Pathological and biochemical changes in Brassica juncea (mustard) infected with Albugo candida (white rust)

Abstract

Components of disease reaction, including incubation period, pustule types, inoculum production and disease index (DI); and contents of protein, phenols, soluble sugars and reducing and non‐reducing sugars were investigated in cotyledonary and true leaves of six genotypes of Brassica juncea: Varuna, Kranti, EC‐399296, EC‐399299, EC‐399313 and EC‐399301, inoculated with Albugo candida. Cotyledonary leaves were examined 14 days after inoculation (d.a.i.), whereas true leaves were scored 14 and 21 d.a.i. Disease indices were assessed on a 0% (resistant) to 100% (susceptible) scale. DIs at the cotyledonary leaf stage in the above six genotypes were 67, 65, 32, 31, 31 and 38%, respectively, whereas at the true‐leaf stage they were 21, 28, 12, 17, 9 and 4%, respectively at 14 d.a.i., and 35, 45, 17, 19, 20 and 6%, respectively at 21 d.a.i. Protein contents were highest in the genotypes with the highest DIs, such as Varuna at the cotyledonary leaf stage and Kranti at the true‐leaf stage, and lowest in the genotypes with the lowest DIs, such as EC‐399299 at the cotyledonary stage and EC‐399301 at the true‐leaf stage. Total phenols, total sugars, reducing sugars and non‐reducing sugars were generally negatively correlated with DI, but were not always consistent, particularly when differences in DI were small. The results indicated that factors conditioning the response of host genotypes to A. candida may differ or operate in different ways at different growth stages.

Validation of molecular markers for marker-assisted pyramiding of white rust resistance loci in Indian Mustard (Brassica juncea L.)

“…Surprisingly, exotic lines EC-399299, EC-399313 and EC-399301 exhibited disease reaction ranging from a moderate to a high degree of susceptibility at both stages. This is in contrast to an earlier observation at the university field experimental station at Pantnagar (northern India) where moderate visible infection with white rust at the cotyledonary leaf stage and little or almost no visible infection with this disease at the true-leaf stage was obtained (Mishra et al 2009). This may be attributed to the variation in racial composition of A. candida isolates at the two locations.…”

“…Varuna, which is amongst the oldest but is still a highly popular variety of Indian Mustard in India, exhibited the maximum ( !70%) disease index under both the stages of plant growth. This was similar to the earlier reports (Li et al 2008;Mishra et al 2009). Indigenous germplasm collections, however, showed wide variation in terms of disease reaction and exhibited moderate to high resistance.…”

“…A wide variation in incubation period and sporulation intensity exhibited among genotypes emphasize the view that besides the single major gene, some modifying factors may also be involved in the control of white rust severity as reported in other Brassica species (Fan et al 1983;Edwards and Williams 1987;Kole et al 1996). The differences observed in the reaction to A. candida between the cotyledonary and true-leaf stages may be attributed to the variation in the contents of some of the important chemical constituents of the plant like protein, phenols, soluble sugars and reducing and non-reducing sugars among different genotypes (Liu and Rimmer 1990;Singh et al 2003;Yadav and Sharma 2004;Mishra et al 2009). Moreover, it indicates that factors for resistance vary at different growth stages and reinforce the importance of testing plants at both growth stages when screening for disease resistance.…”

Leaf position‐dependent effect of Alternaria brassicicola development on host cell death, photosynthesis and secondary metabolites in Brassica juncea

“…It is believed that depletion of carbohydrates enhances plant susceptibility to a pathogen infection (Morkunas and Ratajczak 2014, Bezrutczyk et al 2018, Kanwar and Jha 2018. A decrease in the content of total sugars and reducing sugars in B. juncea during progressive A. brassicae infection (Mathpal et al 2011) and Albugo candida infection (Mishra et al 2009) was reported.…”

Symptoms and Management of White Rust/ Blister of Indian Mustard (Albugo candida)

“…aggressiveness of race, amount of available initial inoculum, time of first appearance of the disease and prevailing weather conditions. A. candida isolates from different Brassica species/cultivar or from different geographical regions may be different in their incubation period, latent period and production of sporangia and zoospores, pustule size, shape and texture and aggressiveness (Lakra and Saharan, 1988;Gupta and Saharan, 2002;Patni et al, 2005 andMishra et al, 2009).…”