Matt Krna

Jana (Sweet) U'Ren & Matt (Krn-Dog) Krna with their Nicotiana seedlings in the greenhouse that they called "home" for many long months in spring & summer of 2000.

Matt was an undergraduate researcher who supported by MU-LSUROP (Life Sciences Undergraduate Research Opportunity) funds.
Matt investigated the effect of environental and population x environmental effects on the relative fitness of N. alata, N. forgetiana, and their F1 hybrids. The environmental variables manipulated were fertilizer levels and crowding. Half of the plants from each density treatment were supplemented weekly with 200 PPM of aqueous fertilizer with an NPK ratio of 20:10:20 to examine the effect of nutrient availability. The other half were supplemented biweekly (they needed this much fertilizer just to keep them alive!) with the same concentration of fertilizer. All plants were watered with equal quantities twice a day. To examine the effects of crowding, plants from both species and both kinds of hybrids (N.a. x N.f. and reciprocal) were each planted in two densities: high, 2 plants/pot, and low, 1 plant/pot. The experiment was replicated over 3 greenhouse benches (blocks). The environmental stressors were chosen because these factors could be important in natural populations -- the roadside populations of these species grow in higher nutrient soil and in higher density than populations that might be considered more "natural", i.e. in rock slides, along creek beds and cracks in rock walls. Anthony Ippolito evaluated the relative fitness in roadside conditions in situ (in southern Brazil, direction of cross that produce the F1 is unknown)

Nicotiana alata
1 plant per pot
2 plants per pot

low fertilizer
6 pots
6 pots

high fertilizer
6 pots
6 pots

Nicotiana forgetiana

low fertilizer
6 pots
6 pots

high fertilizer
6 pots
6 pots

F1: N. alata x N. forgetiana

low fertilizer
6 pots
6 pots

high fertilizer
6 pots
6 pots

F1: N. forgetiana x N. alata

low fertilizer
6 pots
6 pots

high fertilizer
6 pots
6 pots
4 populations x 2 fertilizer levels x 2 crowding levels x 6 pots/treatment x 3 blocks =288 pots; 432 plants

The findings of Matt's study are many -- some highlights are:

Plants produced more biomass (below) and flowered earlier (not shown) when they were fertilized more and were grown at lower density. Results shown below are for all populations lumped.

While F1 biomass was intermediate between the parental species when N. alata was the seed parent (N.a. x N.f., F1ala below), hybrids which had N. forgetiana as their seed parent (N.f. x N.a.; F1For below) showed heterosis. This is interesting because the crossability of these species both in situ and in controlled crosses is assymetrical. Many more F1 hybrids are produced by N. forgetiana x N. alata crosses than the reciprocal -- in part due to differences in pollen tube growth rates. Now we know, not only are they more likely to be produced, but N.f. x N.a. hybrids are more fit (in these conditions anyway). Were these species to meet in great numbers and form a hybrid zone, the direction of gene flow across the (weak) species boundary would be primarily from N. alata to N. forgetiana.

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