Effect of Mn stress on the growth and yield parameters in wheat and triticale cultivars

Narinder P. KAUR and P. N. TAKKAR

Department of Soils, Punjab Agricultural University, Ludhiana, India

Nine promising cultivars of wheat and a triticale were found to be differentially susceptible to Mn deficiency stress when grown in the Mn deficient soil (DTPA Mn 0.8 mg Mn kg^-1) in pots. On the basis of severity of deficiency symptoms, the cultivars were categorised into:

i) highly susceptible (DWL 5023 and KSML 3),

ii) moderately susceptible (WL 1562, WL 711 and WL 410),

iii) slightly susceptible (WG 377, WG 357 and HD 2009) and

iv) tolerant (TL 419 and C 306).

The present paper is an attempt to study the association of tolerance to Mn deficiency, with some yield parameters especially in relation to straw and grain yield, harvest index, reduction in assimilate wastage as well as increase in sink size of different cultivars.

Materials and Methods

Nine promising wheat cultivars and a triticale were grown in Mn deficient soil in polyethylene lined earthen pots. pots. The physico-chemical characteristics of the soil were: pH 8.8; EC 0.3SS; organic carbon 0.21%; available P 7.5 kg/ha; K 210 kg/ha and DTPA extractable Mn 0.8 mg/kg. Three kg soil filled in each pot was supplied with 120 mg N/kg from urea; 60 mg P₂O₅/kg and 33 mg K₂O/kg from KH₂PO₄ and 5 mg Zn/kg from ZnSO₄ - 7H₂O. Mn was supplied @ 0, 5.0, 10.0 and 20.0 mg/kg as MnSO₄ - 5H₂O and the soil was thoroughly mixed. Four replications were provided in a completely randomized design. Five uniform plants were grown in each pot. The deficiency symptoms were recorded at 15, 35 and 55 days of growth. The time of emergence of ears was recorded in various treatments. The number and length of tillers were recorded just before havesting. The number of spikes in each pot and the spike length were recorded and mean length in five plants was calculated.

After harvesting at maturity, the spikes were separated and grains taken out of these. The grains of 5 spikes (top most in each plant) were pooled together and counted. The wt. of one hundred grains (two replications from each pot) was recorded. Total grain yield per pot was calculated and straw yield data included the wt. of glumes and peduncles as well. The seeds were stored for six months and then allowed to germinate on moist filter paper in petridishes (6" dia). Number of seeds germinated (out of 50) were recorded after 3 days and percent seeds germinated were calculated to asses the seed viability.

Results and Discussion

The economic yield in grain crops can be limited due to one or more of the following factors:

1) low biological yield
2) low harvest index
3) low efficiency of allocating assimilates to grain
4) reduction in assimilate production
5) increased assimilate wastage
6) reduced sink capacity (sink strength)
	i) due to sink size (grain number/number of ears)
	ii) due to sink activity (grain size)

There is much evidence that increases in yield are due primarily to partitioning of a greater proportion of total assimilates to the useful part of plant (i.e. by a higher harvest index) rather than total dry matter production. Under mineral nutrient deficiencies, overall growth rate may still be sink limited (Wareing 1979).

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