Collaborative Survey and Collection of Brassica Vegetable Genetic Resources in Myanmar in 2018 and 2019

Exploration and collection surveys were conducted from October 25 to November 9, 2018 and from February 10 to 26, 2019, under the collaboration between Tokyo University of Agriculture (TUA), Japan, and the Department of Agriculture Research, Myanmar. The 2018 survey was conducted at Shan State, Mandalay Region, and in a part of the Sagaing Region. In 2019, genetic resources were collected from the Eastern Shan State. Genetic resources were collected from farmlands, farmers’ houses, local markets, and areas surrounding administrative offices of the Ministry of Agriculture, Livestock, and Irrigation. In all, 110 accessions, including 82 of Brassica juncea, 11 of Brassica oleracea L. Alboglabra Group, one of Brassica oleracea L. Capitata Group, and 16 of Raphanus sativus L, were collected. The collected genetic resources were divided between the Myanmar Seed Bank and TUA for the Plant Genetic Resources in Asia Project, and half of the collected resources was imported to Japan and introduced there as per the Standard Material Transfer Agreement. Imported seeds will be multiplied and evaluated in Japan and will become available from the National Agriculture and Food Research Organization Genebank, Japan, for research, breeding, and educational purposes.ミャンマー連邦共和国において，“Mohn Nyin” と呼ばれるカラシナを中心としたアブラナ野菜の遺伝資源探索収集を行った．2018 年 10 月 25 日から 11 月 9 日までシャン州カロー周辺，マンダレー管区およびザガイン管区の一部で収集を行った．また，2019 年 2 月 10 日から 26 日は東部シャン州において収集を行った．その結果，Brassica juncea 82 点，B. oleracea L. Alboglabra Group 11 点，B. oleracea L. Capitata Group 1 点，Raphanus sativus L. 16 点の計 110 点が収集された．調査はミャンマー農業畜産潅漑省農業研究局および東京農業大学の共同で行われた．収集品は 2 分し，一方はミャンマーシードバンクで，他方は SMTA に基づき日本に導入された後，農業研究，育種，教育目的で配布可能な遺伝資源として，農業・食品産業技術総合研究機構遺伝資源センターにて保存される

Effect of different water regimes on nematode reproduction, root galling, plant growth and yield of a lowland and upland Asian rice cultivar grown in two soil types infested by the rice root-knot nematode Meloidogyne graminicola

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Evaluation of the host response of lowland and upland rice varieties from Myanmar to the rice root-knot nematode Meloidogyne graminicola

The rice root-knot nematode Meloidogyne graminicola is considered one of the most potentially important nematode pathogens of rice, especially in South and Southeast Asia, in a range of rice production systems. Identification of M. graminicola-resistant or -tolerant rice varieties will enable breeding programmes to develop rice varieties which are able to limit yield losses caused by this nematode species. The host response to M. graminicola infection of 15 lowland rice varieties and 9 upland rice varieties, which are being grown in the summer-irrigated lowland and rainfed upland rice ecosystems in Myanmar, was evaluated in two experiments under screenhouse conditions. The lowland rice experiment was carried out under intermittently flooded conditions in a clay loam soil (i.e. simulating the summer-irrigated lowland rice ecosystem) and the upland rice experiment was carried out at field capacity in a sandy loam soil (i.e. simulating the monsoon rainfed upland rice ecosystem). None of the15 lowland and 9 upland rice varieties were resistant to M. graminicola infection although differences in susceptibility and sensitivity were observed. Six (or 40%) out of the 15 lowland varieties examined were classified as less susceptible (LS) to M. graminicola infection, five (or 33.3%) as moderately susceptible (MS) while four (or 26.7%) as highly susceptible (HS). One (or 11.1%) out of the nine upland varieties examined was classified as LS to M. graminicola infection, three (or 33.3%) as MS while five (or 55.6%) as HS. Five (or 33.3%) out of the 15 lowland varieties examined were classified as either less sensitive or tolerant to M. graminicola infection. One (or 11.1%) out of the nine upland varieties examined was classified as tolerant to M. graminicola infection. This study offers interesting information for the farmer regarding which rice variety should be grown in M. graminicola-infested fields under either lowland or upland conditions. © 2013 © 2013 Taylor & Francis.status: publishe

Population dynamics of Meloidogyne graminicola and Hirschmanniella oryzae in a double rice-cropping sequence in the lowlands of Myanmar

The rice root-knot nematode, Meloidogyne graminicola, and the rice root nematode, Hirschmanniella oryzae, are considered potentially important nematode pathogens in lowland rice. A study was undertaken from December 2009 until December 2010 in the Ayeyarwady River Delta, the major lowland rice-producing area of Myanmar, to monitor the population dynamics of M. graminicola and H. oryzae in a naturally infested field. Root samples of the two rice varieties Yatanartoe and Taungpyan that are commonly cultivated in double rice-cropping sequences in Myanmar and represent irrigated and rainfed lowland rice varieties, respectively, were obtained for nematode analysis. During the summer-irrigated rice-growing season the root population density of second-stage juveniles (J2) of M. graminicola showed two distinct peaks – at the maximum tillering stage of the rice plants in January and at the heading stage of the rice plants in March 2010. With the onset of the monsoon rains, the J2 population densities in the roots of ratoon rice plants gradually decreased in May. During the rainfed monsoon rice-growing season, very low population densities of M. graminicola J2 were detected in the roots of rice plants, while the root population density of H. oryzae juveniles and adults showed two distinct peaks – at the maximum tillering stage of the rice plants in August and at the heading stage of the rice plants in October 2010. With the onset of the dry season, population density of H. oryzae in the roots reached the lowest density at harvest in November. Root galling caused by M. graminicola followed the same trend as the J2 population densities throughout the irrigated season. No root galls were observed during the monsoon season. Our results can be used for practical purposes aimed at a better management of both M. graminicola and H. oryzae.http://booksandjournals.brillonline.com/content/journals/10.1163/15685411-0000271

Effect of planting and irrigation practices on nematode reproduction, root galling, plant growth and yield of two Asian lowland rice varieties infected by the rice root-knot nematode Meloidogyne graminicola

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Occurrence of the rice root nematode Hirschmanniella oryzae on monsoon rice in Myanmar

During May-October 2007, soil and root samples from 539 fields were collected from 11 monsoon rice varieties in 12 regions in Myanmar. All regions surveyed and 90% of fields sampled were infested with the rice root nematode Hirschmanniella oryzae. The average H. oryzae population was 10/100 mL soil and 419/20 g roots respectively. In 6.9% of the fields sampled 50 H. oryzae/g root were found. The average root population densities were the highest (640/20 g roots) in Taungpyan variety and the lowest (155/20 g roots) in Immayebaw variety. The lowest soil and the second-lowest root populations of H. oryzae were observed in Shwethweyin which may indicate that this rice variety is less susceptible to H. oryzae. Among three cropping sequences, the highest frequency of occurrence (94%) was found in the rice-rice cropping sequence. Based on the prominence value (a combination of the frequency of occurrence and abundance) of H. oryzae, Hlaingtharyar was the most infested region where susceptible rice varieties are grown and rice-rice cropping sequence is practiced. The rice production in this region may be the most at risk of suffering important yield losses due to H. oryzae

Effect of different water regimes on nematode reproduction, root galling, plant growth and yield of lowland and upland Asian rice varieties grown in two soil types infested by the rice root–knot nematode Meloidogyne graminicola

In a screenhouse experiment, plants of the lowland rice variety Thihtayin and the upland rice variety Kone Myint 2 were grown in two soil types (clay loam and sandy loam), inoculated with 3,000 Meloidogyne graminicola second-stage juveniles (J2) per plant and from 6 weeks onwards maintained until harvest under three water regimes: permanently flooded, intermittently flooded and upland (monsoon rainfed) conditions. Both varieties were susceptible to M. graminicola infection under all three water regimes and in both soil types but differences in susceptibility were observed between the two varieties and among the treatments. The effect of water regime on the number of eggs and J2 of M. graminicola inside the roots was lower than expected: with one exception no significant effects were observed of any of the water regimes on the root population density in both rice varieties in both soil types. This observation may be explained by the delayed flooding, which started 6 days after nematode inoculation for the permanent and intermittent flooding water regimes. In both varieties and in both soil types, the root galling index was significantly lower on permanently flooded plants (< 4.5) compared with plants that had been either intermittent flooded or grown under upland conditions (≥ 5.0). The highest root galling indices were always observed on plants grown under upland conditions (7.0-8.5). Permanent flooding prevented the suppression of most plant growth and yield-contributing traits measured. Moreover, permanent flooding also prevented significant yield loss in plants of both varieties grown in the clay loam soil and in plants of variety Thihtatyin grown in the sandy loam soil. The results of our study confirm again the enormous impact M graminicola infection can have on the yield of both lowland and upland rice varieties. With the exception of one treatment, yield loss was always higher than 20% and even almost 100% (yield failure) in plants of both varieties grown in the sandy loam soil under upland conditions. Although yield losses caused by nematodes carried out under screenhouse experiments tend to result in an overestimation of these losses, the results of our screenhouse experiments show that yield losses caused on Asian rice by M. graminicola must be very high also under field conditions in the farmer's field

Comparison of the damage potential and yield loss of the rice root–knot nematode, Meloidogyne graminicola, on lowland and upland rice varieties from Myanmar

In Asia, the rice root-knot nematode, Meloidogyne graminicola, is an important pathogen of Asian rice (Oryza sativa) in most rice producing countries including Myanmar. In the first part of our study, the damage potential of M. graminicola on commonly cultivated newly released high-yielding lowland rice varieties and upland rice varieties (traditional, improved and aerobic), which are being grown in different regions in the summer-irrigated lowland and rainfed upland rice ecosystems in Myanmar, was investigated under screenhouse conditions. In the second part of our study, a field experiment was carried out in the Ayeyarwady River Delta, the major lowland rice producing area of Myanmar, to investigate the impact of M. graminicola on plant growth and yield of the same lowland rice varieties included in the screenhouse experiment in a naturally-infested farmer’s field. None of the 15 lowland varieties and none of the nine upland varieties included in the screenhouse experiments was resistant to M. graminicola. Although differences in susceptibility were observed among the lowland and upland varieties, and between the two types (lowland and upland) of rice varieties, with an Mf–eggs (multiplication factor of the second-stage juveniles without counting the eggs) ranging from 13.2 to 52.8 for the lowland varieties vs 39.8 to 108.4 for the upland varieties, all varieties included in our study can be considered as highly susceptible to M. graminicola when the nematode population densities are assessed at harvest. Also in the field experiment, all the 15 lowland varieties were susceptible to M. graminicola infection. This part of our study shows that upland rice varieties are more susceptible to M graminicola infection than lowland rice varieties. The percentage reduction in lowland and upland varieties was very similar in six out of the ten plant growth and yield-contributing traits measured. The highest differences in percentage reduction were observed for fresh root weight (41.0 vs 26.1% for the lowland and upland varieties, respectively), number of tillers per plant (29.1 vs 14.1%, respectively), percentage filled grains per plant (11.7 vs 0.8%, respectively) and filled grain weight per plant (34.7 vs 47.6 g, respectively). Within the two types of rice varieties significant differences in percentage reduction of plant growth traits between uninoculated and inoculated plants were observed among the rice varieties, so we suggest that the effect of M. graminicola infection on the different vegetative and reproductive plant growth stages of rice varieties is highly genotype-dependent and that no general conclusions can be made. In the screenhouse experiments, infection with M. graminicola caused on average a yield reduction with 31.1% in the lowland rice varieties vs 44.9% in the upland rice varieties, which indicates that in the upland varieties the higher nematode population densities per root unit (1 g) and per root system resulted in a higher yield loss compared with the lowland varieties. In the field experiment, carbofuran treatment resulted, on average, in a 16.5% increase in yield of the lowland rice varietie