Adoption of Rice Varieties – I. Age of Varieties and Patterns of Variability

Abstract

SUMMARYFarmers who continue to grow old and obsolete varieties do not gain the benefits they could get from growing newer ones. Given the potential large scale of these foregone benefits, relatively few studies have examined the age of varieties that farmers grow. In three surveys, members of over 3300 households were interviewed to find the rice varieties they grew in 2008 and 2011 in 18 districts in the Terai, the low-altitude region of Nepal. This provided the first description of detailed geographical patterns of adoption of rice varieties and their ages that were repeated over time. There were large differences between district and individual varieties that showed specific geographical patterns of adoption. Such detailed knowledge on spatial diversity of varieties is invaluable for planning extension activities and developing breeding programmes, and cheaper ways than household surveys of collecting this information are discussed. Some of the factors considered important in determining this complex pattern of adoption were seed availability, growing environments that differed from east to west and the continued popularity of varieties once they had established markets. Rice diversity was low because a small number of rice varieties occupied large areas. In 2011, nine varieties covered at least 75% of the total rice area in western districts, just four in central districts and eight in eastern districts. Of these, most were released before 1995 resulting in a high average age of the predominant varieties – they always had an average age of over 20 years no matter which region or year was considered. Even though there were some large changes in varietal composition from 2008 to 2011, the average age of the predominant varieties remained almost the same. In a second paper in this series, we examine how these very low varietal replacement rates, that reduce yields and increase risk to farmers, can be accelerated using a participatory research for development approach called Informal Research and Development (IRD) (Joshi et al., 2012).

INCREASED CARBON LOSS VIA ROOT RESPIRATION AND IMPAIRED ROOT MORPHOLOGY UNDER FREE-AIR OZONE ENRICHMENT ADVERSELY AFFECT RICE (ORYZA SATIVA L.) PRODUCTION

“…Kou et al (2017a) found that EO 3 decreased the N, P and K uptakes of SY63 under the same free-air O 3 enrichment facility, whereas Zhao et al (2015) observed a decrease in N uptake of SY63 rice grown under EO 3 in open-top chambers. The delayed occurrence of the maximum root development (except for root volume) may reflect a maintained rice growth under oxidative stress conditions (Coleman et al, 1996;Witcombe et al, 2017). However, this would also imply that less assimilated C could be used for reproductive growth and grain formation.…”

Spatial and temporal diversity in adoption of modern wheat varieties in India

“…However, the average age of top 5 wheat varieties varied from about 10 years in Punjab to 23 years and 22 years in Madhya Pradesh and Rajasthan, respectively. Witcombe et al (2016) have highlighted that the weighted average age measure underestimates the true age of the varieties that is defined by the year of release. In our study, the average age and weighted average age of the varieties varied significantly only in the case of Punjab and Madhya Pradesh states.…”

“…Dixon et al (2006) have made a similar observation stating that though many smallholders throughout the developing world have benefited from the introduction of first-generation green revolution cultivars that replaced lower-yielding landraces, adoption of second-and third-generation cultivars offering improvements in yield, output quality, and stress resistance seems to be occurring at a much slower pace. Witcombe et al (2016) in their recent study have found that the average age of rice varieties adopted in Nepal was 20 years. The authors remarked that the cultivation of older varieties is a widespread phenomenon in the developing world.…”

“…However, it is at the cost of genetic gains and the economic profits thereon which the farmers could have obtained had they used the high-yielding improved varieties. The cultivation of old varieties increases the crops' vulnerability to diseases and pests and dampens productivity (Smale et al,2008;Witcombe et al,2016). This is also evident by the lower wheat-yield levels in the states where the average age of varieties cultivated is higher and varietal replacement rate is lower.…”

New high yielding and disease resistant mungbean [Vigna radiata (L.) Wilczek] variety “NIFA Mung-19”

“…This is mainly because of the limited availability of local mungbean varieties with high yield potential as well as strong base for disease resistance, which in turn is the result of narrow genetic base of most of the local varieties. As pulses are grown by the farmers with small land-holdings, the only attractive trait of a new commercial variety is the higher grain yield [2,3], and easy availability of such varieties to the farmers ensures harvesting of benefits from these varieties [4,5]. New seed varieties ensure yield enhancement as well as higher per unit land production as compared to the traditional crop varieties [6].…”