Breeding of Fruit and Plantation Crops

Guava

• Botanical name: Psidium guajava L.
• Family: Myrtaceae
• Chromosome number 2n-2x-22

• Guava is also known as the ‘Apple of the Tropics. It is a very rich and cheap source of vitamin C and also contains a fair amount of calcium. Important guava growing states in the country are Uttar Pradesh, Bihar, Madhya Pradesh and Maharashtra. Allahabad district of Uttar Pradesh has the reputation of growing the best quality of guava fruits in the world (Mitra and Bose, 1990). The importance of guava is due to the fact that it is the hardy fruit which can be grown in alkaline and poorly drained soil.

Center of diversity

• Tropical America is supposed to be the center of origin of guava where it is found in wild as well as cultivated forms. Guava came to India at a very early time before 17th century.

Germplasm resources

• Guava is mainly a self pollinated crop but occurrence of cross pollination results in great variation in the seedling population. About 103 genotypes are available in the Indian collections (iyer and Subramanian, 1987) while Yadav (1990) has listed 153 genotypes including Psidium species, cultivars and hybrids mainly at CISH, Lucknow, IIHR, Bangalore, NDUAT, Faizabad, and HAU, Hisar. Guava germplasm is being maintained at several centers in the country in field banks which are often not systematically maintained (Pathak and Ojha,1993).

Breeding objectives

• Devlopment of seedless variety
• Less pectin content for edible purpose
• More peetin content for processing
• Uniform ripening
• High keeping quality
• Resistance to tea mosquito bug and wilt.

Botany

• Most of the Cultivars of Indian guava belongs to the genus Psidium and species gujava. Based on the shape of common guava fruits, they are classified into two groups (De Candolle 1904) i.e. Psidium pyriferum, Psidium pomiferum. Genus Psidium contains about 150 species (Hayes, 1970). All cultivated varieties of guava are either diploid 2n-2x-22 or triploid 2n-3x-33 (Atchinson, 1947).

Floral biology and pollination

• Guava bears flower solitary or in cyme of two to three flowers, on the current season growth in the axil of the leaves. About one month is required from flower bud differentiation to complete development upto calyx cracking stage. Peak time of anthesis is between 5.00-6.30 AM in most of the varieties of guava. The dehiscence of anthers starts 15-30 minutes after anthesis and continues for two hours. The pollen fertility is high in almost all the cultivars. The pollen fertility is 78% and 91% in Allahabad Round and Lucknow Safeda, respectiviely.

Inheritance pattern

• Bold seed is found to be dominant over soft seed and governed monogenically.
• Red flesh colour is dominant to white pulp colour and also goverened monogenically.
• Red fleshed cultivars are supposed to be heterozygous
• There is linkage between red flesh colour and bold seed size.
• Triploidy and some other genetic factors are responsible for female sterility