ABSTRACT The application of biochar using inorganic fertilizer has been reported as being more efficient for the effective growth of soil microbes. However, there is no evidence that rice straw biochar (9 t ha-1) and different urea rates have had any effect on greenhouse gas (GHG) emissions of rice (Oryza sativa L.) production in tropical soils. Therefore, this study was conducted to investigate the effects of urea and the application of rice straw biochar (9 t ha-1) on yield and GHG emissions. Treatments were 150 kg N ha-1 (T1 control) and rice straw biochar (9 t ha-1) combined with 30, 60, 90, 120, and 150 kg N ha-1 (T2, T3, T4, T5, and T6, respectively). The experiment had a randomized complete block design with four replicates. Grain yield increased 20.7% in plants grown in T3, T4, and T5 compared with the control. Although all biochar treatments had increased cumulative CO2-C emissions compared with the control (5.0% to 7.6%), the cumulative CH4 emissions significantly decreased compared with the control (20% to 27%). Therefore, it could be suggested that T3 and T4 (9 t ha-1 rice straw biochar with 60 and 90 kg N ha-1) increase yield and reduce CH4 emissions relative to the control. Although this study was limited to a pot experiment with no nutrient leaching, the synergetic effect of rice straw biochar (9 t ha-1) and reduced urea rate is worth mentioning for acidic paddy soil; a field experiment is suggested to determine the long-term effect of biochar.

ABSTRACT Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae is one of the major hindrances in rice (Oryza sativa L.) production across the world including Malaysia. Therefore, the development of disease-resistant varieties remains a very economical and effective method of controlling BLB in rice. Based on this background, this study was conducted to analyze segregation pattern of simple-sequence repeat (SSR) markers associated with BLB resistance genes in an F2 bulk population derived from a resistant variety (IRBB60) and a susceptible variety (MR219). Out of 129 simple sequence repeat (SSR) markers screened, 18 distinct polymorphism markers including R-gene based markers were used to screen 345 F2 progenies for resistance to BLB. Among the polymorphic markers, the chi-square analyses showed that 15 SSR markers (i.e. RM13 (xa5), RM21 (Xa21), RM122 (xa5), RM153 (xa5), RM164 (Xa13), RM206 (Xa10), RM5509, RM20B, RM25, RM163, RM169, RM218, RM267, RM276, and RM334) had a segregation ratio of 1:2:1 for a single gene model (df = 2.0, p ≤ 0.05). For phenotypic ratio, the F2 population segregated in ratio 3:1 (R:S) for resistant and susceptible plants, respectively. This indicated that resistance to BLB caused by pathotype X. oryzae pv. oryzae (Xoo) in the ‘MR219’ × ‘IRBB60’ F2 population is controlled by single dominant genes. The result presented in this study will help breeders to further breeding research in rice by enabling selection based on the genotype rather than on the phenotype. Similarly, the markers reported in this study will serve as a valuable tool for marker-aided selection for BLB resistance gene.

RESUMOO estudo foi realizado no Centro de Arroz da Universidade Putra Malásia (UPM), para avaliar o desempenho produtivo de plantas resistentes a brunose do arroz recém desenvolvidas de BC2F3 gerações derivadas do cruzamento entre MR263, uma variedade de arroz de alta produtividade, embora suscetível a brunose e Ponsu Seribu 1, doador com resistência a brunose [Pi- 7 (t) e Pi-d (t) 1, Pir2-3 (t)genes e qLN2 QTL], e também uma variedade local da Malásia. Com base nas características avaliadas, as plantas 12, 6, 7, 5, 21, 22, 5, 26, 11, 8, 10, 13 e 15 apresentaram o maior rendimento, resistência a brunose e boas características morfológicas. Mais de 70% de herdabilidade foram encontradas em dias para maturação, altura da planta, número de perfilhos por cova, e panículas por cova, 80% de herdabilidade foram encontradas em grãos e rendimento por colina e mais de 90% de herdabilidade foi observada em grãos, largura de grãos e peso das sementes. A análise de agrupamento com base nos traços agruparam 30 plantas, juntamente com MR263 em sete clusters. De acordo com o PCA, os quatro primeiros componentes principais responsáveis por cerca de 69,3% da variação total para todas as características medidas apresentaram alta correlação entre as características analisadas.

ABSTRACTThe study was carried out in the University Putra Malaysia (UPM) Rice Research Centre to evaluate the yield performance of newly developed selected blast resistant plants of BC2F3 generations derived from a cross between MR263, a high yielding rice variety but blast susceptible and Pongsu Seribu 1, donor with blast resistant (Pi-7(t)and Pi-d (t)1, Pir2-3(t)genes and qLN2 QTL), Malaysian local variety. On the basis of assessed traits, the plants 12, 6, 7, 5, 21, 22, 5, 26, 11, 8, 10, 13 and 15 had the higher yield, blast resistant and good morphological traits. More than 70% heritability was found in days to maturity, plant height, tiller numbers per hill, and panicle per hill, 80% heritability was found in filled grain and yield per hill and more than 90% heritability was found in grain length, grain width and seed weight. Cluster analysis based on the traits grouped 30 plants along with MR263 into seven clusters. According to PCA, the first four principal components account for about 69.3% total variation for all measured traits and exhibited high correlation among the characteristics analyzed.

Genetic variability with mutagenic agents has been employed in plant breeding due to its significant contribution to the improvement of the existing rice genotypes by using genetically diverse parents. This study evaluated the genetic variability and diversity of mutant rice using quantitative traits and inter-simple sequence repeats (ISSR) molecular markers. A field experiment was carried out on M5 generation of 31 developed mutant lines and their parent (control). Morphological traits and 25 ISSR molecular markers were used as tools for determining cultivar identities and genetic diversity. The selected primers generated 443 clear polymorphic bands with an average number of 18 per primer. The bands were 85.10 % polymorphic. Un-weighted Pair Group of Arithmetic Means (UPGMA) with similarity coefficients were used for cluster analysis. Through this, all the genotypes were grouped into six clusters. It was shown that crosses between MR219-ML8 and MR219-ML22 could be done for development of high yielding varieties. Also, these mutants could be used as donor parents in rice breeding programs and some can be recommended as new rice varieties suitable for rice cultivation in Malaysia.

La variabilidad genética con agentes mutagénicos se ha usada en el cultivo de plantas debido a su contribución significativa a la mejora de los genotipos existentes de arroz a través de padres genéticamente diversos. En este estudio se evalúo la variabilidad y diversidad de mutantes de arroz mediante rasgos cuantitativos y marcadores moleculares de inter-secuencias simples repetidas (ISSR). El estudio se realizó en campo, en la generación M5 de 31 líneas mutantes desarrolladas y su padre (testigo). Características morfológicas y 25 marcadores ISSR se utilizaron como herramientas para determinar las identidades y diversidad genética de los cultivares. Los iniciadores seleccionados generaron claras 443 bandas polimórficas claras con un número promedio de 18 bandas por iniciador. Las bandas fueron 85.10 % polimórficas. El método no ponderado de pares de grupo de medias aritméticas (UPGMA) con coeficientes de similitud se usó para el análisis de los grupos. Mediante esto, todos los genotipos se agruparon en seis grupos. Las cruzas entre MR219-ML8 y MR219-ML22 podrían generarse para desarrollar variedades de alto rendimiento. Además, estos mutantes se pueden usar como padres donadores en programas de mejoramiento de arroz y algunos pueden recomendarse como variedades nuevas de arroz adecuadas para su cultivo en Malasia.

The BC2F1 population was derived from a cross between rice variety, MR219 (susceptible to blast) and Pongsu Seribu 1 (resistant to blast). The objectives of this research were to know the inheritance pattern of blast resistance and to identify the linked markers associated with blast resistance in BC2F1 population. Sixteen microsatellite markers were found as polymorphic between the parents related to blast resistant genes (Pi-genes). Among the selected blast resistant linked markers, two markers RM6836 and RM8225 showed expected testcross ratio (1:1) for single-gene model in the BC2F1 population with the association between resistant and susceptible progeny. A total of 333-BC2F1 plants were challenged with the most virulent pathotype P7.2 of Magnaporthe oryzae. Chi-square (χ2) analysis for phenotypic segregation in single-gene model showed goodness of fit (P = 0.4463) to the expected segregation ratio (1:1). In marker segregation analysis, two polymorphic markers (RM6836 and RM8225) clearly showed goodness of fit to the expected segregation testcross ratio (1:1) for the single-gene model. The marker RM8225 and RM6836 showed significant R2 values higher than 10 for the trait of the blast lesions degree (BLD). The positions of RM6836 and RM8225 markers on rice chromosome 6 and the distance between these two markers is 0.2 cM. We conclude that single dominant gene control the blast resistance in Pongsu Seribu 1 located on chromosome 6, which is linked to RM8225 and RM6836 microsatellite markers. This information could be useful in marker-assisted selection for blast resistance in rice breeding involving Pongsu Seribu 1.

Deficiência hídrica com ciclos de 5, 10, 15, 20, 25 e 30 dias de intervalo e irrigação incluindo controle irrigado (CF), controle de saturação (CS)] foram usadas para investigar o impacto do estresse hídrico sobre o crescimento cíclico, fito-respostas fisiológicas e rendimento de variedade de arroz MR220. O estudo também teve como objetivo determinar o cronograma de irrigação ideal para melhorar a produção de arroz. Observou-se que a produção de grãos, biomassa total, spiguetas, 1000-peso de grãos, panículas totais, a mortalidade de perfilhos, altura de planta e número de perfilhos por planta foi reduzida com o aumento da duração do ciclo de estresse hídrico. O rendimento de grãos foi maior tanto na CF e CS condição e foi estatisticamente igual a cinco dias do ciclo de estresse. O experimento mostra que o desempenho do crescimento e atividades fisiológicas de arroz diferem ligeiramente para cinco dias de diferença de irrigação, aumentado esse tempo, reduziria o rendimento significativamente. O estudo também mostrou que o acúmulo de prolina e conteúdo de malondialdeído (MDA) em níveis aumentaram com o increremento da duração do ciclo de estresse hídrico. Pode-se afirmar que a variedade de arroz MR220 não necessita de irrigação e ciclos de irrigação de cinco dias de intervalo é mais apropriado, além de aumentar a utilização de água e assim ter uma maior produção de arroz

A series of water stress cycles [5, 10, 15, 20, 25 and 30 days of irrigation intervel including control flooded (CF), control saturated (CS)] were exposed to investigate the impact of cyclic water stress on growth, physiological responses and yield of a famous Malaysian rice variety, MR220. The study also aimed to determine optimum irrigation schedule for better production of rice. It was observed that grain yield, total biomass, filled spikelet, 1000 grain weight, total panicle, tillers mortality, plant height and number of tillers per plant reduces with increased duration of water stress cycles. Grain yield was higher both in CF and CS condition and those are statistically identical to 5 days of stress cycle or irrigation intervel. The present experiment shows that growth performance and physiological activities of rice differ marginally for 5 days of irrigation difference, exceding that time would reduce yield significantly. The study also showed that proline accumulation and malondialdehyde (MDA) contents in levels increased with increasing duration of water stress cycle. Depending on the findings of the present, it can be stated that rice variety MR220 do not require flooding irrigation and irrigation cycle of 5 days interval is more apprapriate to increase water use and higher yield of rice

In this work a field study was conducted to evaluate the effect of coloured plastic mulch on growth and yield of chilli from October 2005 to April 2006. The plastic mulches were transparent, blue, and black and bare soil was the control. Different mulches generated higher soil temperature and soil moisture under mulch over the control. Transparent and blue plastic mulches encouraged weed population which were suppressed under black plastic. Plant height, number of primary branches, stem base diameter, number of leaves and yield were better for the plants on plastic. At the mature green stage, fruits had the highest vitamin-C content on the black plastic. Mulching produced the fruits with the highest chlorophyll-a, chlorophyll-b and total chlorophyll contents and also increased the number of fruits per plant and yield. However, mulching did not affect the length and diameter of the fruits and number of seeds per fruit. Plants on black plastic mulch had the maximum number of fruits and highest yield. Thus, mulching appears to be a viable tool to increase the chilli production under tropical conditions.