Studies on the Interaction of Leaf Folder with Bacterial Leaf Blight in Rice Crop and their Management Strategies

Abstract

Rice (Oryza sativa L.) is one of the most paramount staple foods of the world. It occupies a unique position in cereal crops with respect to area under cultivation and more than 2.7 million populations depending on rice. In Pakistan, rice is an important food and cash crop and has the status of second staple food crop after wheat and the second major exportable produce after cotton. Despite much development in rice production technology research and developments, the yield of rice crop in Pakistan is very low as compared to other rice growing countries. One of the major yield limiting factors is the attack of insect pests and diseases. Among these, leaf folder (LF) Cnaphalocrocis medinalis (Gu.) and bacterial leaf blight (BLB) of rice are of economic importance and cause irreparable yield losses every year. A comprehensive survey was conducted to investigate the farmers’ perception regarding leaf folder and bacterial leaf blight and factors which boost up the infestation of leaf folder and incidence of bacterial leaf blight and their management practices in rice crop. A questionnaire was developed; minimum of 50 farmers were interviewed in selected five districts of Punjab, Pakistan. Majority of the farmers (62%) responded that LF attacked their crop first while 30% farmers were of the opinion that BLB attacked first. Eight percent informed that crop was attacked by LF and BLB simultaneously. As most of the farmers (72%) responded that those fields in which LF attacked first, the incidence of BLB was high, while 64% farmers told that LF enhanced the severity of BLB. Furthermore, the interaction among leaf folder and bacterial leaf blight was also studied. Total damage area (TDA) in the combined treatment (LF+Xoo) was significantly higher (72.08±1.57) than in the combined treatment (Xoo+LF), single LF treatment and single Xoo treatment on rice variety Basmati 385 and same trend was followed by 2nd week and 1st week. This implies a synergistic interaction of LF and xiv Xoo when Xoo was inoculated after LF infestation. However combined treatment of (Xoo+LF) showed a significantly lower TDA (59.28±1.47) compared with other combined treatment (72±1.57) and single LF and Xoo treatments. The data regarding yield contributed factor and yield losses due to leaf folder and bacterial leaf blight alone and combined were also recorded. The data revealed that maximum 1,000 grain weight loss due to BLB was 13.22% and 6.79% for years 2012 and 2013 respectively, on Super Basmati followed by Basmati 515 and Basmati 385. The highest 1,000 grain weight loss due to LF was 7.09% and 1.20% on Super Basmati followed by Basmati 515 and Basmati 385. The maximum 1,000 grain weight loss due to combined treatment (LF and BLB) was 20.06% and 7.07% on Super Basmati followed by Basmati 515 and Basmati 385 during 2012 and 2013 respectively. The maximum yield loss due to BLB was 20.62% and 10.55% on Super Basmati followed by Basmati 515 and Basmati 385. The yield loss due to LF was 10.32% and 3.48% on Super Basmati followed by Basmati 515 and Basmati 385.The yield loss due to combined (LF and BLB) was 27.05% and 11.02% on Super Basmati followed by Basmati 515 and Basmati 385. The leaf damage data revealed that two wild species, Oryza rufipogon and Oryza brachyantha were resistant to LF. Fourteen genotypes were moderately resistant (MR), ten were moderately susceptible (MS), fourteen were susceptible (S) and ten were highly susceptible (HS) against leaf folder. Similarly results exhibited that one wild species (O. rufipogon) was found highly resistant (HR) whereas one species (O. brachyantha) showed resistance (R) response. Two rice genotypes showed moderately resistant (MR) response; nine rice lines represented the moderately susceptible (MS) response, thirty three were represented susceptible response (S) and four were found highly susceptible (HS) against bacterial leaf blight. These identified resistant germplasm can be used in breeding program of rice crop to develop resistant varieties against leaf folder and bacterial leaf blight disease.