B. Fatima

Enhanced in vitro multiple shoot induction in elite Pakistani guava cultivars for efficient clonal plant multiplication

Elite guava ( Psidium guajava L.) strains of cv. Safeda were explored in vitro for multiple shoot induction. Shoot induction was enhanced up to 83% with 3.5 to 4.25 shoots per single node cutting and shoot tip explants, respectively, using higher levels of benzyl amino purine (BAP) in Murashige and Skoog (MS) medium. Enhancing sucrose supplement to 45 gl -1 improved plant growth and development in shoot and root length and leaf size as well (3.8, 5.6 and 0.6 cm, respectively) compared to 30 gl -1 of sucrose in the media. Higher root, shoot length and leaf size (6, 8 and 2.8 cm, respectively) was obtained on transplanting multiplied plants in pots containing silt and compost (1:1) compared to compost and sand. The combined effect of BAP and enhanced sucrose in MS medium is suggested to obtain efficient, cost effective, better plant growth and development in guava for year round supply of healthy plant material to growers. Keywords: Guava, shoot tip, benzyl amino purine (BAP), sucrose, in vitro

Mandarin (Citrus reticulata Blanco) Breeding

Mandarins including clementines, tangerines, satsumas, willowleaf, tangors and tangelos are the second largest cultivated group of citrus after sweet oranges and provide about 25% of world citrus production. Classical breeding has limited potential in citrus crop improvement and is handicapped mainly by nucellar embryony, long juvenility and self-incompatibility. Molecular biology tools have revealed mandarins as one of the primary citrus species and the ancestor of secondary species. A better understanding of genomics, valuable bioinformatics databases and recent advances in molecular breeding have shortened the breeding cycle and accelerated the breeder’s productivity towards improvement in economically-important traits. This chapter elucidates the economic significance, botanical classification and leading cultivars, global distribution of varieties, floral biology and functional genomics, germplasm biodiversity and conservation, origin and genetic backgrounds of polyembryony, haploids and polyploids and their significance in structural genomics, mutation breeding, seedlessness, scope of conventional and somatic hybridization, applications of molecular markers, bioinformatics databases and transgenics. Enhancing international collaboration, accelerated germplasm conservation and exchange programs, integration of classical breeding and the molecular biology tools discussed could enhance the pace of development of high-yielding cultivars with better resistance against changing climatic conditions, emerging biotic and abiotic stresses and help to ensure food security.