Protandrous-protogynous dimorphism in indigenous selections from North Western India and some exotic cultivars of Persian walnut (Juglans regia L.)

Walnut (Juglans regia L.) is one of the most important temperate nuts grown worldwide. In India, however, most of the produce comes from age-old trees of unknown origin. Apart from non-adoption of standard farm practices, certain inherent problems like dichogamy are the major factors of low productivity. The problem of dichogamy is further aggravated by short period of pollen shedding and stigma receptivity. Dichogamy in walnut prevents self-pollination and necessitates cross-pollination to set fruits. For optimum fruit set and consequent yield, an attempt was made with 20 cultivars/selections grafted on seedling walnuts for three consecutive years to determine the nature and degree of dichogamy. Observations were recorded on the time of male and female flowering, duration of pollen shedding and stigma receptivity, nature and degree of dichogamy. Results indicate that out of 20 cultivars/selections fourteen have protandrous nature, ‘Gobind’ in the first and third year, ‘KX Giant’ in second and third year and ‘Plant No. 45’ in the second year have homogamous nature and only ‘Gobind’ have protogynous nature in the second year. Degree of dichogamy varies from zero to 100 per cent among various cultivars/selections. Findings of the present study emphasized on the interplanting of protandrous and protogynous cultivars or homogamous cultivars to ensure adequate pollination to obtain higher nut yields in walnut.