Distribution, life cycle and histological changes by Heterodera sp. in carrot in Puebla

Abstract

In 2009, in the Tepeaca Valley, Puebla, it was found a cyst-forming nematode of the genus Heterodera associated with carrot. At this time, it is unknown the distribution in some producing municipalities, its life cycle and the histological changes on infected plant roots. Between 2008 and 2016, 28 carrot fields were sampled in six municipalities of the Tepeaca Valley. The roots were separated and white females were searched, the cysts were extracted from soil. Carrot cv. Mexicana were grown in naturally infested soil in the greenhouse, the roots were stained with fuchsine lacto glycerol acid to know the development time of each cycle phase. To describe the histological changes, the infected roots were imbibed in paraffin and sections stained with fast green-fuchsine for analysis. Heterodera sp. was found in 93 % of the plots and completed its cycle in 73 days at 20-25 °C. The histological alterations show the presence of feeding sites (syncytia) with dense and granular cytoplasm, with hypertrophied nuclei, dissolution and thickening of cell walls located mainly in the cortex and vascular cylinder. There was also the presence of lignificate areas with hyperplasia and hypertrophy.