In-Vivo Pollination; A Better Option for Longevity Test of Pollen Viability of Cowpea (Vigna unguiculata L. Walp)

Abstract

Abstract: A quick and trusted method for evaluating pollen quality and viability is essential in a conventional breeding program. Techniques used in evaluating pollen viability can be classified into in vivo and in vitro tests. Harrison, Heslop, Harrison and Shivanna (2004) categorize the in vitro test into (a) test of germinability, (b) test of stainability, (c) test for enzyme activity and (d) fluorochromatic procedure (FCR). Using pollen of different age crossability can be suitable in testing pollen viability in the field. This research work was conducted in 2007 and 2008 at the screen house of the Institute for Agricultural Research (IAR) of Ahmadu Bello University Samaru Zaria to study pollen viability and its implication for outcrossing in cowpea. Four genotypes, IT86D1010, IT93K452-1, B301 and kanannado were used in the study. Completely Randomized Design (CRD) was used where each cultivar was sown in four labeled pots containing topsoil mixed with manure and sand. This set of planting was repeated three times but staggered to synchronize the flowering of the genotypes. Pollen grains were collected early in the morning (6:00- 6:30 am) from a matured pollen and kept in a well-labeled Petri dish in a filter paper. The crossing was done immediately after pollen collection at 0 hours, then after 3 hours of collection and 6 hours. The crossing was done in all forms, including reciprocals. Record of successful and failed crosses was taken when pods started to form. A regression analysis of pollen age on percent successful cross was carried out to determine the crossability, pollen viability, and relationships. The study shows that the three varieties, IT86D1010, IT93K452-1 and B301 were readily crossable both as paternal and maternal parents. Kanannado was crossable as a paternal parent only, but no seed was recorded when used as a maternal parent. Regression analysis shows a significant effect of pollen age on pollen viability and crossability. The experiment suggests that pollen from neighboring plants can threaten breeding materials if transferred by an efficient vector since pollen can be viable under ambient temperature for up to three hours. Keywords: In-Vivo, pollen, longevity, cowpea, viability