Clubroot disease, caused by Plasmodiophora brassicae, is a threat to the production of Brassica crops including oilseed B. napus. In Canada, several pathotypes of this pathogen, such as pathotypes 2, 3, 5, 6, and 8, were identified, and resistance to these pathotypes was found in a rutabaga (B. napus var. napobrassica) genotype. In this paper, we report the genetic basis and molecular mapping of this resistance by use of F, backcross (BC), and doubled haploid (DH) populations generated from crossing of this rutabaga line to a susceptible spring B. napus canola line. The F, F, and BC populations were evaluated for resistance to pathotype 3, and the DH population was evaluated for resistance to pathotypes 2, 3, 5, 6, and 8. A 3:1 segregation in F and a 1:1 segregation in BC were found for resistance to pathotype 3, and a 1:1 segregation was found in the DH population for resistance to all pathotypes. Molecular mapping by using the DH population identified a genomic region on chromosome A8 carrying resistance to all five pathotypes. This suggests that a single gene or a cluster of genes, located in this genomic region, is involved in the control of resistance to these pathotypes.

Mapping clubroot resistance of Brassica rapa introgressed into Brassica napus and development of molecular markers for the resistance

The oilseed crop Brassica juncea carries many desirable traits; however, resistance to clubroot disease, caused by Plasmodiophora brassicae, is not available in this species. We are the first to report the clubroot resistant resynthesized B. juncea lines, developed through interspecific crosses between a clubroot resistant B. rapa ssp. rapifera and two susceptible B. nigra lines, and the stability of the resistance in self-pollinated generations. The interspecific nature of the resynthesized B. juncea plants was confirmed by using A- and B-genome specific SSR markers, and flow cytometric analysis of nuclear DNA content. Self-pollinated progeny (S1 and S2) of the resynthesized B. juncea plants were evaluated for resistance to P. brassicae pathotype 3. The S1 and S2 progenies of one of the resynthesized B. juncea lines were resistant to this pathotype. However, resistance was lost in 6 to 13% plants of the S2 progenies derived from the second resynthesized B. juncea line; this apparently resulted from the loss of the genomic region carrying resistance due to meiotic anomalies.

Salah satu kegiatan laboratorium tanaman adalah untuk meneliti mengenai pengelolaan tanaman hortikultura agar didapatkan tanaman yang bersifat unggul dan cepat berproduksi. Ketersediaan bibit berkualitas merupakan salah satu kendala dalam meningkatkan hasil dan kualitas buah mangga. Dalam hal untuk mendapatkan tanaman mangga yang berproduksi lebih cepat dan menghasilkan buah yang berkualitas serupa dengan tanaman induknya. Maka perbanyakan vegetatif melalui cangkok merupakan salah satu alternatifnya. Mencangkok merupakan salah satu teknik perbanyakan vegetatif dengan cara pelukaan atau pengeratan cabang pohon induk dan dibungkus media tanam untuk merangsang pembentukan akar. Penelitian ini bertujuan untuk mengetahui persentase keberhasilan pencangkokan tanaman mangga menggunakan media oasis basah, mengetahui efektifitas penggunaan oasis basah sebagai pengganti media konvensional. Penelitian ini terdiri dari 2 perlakuan dengan jumlah 15 cangkokan pada masing-masing perlakuan, sehingga didapatkan jumlah populasi 30 cangkokan. Perlakuan terdiri dari: (Co) perlakuan cangkok dengan menggunakan media konvensional; (C1) perlakuan cangkok dengan menggunakan media oasis basah. Hasil penelitian menunjukkan bahwa persentase keberhasilan cangkokan tanaman mangga menggunakan media oasis basah sama dengan penggunaan media konvensional. Kajian ini dapat memberikan sebuah solusi alternatif bahwa media oasis basah dapat dijadikan sebagai bahan pengganti media konvensional dalam kegiatan praktikum pencangkokan tanaman.