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The northern root-knot nematode (Meloidogyne hapla) is a critical pathogen with a wide host range. Quantitative real-time polymerase chain reaction (qRT-PCR) has been used to elucidate gene expression and function of M. hapla. Suitable reference genes are required to ensure accurate results of qRT-PCR for normalising gene expression. Eleven candidate reference genes of M. hapla were selected to evaluate gene expression stability under different conditions. The stability of candidate reference genes was ranked using RefFinder analysis, and the optimal number of reference genes was recommended with geNorm. Notably, the most stable reference genes were SDHA, Mdh, and RpS6 for all samples; SDHA and RpS6 were particularly stable during development stage treatments, whereas Mdh and RpS6 were appropriate for temperature and inorganic compound treatments. In contrast, the least stable reference genes were Actin1 during development stages and all other treatments, GAPDH for temperature treatments, and α-Tub for inorganic compound treatments. One target gene, Mh-Hsp90, was used to verify the selection of reference genes, results showed Mdh and RpS6 could be used as suitable reference genes for M. hapla, and Mdh plus RpS6 were better. Our finding contributes to further work on gene transcription analysis in M. hapla. [ABSTRACT FROM AUTHOR]

The northern root-knot nematode, Meloidogyne hapla, is one of the most important nematode pathogens occurring in cold regions. It is a sedentary, biotrophic parasites of plants and overwinter in the soil or in diseased roots. This study showed that the cold tolerance for the second-stage juveniles (J2) of M. hapla was moderate with the 50% survival temperature (S50) of -2.22°C and the fatal temperature was -6°C when cooling at 0.5°C min-1. Cryoprotective dehydration significantly enhance cold tolerance of M. hapla J2 with the lowest S50 of -3.28°C after held being at -1°C for 6 h. Moreover, cold shock and cold acclimation had significant effects on the freezing survival of M. hapla J2. The lethal temperature of eggs was -18°C. Therefore, the cold tolerance of M. hapla is sufficiently favorable to withstand winters in cold temperature environments. [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (SCN) is the most damaging soybean pest worldwide. To improve soybean resistance to SCN, we employed a soybean seed-coating strategy through combination of three rhizobacterial strains, including Bacillus simple, B. megaterium and Sinarhizobium fredii at various ratios. We found seed coating by such rhizobacterial strains at a ratio of 3:1:1 (thereafter called SN101) produced the highest germination rate and the mortality of J2 of nematodes. Then, the role of soybean seed coating by SN101 in nematode control was evaluated under both greenhouse and two field conditions in Northeast China in 2013 and 2014. Our results showed that SN101 treatment greatly reduced SCN reproduction and significantly promoted plant growth and yield production in both greenhouse and field trials, suggesting that SN101 is a promising seed-coating agent that may be used as an alternative bio-nematicide for controlling SCN in soybean fields. Our findings also demonstrate that combination of multiple rhizobacterial strains needs to be considered in the seed coating for better management of plant nematodes. [ABSTRACT FROM AUTHOR]