Rpp-Gene pyramiding confers higher resistance level to Asian soybean rust

Abstract

Asian soybean rust (ASR) causes large reductions in soybean yield, affecting the entire grain market. With low fungicide e ciency, the use of resistant cultivars can be an economical, safe, e cient, and sustainable control alternative. However, the great variability and aggressiveness of ASR and the use of Rpp genes are limited. Thus, gene pyramiding is a promising strategy for the development of cultivars with high resistance to a greater number of isolates. Thus, the aim of this study was to evaluate sister lines with different pyramided Rpp gene for resistance to Phakopsora pachyrhizi and identify which combination of Rpp genes had higher levels of resistance under eld conditions. All Rpp-pyramided lines showed higher levels of resistance, with signi cant reductions in sporulation levels (SL), number of uredinia per lesion (NoU), and frequency of lesions with uredinia (%LU), compared to the resistance sources PI200487 (Rpp5), PI200492 (Rpp1), PI230970 (Rpp2), PI459025A (Rpp4), PI506764 (Rpp3, 5), PI587880A (Rpp1-b), PI594538A (Rpp1-b), and PI594723 (Rpp1-b). Rpp-pyramided lines carrying Rpp1-b + Rpp1-b, Rpp2 + Rpp1-b, Rpp4 + Rpp1-b, and single gene Rpp1-b were classi ed as "highly resistant". Furthermore, one sister line, 52117-57 (Rpp2 + Rpp1-b), showed immunity under eld conditions. The Rpppyramided genes are an alternative for achieving high resistance levels against ASR.

Understanding Phakopsora pachyrhizi in soybean: comprehensive insights, threats, and interventions from the Asian perspective

“…Gene pyramiding is widely regarded as an optimal breeding strategy that develops strong, ASR-resistant soybean varieties. Multigenic interactions between Rpp genes can lead to increased resistance in a diverse array of P. pachyrhizi isolates ( Yamanaka et al, 2013 ; Panho et al, 2022 ). To date, only a few studies have been conducted in Asia targeting the development and evaluation of Rpp -pyramided soybean lines showing resistance against ASR isolates.…”

Soybean‐Phakopsora pachyrhizi interactions: towards the development of next‐generation disease‐resistant plants

“…Rpp1‐b + Rpp5 was the most effective combination of Rpp genes conferring resistance to naturally occurring P. pachyrhizi isolates in soybean fields in Brazil (Meira et al ., 2022 ). Different combinations of Rpp1 , Rpp1‐b , Rpp2 , Rpp3 , Rpp4 and Rpp5 have also been evaluated under field conditions with naturally occurring SBR isolates in Parana state, Brazil, with lines harbouring Rpp2 + Rpp4 or Rpp2 + Rpp1‐b showing the most effective resistance (Panho et al ., 2022 ). Gene pyramiding was also recently developed in 4014–242‐341 and 4018‐4‐1‐1‐212 soybean lines which may contain Rpp2 and Rpp4 and line RN6‐313‐362 containing Rpp1‐b and Rpp4 ; however, it is not known if these lines have higher resistance to SBR than lines containing Rpp4 alone (Stone et al ., 2022 ).…”