Summary: To fulfil different research purposes, five methods to inoculate Aphelenchoides besseyi onto seedlings and panicles of rice, Oryza sativa, were evaluated in this study and the efficiency of the inoculation methods assessed by success rates and recovery rates. Among the three methods leading to the infection of young seedlings without obvious mechanical wounds, i.e., water flotation, seed soaking and leaf spraying, the inoculation of 125 nematodes plant⁻¹ by the water flotation method gave rise to the highest success rate and recovery rate, 95.6 and 8.3%, respectively, in growth chamber experiments. When conducted in the plastic house, seed soaking and leaf spraying of 125 nematodes plant⁻¹ resulted in 75.6 and 66.7% success rate, respectively, and 155.7 and 178.1% recovery rates, respectively. The injection or spraying of 2000 nematodes panicle⁻¹ at the booting or flowering stage gave 100% infection.

Barley (Hordeum vulgare L.) is the most important cereal crop in the Qinghai-Tibet Plateau, and the yield has been seriously threatened by Blumeria graminis f. sp. hordei (Bgh) in recent years. To understand the virulence and genetic traits of different Bgh populations, 229 isolates of Bgh were collected from Tibet, Sichuan, Gansu and Yunnan provinces of China during 2020 and 2021, and their pathogenicity to 21 barley lines of different genotypes was assessed. A total of 132 virulent types were identified. The Bgh isolates from Yunnan showed the highest diversity in terms of virulence complexity (Rci) and genetic diversity (KWm), followed by those from Sichuan, Gansu, and Tibet, in that order. Single nucleotide polymorphism (SNP) in genes coding for alternative oxidase (AOX), protein kinase A (PKA), and protein phosphatase type 2A (PPA) were detected at seven polymorphic sites. Nine haplotypes (H1–H9) with an average haplotype diversity (Hd) and nucleotide diversity π of 0.564 and 0.00034, respectively, were observed. Of these, haplotypes H1 and H4 accounted for 88.8% of the isolates, and H4 was predominant in Tibet. Genetic diversity analysis using the STRUCTURE (K = 2) and AMOVE indicated that the inter-group variation accounted for 54.68%, and inter- and intra-population genotypic heterogeneity accounted for 23.90% and 21.42%, respectively. The results revealed the recent expansion of the Bgh population in Tibet, accompanied by an increase in virulence and a loss of genetic diversity.

The damage caused by the white-back planthopper (WBPH, Sogatella furcifera) and brown planthopper (BPH, Nilaparvata lugens), as well as southern rice black-streaked dwarf virus (SRBSDV), considerably decreases the grain yield of rice. Identification of rice germplasms with sufficient resistance to planthoppers and SRBSDV is essential to the breeding and deployment of resistant varieties and, hence, the control of the pests and disease. In this study, 318 rice accessions were evaluated for their reactions to the infestation of both BPH and WBPH at the seedling stage using the standard seed-box screening test method; insect quantification was further conducted at the end of the tillering and grain-filling stages in field trials. Accessions HN12-239 and HN12-328 were resistant to both BPH and WBPH at all tested stages. Field trials were conducted to identify resistance in the collection to SRBSDV based on the virus infection rate under artificial inoculation. Rathu Heenati (RHT) and HN12-239 were moderately resistant to SRBSDV. In addition, we found that WBPH did not penetrate stems with stylets but did do more probing bouts and xylem sap ingestion when feeding on HN12-239 than the susceptible control rice Taichung Native 1. The resistance of rice accessions HN12-239, HN12-328, and RHT to BPH, WBPH, and/or SRBSDV should be valuable to the development of resistant rice varieties.

Aphelenchoides besseyi is among the most devastating plant-parasitic nematodes and causes severe loss, mainly on japonica rice in China. Recently the nematode has been found to be present in the seeds of indica rice and the hybrid rice cultivars also show symptoms of the nematode damage. To understand the variations in different rice cultivars against A. besseyi, the dynamics of nematode population, the incidence of symptoms and the effects on plant yield were investigated in field experiments during 2017-2018 by inoculation of mixed stages of A. besseyi onto the seeds and seedlings of different types of rice cultivars. The results showed few nematodes could be recovered from the plants at the seedling and the end of tillering stages in all the cultivars. After flowering, the number of nematodes per panicle increased and the highest number was found in ‘Zheyou 18’ in 2017 (1050.2) and 2018 (732.1). The average incidence of the inoculated plants showing white-tip symptoms ranged from 0.5 to 10.3% and from 0.0 to 75.7% at the tillering stage in 2017 and 2018, respectively. The incidences of white-tip symptoms in the indica cultivars, including ‘9311’, ‘Minghui 63’ and ‘Nei 5 you 39’, were significantly lower than in ‘Xingxiang’, a japonica cultivar and ‘Zheyou 18’, a hybrid rice cultivar, both at the flowering stage in 2017 and at the end of the tillering stage in 2018. A strong interaction of the treatments and cultivars on the 1000-grain weight and panicle length was evident. Aphelenchoides besseyi is among the most devastating plant-parasitic nematodes and causes severe loss, mainly on japonica rice in China. Recently the nematode has been found to be present in the seeds of indica rice and the hybrid rice cultivars also show symptoms of the nematode damage. To understand the variations in different rice cultivars against A. besseyi, the dynamics of nematode population, the incidence of symptoms and the effects on plant yield were investigated in field experiments during 2017-2018 by inoculation of mixed stages of A. besseyi onto the seeds and seedlings of different types of rice cultivars. The results showed few nematodes could be recovered from the plants at the seedling and the end of tillering stages in all the cultivars. After flowering, the number of nematodes per panicle increased and the highest number was found in ‘Zheyou 18’ in 2017 (1050.2) and 2018 (732.1). The average incidence of the inoculated plants showing white-tip symptoms ranged from 0.5 to 10.3% and from 0.0 to 75.7% at the tillering stage in 2017 and 2018, respectively. The incidences of white-tip symptoms in the indica cultivars, including ‘9311’, ‘Minghui 63’ and ‘Nei 5 you 39’, were significantly lower than in ‘Xingxiang’, a japonica cultivar and ‘Zheyou 18’, a hybrid rice cultivar, both at the flowering stage in 2017 and at the end of the tillering stage in 2018. A strong interaction of the treatments and cultivars on the 1000-grain weight and panicle length was evident. Aphelenchoides besseyi is among the most devastating plant-parasitic nematodes and causes severe loss, mainly on japonica rice in China. Recently the nematode has been found to be present in the seeds of indica rice and the hybrid rice cultivars also show symptoms of the nematode damage. To understand the variations in different rice cultivars against A. besseyi, the dynamics of nematode population, the incidence of symptoms and the effects on plant yield were investigated in field experiments during 2017-2018 by inoculation of mixed stages of A. besseyi onto the seeds and seedlings of different types of rice cultivars. The results showed few nematodes could be recovered from the plants at the seedling and the end of tillering stages in all the cultivars. After flowering, the number of nematodes per panicle increased and the highest number was found in ‘Zheyou 18’ in 2017 (1050.2) and 2018 (732.1). The average incidence of the inoculated plants showing white-tip symptoms ranged from 0.5 to 10.3% and from 0.0 to 75.7% at the tillering stage in 2017 and 2018, respectively. The incidences of white-tip symptoms in the indica cultivars, including ‘9311’, ‘Minghui 63’ and ‘Nei 5 you 39’, were significantly lower than in ‘Xingxiang’, a japonica cultivar and ‘Zheyou 18’, a hybrid rice cultivar, both at the flowering stage in 2017 and at the end of the tillering stage in 2018. A strong interaction of the treatments and cultivars on the 1000-grain weight and panicle length was evident. Aphelenchoides besseyi is among the most devastating plant-parasitic nematodes and causes severe loss, mainly on japonica rice in China. Recently the nematode has been found to be present in the seeds of indica rice and the hybrid rice cultivars also show symptoms of the nematode damage. To understand the variations in different rice cultivars against A. besseyi, the dynamics of nematode population, the incidence of symptoms and the effects on plant yield were investigated in field experiments during 2017-2018 by inoculation of mixed stages of A. besseyi onto the seeds and seedlings of different types of rice cultivars. The results showed few nematodes could be recovered from the plants at the seedling and the end of tillering stages in all the cultivars. After flowering, the number of nematodes per panicle increased and the highest number was found in ‘Zheyou 18’ in 2017 (1050.2) and 2018 (732.1). The average incidence of the inoculated plants showing white-tip symptoms ranged from 0.5 to 10.3% and from 0.0 to 75.7% at the tillering stage in 2017 and 2018, respectively. The incidences of white-tip symptoms in the indica cultivars, including ‘9311’, ‘Minghui 63’ and ‘Nei 5 you 39’, were significantly lower than in ‘Xingxiang’, a japonica cultivar and ‘Zheyou 18’, a hybrid rice cultivar, both at the flowering stage in 2017 and at the end of the tillering stage in 2018. A strong interaction of the treatments and cultivars on the 1000-grain weight and panicle length was evident.