Pak. J. Bot., 39(7): 2395-2398, 2007. IN VITRO RE-GENERATION OF GUAVA (PSIDIUM GUAJAVA L.) FROM SHOOT TIPS OF MATURE TREES ROSHAN ZAMIR, N. ALI * , S.T. SHAH, T. MUHAMMAD AND S.A. SHAH Nuclear Institute for Food and Agriculture (NIFA), Tarnab, Peshawar, Pakistan * NWFP, Agricultural University, Peshawar, Pakistan Correspondence e-mail: rzamir2005@yahoo.com Abstract Micropropagation of guava through shoot tip culture from five years old bearing plants was carried out at Nuclear Institute for Food & Agriculture, Peshawar. Shoot tips after sterilization was cultured on modified MS medium supplemented with different concentrations and combinations of BAP and L-glutamin. Maximum number of shoots (72 %) was developed in to plantlets when MS was supplemented with BAP 1 mg/L and 500 mg/L L-glutamine. MS control and BAP 1mg/L combined with glutamine 250 mg/L gave minimum (22%) plantlets. Maximum (3.5) number of shoots per culture was found in 0.5 mg/L BAP alongwith 500 mg/L L-glutamine. MS supplemented with 2.5 mg/L IAA + 2.5 mg/L IBA gave maximum (54) plants rooted with average number of roots (3.8) per plantlet. The In-vitro produced plantlets were successfully established in soil. Introduction Guava (Psidium guajava L.) belongs to the family Myrataceae with chromosome number 2n =22 and possesses 150 species. It is considered as the “poor man’s fruit” or apple of the tropics” and is a popular tree fruit of the sub continent. It is native to the tropical America stretching from Mexico to Peru. Despite its origion in tropical America, guava is presently cultivated in every tropical and subtropical country around the world (Samsom, 1986). Guava, an important tree crop in Pakistan is propagated sexually (Zamir et al., 2003, Loh & Rao 1989). For being an open pollinated fruit species, there is an opportunity for the evolution of new genotypes of guava in existing plantings, which if propagated further by seed, will not usually breed true to type. In order to perpetuate selected breeding materials and varieties, therefore, one has to resort to vegetative means of propagation. Asexual propagation in guava has always been a great problem (Zamir et al., 2003, Rehman et al., 1991). Horticulturists have tried traditional methods such as cuttings, buddings, grafting, aerial layering and inarching. Aerial layering in general, is recommended by all the experts as a successful method in regeneration of this plant but such method is expensive and also cumbersome. Tissue culture is a technique, which offers an alternative procedure for the vegetative multiplication of various plant species. This technique has so far proved successful in many woody plants like eucalyptus (Burger, 1987) and fruits plants like Kiwi (Hassan et al., 2000) and guava (Jaiswal & Amin, 1992; Amin & Jaiswal, 1987). Micropropagation allows rapid multiplication of plantlets, production of pathogen- free plants, and maintenance of superior germplasm of elite cultivars and can also be practiced irrespective of the season. In vitro plant regeneration from nodal explants of mature trees of guava has been described by Amin & Jaiswal (1987) and Jaiswal & Amin (1992). Multiple shoot formation was induced using shoot tips and nodal segments of seedlings and grafted materials. In addition, adventitious shoot formation from hypocotyls and leaf segments was also achieved by Singh et al., (2002). The present