Quantification of incubation, latent and infection periods of <i>Phakopsora pachyrhizi</i> in soybean, according to chronological time and degree-days

Danelli, Anderson Luiz Durante; Reis, Erlei Melo

doi:10.1590/0100-5405/1920

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Artigos • Summa Phytopathol. 42 (1) • Jan-Mar 2016 • https://doi.org/10.1590/0100-5405/1920 copy

Quantification of incubation, latent and infection periods of Phakopsora pachyrhizi in soybean, according to chronological time and degree-days

Quantificação dos períodos de incubação, latente e infeccioso de Phakopsora pachyrhizi, em soja, por tempo cronológico e por graus-dia

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

In experiments conducted in a growth chamber, the chronological time and the accumulated degree-days were determined for the duration of incubation, latent and infectious periods of Phakopsora pachyrhizi cultivars BRSGO 7560 and BRS 246 RR. Detached soybean leaflets were placed in gerbox-type acrylic boxes and inoculated with 20 x 10³ uredospores/mL. The study was conducted at 12-h photoperiod and temperatures of 10ºC, 15ºC, 22ºC, 25ºC and 30°C for 30 days. Lesions and uredia/cm²were evaluated and the number of uredia per lesion was quantified after the beginning of sporulation. The sporulation potential was also quantified for cultivars BRSGO 7560 and BRS 246 RR. The steps of the infection process can be quantified based on both the chronological time and the accumulated heat. The cultivar BRSGO 7560 produced 4,012.8 spores/cm² and BRS 246 RR, 7,348.4 uredospores/cm². The largest number of uredia was produced at 25ºC in both cultivars; however, BRS 246 RR presented 372.7 uredia/cm² and BRSGO 7560, 231.6 uredia/cm². At 10ºC and 30°C, leaf infection did not occur in both cultivars.

Keywords
Glycine max; temperature; Asian soybean rust

Factor	Spore (no./cm²)			Lesion (no./cm²)			Uredia (no./cm²)			Uredia (no./lesion)
Factor	MS	F	p	MS	F	p	MS	F	p	MS	F	p
Cultivar	1737001.3	2.4	0.06^ns ns not significant	6.75362	0.0486	>0.050 ^ns ns not significant	3430.4	4.4	0.005^ : Significant at 1% probability	16.2	2.2	0.08^ns ns not significant
Temperature	475275.5	0.6	>0.05^ns ns not significant	1660.86283	11.9474	<0.001^ : Significant at 1% probability	205.7	0.2	>0.05^ns ns not significant	6.8	0.9	>0.05^ns ns not significant
Interaction	1925930.9	2.7	0.04^* * : Significant at 5% probability:	8.30594	0.0597	0.0138^* * : Significant at 5% probability:	3412.4	4.4	0.005^ : Significant at 1% probability	32.7	4.4	0.004^ : Significant at 1% probability

	Spores (no./cm²)	Lesions (no./cm²)	Uredia (no./cm²)		Uredia (no./lesion)
Spores (no./cm²)	1.00000	0.912702	0.938397	p<0.0001^ : Significant at 1% probability	0.344724
		p=0.0034^ : Significant at 1% probability			p=0.0145 ^* * : Significant at 5% probability.
Lesions (no./cm²)		1.00000	0.901299		0.588767
			p<0.0001^ : Significant at 1% probability		p<0.0001***
Uredia (no./cm²)			1.00000		0.817991
					p<0.0001^ : Significant at 1% probability
Uredia (no./lesion)					1.00000

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[1] 1
Parte da Dissertação de mestrado do primeiro autor. Universidade Passo Fundo (2012)

Factor		Incubation period ADD			Latent period ADD			Infectious period ADD
Factor		MS	F	p	MS	F	p	MS	F	p
Cultivar		36205.1	296.8	<0.001^ : Significant at 1% probability	49928.5	313.9	<0.001^ : Significant at 1% probability	187695.7	1206.6	<0.001^ : Significant at 1% probability
Temperature		238.3	1.9	0.16^ns ns not significant.	519.5	3.3	0.07^ns ns not significant.	539.1	3.5	0.069^ns ns not significant.
Interaction		23459.5	192.9	<0.001^ : Significant at 1% probability	38057.9	239.3	<0.001^ : Significant at 1% probability	133932.3	860.9	<0.001^ : Significant at 1% probability
Factor	Incubation period CT				Latent period CT			Infectious period CT
Factor		MS	F	p	MS	F	p	MS	F	p
Cultivar		200.6	166.3	<0.001^ : Significant at 1% probability	281.6	208.9	<0.001^ : Significant at 1% probability	609.6	454.1	<0.001^ : Significant at 1% probability
Temperature		5.8	4.8	0.03^* * : Significant at 5% probability:	4.1	2.9	0.0912^ns ns not significant.	4.1	2.3	0.09^ns ns not significant.
Interaction		200.7	166.4	<0.001^ : Significant at 1% probability	298.6	221.6	<0.001^ : Significant at 1% probability	409.8	305.3	<0.001^ : Significant at 1% probability