Effect of leaflet size and number on agronomic and physiological traits of mungbean S.SRIPHADET 1 , P.KASEMSAP 2 AND P.SRINIVES 1 * 1 Department of Agronomy, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Nakhon Pathom 73140, Thailand 2 Department of Horticulture, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand (Revised MS received 2 August 2009; First published online 5 March 2010) SUMMARY The current work was designed to compare 13 agronomic and four physiological traits in mungbean isogenic lines (ILs) with different leaflet sizes and numbers. The IL population was developed from a cross made in 2006 at Kasetsart University, Thailand, between two pure lines (one with five small and the other with seven large leaflets), followed by continuous selfing of the progenies until F 6 . The resulting four IL families each exhibited seven leaflet types, viz. three normal-sized leaflets per leaf, seven large leaflets, nine large, five small, seven small, nine small or 11 small. A trial was conducted in 2008 to compare the 28 ILs using a randomized complete block design with three replications. The large multiple-leaflet lines gave higher values for seeds/pod, pod size, seed weight, seed yield, leaf area, leaf area index and proportion of light interception, but fewer clusters of pods, branches and pods per plant than the small multiple-leaflet ILs. Seed yield/plant was positively correlated with pods/plant, seeds/pod, mean seed weight, light interception, leaf area and plant height at maturity. Leaflet size showed association with more traits than did leaflet number. INTRODUCTION Mungbean (Vigna radiata (L.) Wilczek) is an im- portant pulse crop ; 5 . 5 million ha are grown annually (Weinberger 2003) and the production rate is in- creasing by 2 . 5 % per annum (Tomooka et al. 2005). Over half of the world’s mungbean production is in India, China and Pakistan ; however, Thailand is among the top exporters of mungbean grain and prod- ucts. In 2007, 163 000 ha in Thailand were planted with mungbean, producing 122 000 tonnes of seed (Office of Agricultural Economics 2008). Mungbean can be grown up to three times per year, which makes it fit well with various cropping systems. Mungbean seeds have a high nutritive value and are utilized in making bean sprouts, starch noodles, different kinds of deep-fried patties and desserts. Seeds that do not meet human food standards can be used as livestock feed, to utilize its high-quality protein. The average yield of mungbean is low due to its indeterminate growth habit, photoperiod sensitivity, late and non-synchronous maturity, susceptibility to lodging, pod shattering and losses due to pests and diseases (Shanmugasundaram 2003). One way to raise yield/ unit area is to manipulate leaflet size and number. Mungbean yield is reported to be correlated positively with leaf area index (LAI), days to flowering, plant height, pod length, number of branches/plant, pods/ plant and seeds/pod (Khan et al. 2001; Makeen et al. 2007). Sung & Chen (1989) reported that soybean canopies comprised of narrow leaflets had increased light penetration. Wells et al. (1993) reported that soybean with more leaflets per leaf produced a greater leaf area, which can intercept more sunlight and thus possibly give greater yields. The multiple-leaflet trait in mungbean is reported to be controlled by a single recessive gene (Sripisut & Srinives 1986). This trait has been transferred to various mungbean lines, some of which bear up to seven leaflets. Soehendi et al. (2007) reported that leaflet number was controlled by two loci of the gene, n 1 and n 2 , while leaflet size (large and small) was controlled by a single locus, s. Kowsurat et al. (1999) reported greater seed yield, plant height and number of pods/plant in trifoliate mungbean cultivars than in * To whom all correspondence should be addressed. E-mail: agrpss@yahoo.com Journal of Agricultural Science (2010), 148, 353–361. f Cambridge University Press 2010 353 doi:10.1017/S0021859610000122