Physiological and molecular characterization of drought responses and screening of drought tolerant rice varieties / Caracterização fisiológica, molecular e seleção da resposta a tolerância à seca em variedades de arroz

Drought stress has now become a severe threat to ensure food security in the developing world as well as in Malaysia. To dertermine physiological and molecular determinants of drought stress and screening of drought tolerant rice varieties, an experiment was conducted in a greenhouse at Universiti Putra Malaysia using eleven rice varieties and two irrigation regimes (well irrigated and water stressed). The present study indicated that traditional rice variety Puteh Perak and Siam is superior drought tolerant while IRRI 2011- IRLON Plot no: 064, MR 220 and BRRI Dhan 56 are moderately drought tolerant, and IRRI 2011- IRLON Plot no: 050 and MR 84 are drought sensitive rice variety. Drought tolerance of those varieties were measured based on rate of tiller reduction, leaf rolling score and drought score during water stress condition. Leaf rolling score was positively correlated to drought score, chlorophyll content and proline accumulation. Significant increase in the proline accumulation and antioxidant enzyme activities (peroxidase and catalase) were also observed under drought stress in all the rice varieties except Siam and Puteh Perak. All the rice varieties including drought tolerant and sensitive showed the existence of OsLEA 30 genes.

Tolerância à seca tornou-se um importante tema da segurança alimentar nos países em desenvolvimento, bem como na Malásia. Com o objetivo de determinar os fatores fisiológicos e moleculares da tolerância à seca em variedades de arroz foi conduzido um experimento em casa de vegetação na Universidade Putra da Malásia usando 11 genótipos e dois sistemas de irrigação (vaso contendo plantas irrigadas e estressadas). O estudo mostrou que a variedade Puteh Perak e Siam foram superiores em condições de estresse hídrico, enquanto IRRI 2011-IRLON ­ PLOT 064 e MR 220 e BRRI Dhan 56 foram de tolerância moderada e IRRI 2011-IRLON 050 foram genótipos que apresentaram sensibilidade à seca. A tolerância à seca foi quantificada pela taxa de crescimento, nota visual para o enrolamento das folhas durante e nível de estresse durante o tempo de estresse hídrico. Enrolamento das folhas foi correlacionado com o nível de estresse hídrico, teor de clorofila e acúmulo de prolina. Aumento significativo no acúmulo de prolina e na atividade enzimática anti-oxidante (peroxidase e catalase) foram também observadas sobre estresse hídrico em todas as variedades de arroz tanto tolerantes quanto as sensíveis que esteve associado a existência de genes OsLEA 30.

Comparative study of the application of jasmonic acid and pesticide in chilli: effects on physiological activities, yield and viruses control / Estudo comparativo da aplicação de ácido jasmônico e pesticida em pimenteira: efeito nas atividades fisiológicas, produção e controle de viroses

The excessive application of pesticides for agricultural production has raised quite some concern about environmental safety and sustainability. To reduce environmental impact of pesticide overuse, there is an increasing interest in using different elicitors including Jasmonic acid (JA) to induce resistance against pathogen and insect in crop. Chilli (Capsicum annuum L.), which is an important vegeTable cum spice crop around the world. The aims of this study were to compare the effectiveness of Jasmonic acid on growth, Phyto-physiological responses, yield and viruses control in chilli plant. It was evaluated the effectiveness of single spray of JA (JA1), double spray of JA (JA2), conventional pesticide (Malathion 50%) and without any of those or control. The experimental results showed that pesticide-treated plants perform much better at early growth stages and become less competitive to JA2 treatment at maturity. Double spray of jasmonic acid showed less stress symptoms in different antioxidant enzymes activities (GPX, APX and CAT), reduce percentage of disease incidence and severity as well as improve growth and yielding characters of chilli plant. Therefore application of Jasmonic acid in chilli could be a possible alternative of pesticide application and its two times exogenous spray (0.5mM) is most effective.

A aplicação excessive de pesticidas na produção agrícola tem provocado algumas alterações na segurança ambiental e na sustentabilidade. Para reduzir este impacto ambiental aumentou o interesse no uso de elicitores incluindo o ácido Jasmônico (AJ) para induzir resistência contra os patógenos e insetos na cultura da pimenteira (Capsicum annum L.), a qual é uma importante hortaliça ou planta olerícola ao redor do mundo. Neste estudo foi comparada a eficácia do ácido Jasmônico no crescimento, resposta fisiológica, produção e controle de viroses na pimenteira. Foi avaliada uma simples aplicação (AJ1), duas aplicações (AJ2), inseticida malathion 50 % e uma testemunha (controle). Os resultados experimentais demonstraram uma redução nos sintomas de doenças viróticas pela atividade das enzimas anti oxidantes (GPX, APX e CAT), que reduziram a porcentagem da incidência e severidade das mesmas e promoveram o crescimento e melhoram os caracteres da produtividade da pimenteira. Portanto, a aplicação do ácido jsmônico em pimenteira pode ser uma alternativa para reduzir o uso de inseticidas e sua aplicação em duas vezes durante o ciclo (0,5 mM) foi mais eficiência.

Impact of cyclic water stress on growth, physiological responses and yield of rice (Oryza sativa L.) grown in tropical environment / Impacto do estresse hídrico cíclico sobre o crescimento, as respostas fisiológicas e rendimento de arroz (Oryza sativa L.)

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.

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.

Studies on seed germination and growth in weed species of rice field under salinity stress.

An investigation was made to see the salt tolerance of 10 weed species of rice. Properly dried and treated seeds of weed species were placed on 9 cm diameter petridishes lined with Whatman No. 1 filter paper under 6 salinity regimes, viz. 0 (control), 4, 8, 16, 24 and 32 dS m-1. The petri dishes were then kept in germinator at 25±1.0oC and 12 hr light. The number of germinated seeds were recorded daily. The final germination percentage, germination index (GI), seedling vigour index, mean germination time and time for 50% germination were estimated. Root and shoot lengths of the weed seedlings were measured at 20 days after salt application and relative growth values were calculated. Results revealed that salinity decreased final germination percentage, seed of germination as measured by GI, and shoot and root length in all the species. Germination of most of the weed seeds was completely arrested (0) at 32 dS m-1 salinity except in E. colona (12%) and C. iria (13.9%). The species C. iria, E. colona, J. linifolia and E. crusgalli showed better germination (above 30%) upto 24 dS m-1 salinity level and were regarded as salt-tolerant weed species. J. linifolia, F. miliacea, L. chinensis and O. sativa L. (weedy rice) were graded as moderately tolerant and S. zeylanica, S. grosus and C. difformis were regarded as least tolerant weed species.

Relative salinity tolerance of warm season turfgrass species.

Fresh water, coupled with soil salinization in many areas has resulted in an increased need for screening of salt tolerant turf grasses. Relative salinity tolerance of eight warm season turfgrass species were examined in this study in sand culture. Grasses were grown in a glasshouse, irrigated with either distilled water or saline sea water adjusted to 24, 48 or 72 dSm-1. Salt tolerances of the grasses were assessed on the basis of their shoot and root growth, leaf firing and turf quality. Regression analysis indicated that Zoysia japonica (Japanese lawn grass) (JG), Stenotaphrum secundatum (St. Augustine) (SA), Cynodon dactylon ( satiri) (BS), Zoysia teneuifolia (Korean grass) (KG), Digitaria didactyla (Serangoon grass) (SG), Cynodon dactylon (Tifdwarf) (TD), Paspalum notatum (Bahia grass) (BG) and Axonopus compressus (Pearl blue) (PB) suffered a 50% shoot growth reduction at 36.0, 31.8, 30.9, 28.4, 26.4, 25.7, 20.0 and 18.6 dSm-1 of salinity, respectively and a root growth reduction at 44.9, 43.7, 33.4, 31.0, 29.5 27.5, 21.5 and 21.4 dSm-1 of salinity, respectively. Leaf firing and turf quality of the selected species, as a whole, were also found to be affected harmoniously with the change in root and shoot growth. On the basis of the experimental results the selected species were ranked for salinity tolerance as JG>SA>BS>KG>SG >TD>BG>PB.

Effect of plastic mulch on growth and yield of chilli (Capsicum annuum L.)

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.