A New Disease of Saccharum officinarum Caused by Heterodera parasacchari n. sp. (Nematoda: Heteroderinae) in China.

Sugarcane (Saccharum officinarum L.) is an important economic crop in tropical and subtropical countries and regions. During an investigation of crop nematodes in Guangdong, a new disease caused by a new species, Heterodera parasacchari n. sp., of the subfamily Heteroderinae was found on sugarcane. In this study, the new species is described, and its pathogenicity to sugarcane is confirmed. The new species is characterized by having lemon-shaped cysts with a prominent neck and vulval cone and being ambifenestrate, with a strongly developed underbridge with finger-like projections, developed bullae, and a fenestral width generally longer than the fenestral length; second-stage juveniles with a well-developed stylet of 25.2 (23.7 to 26.9) μm, concave basal knobs, an anteriorly projecting end, a lateral field areolated with three incisures, a 56.6 (47.5 to 64.8) μm-long tail, and a 32.4 (27.7 to 37.3) μm-long hyaline region, longer than the stylet. The new species is close to H. sacchari in the Sacchari group of the Heterodera genus based on morphologic and morphometric characteristics. The phylogenetic trees, based on the analysis of the ITS-rRNA, the 28S-rRNA D2-D3 region, and the partial COI gene sequences, showed that the new species clustered with Sacchari group species but with separate species status. The results of pathogenicity tests indicated that H. parasacchari n. sp. can invade roots of sugarcane and reproduce in large numbers, resulting in thinner root systems, reduced lateral roots, weakened and stunted plants, leaf chlorosis, and significant yield losses. A key to the species of the Sacchari group is also provided in this study.