A rapid leaf-disc vacuum-infiltration screening for assessing resistance to bacterial leaf spot disease in anthurium

Abstract

Resistance to Acidovorax anthurii, the causal agent of bacterial leaf spot disease (BLS) of anthurium was investigated using leaf-disc vacuum-infiltration inoculation towards developing a rapid non-destructive method of screening for resistance to BLS in segregating populations. The effect of age of the plant, developmental stage of the leaf used, inoculum concentration and type of leaf disc employed (midrib disc vs. lamina disc) were investigated to optimize the leaf-disc infiltration method of inoculation that best differentiates between levels of resistance to BLS. A screening method based on vacuum-infiltration (vacuum = 15 psi, 10 s) of leaf lamina discs (2.52 cm diameter obtained away from the midrib of stage-4 leaves) with an inoculum concentration of 9.7 × 107 CFU per ml was best able to effectively and quantitatively differentiate levels of resistance of 13 anthurium cultivars to BLS, as early as 5 days post-inoculation on a repeatable basis. On the other hand, plant ages between 2 and 5 years of age did not influence resistance levels to BLS. The lesion sizes elicited in response to inoculation using the optimized method showed a strong association (Pearson's r = 0.84; P < 0.05) with cumulative number of diseased leaves of cultivars obtained under natural epiphytotics (Holder et al., 2017) and also a strong correlation (r = -0.72, 0.77 to 0.91, P < 0.01) with resistance to BLS identified from a destructive screening study using the same 13 anthurium cultivars (Holder et al., 2021). The implications of the findings of this study are discussed.