Plasmodiophora brassicae in Yunnan and its Resistant Sources in Chinese Cabbage

The Williams differential system was employed for pathotype identification of 34 Plasmodiophora brassicaeroot samples collected from Yunnan Province and pathotypes 1, 2, 4, 10 and 14 were detected. Pathotype 4 was dominant with 70.59% of all the samples in Yunnan. The distribution of the P. brassicae pathotypes was mapped. Resistance to P. brassicae (clubroot disease) was investigated in 22 Chinese cabbage cultivars and it was found that the cultivar Shangpin had multiple resistances and was immune while Shangpin CR527 and Shangpin CR523 were resistant to P. brassicae. These cultivars can be used by farmers as sources of resistance to P. brassicae, to aid them in reducing disease in their crops. Seven known clubroot-resistant genes were detected in the 22 Chinese cabbage cultivars. CRa and CRb were found to be the most resistant to P. brassicae pathotype 4. Beisheng CR12 was resistant to pathotypes 1, 4, 10 and 14, but did not carry any known resistance genes, which indicated that unknown resistant genes were present. This study will lay the foundation for the control of clubroot disease and promote disease-resistant breeding of Chinese cabbage. © 2021 Friends Science Publishers

Confirmation of Rpp Genes Conferring Resistance to Asian Soybean Rust and Mapping of Rpp1 Allele from PI 594723

In this study, we aim to develop and validate KASP molecular markers in soybean populations for Asian soybean rust (ASR) resistance gene Rpp1 (PI 200492, PI 594538A, PI 587880A), identify the gene hypothetically present in PI 594723, and validate KASP markers for Rpp2 (PI 230970), Rpp3 (PI 506764), Rpp4 (PI 459025A), and Rpp5 (PI 506764, PI 200487). Ten F2 soybean (Glycine max (L.) Merrill) populations derived from crosses between rust-susceptible (55I57RSF IPRO, 63I64RSF IPRO) x rust-resistant sources (PI 200492, PI 594738A, PI 587880A, PI 594723, PI 230970, PI 506764, PI 459025A and PI 200487) were evaluated. All F2 plants were individually evaluated in field conditions for ASR phenotypic reactions, classified according to sporulation level. SNP markers were developed according to markers associated with Rpp genes available at the SoyBase, using KASP methodology. Based on a slight difference in map position and different phenotypic disease reactions of PI 200492, the authors suggest that PI 594723 carries a resistance gene Rpp1-b. The Rpp1-b gene from PI 594723 was mapped in Chr 18 in a 12.4 cM region. The PIs carrying Rpp1-b (PI 594723, PI 587880A, and 594538A) showed strong resistance to ASR compared to the lines carrying Rpp1 (PI 200492). A total of 26 KASP markers were significantly associated (P < 0.01) with ASR. Among those, M1, M5 and M6 (Rpp1), M13 and M14 (Rpp2), M16, M17 and M20 (Rpp3), M25 and M26 (Rpp4), and M27 and M28 (Rpp5) have the potential to be used in marker-assisted selection strategies.