Examination of Multiple Rice Varieties (Oryza sativa L.) to the Development of Leaf Blight Disease Caused by Curvularia oryzae

Rice is the main food commodity in Indonesia, since the majority of Indonesian populations use rice as their staple food. One of the common diseases that attack rice plants is leaf blight caused by pathogenic Curvularia oryzae. The objective of this research was to determine the reaction of five varieties of rice resistance to diseases caused by Curvularia oryzae. This research was conducted at Experimental Research Station and Phytopathology Laboratory of the Departement of Plant Pest and Disease, Faculty of Agriculture, Sriwijaya University from August to December 2016. Randomized block design was applied in this experiment by using 5 treatments and 10 replications. The Results showed that the highest percentage of leaf blight disease occured in P3 (Inpari 30) by 22,36% and the lowest percentage was found in P5 (varieties IR 10) by 2,85%.


INTRODUCTION
Rice (Oryza sativa L.) is main commodity crop in Indonesia, since most of population use rice as main food. Rice consumption increases as the population increases. National and local rice production need to be stabilized since the increase of indonesian population. As consequency, every effor to increase rice yield must take into account. One of main problems to increse rice production is attachment of plant pest and disesase. Plant disesase can develop if there are three mains factors occured such as: availability of vulnerable hosts, virulen patogen and better environmental condition. Plant disease which was cause by fungi contributes high impact to yield both national and international.
One of plant disease which causes leaves blight which attached by patogen was mainly found in aduld leaves, their attachments are not significantly cause real damage. The color were varied ie. Yellow, choclate, black and some of them have ring which was centralized (Semangun, 2007). Fungi of Culvularia sp. Especially species of Culvularia oryzae was firsly found different color of paddy seeds. Fungi of Culvularia sp. Was parasit or saprofit that were occured in paddy, wheat and shorgum (Sanchez Marquez et al., 2008;Busi et al., 2009;Butt et al., 2011).
Besides it attached leaves, this fungi is also attached the seeds which is about 66%. It occured in lemma or palea, as a result there will be change color in seeds which becames black color, degeneration of endosperm. It also infected the embyo which caused lost of seed viability almost 100%. Fungi of Curvularia oryzae which attached paddy eventhough it did not decrease productivity under normal condition, but it will decrese the rice cost. (Moody, 1995;Mew dan Gonzales, 1999;Rashid, 2001;Singh et al., 2001). The report of disease caused by Curvularia oryzae in Indonesia is still limited.
The seedlings were healty, free from pests and disesases and uniform. All the seedings were planted on media which were prepared by using two seedling on each pot with 3-4 cm depth. The objective of this research was to determine the reaction of five varieties of rice resistance to diseases caused by Curvularia oryzae.

Maintenance
Maintenance activities were included replanting, weeding and watering. Replanting was conducted early in the morning or evening when it found damaged or dead plant. In addition, weeding was conducted if there were a lot of weeds occured. It was done naturally. Watering was conducted during vegetative stage and generative stage which depended on water condition in the media.

Propagation of Curvularia oryzae Isolates
Before development of isolate propagation of C. oryzae, identification of attachement plant of C. oryzae which were found from Srimulyo village Air Saleh district of Banyuasin Sumatera Selatan province was done. Development of C. oryzae isolate was done in laboratory of Phytopathology Protection study program Faculty of Agriculture Sriwijaya University. Plants were growth in PDA (Potato Dextrose Agar) media. PDA media was put in petridish in laminar air flow cabinet. After PDA media was ready, C. oryzae was growth and incubated. After that the mycelium of fungi was purified (Crous et al., 2009;Kittimorakul et al., 2013;Lestari et al., 2014).

Aplicasion of Curvularia oryzae
Isolate of C. oryzae which was aplicated by pasted on rice plant stems by using plastic isolation. The isolates were cut by using bor gabus after they were pasted (Dhingra and Sinclair, 1995).

Observations: The growth of C. oryzae on PDA Media
Observation of growth of C. oryzae macroscopicly.

Attachment Symptoms
After the plant was infected with C. oryzae fungi, the attachment symptoms in the leaves were observed. Percentage of attachment Observation of disease attachment was carried out by calculate number of rice plants which were attached by calculate using the formula as followed:

Severity of Disease
Observation was done at the firt time of infection and continued every four days. Observation was done 10 times. The severity of disesase was counted by disease score with catagory as followed: 0 : No symptom of disease 1 : less than 25% infected leaves 2 : 25% -50% infected leaves 3 : 50% -75% infected leaves 4 : more than 75% infected leaves Score value which was collected would be converted to the severity of diseseases (KP) Based on formula as followed: Descriptions: KP = Severity of diseases ni = Number of infected leaves vi = Score value N = Number of Leaves per clump which were observed Z = The highesr score value

Data Analysis
Data was analysed by ANOVA BNJ 5%.

RESULT AND DISCUSSION
The growth of C. oryzae on PDA media The result of identification of colony C. oryzae on PDA media was macroscopicly gray to black in color such as the color of cotton and in the middle part were white (Figure 1), after identification by using microskop, the conidia was chocolate and had 3-4 septa. Usually, in the middle part of septa was bent in shape. In other word it was usually form group ( Figure 1).  Michel et al. (2013) stated that chocolate conidia which consisted of 3-4 septa were irregular shape which bended on the second or the third cell with the size of 16-26 um x 8-12 um. Susanto et al. (2013) stataed that the conidium with sized of 14-28 × 7-13 μm in dark chocolate color and usually has 3 septa. Curvularia sp. was blackist brown with colony surface looks like velvet. Conidiosphore of Curvularia sp. was usually single or in groups which had chocolate color or light brown. Conidiospore has lenght of 650 µm and wide of 5-9 µm. Curvularia sp. had three septa which bended on the second cell and the third cell which more wider and more chocolate with thin walled and size of (20-30) x (9-15) µm (Gandjar, 1999).

Symptoms of Attachment
Leaf blight disease in rice plant occured after 12 days after inoculation in each variety of P1 (variety of Ciherang), P3 (variety of Inpari 30), P4 (variety of Inpara 5), and P5 (variety of IR 10) while P2 (variety of Ciliwung) occured 15 days after inoculation. The dominan part of attachment occured in plant stems ( Figure  2) and leaves (Figure 2). Part of attachment looked like yellow after that there would be necrosis which made all leaves dry and dead. The spotting produced conidium and spreaded in other part of the plant such as leaves and stems and other part of rice plant. Infection would occured after plant produced the panicles. Infected rice grains would changed to black chocolate in color. Infected rice grains would grow the miselium and formed heavy black coating ( Figure 2). Infected rice grains would be easy to determinate by color. Yellow color was uninfected plant. This disesase could caused rice plant was not able to do fotosyntesis as a result the plant would slow in growth especially panicles formation. Severe attachment would cause dead plant.

Percentage of Attachment
Varians analysis showed that percentage of attachment of leaf blight disease caused by C. oryzae were significant different on varieties being used to percentage of attachment. BNJ results showed that the average of diseases showed the highest attachment occured in P3 (variety of Inpari 30) of 22,36% and the lowest attachment in P5 (variety of IR 10) which was 2,85%. This indicated that treatment of P3 (variety of Inpari 30) was dignificant different to all treatments included P5 (variety of IR 10), P4 (variety of Inpara 5), P2 (variety of Ciliwung), P1 (variety of Ciherang). While the treatments of P4 (variety of Inpara 5) was not signifiacnt different to P5 (variety of IR 10) and P2 (variety of Ciliwung) ( Table 1). Figure 3. showed that the percentage of attachments of C. oryzae on five rice varieties from fisrt observation to ten observation were significant. The highest percentage of attachment occured in P3 (variety of Inpari 30). While the lowest attacment occured in P5 (variety of IR 10). Rice leaves which were attached of leaf blight disease would be necrosis and dead. The development of this leaf blight disesease was influence by environmental condition. During study the temperature was about 26°C-32°C. Westcott (1971) stated that optimum temperature for development of fungi was 23,89 o C to 29,44 o C and there was no infection in temperature below 12,78 o C, and the fungi could save in the soil for three years. Figure 4 indicated that intencity of disease attachemnt of leaf blight caused by C. oryzae at five varieties started from first to final observation showed significant different among varieties. These were caused by biotic and abiotic factors. The highest level of resistence level of plant would decrease disease attachment. During the study it found that intensity of disease attachment was increase in number of rice varieities. This indicated that the more infected leaves would more spread out to other part of rice plant. The sopre which blowed by the wind or carried by rain moved to other plant so all plant would attach by disease. Rain would carry all disease to other part of the plant. 14,42 a Note: Numbers which foloowed the same letter at the same colom indicated no significant different at 5% Table 3. Rice resistance to leaf blight disease caused by C. oryzae based on the symptom and percent of disease severity (Taufik et al., 2012) Severity   Susanto et al. (2013) stated that spot with size of 0,5 cm would form conidium and spread out to other part of the plant which formed new spot of leaf blight diseases. Leaf blight diseases attachment caused by C. oryzae were highest during observation in P3 (variety of Inpari 30) followed by P1 (variety of Ciherang), P2 (variety of Ciliwung), P4 (variety of Inpara 5) and variety P5 (variety of IR).

Attachment Intensity
Anova analysis showed that attachment intensity of leaf blight caused by C. oryzae showed five rice varieties were significant different during observation. BNJ showed that intensity of attachment of leaf blight diseases during observation show the highest attachment occured in P3 (variety of 30) which was about 34,71% and the lowest attachment was in P5 (variety of IR 10)

Percentage of Attachment (%)
which was about 14,42%. This showed that intensity of attachment of P3 (variety of Inpari 30) was significant different to other treatments which included P5 (variety of IR 10), P4 (variety of Inpara 5), P2 (variety of Ciliwung), P1 (variety of Ciherang). while P5 (variety of IR 10) was no significant different to P4 (variety of Inpara 5) ( Table  2). Taufik et al. (2012) stated that to know the type of variety which was to evaluate the resistencae of rice varieties to leaf blight disease caused by C. oryzae was described in the attachment ( Table 3). The result showed that intensity of leaf blight disease caused by C. oryzae during study would be group based on resistance tipe condition. (Table 4).

CONCLUSION
Leave Blight disesease caused by C. oryzae was attached five of rice varieties being studied. The symptom occured 12 days after inoculation which were on P1 (variety of Ciherang), P3 (variety of Inpari 30), P4 (variety of Inpara 5), P5 (variety of IR 10), and 15 days after inoculation on P2 (variety of Ciliwung). Percentage of disease attachment from leaf blight disease caused by C. oryzae during evaluation indicated that low attachement occurred in P5 (variety of IR 10) i.e 2,14% while the highest attachment occured in P3 (variety of Inpari 30) which was 19,09%. Average result of attachment intensity and group of rice intensity to leaf blight disease were as followed: P2 (variety of Ciliwung), P4 (variety of Inpara 5), P5 (variety of IR 10) were resistent, while P1 (variety of Ciherang) and P3 (variety of Inpari 30) were susceptible to leaf blight disease caused by C. oryzae.