In outbreak, mainly devastating in the winter season, can

In the 21st century, global agriculture faces the
major challenge for supplying future sustainable food and vegetable production with
a growing population under worsening anthropogenic climate change. This change
result in reducing available water and a rise in air temperatures. Mungbean (Vigna
radiata (L.) Wilczek) is one of the most important leguminous staple crops because
of its short life cycle (about 60 days) with wide adoptability, drought
tolerance, fixing atmospheric nitrogen in its root nodules in association with soil
rhizobium for thriving in N-deficient soils (Yaqub et al., 2010) as well as its valuable
nutritional and health benefits. The global annual production is 3 million tons
of grain from more than 6 million hectares worldwide (Nair et al., 2013). India is the world’s largest
mungbean producers followed by China, Pakistan, Taiwan, Australia, Myanmar and Indonesia.
Although Thailand is not among the major producers, mungbean is a strategic
crop for local and national agribusiness, being lower northern Thailand
responsible for about 0.14 million hectares. Nowadays about 4 thousand tons of
the internal demand are consumed, however the Thailand government supplied only
6 hundred tons of the total demand. (Office of Agricultural Economics, 2016).
The major constraints are inherently low yielding potential of the current
varieties and susceptible to destructive diseases, a notable group of which are
the foliar diseases. Among them, Cercospora leaf spot (CLS) caused by Cercospora canescens Illis & Martin inflict
significantly seed yield losses in mungbean. Under the rainy season coupling
with sufficient number of fungal spores, mungbean was severely and rapidly
infected in the susceptible Uthong1 (UT1) and resistant (Pagasu) varieties to 68% and 35%, respectively (AVRDC, 1984). Powdery mildew (PM) caused
by another fungus Sphaerotheca phaseoli is an important foliar disease
of mungbean worldwide. Its outbreak, mainly devastating in the winter season, can
reduce seed yield more than 50% (Khajudparn et al., 2007) or
even 100% at the seedling stage (Reddy et al., 1994). Currently, these major yield losses were
recognized in all highly susceptible varieties of mungbean recommended to
farmers in Thailand i.e. UT1, Kampaeng Saen 1 (KPS1), KPS2, Chai Nat (CN36),
CN60, CN72, CN84-1 and Suranaree University of Technology 1 (SUT1). However, these recommended varieties,
particularly KPS2, CN36, CN72 and CN84-1 have been still cultivated together with spraying chemicals as long as no new improved
varieties were developed (Ngampongsai et al., 2015a). Chemical usage increases farmers’ production costs and
has adverse effects on human health including the environment. Moreover,
regular spraying can cause the evolutionary change of chemical resistance in
the pathogen. In addition, some disease resistant varieties may be broken down
by new virulent races according to the classic boom and bust cycles of major
gene resistance to plant pathogens. Thus, usefulness of disease resistant
varieties pyramiding disease resistance genes is the most desirable strategy to
provide more durable and broad-spectrum resistance in an economical and eco-friendly
way.                             

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