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Summary: The mechanism of root-knot nematode (RKN) resistance in black oat 'Terara' and its stability under high temperatures were examined. To investigate the suppressive mechanism, we observed root invasion and development of RKN in 'Terara'. Juveniles of Meloidogyne incognita , M. arenaria and M. javanica successfully invaded roots of 'Terara' 3 days after inoculation (DAI), whereas juveniles of M. hapla were hardly observed in black oat roots. The total number of M. incognita and the ratio of successfully developing juveniles were significantly lower in roots of 'Terara' than a susceptible cultivar from 7 DAI. A number of M. incognita developed to sausage-shaped juveniles in 'Terara'; however, juveniles beyond that stage were seldom observed. Histological observation of feeding sites suggested the poor development of giant cells was involved in this arrested development. Juveniles of M. arenaria and M. javanica also only developed to the sausage-shaped stage at 21 DAI. These observations indicated that 'Terara' and resistant common oat cultivars suppressed RKN in a similar way. The effect of high temperature on resistance was evaluated using 'Terara' cultivated at 30°C throughout the experiment and at 32°C for the initial 5 DAI. The number of egg masses of M. incognita under the 32°C treatment was slightly higher than the 25°C control. However, it was still suppressed to 4.9% of the susceptible cultivar. [ABSTRACT FROM AUTHOR]

Summary: Commercially available sorghum cultivars were tested for resistance to Meloidogyne incognita in order to select cultivars that combine fodder production with M. incognita population management. Initially in a pot test with 12 sorghum cultivars, 'Kyushuko 3 go', a sorghum hybrid, supported very low M. incognita reproduction approximately 40 days after inoculation (dai) with 500 second-stage juveniles (J2) pot−1, similar to the resistant green manure 'Tsuchitaro'. Further tests for development of M. incognita in roots (20 dai with 150 J2 (root system)−1) indicated that the resistance of 'Kyushuko 3 go' acts after nematode root penetration. In field tests in 2015 and 2016, 'Kyushuko 3 go' suppressed M. incognita population densities, although some variations in field conditions may influence reproduction of M. incognita on 'Kyushuko 3 go'. These findings demonstrated M. incognita -resistant fodder sorghum cultivars could be a useful alternative to susceptible cultivars for root-knot nematode management. [ABSTRACT FROM AUTHOR]