No abstract

Root-lesion nematode (Pratylenchus zeae) and root-knot nematode (Meloidogyne javanica) are two important pathogens of sugarcane (Saccharum hybrid). No commercial cultivars are resistant to these nematodes in Australia. Twenty accession lines of S. spontaneum, a wild relative of sugarcane, were tested against these two nematode species. S. spontaneum lines were tested twice for resistance to root-lesion nematode and three times for root-knot nematode. Reproduction (final population/starting population) of root-lesion nematodes was significantly lower in 17 of the 20 S. spontaneum accession lines tested in two experiments compared with two commercial cultivars. Four S. spontaneum lines supported a significantly lower number of root-lesion nematodes per gram of root than that of two commercial sugarcane cultivars. Reproduction of root-knot nematodes was significantly lower in 16 S. spontaneum lines compared with two commercial cultivars. Fourteen of the S. spontaneum lines tested supported significantly fewer eggs per gram of root compared with two commercial cultivars. This study showed that S. spontaneum lines possessed resistance for root-lesion and root-knot nematodes. Targeted crossing with commercial hybrid parental lines should be conducted to introduce nematode resistance into sugarcane cultivars for the Australian sugar industry.

No sugarcane cultivar is resistant to root-lesion (Pratylenchus zeae) nematode in Australia. Sugar Research Australia commenced a research project to evaluate new sets of accession lines derived from introgression breeding between wild relatives of sugarcane and commercial parents. No established method of assessment was available for comparing the resistance of sugarcane in the glasshouse. This study aimed to determine the most suitable assessment method for comparing resistance in accession lines. Two resistance parameters were measured, (i) number of nematodes per plant, and (ii) number of nematodes per g of roots. Nine screening trials were conducted from 2011 to 2020. Resistance parameter number of nematodes/plant had less variations within trials compared to nematodes/g roots, although both parameters were equally repeatable. Number of nematodes/g of root were negatively correlated (r = ‒0.29 to ‒0.86, p ≤ 0.001) with root biomass in all nine trials, and with shoot biomass in three out of seven trials (r = ‒0.23 to ‒0.31, p ≤ 0.05). In contrast, the number of nematodes per plant were positively correlated with shoot biomass (r = 0.25–0.53, p ≤ 0.05) in three out of seven trials and with root biomass (r = 0.17–0.27, p ≤ 00.05) in three out of nine trials. These results clearly indicated that nematodes per g root is related to reduction in root biomass and shoot biomass.

Plant-parasitic nematodes are major constraints in the production of sugarcane in Australia. Sugar Research Australia commenced a program to screen sugarcane germplasm accessions and commercial cultivars for nematode resistance in a glasshouse under a subirrigation system. Although the subirrigation system provided reasonable growth of sugarcane plants and significantly reduced the use of irrigation water in the glasshouse, it created a few issues. Sugarcane roots escaped through the bottom of the pots and created networks of roots under the fabrics used in the subirrigation system. This made it difficult to reduce cross contamination among the treatment pots and also facilitated nematodes to migrate outside of the pots. This research was undertaken to determine the effectiveness of two types of Texel fabrics (Tex-R commercial products) in mitigating sugarcane root escape from pots as well as impact on nematode population in the pots. Very few or no roots escaped from the pots placed on both types of Texel fabrics compared with other treatment methods, in which prolific root escape was evident at the bottom of the pots, forming a network of roots on or under the fabrics. Nematode numbers in pots placed on Texel fabrics were significantly higher (approximately 50,000 nematodes per pot) compared with other treatment methods (30,000 to 41,000 nematodes per pot). This research demonstrated that Texel fabrics were effective in stopping sugarcane root escape and preventing nematode migration from pots. This study also indicated that the nematode population inside the pots was not adversely impacted by the use of Texel fabrics.