CHARACTERIZATION OF SHISHAM (Dalbergia sissoo) AGAINST DIEBACK DISEASE IN VARIOUS ECOLOGICAL ZONES OF PUNJAB

Abstract

Shisham (Dalbergia sissoo) is an important tree of Pakistan and is widely grown in different areas of the country mainly for furniture, timber and fuel. Dieback is a serious threat to this tree and has caused huge damage not only in Pakistan but also in India, Nepal and Bangladesh. A nursery experiment of sexually (seedlings) and asexually (cuttings) propagated D. sissoo was conducted during 2009 and 2010. Both seedlings and cuttings were inoculated with the most commonly found fungi in the dieback affected trees i.e Fusarium solani, Botryodiplodia theobromae, Curvularia lunata and Ganoderma lucidum. Overall highest disease incidence was observed in plants inoculated with F. solani (31.39%). In seedlings F. solani caused 46.18% disease while in cuttings it was only 16.61%. No disease was recorded in controlled conditions. A significant (P<0.05) correlation of seedlings and cuttings was observed with climatic variables. Good association of seedlings (r= 0.734) and cuttings (r=0.629) was observed with maximum temperature. Disease predictive models of seedlings and cuttings were developed with climatic variables; Y = -58.3 +7.58x 1 +0.0054x 2 -1.14x 3 +2.47x 4 -1.09x 5 R 2 = 0.62 (2 years data) Where Y= Disease in cuttings, x 1 = Rainfall, x 2 = Relative humidity, x 3 = Minimum temperature, x 4 = Maximum temperature and x 5 = Wind velocity R 2 =0.48 (2 years data) Y = -134 +15x 1 +0.158 x 2 -2.32 x 3 +5.27 x 4 -3.70x 5 Where Y= Disease in seedlings, x 1 = Rainfall, x 2 = Relative humidity, x 3 = Minimum temperature, x 4 = Maximum temperature and x 5 = Wind velocity A comprehensive survey of shisham was carried out in four agro-ecological zones (Sandy deserts, Northern irrigated plains, Barani areas and Sulaiman piedmont) of Punjab province. For survey eleven districts were selected being the most productive and shisham frequenting districts from the above said zones. Trees were divided into age classes and on the basis of disease severity into healthy, partially affected and fully affected trees. Age class one (1-20 years old trees) was observed as the healthiest while age class three (above 40 years) was found to be the most affected in all zones and districts. Maximum number of healthy trees was observed in age class one of Barani areas (92.16%) Maximum number of partially affected trees was seen in Sulaiman piedmont (22.89%) and less number was in Barani areas. Maximum number of dead or fully affected trees was found in class three of Northern irrigated palins (23.60%) and only 4.68% dead trees were recorded in age class one of Barani areas. In selected districts maximum number of healthy trees was in class one of Rawalpindi district (95%) and maximum partially affected trees were in age class three in Dera Ghazi Khan (22.89%). Maximum number of dead trees (33%) was found in age class three of Toba Tek Singh. Rawalpindi was the least affected district with only 5 % dead trees in class one. Water table between 15-20 feet of depth was considered as the most suitable depth where less number of dead trees were recorded in all age classes. Significant (P<0.05) correlation was observed between age class, relative humidity, minimum temperature, maximum temperature and wind velocity. Correlation was non significant with rainfall and water table. Good association was observed between tree age and dieback disease in Healthy (r=0.626), partially affected (r=0.539) and fully affected trees (r=0.613). A disease predictive model based on two years disease survey data was developed: FA = 2.51 + 4.15 x 1 + 5.25 x 2 + 0.00866 x 3 - 0.113 x 4 - 0.0611 x 5 - 0.0115 x 6 - 0.0092 x 7 + 0.541 x8 R 2 = 0.89 Where FA= Fully affected, x 1 = Age, x 2 = Year, x 3 = Water table, x 4 = Rainfall, x 5 = Relative humidity, x 6 = Minimum temperature, x 7 = Maximum temperature, x 8 = Wind velocity