a direct lethality. In addition, RNA interference increasingly in tandem with genomic studies is providing a range of potential resistance traits that involve no novel protein production. Transgenic resistance can be delivered by tissue specific promoters to just root tissues where most economic nematodes invade and feed rather than the harvested yield. High efficacy and durability can be provided by stacking nematode resistance traits including any that natural resistance provides. The constraints to uptake centre on market acceptance and not the availability of appropriate biotechnology. The need to deploy nematode resistance is intensifying with loss of pesticides, an increased need to protect crop profit margins and in many developing world countries where nematodes severely damage both commodity and staple crops. Copyright © 2011 Elsevier Ltd. All rights reserved.