Induction of resistance to Meloidogyne graminicola in rice

Figures & data

Table 1. Treatments used in the study, resistance elicitors and applied doses

Commercial product	Active ingredient	Dose (g or mL 100 L^−1 water)
Bion 500 WG	Acibenzolar-S-methyl	12.5 g
Ecolife®	Organic fertilizer: 108.3 g of organic carbon, 1.7% B, polyols, and carboxylic acids	500 mL
AgroMos®	Mannanoligosaccharide-based fertilizer: 3.0% Cu, 2.0% Zn, and 2.7% S	300 mL
Soil Set®	S fertilizer: 3.7% S, 3.2% Zn, 2.0% Cu, 1.6% Fe, and 0.8% Mn	300 mL
Copper Crop®	Cu fertilizer: 10.0% Cu and 5.0% N	200 mL
Phytogard Mn®	Manganese phosphite: 30.0% P and 9.0% Mn	1000 mL
Microgeo®	Biological compost	300 mL
Rocksil®	Silicate clay: 20.6% Al, 17.4% Si, 9.8% S, and 1.3% Ca	1000 g
Control with nematodes	-	-
Control without nematodes	-	-

Table 2. Shoot dry weight, root fresh weight, nematode per gram of root, and nematode reproduction factor of rice (Oryza sativa cv. IRGA 424) plants inoculated with 1500 eggs and second-stage juveniles of Meloidogyne graminicola and treated every two weeks with resistance elicitors at 60 days after inoculation

Treatments	Shoot dry weight (g)	Root fresh weight (g)	Nematodes per gram of root	Reproduction factor
	February to April 2016
Acibenzolar-S-methyl	0.52 ^b	1.48 ^ns	57025 ^a	46.74 ^ns
Organic fertilizer	0.65 ^b	1.36	47510 ^b	46.68
Mannanoligosaccharide	0.65 ^b	1.14	36147 ^b	39.20
S fertilizer	0.59 ^b	1.60	40703 ^b	33.11
Cu fertilizer	0.40 ^b	1.56	44244 ^b	43.85
Manganese phosphite	0.46 ^b	1.50	55639 ^a	52.69
Biological compost	0.40 ^b	1.60	44669 ^b	36.50
Silicate clay	0.59 ^b	1.23	42477 ^b	42.75
Control with nematodes	0.35 ^b	1.46	70680 ^a	47.10
Control without nematodes	1.27 ^a	2.3	-	-
Standard deviation	0.13	0.19	32.42	1.56
	May to July 2016
Acibenzolar-S-methyl	0.59 ^ns	2.76 ^ns	22036 ^b	39.15 ^a
Organic fertilizer	0.85	5.05	13279 ^c	44.94 ^a
Mannanoligosaccharide	0.56	3.76	4161 ^c	9.57 ^b
S fertilizer	0.79	4.08	22951 ^b	59.66 ^a
Cu fertilizer	0.49	2.14	38686 ^a	42.68 ^a
Manganese phosphite	0.49	2.96	49084 ^a	67.30 ^a
Biological compost	0.72	4.09	21464 ^b	62.81 ^a
Silicate clay	0.62	3.42	6315 ^c	17.78 ^b
Control with nematodes	0.46	2.86	44763 ^a	72.62 ^a
Control without nematodes	0.74	4.38	-	-
Standard deviation	0.15	0.77	47.98	2.15

Results are the mean of two independent experiments performed with 10 replications in 2016. Means followed by the same letter do not differ significantly at P < 0.05 by the Scott–Knott test. ns, not significant.

Table 3. Shoot dry weight, root fresh weight, nematode per gram of root, and nematode reproduction factor of rice (Oryza sativa cv. IRGA 424) plants inoculated with 1500 eggs and second-stage juveniles of Meloidogyne graminicola and treated every two weeks with resistance elicitors at 30 and 60 days after inoculation

Treatments	Shoot dry weight (g)	Root fresh weight (g)	Nematodes per gram of root	Reproduction factor
	30 days after inoculation
Control with nematodes	0.13 ^ns	0.62 ^ns	136378 ^a	51.82 ^a
Acibenzolar-S-methyl	0.09	0.50	37373 ^b	12.33 ^b
Mannanoligosaccharide	0.14	0.60	47538 ^b	20.54 ^b
Silicate clay	0.10	0.50	40665 ^b	14.50 ^b
Standard deviation	0.02	0.08	82.54	1.41
	60 days after inoculation
Control with nematodes	0.66 ^ab	2.88 ^ab	29925 ^ns	36.76 ^a
Acibenzolar-S-methyl	0.41 ^b	1.56 ^b	12090	13.14 ^b
Mannanoligosaccharide	1.18 ^a	4.90 ^a	5909	18.64 ^b
Silicate clay	0.97 ^ab	3.55 ^ab	20041	21.76 ^b
Standard deviation	0.19	0.47	49.61	0.97

Results are the mean of an experiment performed with six replications in 2017. Means followed by the same letter do not differ significantly at P < 0.05 by the Student–Newman–Keuls test. ns, not significant.

Fig. 1 Number of J2, J3, J4, and females of Meloidogyne graminicola in rice (Oryza sativa cv. IRGA 424) plants treated every 2 weeks with resistance elicitors at 6 (a), 12 (b), 18 (c), 24 (d), and 30 (e) days after inoculation. (f) Total number of nematodes at 30 days after inoculation. Means followed by the same letter do not differ significantly at P < 0.05 by the Student–Newman–Keuls test

Table 4. ANOVA for enzyme activity in roots of rice (Oryza sativa cv. IRGA424) plants treated with resistance elicitors and inoculated with 1500 eggs and second-stage juveniles of Meloidogyne graminicola at 6, 8, 10, and 12 days after inoculation

ANOVA	Phenylalanine ammonia-lyase	Catalase	Peroxidase	β-1,3-Glucanase
Treatment	4.20*	1.28^ns	6.87*	6.59*
Period	31.81*	4.63*	9.26*	98.20*
Treatment × period	2.98*	10.15*	4.43*	7.65*
Standard deviation	0.18	2.66	4.57	0.07

*significant at P < 0.05. ns, not significant.

Fig. 2 Enzyme activity in roots of rice (Oryza sativa cv. IRGA424) plants treated with resistance elicitors and inoculated with 1500 eggs and second-stage juveniles of Meloidogyne graminicola at 6, 8, 10 and 12 days after inoculation (DAI). Within each period, means followed by the same lowercase letters do not differ at p < 0.05 by the Student–Newman–Keuls test. Within each treatment, means followed by the same uppercase letters do not differ at P < 0.05 by the Student–Newman–Keuls test