Meloidogyne graminicola’s Effect on Growth Performance of Rice under Low Population Density

Aatika Sikandar,Bochang Chen,Shakeel Ahmad,Man Luo,Haiyan Wu

doi:10.3390/agronomy12030587

Abstract

Meloidogyne graminicola is a destructive soil-borne pathogen that causes rice yield losses (Oryza sativa L.) in tropical and subtropical areas. This study investigated the effect of M. graminicola population densities on plant height, heading, and the photosynthetic parameters of rice in a greenhouse. Two-week-old rice plants were inoculated with different M. graminicola densities (250, 500, 750, 1000, 1500, and 2000 J2s/plant) and observations were recorded at 30, 60, and 90 days after inoculation (DAI). Reductions in growth and photosynthetic parameters caused by M. graminicola densities were calculated in relation to a control (non-inoculated rice). Results revealed that M. graminicola infection with low population densities (0–500 J2s/plant) did not influence the rice plant height during 30–60 DAI, but significantly lowered the plant height, panicle growth rate, and panicle length of rice at 90 DAI. The chlorophyll content of rice inoculated with 500–2000 J2s was significantly lower than that of the control. Furthermore, M. graminicola infection with 500 J2s/plant significantly lowered the transpiration rate and net photosynthetic rate by 21.21% and 21.81%, respectively, compared with the control (p < 0.05). M. graminicola with a low population density significantly reduced the net photosynthetic rate of rice, which affected organic matter accumulation, resulting in growth retardation and lower yields (p < 0.05).

Highlights

Rice (Oryza sativa L.) is considered a staple cereal in the Asia–Pacific region, producing and consuming more than 90% of the world’s rice
Significant differences were observed for the plant height growth rate (PHR) between rice inoculated with 1000–2000 J2s and the 0–500 J2-inoculated rice, and the difference was even greater at 90 days after inoculation (DAI) (p < 0.05); here, the PHR values of the nematode-free control were 1.24, 1.87, 1.66, and 1.70 times higher than the 500, 1000, 1500, and 2000 J2-inoculated rice, respectively
By comparing the differences in chlorophyll content between inoculated rice and the control, we found that the degree of decreasing chlorophyll content in rice with the increasing nematode inoculum density (≥500 J2s) was higher than rice inoculated with fewer nematodes (250 J2s) (Figure 2B)

Summary

Introduction

Rice (Oryza sativa L.) is considered a staple cereal in the Asia–Pacific region, producing and consuming more than 90% of the world’s rice. As the dominant rice-producing country, China cultivated 30.08 million hectares of rice in 2020 with an annual rice output of 21.86 million tons [1]. Various biotic and abiotic factors are responsible for the lower productivity of rice under field conditions. Plant-parasitic nematodes (PPNs) play an important role and account for yield losses to the extent of. Root-knot nematodes (RKNs) are responsible for about 15% of the total economic losses in rice production in Asia [3]. The major RKNs associated with rice are Meloidogyne graminicola, M. incognita, M. javanica, M. triticoryzae, M. arenaria, M. oryza, M

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